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NYCC Microbiology > 6A Requirements for Infection > Flashcards

6A Requirements for Infection Flashcards

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1
Q

name 5 requirements/steps for successful infection

A
  • entry: getting in
  • establishment: staying in
  • defeat host defenses
  • damage the host: release resources
  • exit host to transmit to other host
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2
Q

what are portals of entry? name 3 examples

A

any point at which a pathogen enters
- mucous membranes
- skin
- parenteral route

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3
Q

mucous membranes are in direct contact with ____

A

external environment

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4
Q

name 3 places mucous membranes are found in the order of most to least common portal of entry

A
  • respiratory tract
  • GI tract
  • genitourinary tract
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5
Q

name 8 common respiratory pathogens

A
  • adenoviruses: streptococcus pneumoniae, staphylococcus aureus, myobacterium tuberculosis, bordetella pertussis
  • influenza
  • rubella
  • varicella-zoster
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6
Q

name 10 common GI pathogens

A
  • E(scherichia) coli
  • clostridium botulinum
  • enterococcus faecalis
  • shigella spp
  • salmonella
  • helicobacter pylori
  • candida
  • poliovirus
  • norovirus
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7
Q

what is the portal of entry of sexually transmitted infections?

A

genitourinary tract

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8
Q

why are urinary tract infections more common in women than men?

A
  • shorter urethra
  • proximity to anus
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9
Q

name 8 common genitourinary pathogens

A
  • myobacterium smegmatis
  • chlamydia trachomatis
  • neisseria gonorrheae
  • trichomonas vaginalis
  • herpesviruses
  • human immunodeficiency virus
  • E(scherichia) coli
  • candida
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10
Q

what is the cause of 90% of UTIs?

A

E(scherichia) coli

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11
Q

what is the largest organ OF the body?

A

skin

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12
Q

what is the impermeable barrier unless broken, where many microorganisms reside?

A

skin

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13
Q

what does the parenteral route refer to?

A

breaks in skin that allow passage of microbes

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14
Q

normal flora causing infection are called ____

A

opportunistic pathogens

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15
Q

opportunistic pathogens entering via the parentral route depend on…

A
  • cuts
  • abrasions
  • injections
  • wounds
  • surgical incisions
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16
Q

how do pathogens attach to the surface or cells or tissues?

A
  • use virulence structures such as capsules or fimbraie
  • use adhesins to attach to tissues
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17
Q

name an example of an adhesion beginning a process resulting in an accumulation of bacteria called a biofilm

A

plaque on teeth
(life activities of bacteria plus their presence results in formation of plaque)

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18
Q

how do spirochetes enter tissues?

A

lengthy process of corkscrewing

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19
Q

some pathogens can double their numbers every ____

A

20 mins

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20
Q

how do bacteria reproduce?

A

binary fission

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21
Q

what is passive defense?

A

using intrinsic features of the pathogen to protect themselves
(eg. cell walls, lipopolysaccharide mem, or extrinsic factors produced from existing resources at expense of host (capsules, M protein))

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22
Q

name an example of a passive defense

A

bacterial cell walls (peptidoglycans)

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23
Q

name an example of how a pathogen with a gram+ cell wall defends itself

A

streptococcus spp
- uses M proteins to increase adhesion to host tissue and inhibit phagocytosis

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24
Q

how do pathogens with a gram- cell wall defend themselves?

A
  • very thin but compensate by having outer lipopolysaccharide membrane (endotoxin)
  • endotoxin lipid A elicits very powerful immune response
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25
Q

name an example of how acid-fast organisms protect themselves

A

myobacterium species (tuberculosis, leprae)
- inhibits phagocytosis
- inhibits antibiotics

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26
Q

capsules protect against ____

A

phagocytosis

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27
Q

what is active defense?

A

attacking host defenses
- produced by microbes solely for “attack” (eg. toxins & enzymes)

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28
Q

why do pathogens hide inside host cells?

A

as a way to defeat the host
- protection from host immune response
- viruses are obligate intracellular parasites

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29
Q

what do bacteria use as a transport system?

