Microbiology Flashcards
(122 cards)
1
Q
What is microbiology?
A
The study of all living organisms too small to be seen with the naked eye
2
Q
What are living organisms that are too small to be seen with the naked eye?
A
microbes
3
Q
What are some examples of microbes?
A
Bacteria, fungi, protozoa, viruses, archaea, prions, algae (helminths?)
4
Q
T/F Microbes are vitally important to virtually all processes on Earth with a key role in causing & controlling disease.
A
T - also have key roles in nutrient cycling, biodegradation, climate change, food spoilage & biotechnology
5
Q
_______ - disease in which a transmissible agent invades through physical barriers (skin, GI, respiratory mucosa) and overcomes the innate & adaptive immune defenses to cause injury/disease.
A
infectious disease
6
Q
What is an infectious disease?
A
disease in which a transmissible (infectious) agent invades through the physical barriers (skin, GI, respiratory mucosa) and overcomes the innate & adaptive immune defenses to cause injury/disease
7
Q
T/F Viroids and prions can cause infection.
A
T - Bacteria, viruses, viroids, & prions can all cause infection.
8
Q
Eukaryotic cells are _____ than prokaryotic cells regarding their size
A
larger (eukaryotic cells ~10,000 - 100,000 nm; prokaryotic cells ~200 - 10,000 nm)
9
Q
Viruses, viroids, & prions are ______ than prokaryotic cells regarding their size
A
smaller (viruses ~50-200 nm; viroids ~5-150 nm; prions ~2-10 nm)
10
Q
What are the differences between prokaryotes and eukaryotes?
A
Prokaryotes - simple, mostly UNICELLULAR organisms that LACK membrane bound organelles, nuclei, & mitochondria; 2 domains: Archaea & BACTERIA
Eukaryotes - mostly multicellular organisms whose cells CONTAIN a nucleus surrounded by a membrane & DNA bound together by proteins (histones) into chromosomes (I.e., fungi & helminths)
11
Q
T/F Viruses are noncellular
A
T - they are noncellular but are an obligate INTRACELLULAR pathogen
12
Q
Viruses contain ______ - packets of nucleic acid encased in a protein capsid/coat
A
infectious particles
13
Q
Spore-producing eukaryotic organisms that include yeasts and molds
A
Fungi
14
Q
Mitochondria are absent in which of the following?
A. viruses
B. bacteria
C. fungi
D. parasites
E. Both A & B
F. Both A & C
A
E. Both A & B (viruses & bacteria)
15
Q
Which of the following contains EITHER DNA or RNA in its protein capsid & lipoprotein envelope?
A. viruses
B. bacteria
C. fungi
D. parasites
A
A. viruses
- the rest of the options contain BOTH DNA & RNA
16
Q
Protozoa & helminths are…
A. viruses
B. bacteria
C. fungi
D. parasites
A
D. parasites
17
Q
Which of the following’s outer surface is a rigid wall containing peptidoglycan?
A. viruses
B. bacteria
C. fungi
D. parasites
A
B. bacteria
18
Q
Which of the following’s outer surface is a rigid wall containing chitin?
A. viruses
B. bacteria
C. fungi
D. chitin
A
C. fungi
19
Q
What can be classified as either gram positive or gram negative?
A
Bacteria
20
Q
How is the human body a hospitable site for microorganisms to grow and flourish?
A
- Sufficient nutrients*
- Appropriate temperature* & humidity*
21
Q
Microorganisms make up normal microbiome, also known as _____, of body
A
flora
22
Q
What is the major reservoir of the human body where microorganisms thrive?
A
GI tract (but also female genital tract, oral cavity, nasopharynx, etc.)
23
Q
How is beneficial homeostasis between humans & microorganisms maintained?
A
via:
1. physical integrity of the gut
2. mechanisms that sequester these microorganisms on the mucosal surface (MALT)
24
Q
What are the 3 major ways microbiome is thought to contribute to health and disease?
