Microbiology Final (Sessions 9 - 20) Flashcards
(275 cards)
1
Q
What infections are currently at Threat Level urgent?
A
Clostridium difficile (C.difficile) Carbapenem-resistant Enterobacteriaceae
2
Q
What infections are currently at Threat Level serious?
A
Vancomycin-resistant Enterococcus (VRE)
Methicillin-resistant Staphylococcus aureus (MRSA)
Drug-resistant tuberculosis
3
Q
What infections are currently at Threat Level concerning?
A
Vancomycin-resistant Staphylococcus aureus (VRSA)
4
Q
What is the meaning of generation time?
A
Generation time is the time required for microbial cells to double in number.
5
Q
What is a culture medium usually made up of?
A
Water, Source of energy (sugar), Mineral nutrients (e.g. N, P, Fe), Certain growth factors (i.e. organic micronutrient) such as vitamins B1 and B12.
6
Q
Explain how the number of microbial cells in a sample can be enumerated when it is cultured on a medium.
A
Sample (e.g. blood) is spread on a culture medium and after a few days the number of colonies are counted. Each colony represents a viable cell in the original sample.
7
Q
If you work with human pathogen you must work under a …………………………………….
A
Biosafety cabinet
8
Q
What sterilization means?
A
Killing all the microbes including the endospores in or on an object.
9
Q
Microbial control measures fall into two categories:
A
Physical, Chemical
10
Q
What is an autoclave?
A
The autoclave is a sealed device that uses steam under pressure to kill microbes and their spores. Presence of water vapor helps heat to penetrate deeper.
11
Q
UV is commonly used for sterilizing …………………………….. and …………………..
A
Surfaces and air
12
Q
A chemical that destroys all microorganisms, including endospores is called: a- Sterilant b- Sterilizer c- Sporicide d- a,b,c e- a,b
A
e - a, b
13
Q
What is the definition of Fungistatic.
A
Prevent the fungus from growing but does not kill or lyse it.
14
Q
What is the mode of action of Actinomycin?
A
It prevents RNA elongation (i.e. RNA production).
15
Q
Give an example of a narrow-spectrum antibiotic.
A
Isoniazid (to make it easier, in Figure 27.21 only Tetracycline is a true broad spectrum)
16
Q
Explain how Interferons can be used as an antiviral drug.
A
Interferons alarm healthy cells about an existing viral infection in the body so uninfected cells can get ready to prevent viral infection. They also inform the immune system to kill the virus.
17
Q
Explain how Etest is used as an antibiotic sensitivity test (explain the procedure).
A
Etest is a non-diffusion-based technique that employs a preformed and predefined gradient of an antimicrobial agent immobilized on a plastic strip. Unlike paper disc, this technique is not prone to the effect of molecular structure of antibiotic (molecular structure of the antibiotic does not affect the inhibition zone).
18
Q
Why is microbial control important in healthcare?
A
What you want is to get rid of pathogens
E.g. sterilizing surgical tools
Reducing the spread within a health care setting
19
Q
Define decontamination.
A
Treating microbes associated with an item or material so that it is safe to handle.
20
Q
What is the difference between sterilization, disinfection, and pasteurization?
A
Sterilization is when all of the microbes are killed, including endospores. Disinfection is when most but not all are killed, enough for it to be safe to handle. Doesn’t mean endospores are killed. Pasteurization is using moderate heat to inhibit the growth of microbes in food or liquid.
21
Q
What are the main types of physical control methods?
A
Physical control methods include heat (dry heat sterilization, autoclave, incineration), radiation and filtration. Chemical control methods include cold sterilization, sterilant, disinfectant, antiseptic/germicides.
There are also self-disinfectants (like copper and silver)
22
Q
What are the general temperatures for each of the physical control methods?
A
Dry heat sterilization (200) - metal and glass
Wet heat sterilization (121)
Incineration (1000) - prions and medical waste
23
Q
Describe how radiation works as a disinfectant.
A
It destroys the genome of the pathogen. Best used on surfaces and air.
24
Q
Describe how filtration works.
A
(think vitamins and antibiotics) - uses a filter to screen out the pathogen - it can’t fit through.
25
How does cold sterilization differ from autoclave?
Uses gases to sterilize objects within an enclosed device. Used for things that can’t be heated up.
26
Are health-care associated MRSA infections increasing or decreasing?
Decreasing
27
What is deadlier, MRSA or MSSA related infections?
MRSA - mortality rate 5x higher than MSSA
28
What is the most frequent form of transmission for MRSA infection?
Skin-to-skin
29
What is the difference between bacteriostatic, bacteriocidal and bacteriolytic antimicrobial agents?
- static - prevents growth but the overall number stays the same
- cidal - kills living cells but dead cells remain (viable count goes down but total count remains the same)
- lytic: reduces overall count by degrading cells
30
What does the term selective toxicity mean?
It means that the drug will inhibit or kill the pathogen but will not adversely affect the host. Microbes are not in and of themselves difficult to kill - the challenge is not harming the host in the process.
31
Give me an example of a broad spectrum antibiotic.
Tetracycline
32
Give me two examples of narrow spectrum antibiotics.
Penicillin, echinocandins, streptomycin, Isoniazid
33
Give me an example of an antibiotic that kills fungi.
Echinocandins
34
Name the two antifungal drugs and how they work.
Echinocandins act to inhibit cell wall synthesis and ergosterol inhibitors target the unique fungal plasma membrane component ergosterol. This results in the cell membrane not working the way that it should work.
35
Define minimum inhibitory concentration (MIC)
The smallest amount of an agent needed to inhibit growth of a microorganism.
36
Define Multidrug Resistance (MDR), Extensively drug resistant (XDR), and Pandrug resistance (PDR) and provide an example for each.
MDR: “MDR was defined as acquired non-susceptibility to at least one agent in three or more antimicrobial categories (e.g. Methicillin-resistant Staphylococcus aureus (MRSA))
XDR: non-susceptibility to at least one agent in all but two or fewer antimicrobial categories (i.e. bacterial isolates remain susceptible to only one or two categories)” [1]. Certain strains of Mycobacterium tuberculosis Extensively Drug-Resistant Tuberculosis (XDR TB)
Pandrug resistance: “non-susceptibility to all agents in all antimicrobial categories.” [1]. Klebsiella pneumoniae - can use colistin as an antibiotic but it can have harsh side effects
37
Where are most drug resistant genes located and how are they transferred?
Located on plasmids and are transferred to other bacteria through horizontal gene transfer.
