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BI 234 > Exam 2: Ch 11: Interactions btwn Humans and Microbes > Flashcards

Exam 2: Ch 11: Interactions btwn Humans and Microbes Flashcards

1
Q

Host

A

any organism that harbors another organism or particle

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2
Q

Symbiosis

A

association btwn 2 species

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3
Q

Mutualism

A

both members benefit

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4
Q

Parasitism

A

one member benefits, one member (host) is harmed

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5
Q

Commensalism

A

one member benefits, one member is not benefited or harmed

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6
Q

Resident microflora

A

microbes always present in/on body

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7
Q

Transient microflora

A

microbes present for shorter periods of time (minutes to months)

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8
Q

Microbial antagonism

A

chemical/physiological environment created by resident biota is hostile to other bacteria

normal biota unlikely to be displaced by incoming microbes b/c there are limited # of attachment site

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9
Q

Normal biota

A

beneficial or commensal to a host in good health w/a functioning immune system

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10
Q
  1. Contact
A

microbes are present

doesnt usually lead to infection and disease

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11
Q
  1. Colonization
A

presence of bacteria on body surface w/out causing disease

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12
Q
  1. Infection
A

multiplication of microbes; microbes penetrate host defenses → enter tissue → multiply

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13
Q
  1. Disease
A

disturbance in normal homeostasis

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14
Q

True pathogen

A

causes disease in healthy individuals;

associated w/ a specific and recognizable disease

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15
Q

Opportunistic pathogen

A

causes disease in immune compromised host
gain access (injury) to sterile regions
cause disease when “opportunity” arises

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16
Q

Conditions for opportunistic pathogens to flourish:

A
  • failure of the host’s normal defenses
  • intro of the organism into unusual body sites
  • disturbances in normal/resident microflora
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17
Q

Pathogen

A

disease causing agent; etiological agent

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18
Q

Pathogenicity

A

ability to cause disease

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19
Q

Virulence

A

the degree of pathogenicity

determined by its ability to: establish itself in a host and cause damage

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20
Q
  1. Portal of entry
A

the route that a microbe takes to enter the tissues of the body to initiate an infection
exogenous
endogenous
usually have 1 and if they enter wrong one wont cause infection
occasionally have more than 1 = more pathogenic

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21
Q

Exogenous

A

microbe from a source outside the body

environment, another person/animal

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22
Q

Endogenous

A

microbe already existing in/on the body

from normal biota or previously silent infection

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23
Q

Infectious dose

A

minimum # of microbes necessary to cause an infection to proceed
smaller infectious doses = greater virulence
ex. TB is about 10 cells, typhoid fever is 10,000 cells

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24
Q
  1. Attachment/adhesion
A

gain a stable foothold on host tissues
dependent on binding btwn specific molecules on both the host and pathogen
pathogen is limited to only those cells (and organisms) to which it can bind
prereq for causing disease b/c the body has so many mechanisms for flushing microbes from tissues
Structures: pili/fimbriae, hooks, spikes, biofilms

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25
Q
  1. Surviving host defenses
A

microbes not established as normal biota will likely encounter the host immune defenses when first entering

phagocytes
antiphagocytic factors (leukocidins, slime/capsule)
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26
Q

Phagocytes

A

cells that engulf and destroy host pathogens

w/ enzymes and antimicrobial chemicals

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27
Q

Antiphagocytic factors

A

virulence factors that help pathogens avoid phagocytes
can cause death of WBCs
Leukocidins
Slime/capsule

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28
Q

Leukocidins

A

kill phagocytes

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29
Q

Slime/capsule

A

makes it difficult for the phagocyte to engulf the pathogen

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30
Q

Virulence factors

A

adaptations a microbe uses to establish itself in a host
contributes to its ability to establish itself in the host and cause damage (ex. flagella, capsule, structure/chemical/toxin)

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31
Q
  1. Causing disease
A

3 ways microbes cause damage to their hosts:

  1. directly thru the action of enzyme
  2. directly thru the action of toxins (both endotoxins and exotoxins)
  3. indirectly by inducing the host’s defenses to respond excessively or inappropriately

virulence factors
exoenzymes (hyaluronidsae, coagulase, streptokinase)
toxins (neurotoxins, enterotoxins, hemotoxins,, nephrotoxins)
exotoxins and endotoxins

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32
Q

Exoenzymes

A

enzymes secreted by microbes
break down and inflict damage on tissues
often dissolve the host’s defense barriers to promote the spread of disease to other tissues

hyaluronidase: breaks down tight junctions in epithelial tissue so it can go deeper
coagulase: causes clotting of blood or plasma around pathogens
streptokinase: dissolves clots and releases bacteria