A
- Provides instruction to the developing immune system
- Can confer susceptibility or resistance to pathogen colonization
- harbors a diverse reservoir of antibiotic resistance genes
- colonization resistance = ability of members of the normal flora to limit the growth of pathogens - Contributes to nutrition & human health
- gut bacteria aid digestion by breaking down otherwise indigestible plant fibers
- synthesize variety of micronutrients including several of the B vitamins, vitamin K
- Impact on the absorption of key minerals (I.e., iron)
25
_____ microbiotas likely impacts a patient's susceptibility to infectious diseases & responses to vaccines
Individuals' microbiotas
26
__________ - any change in composition of resident commensal communities (associated with many chronic diseases (obesity, IBDs, T2D, CVD, colon CA, depression))
microbiome dysbioses
27
Microorganisms of the human body can be organized into what 2 groups?
1. resident microbiota - relatively fixed types of microorganisms regularly found in a given area at a given age; if disturbed => promptly reestablishes itself
2. transient microbiota - nonpathogenic or potentially pathogenic microorganisms derived from ENVIRONMENT that inhabit body sites for hours/days/weeks
- Does NOT typically produce disease & does NOT establish itself permanently
- Generally little significance as long as normal resident flora remains intact
28
Under what circumstance may transient microbiota colonize, proliferate & cause disease?
when resident microbiota is disturbed
29
T/F - Most infections are caused by organisms not part of normal microbiota/flora and are strictly pathogens.
F - most infections are caused by organisms that are part of normal microbiota (Ex. S. aureus, S. pneumoniae, Pseudomonas aeruginosa)
30
What are true pathogens?
"all the time bad guys" - bypass normal defenses; in adequate numbers (minimum infective dose) = infection
31
T/F A minimum number of true pathogens/microorganisms is needed to cause infection.
T - called the "minimum infective dose"; varies by pathogen
32
What are opportunistic pathogens?
"sometimes bad guys"; frequent members of body's normal flora
rarely, if ever, cause disease in immunocompetent people; can cause serious infection in patients with reduced host defenses (immunocompromised)
Ex. physical trauma to GI tract during surgery; oral/systemic (candidiasis in HIV/AIDS)
33
Infectious diseases disproportionately affect ______, ____ & persons in ____ countries.
children < 1 year; adults > 70 years; low-/middle-income
34
What are Koch's 4 Postulates which would consider something to be a bacterial infection?
1. Bacteria must be present in EVERY case of the disease
2. Bacteria must be isolated from the host with the disease and grown in pure culture
3. Specific disease must be reproduced when a pure culture of the bacteria is inoculated into a healthy susceptible host
4. Bacteria must be recoverable from the experimentally infected host
35
What were the top 5 leading causes of death globally between 2000 and 2019?
1. Ischaemic heart disease
2. Stroke
3. COPD
4. Lower respiratory infections
5. Neonatal conditions
36
What were the top 3 leading causes of death in low-income countreis between 2000 & 2019?
1. Neonatal conditions
2. Lower respiratory infections
3. Ischaemic heart disease
37
COVID-19 (SARS-CoV-2) is an example of _______ as it is a new strain of coronavirus
reemergence - a new strain of "old" infections
38
How does reemergence of infectious diseases occur?
1. New strains of old infections (cholera, malaria, yellow fever, dengue fever, diphtheria)
2. Antibiotic resistance (malaria, TB, Strep pneumoniae, Staph aureus, etc.)
3. Decreased vax's (measles, polio, pertussis)
4. Bioterrorism (smallpox, anthrax, & plague)
39
What causes emerging infectious diseases?
1. vast & rapid urbanization
2. poverty, social inequality, war & famine
3. Global travel
4. Global warming
5. Poor antibiotic stewardship
6. Human encroachment into wilderness areas
40
"Emerging epidemics of noncommunicable diseases & injuries becoming more prevalent in both industrialized and developing countries alike, in addition to ongoing major communicable diseases" describes ________
Dual burden of disease
41
22 cases of legionellosis occurred within 3 weeks among residents of a particular neighborhood (usually 0 or 1 per year) is an example of a:
A. outbreak
B. endemic
C. Pandemic
D. Epidemic
A. outbreak - rise in disease cases over what is normally expected in a small & specific location generally over a short period of time (I.e., salmonella infections)
42
Number of new infections in a particular population that GREATLY exceeds number usually observed
epidemic (Ex. ebola (2014-2016)
43
>20 million people worldwide died from influenza in 1918-1919 is an example of:
A. outbreak
B. epidemic
C. pandemic
D. endemic
C. Pandemic - epidemic that spreads over a large area as a continent or worldwide (I.e., COVID)
44
~60 cases of gonorrhea are usually reported in this region per week, slightly less than the national average is an example of:
A. outbreak
B. epidemic
C. pandemic
D. endemic
D. endemic - diseases with relatively high, but constant, rates of infection in a particular population
45
_____ - any disease that spreads from animals to people
zoonotic disease
46
What is a "spillover event"?
reservoir population with a high pathogen prevalence comes into contact with a novel host population of DIFFERENT species
47
Which of the following describes a reservoir?