38
What are two short-term solutions to address drug resistance?
Drug combinations, management and limit use in agriculture (only use as appropriate with medical confirmation)
39
Name one drug combination that can help overcome antibiotic resistance.
Combining a beta-lactam antibiotic with a beta lactamase inhibitor, the antibiotic resistance of staphylococcus species can be overcome.
40
What does decolonization involve?
Eradication of the pathogen from living tissue It usually involves the use of topical antibiotic - mupirocin.
41
Sources of antimicrobial drug resistance genes are:
Nature, mutation
42
The primary cause of antimicrobial drug resistance is:
overuse of antibiotics
43
Saquinavir is a …… …………………….. inhibitor that is used against HIV.
protease
44
List five main strategies to control MRSA in healthcare systems:
Surveillance for MRSA.
B. Proper infection control measures during patient care.
C. Cleaning and disinfection of the patient care environment and equipment.
D. Proper biosafety training of medical staff and other healthcare workers.
E. Dedicated single patient application of medical equipment
F. Decolonization therapy.
45
There are a few mechanisms that enables microorganisms to become naturally resistant to certain antibiotics, list two of them:
The organism is (become) impermeable to the antibiotic (i.e. prevents the drug from getting inside the cell).
• Using certain enzymes, the microbe can alter the chemical structure of the drug (drug does not function anymore).
• Organism may be able to pump out the antibiotic (efflux)
• The microbe may develop a resistant biochemical pathway
46
What VRSA stands for?
Vancomycin Resistant Staphylococcus aureus
47
How decolonization of MRSA is done?
Decolonization of MRSA means eradication of the pathogen from living tissues. It usually involves the use of a topical antibiotic (most commonly mupirocin).
48
CDC has some tips for healthcare provides dealing with MRSA patients list four of them:
Know what types of drug-resistant infections are present in your facility and patients.
• Request immediate alerts when the lab identifies drug-resistant infections in your patients.
• Alert receiving facility when you transfer a patient with a drug-resistant infection.
• Follow relevant guidelines and precautions at every patient encounter.
49
Name a bacterial disease outbreak and a viral disease outbreak that cannot be
controlled by alcohol based hand sanitizers
Bacterial - C.difficile
| Viral - norovirus (Causes most forms of gastroenteritis)
50
Is MRSA considered a sexually transmitted disease?
No, MRSA is not considered a sexually transmitted disease
51
Can MRSA be transmitted to others through sex?
Yes - it is passed by skin-to-skin contact, which is not limited to sexual activity but that can be transmitted by sexual contact
52
Explain how MRSA screening is done?
The actual test is often done via a swab taken from the nasal area. This is then evaluated in the laboratory. Some times swabs will be taken from other areas including active skin infections, the under arm area or around the groin.
53
List three areas of the body that are tested for MRSA colonization.
Nasal area, under arm area or groin area
54
True or false: Each time we use a given antibiotic it becomes less effective in us and in others.
True
55
According to the video, how many people per year are killed by antibiotic resistance worldwide?
700,000 - projected to be 10 million
56
For what purposes microbial cultures are used in medical microbiology?
Determine the type of organism, its abundance in the sample being tested, or both.
It is one of the primary diagnostic methods of microbiology and used as a tool to determine the cause of infectious disease by letting the agent multiply in a predetermined medium.
57
For decades, eggs have been considered an ideal culture medium for flu virus and is used in flu vaccine production process. However, it is shown that the flu vaccines that are produced through egg culture of most types of flu viruses are not as efficient as the original virus. Can you think of any reason for this issue? Any alternative solution?
Put human virus in chicken
Virus has to use the chicken to replicate
Virus has to change a little bit (e.g. receptors)
Has to or won’t be able to replicate
When you give the chicken egg virus to human it works, but not as well as the human virus
Vaccine won’t create 100% immunity
Potential solution is to grow human cells and then introduce viruses
This is easier said than done
58
How high pressure inside an autoclave helps the process of sterilization?
Pressure within an autoclave allows water to boil beyond 100 Celsius; about 20 degrees beyond its boiling point
Pressure allows heat to get deeper into the substance; helps it penetrate into the object/medium
Mostly water vapour inside the chamber
59
Where are microbes usually found on the human body?
- skin
- oral cavity
- GI tract
- Respiratory tract
- urogenital tract
60
At times, host and the microbial microflora can be collectively referred to as what?
super-organisms
61
Define microflora.
combined microbial communities that live in a specific environment (e.g. human gastrointestinal microflora)
62
Define dysbiosis.
alternation or imbalance of an individual's microflora relative to healthy state
63
What are the three groups of human body microorganisms?
- benign or neutral
- beneficial
- opportunistic pathogens
64
Describe the benign group of human microorganisms and provide 2 examples of pathogens that they indirectly protect against.
- most common group
- indirectly help human health by preventing pathogens from growing (e.g. compete for space or resources)
- normal skin flora suppresses MRSA growth
- certain neutral skin microbes boost immunity against s. aureus
65
Describe beneficial microbes.
Some microbes produce certain nutrients that are used by the body. (e.g. vitamins)
66
Describe opportunistic pathogens.
Can cause diseases when conditions are favourable to them, such as when a person is immunocompromised or their microflora has been damaged.
Example: s. Epidermidis can cause issues if it finds its way into the inner tissue, instead of on the skin's surface.
67
True or False: Microbes can survive on the skin's surface without triggering an immune response.
True. It seems that normal skin microflora is not only able to survive despite the immune system, it is able to communicate with it.
68
How many different genera of bacteria and fungi including a few yeast species live on our skin?
200
69
Why are gram positive bacteria better able to survive on our skin?
they are better able to survive in a relatively dry environment that is sometime salty
70
Microbial colonization begins at birth. What defines the type of microbes that will be found on the baby's skin?
Primarily defined by the delivery mode. Vaginal birth will result in colonization by microbes present in the mother's vagina. C sections will result in colonization by microbes present on the mother's skin.
71
In a case study of microflora on hands, what seemed to influence the composition of microbes?
- gender
- time since last hand wash
- dominant hand
- family member in same household
- pet owners
72
What are the two groups of skin microflora?
resident microflora and transient microflora
73
What is the composition and diversity of skin microflora primarily based on?
- moisture
- weather
- health condition (e.g. HIV patients can have elevated levels of Candida colonized on their skin - can lead to serious infection)
- age (children can carry more potentially pathogenic gram negative bacteria)
- personal hygiene
74
Where is most of the microflora in the body found?
human GI tract
75
Where in the GI tract is the density of microbes very high?