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33
Q

Toxin

A

a specific chemical product of microbes
causes cellular damage in other organisms

named according to their target:
neurotoxins, enterotoxins, hemotoxins, nephrotoxins 
2 types in pathogenic bacteria:
exotoxin
endotoxin
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34
Q

Exotoxins

A

released from the inside; specific cell type is attacked
damage the cell membrane and initiating lysis

ex. hemolysins: disrupt membranes of RBCs to release hemoglobin –> break apart RBCs to digest hemoglobin for energy

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35
Q

Endotoxin

A

not coming from the inside, but from the outer membrane
causes systematic problems
LPS - part of outer membrane gram (-) cell walls
released when cells die
has variety of systemic effects on tissues and organs
causes fever, inflammation, hemorrhage and diarrhea
pyrogenic = causes FEVER

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36
Q
  1. Portal of exit
A

enables pathogen to spread to other hosts
shed thru excretion, secretion, discharge, or sloughed tissue (anything w/access to outisde world)

high # of microbes in these materials increases the likelihood that the pathogen will reach other hosts
usually same as portal of entry; but some pathogens use different route

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37
Q

Pathogenicity

A 
the ability to cause disease
depends on pathogen's ability to:
1. enter
2. attach
3. survive host defenses
4. cause disease
5. exit
virulence factors allow them to be good at those things
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38
Q

Virulence

A 
intensity of disease produced
virulence can be decreased as a pathogen is sub-cultured time after time
many virulence factors (weapons) exist to increase pathogen's ability to:
1. enter
2. attach
3. survive host defenses
4. cause disease
5. exit
39
Q

Localized infection

A

limited to a specific body part of the body and has local symptoms

40
Q

Systemic infection

A

pathogen is distributed throughout the body

41
Q

Focal infection

A

localized in a specific part of the body but spreads to other parts of the body

42
Q

Mixed infection

A

composed of different species of bacteria

43
Q

Primary and secondary infections

A

illness caused by a new microbe becoming established in the wake of an initial (primary) infection
ex. primary urinary infection –> secondary vaginal infection

44
Q

Acute infection

A

rapid onset of infection, short course of infection

45
Q

Chronic infection

A

long duration of infection

46
Q

Asymptomatic or subclinical

A

not noticed by host

47
Q

Signs

A

objective/measurable

fever, inflammation

48
Q

Symptoms

A

subjective

pain

49
Q

Syndromes

A

combo of signs and symptoms that occur together

50
Q

Latency

A

dormant state of microbes in certain chronic infectious diseases
Recovery of host doesnt always mean the microbe has been removed or destroyed by host defenses
Viral latency - herpes
Bacterial/protozoan latency - syphilis, TB

51
Q

Epidemiology

A

the study of disease within populations

helps us investigate the factors regarding a specific disease:

  • what causes a disease
  • how its transmitted
  • how do we prevent and treat it
  • how many people are afflicted
52
Q

Epidemiologists

A

“disease detectives”

scientists who study epidemiology

53
Q

Etiologic agent

A

the cause of a disease

54
Q

Morbidity

A

illness

55
Q

Mortality

A

death

56
Q

Incidence

A

number of NEW cases within a period of time

57
Q

Prevalence

A

TOTAL number of cases within a period of time

prevalence > incidence

58
Q

Reportable/Notifiable diseases

A

certain diseases must be reported to authorities

a network of agencies keep track of infectious diseases

59
Q

Endemic

A

pathogen continually present in a population

cold, flu

60
Q

Sporadic

A

occasional cases are reported at irregular intervals at random locales

61
Q

Epidemic

A

an “outbreak” or higher than normal # of cases

62
Q

Pandemic

A

spread of an epidemic across continents

63
Q

Epidemiologic studies

A

epidemiologists collect data on diseases to help prevent outbreaks in the future
3 types:
descriptive
analytical
experimental
John Snow - first epidemiologic study in 1854, traced the source of cholera epidemic to a certain water pump, proved ppl became infected by fecally contaminated drinking water

64
Q

Descriptive studies

A

physical aspects of an existing disease and disease spread
who, what, when, where
records as many details as possible: # of cases, populations affected, locations and time, age, gender, race, SES

65
Q

Analytical studies

A

why and how
determine causes and factors that influence the rate of disease
factors include: demographic, biological, behavioral, and environmental influences
Disease groups compared to control groups and data is analyzed for similarities and differences