A

cell microtubules and microfilaments

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30
Q

name 2 types of damage to a host

A
  • presence and activity of pathogens (eg. pus)
  • host defense mechanisms (eg. vomitting, diarrhea, sneezing)
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31
Q

direct damage to the host…

A
  • is obvious
  • includes destruction of host cells & tissues
  • controlled by host immune response
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32
Q

indirect damage to the host…

A

involves systemic infection as a result of toxin production by the pathogen

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33
Q

active defense involves the production of ____ which function to…

A
  • extracellular enzymes
  • increase protection against host defenses
  • enable spread of infection by attacking and killing host defensive cells
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34
Q

name 6 examples of bacterial enzymes

A
  • leukocidins
  • hemolysins
  • coagulase
  • kinase
  • hyaluronidase
  • collagenase
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35
Q

function of leukocidins

A

destroy WBCs

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36
Q

function of hemolysins

A

attack both RBCs and WBCs

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37
Q

function of coagulase

A

formation of fibrin clots (wall away tissue)

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38
Q

function of kinase

A

breaks down fibrin and destroys clots

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39
Q

function of hyaluronidase

A

breaks down CT

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40
Q

function of collagenase

A

breaks down collagen

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41
Q

name 2 types of bacterial toxins

A
  • exotoxins
  • endotoxins
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42
Q

name 3 characteristics of bacterial toxins

A
  • very poisonous
  • soluble in aqueous solutions
  • easily diffusible into blood & lymph causing distal pathology
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43
Q

outcomes of bacterial toxins

A
  • can be fatal
  • S&S: fever, shock, diarrhea, cardiac & neuro trauma, destruction of BVs
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44
Q

characteristics of bacterial endotoxins

A
  • produced by and exported from certain pathogens and then enter host cells
  • some of most lethal substances known
  • usually an enzymatic protein soluble in blood & lymph
  • rapidly diffuse into tissues where they inhibit metabolic function
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45
Q

what are plasmids?

A

genes coding for toxin production

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46
Q

name 3 types of exotoxins

A
  • cytotoxins
  • neurotoxins
  • enterotoxins
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47
Q

function of cytotoxins

A

kill cells

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48
Q

function of neurotoxins

A

interfere w neurological signaling
(produce exotoxins for affinity for CNS tissue)

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49
Q

function of enterotoxins

A

affect lining of digestive tract

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50
Q

name 2 examples of cytotoxins

A
  • bacillus anthracic
  • corynebacterium diphtheraie
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51
Q

characteristics of bacillus anthracis

A
  • gram+ spore-forming bacillus
  • increases vascular permeability in host tissues
  • cytotoxin
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52
Q

characteristics of corynebacterium diphtheraie

A
  • gram+ bacillus
  • inhibits protein synthesis
  • single molecule can kill a host cell (cytotoxin)
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53
Q

name 2 etiologic agents of neurotoxins

A
  • clostridium tetani
  • clostridium botulinum
54
Q

when is antibiotic therapy ineffective for neurotoxins?

A

once exotoxin has been produced

55
Q

characteristics of clostridium tetani

A
  • gram+ spore-forming bacillus
  • produces toxin “tetanospasm”
  • neurotoxin
56
Q

what are the effects of tetanospasm?

A
  • prevents muscle relaxation
  • uncontrollable convulsive muscle contractions
  • “lockjaw”
  • opisthotonus
57
Q

tetanus spores require ____

A

low O2 levels
(area of necrosis surrounding injury, spores germinate)

58
Q

how do bacteria cause tetanus?

A
  • bacteria do not cause damage to tissue, but produce toxin
  • toxin enters presynaptic terminals of LMNs
  • travel to CNS
59
Q

factors affecting mortality in tetanus

A
  • location of lesion
  • incubation period
  • age (highest in infants & elderly
  • death results from exhaustion and respiratory failure
60
Q

characteristics of clostridium botulinum

A
  • gram+ spore-forming bacillus
  • inhibits release of Ach
  • flaccid (limp) paralysis of skeletal m
  • “botox”
  • neurotoxin
61
Q

pathogenesis of botulism

A
  • begins w cranial n palsy
  • develops into descending symmetrical motor paralysis
  • may involve diaphragm
  • no fever or inflammation
  • no obvious sign of infection
62
Q

progression of botulism

A
  • symmetrical paralysis
  • most serious complication = complete respiratory paralysis
  • limp/flaccid paralysis
  • mortality rates: 10-20%
  • nervous system dysfunction
63
Q

describe the nervous system dysfunction seen in patients with botulism

A
  • ocular (blurred vision, REM)
  • laryngeal
  • diaphragm
  • trunk
  • extremities
64
Q

name 3 categories of botulism

A
  • food poisoning
  • infant botulism
  • wound contamination
65
Q

foodborne botulism is classified as and ____

A

intoxication (not an infection)