The large intestine
76
What are some key products of the intestinal microflora?
- vitamin K
- vitamin B12
- some steroids are produced by the liver but first released into the GI and the GI microflora modifies them so that they can be absorbed and used by the body
- some essential amino acids
77
List some factors that may affect gut microflora.
- antibiotics (can lead to diarrhea and giving the advantage to antibiotic resistant strains of staph, c difficile, and candida)
- illness
- stress
- diet
- age
78
Recent studies have identified what range of bacterial species living inside the human gut?
3500 to 35,000
79
True or false: An individual's GI microbial community varies greatly throughout his or her life.
False. An individual's GI microbial community is relatively stable during his/her life.
80
In what unique circumstances do we see changes in microflora? Give a brief description of each.
- GI microflora and obesity
certain bacteria are able to produce more fatty acids that are absorbed by the host - these are more abundant in obese people
- GI microflora and pregnancy
period between 1st and 3rd trimester microbial colony of GI tract changed because there will be an increase in body fat; body prepares for that.
- GI and cancer (suggested that changes in the balance of human GI can be associated with certain types of cancer)
diets high in fats and proteins can result in more cancerogenic compounds produced by GI microflora while diets high in fiber may benefit the host
- human inflammatory bowel disease
not caused by a pathogen but rather disruption of homeostasis in the GI microflora
Also, some studies suggest GI microflora can affect mood
81
Name two potential new therapies involving GI microflora.
- promoting the growth of beneficial microbes through probiotics
- fecal transplants from health to diseased individuals
82
True or false: The bladder and kidney in healthy people is sterile.
True
83
What kind of bacteria usually colonize the urethra?
facultative aerobic bacteria
84
What opportunistic pathogens are the common causes of urinary tract infections in women and what change in conditions can lead to the infection?
E.coli and P. mirabilis. pH change.
85
Explain the different microbial communities in the vagina as an adult, pre-puberty and post menopause.
As an adult, the vagina is weakly acidic. A bacterium called lactobacillus acidophilus produces lactic acid and the acidic condition is believed to reduce infections.
In pre-puberty, L. acidophilus is rare and vagina doesn't produce glycogen. pH is neutral. Microflora includes streptococci, staphylococci and e.coli.
After menopause, glycogen production ceases and the vagina microflora is similar to pre-puberty.
86
What microbes are present in the adult vagina?
lactobacillus acidophilus, candida, streptococci, and e.coli
87
What can cause vaginosis and why is it important to determine the cause?
exogenous pathogens, bacteria, fungi (yeast), or protists (protozoa). Important to identify in order to be able to treat properly.
88
Define microbial pathogenesis.
The process by which a pathogen causes disease in a host.
89
Define disease.
The tissue damage or injury to the host caused by a pathogen or other factor, that impairs host function.
90
Define pathogen.
A microorganism that grows in or on a host and causes disease. Basically the pathogen benefits at the expense of the host.
91
Define pathogenicity.
The ability of a pathogen to cause disease in the host.
92
Define virulence.
A measure of pathogenicity of the pathogen or the relative ability of a pathogen to cause disease.
93
How is a pathogen's virulence defined?
Primarily by its genotype.
94
True or false. One strain of a pathogen could be highly virulent while another strain of the species is not.
True
95
How can you measure virulence?
Virulence can be estimated from experimental studies of the LD50 (lethal dose50).
- The number of pathogen cells that kills 50% of the host in a test group
- Less number of a highly virulent pathogen is required to kill 50% of the target population.
96
True or false: Highly virulent pathogens show little difference in the number of cells required to kill 100% of the population as compared to 50% of the population
True
97
Define attenuation
Attenuation is the decrease or loss of virulence especially when microorganisms are kept in laboratory condition for a long time.
98
Why does attenuation happen?
Attenuation happens because weakly virulent mutants grow faster on culture medium where virulent pathogens have no advantage.
99
Can attenuated microbes regain their virulence? If so, how?
Sometimes they can, if they are inoculated to a host.
100
Describe the high level sequence of events that result in microbial pathogenesis.
First, exposure to the pathogen.
Infection phase includes:
- adherence
- invasion
- multiplication
The disease process includes:
- toxicity, or:
- invasiveness
Both lead to tissue or system damage.
101
Describe the adherence stage of microbial pathogenesis.
Adherence to skin or mucosa.
Bacterial adherence can be facilitated by
- Extracellular structures such as slime layer, capsule, fimbriae, and pili
102
Describe the invasion phase of microbial pathogenesis.
The ability of a pathogen to enter into a host cell or tissue.
103
Describe the multiplication phase of microbial pathogenesis. Give an example of how bacteria can overcome the challenges of finding resources to reproduce.
The growth of a microorganism within the host, whether or not the host is harmed. The initial inoculum of a pathogen is insufficient to cause host damage, therefore pathogen needs to reproduce. Nutrients are a major limiting factor in microbial reproduction (growth) inside the host. A good example is Iron. Transferrins is a glycoprotein in the human body that carries Iron in the human body. To be able to retrieve iron for their reproduction, some bacteria produce siderophores that have a higher affinity for iron than Transferrins. This enables the pathogen to retrieve iron from the host cells.
104
True or false: Most pathogens produce virulence factors compounds that directly or indirectly promote their pathogenicity
True
105
What are some examples of virulence factors that pathogens produce to promote their pathogenicity?
Enzymes such as protease and lipase that help pathogen to degrade host structures and helps the pathogen to spread through the body.
106
Using Salmonella as an example, provide examples of the diversity of virulence factors.
- siderophores (iron uptake)
- Type 1 fimbriae (adherence)
- virulence plasmid
- flagellum (motility)
- H antigen ( adherence; inhibits phagocyte killing)
- anti-phagocytic proteins induced by oxyR
- Endotoxin in LPS layer/fever)
107
Describe the microbial pathogenesis factor of toxicity.
the ability of an organism to cause disease by means of a toxin that inhibits host cell function or kills host cells
Toxins can travel to sites within the host that are not infected by the pathogen.
108
List the two groups of toxins in microbial pathogenesis.
exotoxin
| endotoxin
109
What are exotoxins?
Toxin (usually a protein) is released from the pathogen cell as it grows.
Exotoxins are divided into more specific groups such as:
AB toxins
Enterotoxin
110
What is an endotoxin?
