Lecture 11: Interactions between microbes and humans Flashcards
1
Q
What is an infectious disease?
A
When the tissue or organism is disrupted by microbes or their products
2
Q
How does an infectious disease come about?
A
contact –> colonization–> infection –> disease
3
Q
Does contact always lead to colonization then infection then disease?
A
NO
4
Q
What are 2 other names for resident flora?
A
Indigenous flora or normal flora
5
Q
What are examples of resident flora?
A
bacteria fungi protozoa viruses arthropods
6
Q
Where is resident biota acquired?
A
most areas of the body that have contact with the outside world
7
Q
What areas of the body are sterile?
A
internal organs, tissues, and their fluids
8
Q
Are most microbes destroyed by the immune system before they are able to colonize?
A
YES
9
Q
What sites of the body are known to harbor normal biota?
A
Skin Upper Respiratory Tract Gastrointestinal Tract Outer opening of urethra external genitalia vagina external ear canal external eye
10
Q
How much of your weight is made up by skin?
A
15%
11
Q
Compared to the geographic regions of the earth what is the forearm compared to?
A
the desert
12
Q
Compared to the geographic regions of the earth what is the scalp compared to?
A
the cool woods
13
Q
Compared to the geographic regions of the earth what is the armpit compared to?
A
the tropical forest
14
Q
What things are found on the skin?
A
Fatty acids, lysozymes, and salt
15
Q
Where are lysozymes found ?
A
sweat, tears, and saliva
16
Q
What prevents overgrowth of bacterial population?
A
Sloughing (the shedding of the skin)
17
Q
What specific bacteria make up the normal flora of the skin?
A
s. epi
s. aureus
pro acnes (Diptheroids)
yeast (Fungi)
canidida albicans (Fungi)
dermidex folliculorum (arachnid)
18
Q
What is used to remove nonresident bacteria?
A
soap with hexachlorophene or other disinfectants
19
Q
What factors affect the normal flora of the skin?
A
weather, age, and hygiene
20
Q
What is the conjunctiva?
A
mucous membrane that covers the exposed surface of the eyelid
21
Q
What does the microbial environment of conjunctiva consist of?
A
an impenetrable surface and is flushed by tears which contain lysozymes. Many normal flora are not found due to the constant flushing, but staphylcoccus and diptheroids are found.
22
Q
When are the bacteria of the nasal cavity and nasopharynx colonized?
A
4 to 12 hours after birth
23
Q
How many organisms are inhaled daily?
A
10,000
24
Q
What is the microbial environment of the nasal cavity and nasopharynx like?
A
Its warm and moist and has a mucociliary system
25
What can affect the mucocilliary system be affected?
cystic fibrosis and smoking
26
What is the main flora found in the nasal cavity and nasopharynx?
s. aureus
27
What bacteria causes middle ear infections?
moraxella catarrhalis
28
When is the bacteria of the mouth colonized?
at birth when passing through the birth canal
29
What is the microbial environment of the mouth like?
warm and moist and it contains saliva and lysozymes
30
How many different species of bacteria are found in the mouth?
80
31
What bacteria causes tooth decay?
streptococcus mutans
32
Where do bacteria in the intestinal tract come from?
from the mouth and through the GI tract
33
What can affect the flora present in the intestinal tract?
your diet
34
What is the microbial environment of the intestinal tract like?
very few microbes survive upper GI, peristalis is less in the large intestine, and 100 billion to 100 trillion are eliminated per day
35
What are most of the bacteria of the intestinal tract?
anaerobes
36
What complicated interactions occur in the intestinal tract?
competition, genetic changes (antibiotic resistance) and peristalsis (contraction to move things through)
37
What is the microbial environment of the urethra like?
the movement of urine can remove the bacteria of the tightly joined cells and the normal flora
38
What are the 2 bacteria of the urethra?
enterococci and s. epi
39
When is the vagina bacteria colonized?s
soon after birth
40
What is the microbial environment of the vagina like?
It has very few nutrients and low pH then becomes normal before puberty then drops again
41
What bacteria is present in 25% of women?
Group B streptococcus
42
After a vaginally delivered baby how long until its been colonized and by what?
8 to 12 hours and streptococci, staphylococci, and lactobacilli
43
How are c section babies colonized?
by adult skin bacteria
44
What are formula fed babies large intestines colonized with?
mixed population of coliforms, lactobacilli, enteric streptococci, staphylococci
45
What are breast-fed babies large intestines colonized with?