66
Q

Experimental studies

A

designs experiments to test a hypothesis
the “cleanest” studies; considered gold standard
many are performed for pharmaceutical (“clinical trials”) or other treatments

67
Q

Disease transmission

A

affected by:

  1. reservoirs of infection
  2. portals of entry and exit
  3. mechanisms of transmission
68
Q

Reservoir

A

the natural host or habitat (living or nonliving) of a pathogen

69
Q

Source (transmitter)

A

the person or item from which an infection is directly acquired

70
Q

Carrier vs asymptomatic carrier

A

organism that harbors infections and can spread them to others
may show symptoms or not

71
Q

Biological vector

A

organism transports and plays role in life cycle of pathogen

ex virus inside of mosquito, bacteria inside of tick

72
Q

Mechanical vector

A

an organism which only transports a pathogen (fly)

73
Q

Zoonosis

A

infectious disease humans can acquire from animals
caused by vectors and animal reservoirs spreading their own infections to humans
70% of all new emerging diseases worldwide
impossible to eradicate w/out also eradicating the animal reservoir

74
Q

Human reservoirs (source of infection)

A

symptomatic carrier

asymptomatic carrier

75
Q

Animal reservoirs (source of infection)

A

wild animals (rabies), deer mice (hanta virus), insects

76
Q

Nonliving reservoirs (source of infection)

A

soil (tetanus), water (giardia), food (e. coli)

77
Q

Communicable

A

spread from one host to another

receiving host must become infected

78
Q

Non-communicable

A

host gets it but cant transmit to another
from self (compromised individual) - microflora
nonliving reservoir - soil (tetanus)

79
Q

Contagious

A

easily communicable

measles, flora

80
Q

Horizontal transmission

A

spread thru a population from one infected person to another

ex. kissing, sneezing

81
Q

Vertical transmission

A

transmitted from parent to offspring

ex. ovum, placenta, milk

82
Q

Direct (contact)

A

kissing, sex
droplets (sneezing)
vertical
vector

83
Q

Indirect

A

contaminated materials:

  • vehicle: food, water, biological products (blood, semen, tissue)
  • fecal/oral

air (more than 3 ft away)

  • droplet nuclei
  • aerosols
84
Q

Herd immunity

A

proportion of people immune to a certain disease

85
Q

Nosocomial infection

A

infection acquired in a hospital
5-20% of patients acquire one
contributing factors:
-compromised patients
-collection point of pathogens
-lowered defenses permit normal biota to enter the body
-infections acquired directly or indirectly from fomites, medical equipment, other patients, medical personnel, visitors, air, water

86
Q

The progress of an infection (5 steps)

A

pathogen needs to become established by being successful at the following:

  1. Portals of entry
  2. Attachment
  3. Surviving host defenses
  4. Causing disease
  5. Portals of exit

if you stop a pathogen from being able to do any of these steps, they will not be able to infect the host

87
Q

Stages of infectious disease

A 
# of infectious agent x time
Incubation period (no signs or symptoms)
Prodromal phase (vague symptoms)
Disease stage:
-invasive phase (most severe signs and symptoms)
-acme (peak)
-decline phase (declining signs and symptoms)
Convalescence period
88
Q

Sequelae

A

long term or permanent damage to tissues or organs caused by infectious disease
meningitis –> deafness
lyme disease –> arthritis
polio –> paralysis

89
Q

John Snow

A

first epidemiologic study in 1854
Traced the source of cholera epidemic to a certain water pump
Proved ppl became infected by fecally contaminated drinking water

90
Q

Prevention of disease transmission

A 
sanitation
immunization
isolation
quarantine
control vectors
education about prevention and treatment
91
Q

Most common nosocomial infections

A

Most common infections:

  • urinary tract (40%)
  • surgical sites (19%)
  • respiratory (15%)
  • other (meningitis, gastroenteritis) (12%)
  • skin (8%)
  • septicemia (6%)
92
Q

Common nosocomial pathogens

A

Common pathogens:

  • E. coli
  • S. aureus
  • Streptococcus
  • Candida
  • S. epidermidis
93
Q

Healthcare processes that lead to nosocomial infections

A 
treatments using reusable instruments (respirators, thermometers)
indwelling devices (catheters, prosthetic heart valves, grafts, drainage tubes, tracheostomy tubes)
high proportion of hospital population receives antimicrobial drug therapy --> drug resistant microbes are selected for at a much higher rate
94
Q

Nosocomial infections: prevention and control

A

more than 1/3 of these infections could be prevented by consistent and rigorous infection control methods
use universal precautions
assume all patients and fomites may harbor pathogens

BI 234 (16 decks)

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