The lipopolysaccharide portion of the outer membrane of certain gram-negative bacteria, is released as bacterial toxin.
111
How does AB toxin work?
Consist of two subunits, A and B. Works by binding to host cell receptor (B subunit) and transferring damaging agent (A subunit) across the cell membrane
Example: Botulinum toxin (Bacterium Clostridium botulinum produces a potent AB exotoxins (Botulinum toxin) that affect nervous tissue. One milligram of Botulinum toxin is enough to kill one million pigs).
112
Describe the enterotoxin subgroup of exotoxins.
Exotoxins whose activity affects the small intestine
Generally cause massive secretion of fluid into the intestinal lumen, resulting in vomiting and diarrhea
Example: cholera toxin
113
Which is more toxic: exotoxins or endotoxins?
exotoxins
114
What kinds of physiological reactions can endotoxins cause?
fever and diarrhea
115
What are the most important factors defining host’s susceptibility to diseases?
- age (very old and very young)
- stresses (e.g. fatigue, dehydration)
- poor diet (e.g. low protein and low calorie)
- compromised host (e.g. immunosuppressant drugs or surgery, infection from another pathogen - HIV)
- host genetics
116
What two parts usually make up the naming convention for microbes?
A genus name (first word) and a specific epithet (second word) Ex: Staphylococcus aureus
117
What are the most important sub species ranks in microbiology?
- strain
| - serotype or serovar
118
Why is sub species ranking important?
Sub-species identification is very important in medical microbiology because different sub-species of one pathogen can be very different regarding their pathogenicity and the way that they need to be treated.
119
What is the difference between sub species ranks of species and serovar?
Strain: is a sub-species rank in microbiology and it means a group of microorganisms belonging to the same species, but with some distinct characteristics
Serotype or serovar: is another sub-species rank of microbes that are grouped together because they have identical antigens
120
What are some best practices in obtaining clinical samples for identification?
Specimens must be obtained and handled properly:
If possible, the specimen should be obtained from the site of infection.
The sample must be taken aseptically (to prevent other microbes to interfere with the diagnosis).
Proper handling, storage, and transport protocols should be followed.
121
List three different types of microbial diagnosis.
- Direct detection of pathogens using microscope
- Using special culture media for identifying pathogens
- Growth-Independent Diagnostic Methods
122
What is an example of a microbe that can be diagnosed under direct detection using a microscope?
N. gonorrhoeae
123
What is a selective medium?
A culture medium that permits the growth of only a specific type of pathogen. There is a selective medium for Neisseria gonorrhoeae
124
What is a differential medium?
Type of culture medium that allows the identification of microbes based on their color or shape after they grow on the medium. For instance, different microbes produce different color when they grow on CHROMagar medium.
125
What are the advantages and limitations of culture based identification techniques?
Advantages
- They are simple and inexpensive
- Pure culture of the pathogen is available for further experimentation (e.g. antibiotic sensitivity test)
Limitations
Usually at least a couple days is needed for microbe to grow (some microbes need significantly more time).
Some microbes are obligate parasite it means they do not grow on synthetic media.
126
What are two types of growth-independent diagnostic methods?
- immunofluorescence
| - nucleic acid amplification
127
What is the growth independent diagnostic method of immunofluorescence comprised of?
- Based on antibody–antigen reaction.
- Antibodies can be chemically modified with fluorescent dyes. It means when they are exposed to UV light, they will fluoresce
- Using this method, when a florescent antibody bind its specific antigen we can visualize it under a specific type of microscope called UV microscope
128
Name the two methods of immunofluorescence. Which one is more accurate?
- direct (fluorescent antibody targets an antigen on the surface of the pathogen)
- indirect (presence of a nonfluorescent antibody on the surface of a pathogen is detected using a fluorescent antibody that binds to the nonfluorescent antibody (first antibody)
indirect is more sensitive and accurate, but more expensive. It is like doing to two experiments ( 2 step procedure versus one in direct).
129
What are three advantages of immunofluorescence methods?
- Can be used to detect pathogens that do not grow on synthetic medium (e.g. viruses)
- Very specific (it can identify a specific serotypes of a given pathogen)
- Very fast
- Can be used to identify a pathogen inside the infected tissue.
- Can detect multiple pathogens simultaneously
130
List the steps involves in nucleic acid amplification.
1. Take genomic DNA (often from ribosomal DNA) and identify target sequence.
2. Prepare it and put it in tube that go into the PCR machine.
3. Now you have millions of copies of the target sequence.
4. You can submit for sequencing and identification.
131
What are the advantages and limitations of the PCR based identification?
Advantages
Very fast (usually in a few hours)
Inexpensive
It can detect the microbes that cannot be cultured on synthetic medium
Disadvantages
Requires molecular biology skills
PCR inhibition can be an issue (some samples such as blood inhibit PCR reaction and can result in a false negative)
132
What is epidemiology and what do epidemiologists study?
- The study of the occurrence and distribution of diseases in a population.
- Epidemiologists study the spread of a diseases to identify its origin and mode of transmission.
133
What is the difference between incidence and prevalence?
Incidence of a disease is the number of new cases of the disease in a given period of time in a specific population. Prevalence is the total number of new and existing cases at a population in a given time.
134
Define the term outbreak.
A sudden and unexpected large number of cases of a disease are reported in a short period of time in an area that only sporadic cases were reported previously. An outbreak is usually specific to a limited geographical area (e.g. downtown Edmonton).
135
What is an endemic?
Disease is constantly present in a population at a relatively stable rate and usually are regular intervals, but at relatively low incidences (e.g. common cold).
136
When is a disease an epidemic?
When it occurs in a large number of people in a population (higher than what usually is expected) at the same time. Term “epidemic” is similar in meaning to outbreak, but epidemic refers to a broader geographic area than the outbreak (e.g. seasonal flu in Alberta).
137
What is considered a pandemic?
When the high incidence of the disease happens in a large number of people in several countries or different continents (HIV, H1N1 in 2009).
138
Define mortality.
the incidence of death in a population in general or due to a specific case
139
Define morbidity.
the incidence of the disease including fatal and non-fatal diseases. Morbidity statistics is a better indicator of public health in a population.
140
Which is a better indicator of public health in a population, morbidity or mortality?
Morbidity
141
What are diseased individuals who show no or mild symptoms called? Why can they be dangerous?
Subclinical infections. These individuals can be carriers of the disease and spread it in community.
142
What periods can the progression of an acute infectious disease be broken into?
- infection
- incubation period
- acute period
- decline period
- convalescent period
143
Match the following.