66
Q

manifestation of foodborne botulism

A
  • starts 12-36hrs post-ingestion of toxin
  • nausea, dry mouth, occasional diarrhea
67
Q

pathogenesis of foodborne botulism

A
  • toxin absorbed directly through intestinal tract
  • reaches neuromuscular junction via bloodstream
  • binds & inhibits release of Ach
  • causes muscular paralysis
68
Q

pathogenesis of infant botulism

A
  • occurs between 3wks to 8mo
  • organism introduced upon weaning or raw honey
69
Q

signs & symptoms of infant botulism

A
  • constipation
  • poor muscle tone
  • lethargy
  • feeding problems
  • vision problems
  • paralysis
70
Q

wound botulism

A
  • very rare
  • seen in IV drug users
  • begins w weakness in extremities used as injection sites
71
Q

name 2 examples of enterotoxins

A
  • vibrio cholerae
  • staphylococcus aureus
72
Q

characteristics of vibrio cholerae

A
  • gram- vibrio (bacillus)
  • causes release of large amount of electrolytes resulting in: lethal diarrhea (‘rice water stools’), vomiting
  • enterotoxin
73
Q

characteristics of staphylococcus aureus

A
  • gram+ coccus
  • toxic shock syndrome
  • enterotoxin
74
Q

toxic shock syndrome

A
  • AKA common food poisoning
  • excessive loss of electrolyte fluids resulting in hypotensive shock
  • caused by staphylococcus aureus
75
Q

characteristics of bacterial endotoxins

A
  • intrinsic part of gram- bacterial cell wall
  • released upon death of bacterium
  • released in form of lipid A
76
Q

what do endotoxins (lipid A) cause?

A
  • chills
  • fever
  • aches
  • muscle weakness
  • disseminated intravascular clotting
77
Q

viral host cell damage is called ____

A

cytopathogenic effect (CPE)

78
Q

name 3 ways that viral pathogenic effects can occur

A
  • viral overload
  • cytocidal effects (killing of host cells)
  • non-cytocidal effects (damage caused by host defenses)
79
Q

transmission is dependent upon…

A

organism and system infected
(how it got in is how it gets out)

80
Q

what are 3 principles of transmission?

A
  • where are pathogens found
  • what are the mechanisms of transmission
  • how can the chain of transmission be broken
81
Q

what are reservoirs of infection?

A

places where pathogens grow and accumulate

82
Q

what are mechanisms of transmission?

A

various ways pathogens move from place to place

83
Q

name 3 potential reservoirs of pathogens

A
  • human
  • animals
  • non-living
84
Q

human reservoirs

A
  • sick people: easy to identify
  • carriers: those who are infectious but never show signs or symptoms
85
Q

what are zoonotic diseases?

A

those infections that may be transmitted from animals to humans

86
Q

name 8 examples of zoonotic diseases

A
  • anthrax
  • brucellosis
  • cat scratch fever
  • lyme
  • plague
  • TB
  • ringworm
  • rocky mountain spotted fever
87
Q

non-living reservoirs

A
  • include water, food, soil
  • fecal-oral transmission
  • food spoilage
  • soil dwelling bacteria may be transmitted through human activity or animal husbandry
88
Q

name 3 mechanisms of transmission

A
  • contact
  • vehicle
  • vector
89
Q

when does contact transmission occur?

A

when an uninfected person is exposed to a pathogen via touching or proximity with an infected individual, animal or object

90
Q

name 3 types of contact transmission

A
  • direct
  • indirect
  • droplet
91
Q

direct contact transmission

A

there is no intermediary between the infected person/animal and uninfected person

92
Q

indirect contact transmission

A

occurs through intermediates that are non alive such as tissues, handkerchiefs, towels, bedding, contaminated needles

93
Q

intermediates that are not alive are called ____

A

fomites

94
Q

droplet transmission

A

spread through aerosolized saliva, mucous, sputum
(i.e. talking, laughing, sneezing)

95
Q

vehicle transmission

A

pathogens “ride” via water, food, air

96
Q

vector transmission

A

pathogens are transmitted to a healthy person by a carrier known to be associated with a certain disease

97
Q

what is the most common vector transmitter? name examples.