A. Organism that harbors parasite or another organism where there is a symbiotic relationship between 2 organisms
B. Animal, plant, or environment in which disease can subsist for extended periods of time
C. Living creature (usually insects) that passes a disease to another living creature
B. Animal, plant, or environment in which disease can subsist for extended periods of time
I.e., contaminated soil/water, breast milk, other animals (zoonotic ticks), another human
I.e., fruit bats (Ebola)
48
Which of the following is a living creature that passes a disease to another living creature?
A. reservoir
B. host
C. vector
C. vector
49
Which of the following is a host?
A. Organism that harbors a parasite
B. An organism has a relationship with another organism that is mutually beneficial (commensal)
C. An animal, plant, or environment where a disease can subsist for extended periods of time
D. Organism that passes disease to another living creature
E. Both A & B
E. Both A & B
50
What are the two types of vectors?
1. Mechanical (house fly - spreads by touching)
2. Biological (mosquitos - biting)
51
How do mechanical vectors spread disease?
PASSIVELY transfer parasitic, bacterial, fungal, or viral microorganisms on OUTSIDE of their body from contaminated material to an individual
(I.e., housefly picks up pathogen from fecal matter, fly transfers pathogen to food, person eats contaminated food and gets sick)
52
How do biological vectors spread disease?
These vectors (I.e., insects [arthropods]) feed off blood of infected individuals
infectious agent usually undergoes part of its life cycle within arthropod (insect) and is transmitted through bites or stings
(I.e., Infected mosquito bites uninfected person, infection spreads through body and into RBCs, then second mosquito bites infected person and can now transmit infection to another person.)
53
What are 3 important arthropods that serve as biological vectors and what disease are they associated with spreading?
1. mosquitos - malaria [Plasmodium spp.]
2. fleas - plague [Yersinia pestis], typhus [Rickettsia prowazekii]
3. deer tick - Lyme disease [Borrelia burgdorferi]
54
What is the vector for Lyme disease?
deer ticks
55
What serves as the pathogen reservoir for Lyme disease?
Peromyscus - mice
56
What organism is a dead-end host for ticks and pathogens for Lyme disease?
humans
57
What organism is a host for adult ticks but not a pathogen reservoir for Lyme disease?
deer
58
What is the vector for west nile and dengue fever?
mosquito
59
What organism is the reservoir for west Nile disease?
bird
60
What organism is the reservoir for dengue fever?
human
61
How does infection from west Nile occur?
Bird with virus is bitten by mosquito, mosquito then bites human
62
How does dengue fever infect humans and non-human primates?
mosquito bites human with virus and then bites human or non-human primate & spreads the virus
63
What are the 4 steps of the process of infection?
1. Colonization - initial infection
2. Invasion
3. Multiplication
4. Dissemination
64
Infectious microorganisms exist in _______
Reservoirs
65
What is the colonization process (the first step to the infection process)?
Initial infection - adhere to tissue through specific surface receptors (tissue tropism) to protect organism from removal by mechanical, nonspecific forces (I.e., coughing)
66
The adherence of a pathogen to tissue through specific receptors during colonization is also known as _________
tissue tropism
67
What are the 4 transmission types?
1. Direct vs. indirect transmission (vectors)
2. Droplet vs. airborne
3. Fecal-oral
4. Vertical (mother-to-child) vs. horizontal (person-to-person)
68
______ - route organism takes to enter host
portal of entry
69
To enter the body, microbes penetrate what 2 barriers?
1. epithelial barriers (skin)
2. mucosal barriers (respiratory & alimentary tract)
70
What is the difference between direct and indirect transmission?
Direct transmission - direct contact with infections of another individual (I.e., skin lesions of impetigo (S. aureus, Strep. pyogenes), fungal skin infections (athlete's foot), scabies (mites), STIs)
Indirect transmission - contact with contaminated materials (I.e., towels (fomites), food, through a vector)
71
T/F Most zoonotic infections are transmitted directly.