1. infection
2. Incubation period
3. acute period
4. decline period
5. convalescent period
a) the disease is at its height with apparent symptoms.
b) patient regains strength and returns to normal.
c) the pathogen invades and grows in the host.
d) disease symptoms are dropping.
e) the time between infection and occurrence of disease symptoms.
1. c
2. e
3. a
4. d
5. b
144
What can happen during co-evolution?
During co-evolution of the pathogen and host, gradually the virulence of the pathogen diminishes, and resistance of the host increases.
(think rabbits in Australia)
145
What factor can result in a pathogen maintaining its virulence? What are three examples?
If a pathogen does not rely on host-to-host transmission, it may remain extremely virulent. Examples of these:
- Soil-borne pathogens like Clostridium
- Vector-borne pathogens like malaria
- E. coli causing severe diarrhea even death in newborns in hospital nurseries. The pathogen replicates in the host and is transmitted to another through healthcare providers or contaminated furniture.
146
Define herd immunity.
Herd immunity is the resistance of a group to infection due to immunity of a high proportion of the group.
147
How is mode of transmission of a pathogen usually defined?
A- Which part of the body is primarily infected by the pathogen: For instance respiratory pathogens (e.g. influenza) usually transmit via air but GI-associated pathogens transmit through food and water contaminated by feces.
B- Environmental factors: For instance, California Encephalitis Virus in the US causes acute inflammation of the brain. Since the disease is transmitted by a mosquito that dies in winter, the incidence or the disease is very rare in winter
148
What type of transmission is it when a disease directly infects a susceptible host without the assistance of an intermediary?
Host-to-host transmission
149
In indirect transmission, what are two types of transmission agents?
```
Living = vector (like a mosquito for malaria)
Non-living = fomite (like furniture)
```
150
Define vehicle of infectious disease and give three examples.
Nonliving sources of the pathogen that transmit the disease to a large number of individuals are called vehicle of infectious disease. Common vehicles include:
- Food
- Water
- Air
151
A disease outbreak that is sees a sharp rise in the number of infected people in a short time is characteristics of what kind of epidemic?
Common-source
152
Differentiate between common-source and host-to-host epidemics and give an example of each.
Common-source usually arises from contamination of food or water source shared by a group of people. It is characterized by a sharp increase in the number of infected people, followed by a sharp decline as people become aware and avoid the sources. An example is a well infected with cholera.
Host-to-host transmission is when a disease is passed from one host to another. This type of transmission is characterized by a slow, progressive rise of incidences and a gradual decline. Examples of this type of transmission are influenza and COVID-19.
153
What can the basic reproduction number do?
estimate how infectious a pathogen will be in a susceptible community.
R0 is calculated based on mathematical models and predicts how many secondary transmission of the disease to other individuals is expected to happen for a given pathogen.
154
What is a disease reservoir and what are some common types? Please include an example of a pathogen that can survive in the reservoir.
Reservoirs are sites at which pathogen can survive, and transmitted to new hosts.
- Soil: e.g. Clostridium
- Living organism: HIV (the reservoir is the human body).
- Zoonosis: animals (e.g. SARS).
155
What are the primary reasons that infectious diseases have dropped in the twentieth century?
- access to safe food and water (water purification)
example: typhoid
- antimicrobial drugs
- vaccination (controlled many diseases such as diptheria and measles)
156
How do the Americas and Africa differ in terms of infectious diseases?
In Africa, 47% of annual deaths are from infectious diseases while in the Americas only 12% are from infectious diseases. Due to differences in access to safe food and water, healthcare immunizations and medicine.
157
What is an example of an emerging disease?
Covid-19
158
What is an example of a re-emerging disease?
measles; when people stopped getting vaccinated
159
What factors can result in emerging or reemerging diseases? Provide an example of each.
Introduction of pathogen from other regions (dengue fever to the Americas on cargo ships)
Changes in the environment (Lyme or Nile River dam and mosquito-borne viral diseases)
Changes in pathogen (influenza)
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What is antigenic drift?
Mutation can cause minor changes in antigens called antigenic drift. It can cause outbreak but usually does not cause a pandemic.
161
What is antigenic shift and what are some examples?
Major change in viral antigen and resulting from genome reassortment. Genome reassortment happens when different influenza viruses infect one host and viral genome segments from different viruses are packaged in one viral capsule producing a new virus and a new pandemic. New virus may have new antigens that no human was exposed to them before, therefore no immunity against new virus exist causing a new pandemic.
E.g. 2009 swine flu (H1N1)
H5N1 - avian flu (60% mortality rate) - in trouble if it gets better at person-to-person infection
162
Why do we have to get flu vaccines every year?
Because the flu virus mutates very fast.
163
What kind of immunity does not require previous exposure to a pathogen or its products.
innate immunity
164
What is innate immunity made up of?
Physical and chemical barriers (e.g. skin and Lysozyme in saliva).
Cellular defense
165
Explain cellular defense within the innate immune system. What pathogens features can be recognized?
Cellular defense component of innate immunity is mediated by a number of white blood cells called phagocytes.
Phagocytes recognize a range of molecules and structures on pathogens such as:
- Lipopolysaccharides (LPS) of Gram-negatives
- Bacterial flagellin (a protein found in flagellum)
- Genomes and capsids of viruses
166
What type of immunity is the acquired ability of the host to recognize and destroy a particular pathogen or its products.
adaptive immunity
167
What are some characteristics of adaptive immunity?
- Slower (at least a few days) and more specific than the innate immune system.
- Dependent on previous exposure to the pathogen or its products.
- Directed toward an individual molecular component of the pathogen called antigen.
- It can remember the pathogen and acts against it in future
168
Name the two types of natural immunity and briefly explain each one.
Natural active immunity
- By acquiring an infection that initiates an adaptive immune response.
Natural passive immunity
- Through antibody transfer across the placenta or in breast milk. (limitation is that you are not connected to your mom forever and so this type of immunity is also temporary - it doesn't create memory.
169
List one advantage and one risk of natural active immunity.
Advantage: if you survive, immunity is strong and sometimes for life.
Risk or limitation: you have to survive it to acquire it. Also, you might not necessarily get the disease when you are healthy and you may be immunocompromised, making it difficult to acquire immunity to something; no time and more likely to die.
170
What are two types of artificial immunity?
1. artificial passive immunity
| 2. artificial active immunity
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What is artificial passive immunity?