Bifidobacterium whose growth is favored by a growth factor in milk; metabolizes sugars into acids to protect the infant from intestinal pathogens
46
What is a pathogen?
a microbe whose relationship with its host is parasitic and results in infection and disease
47
What does the severity of an infection depend on?
pathogenicity of the organism
| condition of the host
48
What is pathogenicity?
an organism’s potential to cause infection or disease
49
What are true pathogens?
capable of causing disease in healthy persons with normal immune defenses
50
What are examples of true pathogens?
examples include the influenza virus, plague bacillus, and malarial protozoan
51
What are opportunistic pathogens?
cause disease when the host’s defenses are compromised or when they become established in a part of the body that is not natural to them
52
What are examples of opportunistic pathogens?
examples include Pseudomonas species and Candida albicans
53
What is virulence?
The ability of a microbe to establish itself in a host and cause damage
54
What is the virulence factor?
any characteristic or structure of the microbe contributes to its ability to establish itself in the host and cause damage
55
What are the steps of a microbe causing disease?
1. find a portal of entry
2. attach firmly
3. survive host defenses
4. cause damage (disease)
5. exit the host
56
Do pathogens have specific portal of entries?
Yes and if they enter the wrong one they wont be infectious
57
What 2 diseases can enter multiple places and still causes disease?
Mycobacterium tuberculosis can enter through both the respiratory and gastrointestinal tracts
Streptococcus and Staphylococcus can enter through the skin, urogenital tract, and the respiratory tract
58
What are the direct modes of transmission?
horizontal- person to person
| vertical- mom to baby
59
What are the indirect modes of transmission?
fomites from objects
droplets from sneeze/cough
aerosols from air
60
What are the parenteral modes of transmission?
Directly into the blood from the skin such as from a bite or piercing
61
What are the fecal-oral modes of transmission?
Infected feces into mouth
| Can occur by direct body contact or water, food, fomites, vectors
62
What is the infectious dose (ID)?
the minimum number of microbes necessary to cause an infection to proceed
63
What is the ID for rickettsia?
1 cell
64
What is the ID for tuberculosis ?
10 cells
65
What is the ID for gonorrhea?
1,000 cells
66
What is the ID for typhoid fever?
10,000 cells
67
What is the ID for chlorea?
1,000,000,000 cells
68
What are the resevoirs of pathogens?
primary habitat in the natural world from which a pathogen originates
often a human or animal carrier
also soil, water, and plants
69
Where do many infections that affect humans have their resevoirs?
in other humans
70
What is a carrier?
an individual who inconspicuously shelters a pathogen, spreads it to others without any notice, and who may not have experienced disease due to the microbe
71
What are biological vectors?
actively participates in a pathogen’s life cycle, serving as a site in which it can multiply or complete its life cycle
72
What are mechanical vectors?
carries the microbe more or less accidentally on its body parts
73
What do mammals spread?
rabies
74
What do birds spread?
psittacosis
75
What do lizards spread?
salmonellosis
76
What is zoonosis?
an infection indigenous to animals but naturally transmissible to humans
77
How is zonotic spread of disease promoted?
by close associations between humans and animals
78
How much of all new emerging diseases are zoonosis?
70%
79
What is a communicable/infectious disease?
a disease in which an infected host can transmit the infectious agent to another host and establish infection in that host
80
What is a noncommunicable disease?
an infectious disease that does not arise through transmission of the infectious agent from host to host
81
What is herd immunity?
Indirect protection from infection of susceptible members of a population and the protection of the population as a whole
82
What are the mechanisms of adhesion?
- fimbriae (pili)
- surface proteins
- adhesive slimes or capsules
- viruses attach by specialized receptors
- parasitic worms fastened by suckers, hooks, and barbs
83
What are phagocytes?
cells that engulf and destroy host pathogens by means of enzymes and antimicrobial chemicals
84
What is another name for virulence factors?
antiphagocytic factors
85
What are leukocidins?
kill phagocytes outright; Streptococcus and Staphylococcus
86
What are the 3 ways a microorganism can cause damage to a host?
directly through the action of enzymes
directly through the action of toxins (both endotoxins and exotoxins)
indirectly by inducing the host’s defenses to respond excessively or inappropriately
87
What are exoenzymes?
enzymes secreted by microbes that break down and inflict damage on tissues by dissolving the host’s defense barriers to promote the spread of disease to other tissues
88
What is mucinase?
digests the protective coating on mucous membranes
89
What is hyaludronidase?
digests the ground substance that cements animal cells together
90
What is coagulase?
causes clotting of blood or plasma
91
What is Kinase?
dissolves fibrin clots
92
What are exotoxins?
proteins with a strong specificity for a target cell and extremely powerful, sometimes deadly effects that affect cells by damaging the cell membrane and initiating lysis and disrupting intracellular function
93
What are hemolysins?
disrupt the membrane of red blood cells to release hemoglobin
94
What is an endotoxin?
lipopolysaccharide (LPS), part of the outer membrane of gram-negative cell walls that has a variety of systemic effects on tissues and organs and can causes fever, inflammation, hemorrhage, and diarrhea
95
What are the 6 patterns of infection?
