Ch 11: Host-Microbe Interactions Flashcards by Stephen McCartney

How are host microbes acquired?

during and after birth through contact with people, food and the environment

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Which body sites are colonized mainly by bacteria?

skin
upper respiratory
GI tract
external genitalia
outer urethra
vagina
external ear &amp; eye

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Sterile sites in the body contain no microbes in a healthy host. What are these areas?

internal tissues and organs

heart, lungs, liver, etc.
upper reproductive tract
sinuses & middle ear

fluids

blood
CSF
urine, saliva, semen
amniotic fluid

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What are the benefits of normal flora?

microbial antagonism

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What are probiotics?

supplements of live beneficial microbes (e.g. Lactobacillus)

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What can normal flora deficiencies lead to?

antibiotic superinfections

infant botulism

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What are the adverse effects from normal flora?

endogenous infections by opportunists
- staph infections (wounds, surgical sites)

- urinary tract infections (UTIs) are often caused by 
   intestinal bacteria (fecal contamination)

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In a healthy host, normal flora bacteria are expected to be found in all the following locations EXCEPT:

A.  Oral cavity
B.  Vaginal tract
C.  Urinary bladder
D.  Skin
E.  Colon

C. Urinary bladder

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“Good” bacteria, or _____ , can be ingested to boost the normal flora of GI tract.

probiotics

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What are the biosafety levels?

BSL-1 (non-pathogens)
 - Open bench
BSL-2 (opportunists)
 - Gloves &amp; coats
BSL-3 (treatable true pathogens)
 - Safety cabinets &amp; vaccinations
BSL-4 (untreatable true pathogens)
 - Isolation &amp; decontamination

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What factors influence infection?

microbial pathogenicity
- virulence factors (e.g. adhesins, toxins) promote infection

condition of host defenses
- healthy or compromised

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What is the difference between true and opportunistic pathogens?

true pathogens cause infection in anyone

opportunistic pathogens cause infection in compromised hosts

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compromised hosts are more susceptible to infection. What can compromise the host?

injury or surgery
age
immune deficiencies
other disease or infections
drug therapies
pregnancy
stress

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What does a host provide for a pathogen?

host provides resources for the pathogen’s reproduction and transmission

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What must a pathogen be able to do?

a pathogen must be able to…

access portal of entry
colonization
survive host defenses
causing damage
access portal of exit

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What are the portals of entry a pathogen must access to get into host?

skin & eyes
gastrointestinal tract
respiratory tract
genitourinary tract

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What is the infectious dose?

the minimum number of microbes at the portal of entry required to establish infection

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What are adhesion factors?

Factors affecting pathogen colonization

bacteria

glycocalyx
fimbriae

viruses
- spikes

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What are the features of surviving host defenses?

antiphagocytic factors prevent elimination by host phagocytes

leukocidin is a toxin that kills WBCs (S. aureus)

capsule prevents adherence to phagocytes (S. pneumoniae)

some bacteria can survive inside phagocytes (M. tuberculosis)

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What are the antiphagocytic factors of S. aureus?

coagulase produces a protective fibrin “shield” around the bacteria

phagocytes cannot eat bacteria

staphylokinase dissolves clot and releases the bacteria after multiplication

and the process repeats…

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How do pathogens cause damage to host?

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Exoenzymes
Endotoxins
Exotoxins

What are exoenzymes?

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damage host tissues and promote invasion

mucinase
hyaluronidase
collagenase

What are exotoxins?

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proteins excreted by some G+ & G- that are toxic in small doses and specific to cell type

What are the types of exotoxins?

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CYTOTOXINS
cell lysis/tissue damage
invasion, nutrients, weaken host, transmission
anthrax and whooping cough

NEUROTOXINS
paralysis
weaken host
tetanus and botulism

ENTEROTOXINS
fluid secretion and peristalsis in GI tract
transmission
food poisoning

What are endotoxins?

lipopolysaccharide (LPS) released from outer membrane of dead G- bacteria is toxic in large doses and produces general damaging effects

What are the effects of endotoxins?

inflammation fever coagulation

What are the portals of exit for a pathogen?