Injection of an antiserum derived from an immune individual. Antiserum (serum containing antibody), purified antibodies obtained from an immune individual is injected to a non-immune person.
Examples (Rabies, Ebola)
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What are advantages and disadvantages of artificial passive immunity?
Advantages (quick and can be used in immunodeficient people)
Limitations: low supply relative to demand and the procedure to get the antibodies is complicated
173
Generally speaking, how does a vaccine work?
A vaccine teaches our immune system what a pathogen looks like (antigen) and how they are supposed to kill it. The body doesn't care if it is alive or dead.
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What is immunization?
The process of generating an artificial active immune response by exposure to weakened or killed pathogen, or microbial products (e.g. toxins, or an antigen or antigen mixture). These products are called vaccines and the process is called vaccination
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What are the two main goals of vaccination?
- Immunization of individuals against disease.
| - Eradication of pathogen
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What is an attenuated agent relative to a vaccine?
```
Alive microbe that can reproduce but is weakened and in its current condition cannot cause disease. Example:
MMR vaccine (measles, mumps and rubella)
```
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What are advantages or risks of using attenuated agents?
Advantage: induces strong and sometimes lifelong immunity
Risks:
- A major risk is the possibility of pathogen regaining virulence.
- It could be risky especially in immunocompromised individuals (HIV).
- The other issue is the shelf life of the vaccine.
178
What are three different types of vaccines?
- attenuated (alive but weakened)
- inactivated but whole agent
- subunit vaccines
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What is an inactivated but whole agent vaccine and what are the advantages and disadvantages?
The microbe is killed and cannot reproduce (no chance of mutation and becoming virulent).
Advantages: Can't cause disease/safer.
Disadvantage: Not as much immunity as attenuated vaccine.
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What is a subunit vaccine?
Uses a non-pathogenic antigen; a part of a pathogen.
Large-scale production of antigen could be a challenge and you may have even less immunity than a dead agent.
Example:
Hep B vaccine.
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Why are DNA and RNA vaccines better than attenuated?
- can give them to immunocompromised people without them getting sick
- if mutation in the pathogen occurs, you can introduce the change to the mRNA; less time consuming that figuring out a whole new vaccine
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What is a DNA vaccine?
Antigen encoding gene is inserted into the host cell in form of a bacterial plasmid. Once DNA is taken up by the host cell, it is being expressed and antigen is being produced and triggers an immune response.
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What are some advantages of DNA vaccines?
Easy to mass produce and inexpensive
Easy to store and transport
It is shown to prevent cancer development in mice infected with papillomavirus (a cancer-causing virus).
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What are some myths around vaccines?
- Vaccines have several damaging and long-term side-effects that are yet unknown. Vaccination can even be fatal
- Vaccines cause autism
- Some vaccines cause sudden infant death syndrome
- Vaccines contain mercury which is toxic
- Vaccine-preventable diseases are eradicated in developed countries, so we do not need vaccinations anymore
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Vaccine-preventable diseases are eradicated in developed countries, so we do not need vaccinations anymore. Why is this claim false?
Our global travel and global shipping practices.
186
What is the most widespread and dangerous water-borne pathogen?
Cholera, caused by Vibrio cholerae
187
Is a larger number of cells required for water or food borne cholera?
Water borne. Cholera hides in the food particles which protects it from stomach pH.
188
What are the two main categories of food-borne disease? Briefly describe them.
Food poisoning
A disease that results from ingestion of foods containing microbial toxins even if the microorganisms do not infect the host.
Food infection
Microbial infection resulting from the ingestion of pathogen-contaminated food followed by growth of the pathogen in the host.
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How does Staphylococcal food poisoning take place?
- caused by toxins produced by Staphylococcus aureus.
- can grow in food (e.g. meat, egg, creamy salad dressing) and produce a heat stable (60 °C) toxin that is resistant to acidic pH in the stomach.
- Some of the toxins produced by S. aureus are superantigen (causes inappropriately strong immune response) and can cause lethal toxic shock syndrome
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How is Staphylococcal Food Poisoning spread and prevented?
If food is contaminated by the microbe and is not refrigerated soon enough, S. aureus can grow in it and produce the toxin.
A common reason for food contamination by S. aureus is when food prepare introduces bacterium to food from nasal secretion or uncovered skin.
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What are some bacterial examples of food infection?
Salmonellosis
Pathogenic Escherichia coli
Listeriosis
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What are two non-bacterial food infections?
Norovirus
| Prion
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What is salmonellosis?
common gastrointestinal illness caused by foodborne Salmonella infection caused by eating contaminated food or handling infected animals.
(main sources egg and meat)
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What is Salmonella's pathogenicity?
Salmonella ingested in food or water invades phagocytes and grows as an intracellular pathogen and produces several virulence factors such as toxins.
195
Where do pathogenic E.coli strains usually infect and what is an example of one?
All pathogenic strains are intestinal parasites and usually produce potent toxins. Example:
Shiga Toxin-Producing E. coli (STEC) => bloody diarrhea and kidney failure. Mostly resulted from contaminated uncooked or undercooked meat.
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What is Listeriosis?
Listeriosis caused by bacterium Listeria monocytogenes not common but causes serious health conditions such as bacteremia (bacteria in the blood).
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True or false: Refrigeration is ineffective against the listeriosis bacterium because it can grow at cold temperature.
True
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What is the fatality rate of listeriosis?
25% ( even though annual infection rates are low - 130 in Canada annually)
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Why is Listeria monocytogenes a challenge for the immune system?
A- Phagocytes are unable to digest it because it has a toxin that degrades the membrane of the phagosome.
B- Also the pathogen lives in the cytoplasm of the host cell and can travel from one cell to another one without encountering immune system.
200
Are the largest numbers of annual foodborne infections are caused by viruses or bacteria?
Viruses
201
What is one of the most common viral food-borne infections?
norovirus (stomach flu) is most common. Causes diarrhea and vomiting. Recovery is usually fast and spontaneous (1-3 days, it is nicknamed as the 24h bug).
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How is Norovirus spread?
Norovirus is found in stool or vomit of infected people. Is highly contagious and can be transmitted through:
Direct contact with an infected person
Consumption of contaminated food or water
Most foodborne outbreaks of stomach flu occur when food handlers have the virus and contaminate the food (especially if they don’t wash their hands properly after using the washroom).
203
Can cooking kill prions?
No, they are very difficult to kill and incineration (at 3000 degrees Celsius) is recommended).