A

arthropods
- fleas
- ticks
- body lice
- mosquitoes
- flies

98
Q

name 2 methods of vector transmission

A
  • biological (eg. insect bite)
  • mechanical (eg. insects depositing on food)
99
Q

name 6 factors affecting disease transmission

A
  • age
  • gender
  • lifestyle
  • occupation
  • geography
  • general health
100
Q

the host’s ability to mount a defense is called ____

A

immunocompetence

101
Q

damaged host defenses result in…

A

disease potential

102
Q

name 7 examples of people considered vulnerable or immunocompromised

A
  • HIV-AIDS
  • genetic immunodeficiency diseases
  • chemotherapy
  • broad-spectrum antibiotics
  • premature and neonates
  • health care workers
  • elderly
103
Q

Koch’s Postulates

A

conditions in order to “communicate” disease:
- same pathogen must be present in every case of the disease
- pathogen must be isolated from sick host and purified
- pure pathogen must cause the same disease when given to infect hosts
- pathogen must be re-isolated from newly infected hosts

104
Q

name the 5 periods of disease development

A
  • incubation period
  • prodromal period
  • period of illness
  • period of decline
  • period of convalescence
105
Q

incubation period

A

no signs or symptoms

106
Q

prodromal period

A

mild symptoms

107
Q

period of illness

A

major signs & symptoms

108
Q

at what period of disease development is the immune response the strongest?

A

period of illness

109
Q

period of decline

A

signs & symptoms wane but highest chance of secondary infection

110
Q

period of convalescence

A

recovery

111
Q

what is epidemiology?

A
  • study of factors and mechanisms involved in frequency and spread of diseases or other health-related problems
  • used to study disease and also to design methods for control and prevention
112
Q

what is prevalence and what is it used for?

A
  • total # of people infected within a population at any given time
  • used to measure strength and length of a particular disease
    “streaming video”
113
Q

what is incidence and what is it used for?

A
  • number of new cases contracted within a set population in a specific period
  • provides a reliable indication of the spread of a disease
    “snapshot”
113
Q

what is morbidity?

A

number of people affected by disease during a set period divided by total population

114
Q

what is mortality?

A

number of deaths due to a specific disease during a specific period divided by total population

115
Q

name 3 levels of disease occurrence

A

endemic
epidemic
pandemic

116
Q

endemic disease

A

diseases found constantly within a population

117
Q

epidemic disease

A

incidence of disease suddenly higher than expected in a specific region

118
Q

name 2 types of epidemic disease

A

common-source
propagated

119
Q

common source epidemic

A
  • arises from contact with contaminated substances (fecal contamination of water; improperly prepared/stored food)
  • affect large numbers of people but once source is identified quickly subside
120
Q

propagated epidemic

A
  • amplification of number of infected individuals as person-to-person contact occurs
  • stay in population for long periods
  • more difficult to control until patient zero found
121
Q

pandemic

A

diseases that occur in epidemic proportions

122
Q

name 2 types of epidemiological studies

A

descriptive
analytical

123
Q

what are descriptive epidemiological studies concerned with?

A
  • physical aspects of patients and spread of disease
  • traces outbreak and identifies first case
124
Q

what are analytical epidemiological studies concerned with?

A
  • correlation: cause and effect hypothesis
  • always uses a control group
125
Q

what is often the most practical and feasible study to conduct?

A

observational

126
Q

observational/descriptive studies

A
  • investigator observes occurrence of condition/disease in population groups that have assigned themselves to a certain exposure
  • more natural settings, representative of target pop
  • little control, susceptible to distorting influences
127
Q

cohort study

A

type of medical research used to investigate the causes of disease, establishing links between risk factors and health outcomes

128
Q

prospective cohort study

A
  • hypothesis formed about potential cause of disease
  • observe a cohort of ppl over time & collect relevant data
  • detect changes in health in relation to potential risk factors
129
Q

disease reporting

A

health departments of local and state gov’t require reports of certain diseases

130
Q

what are nationally notifiable diseases?

A

diseases that must be reported to the CDC

131
Q
A

NYCC Microbiology (17 decks)

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