F - they are transmitted INDIRECTLY by means of vector-borne transmission (primarily insects)
72
Which of the following are examples of indirect transmission?
A. Scabies (mites)
B. Through a vector
C. Athlete's foot
D. STIs
B. Through a vector
73
What type of transmission does the following statement describe: "dissemination of either airborne nuclei or small particles in the respirable size range containing infectious agents that remain infective over time and distance"?
airborne transmission
74
What type of transmission does the following statement describe: "when a person coughs/sneezes and particles from the infected person travel in air and contact another person's conjunctiva, mouth or nasal mucous"?
droplet transmission
75
What is the difference between droplet and airborne transmission?
Droplet transmission:
- particles are usually larger
- readily transmits many viral diseases (common cold, certain strains of influenza, mumps, rubella, pertussis)
Airborne transmission:
- small particles of respirable size or airborne droplet nuclei
- Infectious agents REMAIN infective over time & distance
- can be dispersed over LONG distances by air currents & inhaled by susceptible individuals who may not have had face-to-face contact with infectious individual
- Other microorganisms may be airborne by circulating air that carries microorganisms picked up from soil, dried droppings or other sites (I.e., fungi)
76
Which mode of transmission is described in this statement: "ingested substances (food, water) contaminated by minuscule amounts of human feces usually from unwashed hands or contaminated food/water due to lack of sanitation & hygiene"?
Fecal-oral (ex. Salmonella (food poisoning), cholera, hep A, poliovirus, rotavirus, norovirus, Giardia lamblia)
77
What are 3 examples of vertical transmission?
1. From mother to child across the placenta
2. Organisms that ascend the birth canal from vaginal colonization or during delivery
3. Through the breast milk
78
Which mode of transmission is described: spread of microorganisms from one person to another?
horizontal transmission
79
What is a biofilm?
mixed species of microorganisms (i.e., fungi & bacteria) immersed in a highly organized extracellular matrix produced by microorganisms (often found on implanted medical devices such as catheters, PMs, heart valves & prosthetics)
80
What advantages does a biofilm provide to the microorganisms that produced it?
1. Offers survival advantages by trapping components of host's defenses
2. Closely organized structure allows for exchange of genetic information for antibiotic resistance!* and other defense mechanisms
81
T/F Dental plaque is a complex biofilm composed of normal micriobiota
T
82
T/F Biofilms are associated with chronic infections.
T - I.e., osteomyelitis
83
Under which step of infection does tissue damage occur?
Invasion
84
How do pathogen's invade surrounding tissues?
1. By evading host's defenses => tissue damage
2. Successful spreading requires variety of virulence factors (adhesion molecules, toxins, ability to evade immunity)
- Extracellular organisms direct extension into surrounding tissues => lymphatics & bloodstream => organs
- Obligate intracellular organisms - spread from cell to cell or by release of infectious material into ECF & SUBSEQUENT infection of other cells
85
T/F Pathogens can also enter a latency phase without spread or damage until reactivated later.
T - herpes zoster, TB, CMV
86
What 2 characteristics of human tissue cause most microorganisms to grow rapidly?
1. Warm &
2. nutrient-filled environment
87
Viral pathogens replicate within _____ cells
infected cells - they are obligate intracellular organisms
88
Dissemination typically occurs via _____ or _____ system either freely or within inflammatory cells
blood (hematogenous); lymphatic (certain viruses may travel through nerves as well such as varicella & rabies)
89
T/F Detection of microbes in blood via blood cultures is always abnormal
T - it is ALWAYS abnormal to find contaminants/microbes in blood because blood is normally a STERILE environment
90
Presence of bacteria in blood
bacteremia
91
presence of fungi in blood
fungemia
92
presence of virus in blood
viremia
93
Presence of AND multiplication of microorganisms (particularly bacteria +/- toxins) in blood
septicemia (sepsis or "blood poisoning")
94
List the 4 "-emias" from most to least life threatening.
Septicemia > bacteremia > fungemia > viremia
95
Septicemia can progress to _____ then to ____ & _____ and then ______
sepsis, septic shock, organ failure, death
96
What are the 4 bacteria that develop into sepsis most frequently?