1. localized infection
2. systemic infection
3. focal infection
4. mixed infection
5. primary infection
6. secondary infection
96
What is a localized infection?
microbes stay in one area
97
What is a systemic infection?
infection spreads to many places via blood
98
What is a focal infection?
infection spreads to other tissues
99
What is a mixed infection?
many agents at one infection site
100
What is a primary infection?
the initial infection
101
What is a secondary infection?
the second infection caused by another microbe
102
What is a syndrome?
a disease identified by a certain complex of signs and symptoms
103
What is leukocytosis?
increase in white blood cells
104
What is leukopenia?
decrease in white blood cells
105
What is septicemia?
when microbes are multiplying in the blood in large numbers
106
What is bactermia or viremia?
when bacteria or viruses are in the blood, but not multiplying
107
What are infections that go unnoticed called?
asymptomatic, subclinical, or inapparent
108
Is the portal of exit the same as portal of entry?
Most of the time, but not always
109
Does recovery mean the microbe has been removed or destroyed?
NO!!!
110
What is latency?
a dormant state of microbes in certain chronic infectious diseases
111
What is sequelae?
long-term or permanent damage to tissues or organs caused by infectious disease
112
What is the sequelae of menigitis?
deafness
113
What is the sequelae of strep throat?
rheumatic heart disease
114
What is the sequelae of lyme disease?
arthritis
115
What is the sequelae of polio?
paralysis
116
What is the incubation period of a disease?
the time from initial contact with the infectious agent to the appearance of symptoms. During this time the agent is multiplying at the portal of entry but has not caused enough damage to elicit symptoms
117
What does the incubation period range from?
several hours to several years, but majority are 2 to 30 days
118
What is the prodromal stage?
1 – 2 day period when the earliest notable symptoms of infection appear
vague feeling of discomfort: head and muscle aches, fatigue, upset stomach, general malaise
119
What is the period of invasion?
infectious agent multiplies at high levels, exhibits greatest toxicity, becomes well established in host tissue
marked by fever and other prominent and specific signs and symptoms
extremely variable in length of period
120
What is the convalescent period?
patient begins to respond to the infection and symptoms decline
patient’s strength and health gradually return due to the healing nature of the immune response
many patients stop taking antibiotics during this period, even though pathogens are still in their system leading to antibiotic resistance
121
When can measles be passed on>
incubation period
122
When can shigella be passed on?
Invasive period
123
When can hep b be passed on?
all periods
124
What are nosocomial infections?
infections acquired or developed during a hospital stay
125
How many nosocomial infections could be avoided by infection control methods
1/3
126
What are Koch's postulates?
1. a series of proofs that became the standard for determining causation of infectious disease
2. continue to play an essential role in modern epidemiology
3. reliable for many diseases, but cannot be completely fulfilled in certain situations
127
What are exceptions to koch's postulates?
some infectious agents cannot be readily isolated or grown in the laboratory
some infections cannot be elicited in animals; viruses have a limited host range, human viruses will only cause disease in humans, etc.
not possible to determine causation in polymicrobial diseases
128
What did florence nightingale do?
laid the foundations of modern epidemiology
before the discovery of the germ theory, she understood that filth contributed to disease
instituted revolutionary methods in military field hospitals, including separate linens and towels for each patient, cleaning of floors, and unclogging of sewage pipes
kept meticulous notes and demonstrated that more men died of disease than traumatic injuries
129
What is the prevelance of a disease?
the total number of existing cases with respect to the entire population reported as the percentage of the population having a particular disease at a given time
130
What is the incidence of a disease?
measures the number of new cases over a certain time period
also called the case or morbidity rate; indicates both the rate and risk of infection
131
What is an endemic?
an infectious disease that exhibits a relatively steady frequency over a long time period in a particular geographic locale
132
What is a sporadic disease?
occasional cases are reported at irregular intervals at random locales
133
What is an epidemic?
when statistics indicate that the prevalence of an endemic or sporadic disease is increasing beyond what is expected for a population
time period is not defined; can be measured in hours to years
exact percentage of increase needed before an outbreak qualified as an epidemic is also not defined
134
What is a pandemic?
spread of an epidemic across continents