204
_________________ infections are the most common types of human diseases.
Respiratory
205
What are some major vehicles of respiratory infections?
sneezing, coughing, talking and breathing
206
While most airborne pathogens do not survive for a long time in the air, name two exceptions and why they are exceptions.
Staphylococcus and Streptococcus and Mycobacterium due to gram-positive bacteria like S that has a waxy cell wall.
207
What are three examples of airborne viral diseases?
Influenza
Measles
Mumps
208
What are some important products of intestinal microflora?
- Vitamins K and B12
Our body does not produce these vitamins and vitamin B12 is not produced by plants.
- certain steroids are produced by the liver, but first released into the GI and the microflora modifies them in a way that can be absorbed and used in the body
- some essential amino acids
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What is one of the main symptoms of S. pyogenes (aka group A streptococci)?
Severe sore throat (also known as strep throat).
210
Why is it so important to diagnose and treat the microbe in a sore throat?
Strep throat can cause severe and sometimes fatal secondary diseases such as streptococcal toxic shock syndrome.
211
Name two secondary diseases that can be caused by S. pyogenes
- Scarlet fever
- Necrotizing faciitis (rapid, progressive, and sometimes fatal disease resulting in extensive destruction of muscle and fat. This happens because bacterial exotoxin functions as a super-antigen resulting in inflammation causing tissue destruction. )
- Toxic shock syndrome
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What do some group A streptococci strains produce?
Have a bacteriophage in their cells that produces an exotoxin which is a super-antigen, which can create an unecessarily strong immune response.
213
What is toxic shock syndrome and when can it happen?
TSS is a rare disease that happens suddenly after an infection by staphylococci or streptococci bacteria and due to their super-antigen toxins. It quickly can damage several different organs such as the lungs, the kidneys, and the liver, and it can be fatal.
```
TSS can happens after:
Childbirth
Surgery
Minor skin cuts or wounds.
After a tampon is kept in too long
It can also be caused by staphylococcal food poisoning.
```
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What is tuberculosis caused by?
Mycobacterium tuberculosis, airborne droplets
215
How can you prevent the spread of tuberculosis and treat it?
- Hospitalization of patients in negative-pressure rooms.
- Use of face masks for healthcare workers
- Antimicrobial therapy with isoniazid.
Treatment usually requires a 9-month regimen.
216
What are some complications of measles?
Pneumonia
In rare cases measles encephalitis
Compromised immune system long term
217
Globally, what is the leading cause of death in children?
Measles, 114,900 in 2014 (most under 5 years old)
218
What are some complications occasionally caused by mumps (especially in adults)
- Inflammation of the reproductive organs
- Inflammation of the brain (encephalitis)
- Inflammation of the tissue covering the brain and spinal cord (meningitis)
- Deafness
219
What can untreated STIs cause?
Infertility or birth defects
Cancer
Heart diseases
Death
220
What are a few explanations for the increase in reported rates for STIs?
- More sensitive laboratory tests
- Antimicrobial resistance, a particular concern in gonorrhea, may result in treatment failure and continued transmission of infection.
- Finally, changes in sexual practices may increase the number of people contracting STIs, as evidenced by the syphilis outbreaks seen across Canada.
221
What are the 3 types of syphilis?
- primary
- secondary
- tertiary
222
Describe the three stages of syphilis.
Primary: The bacterium multiplies at the initial site of infection and causes a characteristic lesion.
Secondary: Untreated primary syphilis can result in secondary syphilis. This happens when some cells travel to other parts of the body such as eye, bones, or central nervous system. A generalized skin rash is characteristics of secondary syphilis.
Tertiary: In the absence of treatment three different scenarios can take place in different people:
A- 25% of people are spontaneously cured
B- 25% of patients show no further symptoms but maintain a chronic syphilis infection.
C- Some 50% of people develop tertiary syphilis and show a wide range of symptoms from mild skin or bone infection to severe and sometimes fatal cardiovascular or central nervous system infections.
223
What kinds of HPV infections are there?
More than 100 different strains.
- benign infections
- cancer causing HPV
- warts producing HPV infections
224
What are risk factors of HIV?
Gender and ethnicity. For instance in the US:
HIV incidences was significantly higher in Homosexual men, but among women heterosexuals are the largest risk group.
Injection drug use is a major HIV risk factor in African American and Hispanic men.
225
What are the different types of HIV?
HIV is divided into two types:
HIV-1 is the more virulent type.
HIV-2 is less common (1%) and less virulent (takes longer time to cause AIDS)
226
Who is considered an AIDS patient?
An AIDS patient is someone who is tested positive for HIV virus in immunological or DNA test and has one of these conditions:
A CD4 T cell number of less than 200/ μL
A CD4 T cell number of more than 200/ μL, any of the long list of infectious diseases associated with HIV infection such as:
- Candidiasis
- Kapiosi’s sarcoma
- Invasive cervical cancer
227
Define healthcare-associated infection.
A healthcare-associated infection (HAI) is an infection acquired by a patient in a healthcare facility.
228
What does Nosocomial mean?
related to hospital
229
How many patients will get HAIs in Canada each year and how many will die?
200,000 and 8,000
230
What % of HAIs are spread by HCW, patients, and visitors
80%
231
Why are healthcare facilities are considered high-risk area regarding the transmission of infectious diseases?
- Patients with infectious diseases serve as reservoirs for highly virulent pathogens.
- Due to the illness, many patients are more susceptible to infection.
- Patients, hospital personnel, and visitors can transmit the pathogen to others.
- Newborn infants are unusually more susceptible to certain infections.
- Hospital procedures (e.g. surgeries.) increase the risk of introducing pathogens into the patients’ body .
- Patients who receive immunosuppressive drugs are more at risk.
- Some microbial control methods (e.g. antibiotic chemotherapy and the use of disinfectants) favor the selection of resistant microorganisms.
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What are the most common healthcare-associated infections?
- C. difficile
- VRE (vancomycin-resistant enterococcus)
- Hepatitis
- HIV
- Influenza
- Mycobacterium tuberculosis
- Norovirus
- Staphylococcus aureus (MRSA, MSSA, VRSA)
233
What is the most common type of HAI?
staphylococcus aureus
234
What are two HAI microbes that can become part of your natural microflora?
E.coli and S. aureus (and they are really hard to get rid of)
235
How can you prevent HAI?
- hand washing
- cooperation of staff and visitors within a healthcare setting
- point of entry control
236
What are some examples of close contacts (re: SARS, COVID)?