1. S. aureus
2. E. coli
3. Strept. spp (pneumoniae)
4. Klebsiella pneumoniae
97
*Capacity of pathogen to cause disease depends on:
1. ______ - route microorganisms take
2. ______ - ability to spread person-to-person
3. ______ - ability to induce/neutralize an immune response
4. ______ - ability to invade & multiply in host
5. ______ - How microorganism damages tissue
6. ______ - ability to produce disease
7. ______ - capacity to cause SEVERE disease; measure of pathogenicity (I.e., measles = low virulence; rabies = highly virulent)
8. ______ - production of toxins or endotoxins ; influences degree of virulence
1. portal of entry
2. communicability
3. immunogenicity
4. infectivity
5. Mechanism of action
6. Pathogenicity
7. Virulence
8. Toxigenicity
98
What is communicability measured by?
R0 = basic reproduction number
99
What is R0, the basic reproduction number?
measures communicability; it is the number of people a single infected person can be expected to transmit the disease to, on average (I.e., # of secondary infections from one infected individual)
100
What 3 factors are used to calculate R0?
1. Infectious period (time)
2. Mode of transmission
3. Contact rate
101
What would be an interpretation of an R0 < 1?
each existing infection causes < 1 new infection => dies out
102
What would be an interpretation of an R0 = 1?
each existing infection causes 1 new infection => persists
103
What would be an interpretation of an R0 > 1?
each existing infection causes > 1 new infection => increases (outbreak, epidemic, or pandemic)
104
The higher the R0, the ____ communicable a disease is and requires a _____ herd immunity threshold.
more; higher (more people needed for the disease to stop/decline)
105
Ability to neutralize the immune response to a pathogen in some way
immunogenicity
106
How do pathogens neutralize immune response to it?
1. some attack immune effector cells
2. others undergo changes that evade immune response
107
What is a pathogen's primary interest when it comes to immunogenicity?
Is there natural immunity?
If so, is it cell-mediated (Th1) or humoral/antibody-mediated (Th2)?
108
CMI & humoral responses are _______ stimulated with most infections, but _____ response to a particular molecular structure is usually dominant in mediating immunity to reinfection
Broadly; specific
109
How does Neisseria gonorrhoeae practice immunogenicity?
undergoes antigenic variation so rapidly Abs directed against it become irrelevant
110
Virulence is a measure of _____
pathogenicity
111
______ is a measure of pathogenicity
Virulence
112
What is median lethal dose (LD50)?
lethal dose 50%; dose required to kill half the members of tested population after specified test duration; measure for virulence
113
lower LD50 = ____ toxicity
higher (less amount for it to be toxic)
114
What are the 3 virulence factors (factors produced by microorganisms that evoke disease)?
1. toxins
2. surface coats that inhibit phagocytosis
3. surface receptors that bind to host cells
115
What are the 4 clinical infectious disease stages?
1. Inoculation - initial exposure to 1st onset of symptoms (hours => years)
2. Prodromal - occurrence of initial symptoms (often very mild, I.e., discomfort or fatigue)
3. Invasion - pathogen multiplies rapidly in host, invading & affecting tissues, immune & inflammatory responses triggered, Sx from pathogen OR inflammatory response
4. Convalescence - 3 possible outcomes:
1. Recovery - symptoms decline
2. Death - host dies
3. Latency period - resolution of symptoms until reactivated at a later time
116
When an infected individual has measurable infection-related symptoms the manifestation of the disease is ______
clinical (acute life-threatening conditions or chronic diseases of varying severity)
117
When an individual is asymptomatic for an illness, the manifestation of the disease is said to be _____
subclinical (I.e., latent TB infection)
118
What is the ROS for clinical manifestations of infectious disease (6)?
Fatigue, malaise, loss of concentration, generalized aches, loss of appetite, and fever
119
____ - the hallmark of infection
Fever
120
lipopolysaccharides on bacterial walls = _______
IL-1, IL-6, TNF-alpha (result of inflammatory response) = __________
exogenous pyrogens
endogenous pyrogens
- both associated with fever?
121
What temperature reading is considered to be fever?
>/= 38 degrees Celsius or >/= 100.4 degrees F
122
In regards to HR, one can expect bradycardia or tachycardia with fever.
tachycardia ( every 1 degree C in core temp = HR ~15-20 bpm)