Used to transmit to other hosts ``` Feces Urine Open lesions Coughing/Sneezing Insect Bites ```

Which enzyme is produced by Staphylococcus aureus that hides the bacteria from host phagocyte?

coagulase

When lipopolysaccharide is released from dead gram-negative bacteria, it is called ______ because it causes inflammation and fever.

endotoxin

What is a disease reservoir?

can be living or nonliving where the pathogen survives and multiplies allows transmission to host

What are the characteristics of a human disease reservoir (carrier)?

``` asymptomatic incubating convalescent chronic passive ```

What are the characteristics of a animal disease reservoir (carrier)?

zoonotic infections - Rabies from animal bite - Salmonellosis from eating contaminated poultry - Lyme disease from deer/mice via ticks

What are some examples of non-living disease reservoirs?

soil - tetanus water - cryptosporidiosis

What are the types of transmission?

communicable or noncommunicable - contagious direct or indirect - vehicle horizontal or vertical - placental or perinatal

What are examples of direct transmission?

A to B contact - touching, kissing, biting, sex droplet - sneeze, cough - <1 m distance between reservoir and host

What are biological vectors?

Method of direct transmission - blood-feeding arthropods - ticks, mosquitoes, fleas, etc.

What are examples of indirect transmission?

A to B to C using vehicles ``` fomites blood, serum, & tissues soil & water food fecal-oral transmission ```

What is a nosocomial infection?

healthcare-acquired (HA)

How do nonsocomial infections occur?

compromised hosts pathogens chain of transmission

How do we prevent nosocomial infections?

``` WASH HANDS! universal precautions PPE microbial control isolation monitor for outbreaks ```

An inert object or surface, like a doorknob or money, that serves indirectly transmit infection is called a:

fomite

Rabies is a ______ infection because it is acquired from an animal reservoir.

zoonotic

What are koch's postulates?

systematic method used to establish the etiologic agent of disease 1. Find evidence of a particular microbe in every case of a disease. 2. Isolate that microbe from an infected subject and cultivate it in pure culture in the laboratory (b); perform full microscopic and biological characterization (a). 3. Inoculate a susceptible healthy subject with the laboratory isolate (c) and observe the same resultant disease (d). 4. Reisolate (f) the same agent (e) from this.

Why did Warren & Marshall win the 2005 Nobel Prize in Physiology or Medicine?

showed that gastric ulcers were caused by a bacterium called H. pylori

What is epidemiology?

the study of disease in populations | frequency & distribution data

What is the difference between incidence and prevalence?

incidence - new cases in time period (per 100,000) prevalence - total existing cases (% of population)

What was recommended once it was learned that the pertussis vaccine only protected for 10 years?

Booster shot

What was recommended once it was learned that mosquito-borne WNV was spreading westward?

Eliminate standing water Spray for mosquitoes Monitor birds for WNV Warn public

What terms can be used to describe the incidence of disease?

endemic - only among specific group of people sporadic - occasional epidemic - widespread in community pandemic - worldwide

What are the types of epidemics?

point-source epidemic: e.g., contaminated food at party common-source epidemic: e.g., contaminated town water supply propagated epidemic: eg. TB is spread person-to-person

Warren and Marshall discovered the link between H. pylori and gastric ulcers. What observation did NOT follow Koch’s postulates? A. H. pylori was isolated from the stomachs of patients with ulcers B. When Marshall drank a H. pylori culture he developed ulcers C. When H. pylori was eliminated with antibiotics, the ulcers went away D. Some people who did not have ulcers had H. pylori in their stomachs

D. Some people who did not have ulcers had H. pylori in their stomachs

When John Snow discovered a sewage-contaminated well was the source of a cholera outbreak, he asked city officials to remove the Broad Street water pump handle. This epidemic can be described by all the following EXCEPT: ``` A. Common-source epidemic B Fecal-oral transmission C. Vehicle transmission D. Indirect transmisison E. Nosocomial infection ```

E. Nosocomial infection

Ch 11: Host-Microbe Interactions Flashcards

(52 cards)