Kissing or hugging
Sharing eating or drinking utensils
Talking to someone within 3 feet
Touching someone directly
237
True or False: SARS was deadlier than COVID.
True. 10% fatality rate (but less infectious)
238
What percentage of SARS infected people were HCW?
20%
239
What changes in infection control protocols were put in place due to SARS?
- Patients were kept in strict isolation in negative pressure rooms.
- Healthcare staff providing care to patients wore respirators.
- Above mentioned measures reduced the R0 value of the disease from 3.6 to 0.7.
240
How decolonization of MRSA is done?
Decolonization of MRSA means eradication of the pathogen from living tissues. It usually involves the use of a topical antibiotic (most commonly mupirocin).
241
What is a definition of serotype or serovar?
Serotype or serovar is a sub-species rank of microbes that are grouped together because they have identical antigens
242
Explain why misidentification of a pathogen can have fatal consequences in medical microbiology.
If we misidentify a pathogen we may chose wrong treatment for the disease and this may have fatal results.
243
11- Neisseria gonorrhoeae can be identified using:
a. Direct observation under microscope
a. Culturing on selective medium.
b. Both
c. None
both
244
What is the main advantage of culture based microbial identification techniques?
Pure culture of the pathogen is available for further experimentation (e.g. antibiotic sensitivity test)
245
What is an opportunistic pathogen?
A microbe that only under favorable conditions such as compromised immune system or when normal microflora is damaged can cause diseases. For instance, Staphylococcus epidermidis which is a normal component of skin microflora can cause infection if it finds its way into the inner tissues.
246
Define microflora.
Microflora is combined microbial communities that live in or on a specific environment (e.g. human gastrointestinal microflora).
247
What is transient microflora of skin?
Transient microflora: They are microbes that reach the skin through contacts with objects and skin to skin contact, but are usually unable to establish due to the competition of resident microbes or are removed by washing.
248
Why the production of vitamin B12 by GI microflora is critical for human health?
Because our body does not synthesize these vitamins and vitamin B12 is not produced by plants.
249
Explain how high fat and protein diets can increase risk of developing cancer.
It is suggested that high fat and protein diets may alter GI microflora in a manner that more cancerogenic compound is produced by GI microflora.
250
Explain how fecal microbiota transplant (FMT), or stool transplant can be used as a treatment for some patients?
It means microbial communities from healthy individuals can be transplanted to diseased people to restore a healthy microbial communities in their gastrointestinal tracts.
251
How urinary tract infections happens?
Under certain conditions such as a change in pH opportunistic pathogens inhabiting urethra (such as Escherichia coli and Proteus mirabilis) can multiply and cause urinary tract infections.
252
20- What happens to the microflora of vagina after menopause?
Glycogen production ceases, pH raises and microflora become similar to before puberty.
253
21- What is LD50 (lethal dose50 ) of a pathogen?
The number of pathogen cells that kills 50% of the host in a test group.
254
22- Define attenuation.
Attenuation is the decrease or loss of virulence especially when they are kept in laboratory condition for a long time.
255
23- Define Infection
The growth of a microorganism within the host, whether or not the host is harmed.
256
24- List three host factors that affect the outcome of pathogen-host interaction.
Age
Stress
Diet
Genetics
257
25- List three sources where you can find reliable information about infectious disease:
a- Health Canada’s infectious disease website
b- CDC (centre for disease control and prevention)
c- Infectious disease page of WHO (World Health Organization)
258
26- Define disease outbreak.
A disease outbreak occurs when a sudden and unexpected large number of cases of a disease are reported in a short period of time in an area that only sporadic cases were reported previously. An outbreak is usually specific to a limited geographical area (e.g. downtown Edmonton).
259
27- What is a fomite?
Nonliving microbe transforming agents are called fomites
260
28- What is the definition of carriers of infectious diseases?
A pathogen infected individual who have a subclinical infection and shows no symptom or mild symptoms. Carriers are potential sources of infection for others.
261
29- Explain how antigen drift in influenza happens.
Flu virus is an RNA virus and it mutates very often. Any changes in antigen structure caused by mutation in flu virus is called antigenic drift.
262
30- Explain how subunit vaccines is produced?
A specific protein (i.e. antigen) from the pathogen is mass-produced and used as a vaccine.
263
31- What is natural passive immunity and what is its main disadvantage?
When mother gives antibodies to the child through placenta or breast milk.
Main disadvantage is that it is temporary.
264
32- What is a common scenario through which S. aureus contaminates food?
A common reason for food contamination by S. aureusis when food prepare introduces bacterium to food from nasal secretion or uncovered skin.
265
33- Salmonella ingested in food or water invades ……… phagocytes
……….. and grows as an intracellular pathogen and produces several virulence factor such as
toxins.
see Q
266
34- Group A streptococci are commonly found in the upper respiratory tract of healthy people. Can cause serious infections if:
* If the immune system is weakened
| * A highly virulent strain is introduced
267
35- Toxic shock syndrome caused by bacteria most often happen after:
* Surgery
* Minor skin cuts or wounds.
* After a tampon is kept in too long or
* It can also be caused by staphylococcal food poisoning.
268
36- Give four reasons why healthcare facilities are considered high risk area regarding transmission of infectious diseases.
* Patients with infectious diseases serve as reservoirs for highly virulent pathogens.
* Due to the illness, many patients are more susceptible to infection.
* Patients, hospital personnel, and visitors can transmit the pathogen to others.
* Newborn infants are unusually more susceptible to certain infections.
269
37- Prevention of health care associated infections needs Co-operation between:
* Healthcare facility infection-control team
* Healthcare professionals
* Support staff (housekeeping)
270
38- What is the causal agent of Anthrax?
a. Bacteria
b. Virus
c. Fungus
d. Prion
271
39- Most common mode of transmission of Diphtheria is…………………………………………..
Diphtheria is most commonly transmitted via the respiratory tract through droplets
272
40- Give an example of risks to HCWs who are providing care to HIV infected patients?
Being stuck with a needle or sharp object that was contaminated with HIV (risk is low)
273
41- HCWs providing care to CJD patients should avoid contact with tissues such as:
d- Cerebral spinal fluid
| brain and spinal cord tissues, eye tissues, and tissues from immunity-regulating organs
274
42- Influenza viruses are …………………….. viruses
a. DNA
b. RNA
c. Retro-virus
d. None
275
43- How the Hep B virus infection can be diagnosed (one method is enough).
Blood Test: This is done to detect the presence of Hepatitis B surface antigen, or antibody
