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Microbiology- Bacteriology
Enteric Infections (T Pierce)
36
Medical
Professional
09/22/2009

Additional Medical Flashcards

 


 

Cards

Term
complications and long term sequalae of enteric infections
Definition
  • hemolytic uremic syndrome and renal failure via Shiga toxin producing E. coli
  • Guillain Barre syndrome via Campylobacter
  • IBS
  • chronic malnutrition
Term
What types of bacteria tend to cause enteric infections? Name the major causative agents of enteric infection
Definition
  • mostly gram negative rods
    • Salmonella
    • Campylobacter
    • Sigella
    • E coli

 

Term
define acute diarrheal episode
Definition
  • increased frequency of defication
    • less than 14 days duration
Term
define persistent diarrhea
Definition
  • more than 14 days but less than 30 days of diarrhea
Term
define chronic diarrhea
Definition
  • diarrhea lasting greater than 30 days
Term
function of enteric flora in host defense against enteric pathogens
Definition
  • mostly anaerobes
    • produce toxic acidic products and volatile fatty acids
    • interfere with colonization by pathogens
Term
modes of transmission of enteric infection
Definition
  • waterborne
    • more so in developing countries
  • foodborne (esp. in outbreaks)
    • more so in industrialized
  • person to person
Term
Outbreaks: what usually causes them?
Definition
  • in industrialized world, foodborne disease
  • developing world, linked to environmental or social disasters (esp. with cholera)
Term
VF's prevelant in enteric infection
Definition
  • toxins
  • attachment
  • invassiveness
Term
Toxins that cause enteric infection
Definition
  • enterotoxin- direct effect on intestinal mucosa to elicit net fluid and electrolyte secretion
    • increase cAMP or cGMP
  • cytotoxin- mucosal distruction
  • neurotoxins (preformed and act on ANS)
    • food poisoning by S. aureus, Clostridium botulinum, B. cereus
Term
clinical syndromes of enteric infection
Definition
  • food poisoning
  • secretory diarrhea
  • inflammatory diarrhea
  • enteric fever
Term
Effect of C. botulinum toxin
Definition
  • block ACh release from motor nerves at neuromuscular junction (irreversable)
  • initiates GI symptoms, progressing to paraylsis and resp. failure
Term
Course of food poisoning
Definition
  • injest pre-formed neurotoxins and enterotoxins
  • acute onset of nausea and vomitting within 1-6 hrs followed by watery diarrhea
  • symtpoms resolve within 12 hrs
Term
Example of causative agent of secretory diarrhea. Char. of secretory diarrhea
Definition
  • characteristics
    • acute, non-inflam.
    • enterotoxin mediated
    • proximal small bowel
    • watery diarrhea
  • ex: cholera
Term
Hallmark of V. cholera
Definition
abrupt onset of profuse watery diarrhea with flecks of mucus (aka rice water stool)
Term
V. cholera: transmission and reservoir
Definition
  • reservoir- aquatic environments and humans
  • transmission- food borne and waterborne
Term
Secretory diarrhea- V. parahemolyticus: transmission and where seen most often?
Definition
  • seen most often on Gulf coast
  • acquired from raw/undercooked shellfish
Term
Enterotoxigenic (ETEC) E coli: VF and clinical syndrome
Definition
  • VF- enterotoxins
    • heat labile toxin (basically the cholera toxin- increase cAMP)
    • heat stable toxin (increase cGMP)
    • both cause opening of ion channels
  • clinical syndrome- watery diarrhea
Term
Primary causative agent of travelers diarrhea
Definition
ETEC E coli
Term
Coarse of ETEC E coli
Definition
  • self limited (resolve 2-4 days)
  • widespread resistance to amoxicillin, TMP-SMX therapy
Term
Inflammatory diarrhea: causative agents, def.
Definition
  • def.- bloody diarrhea with fever
  • causative agents
    • Shigella
    • STEC
    • Salmonella
    • C. difficile
    • Campylobacter
Term
Shigellosis: epidemiology, VF
Definition
  • humans are only reservoir
  • low inoculum causes disease
    • transmission via fecal-oral, may be food or water born
  • short incubation period (common among the enteric bugs)
  • VF- Shiga toxin (AB5 structure)
    • enter via receptor mediated endocytosis
    • inhibit protein synthesis
Term
Campylobacter: epidemiology, major pathogens
Definition
  • epidemiology- worldwide zoonosis
  • major pathogens
    • C. jejuni: reservoir is poultry
      • grow at 42 degrees C
      • self limited illness (only GI)
    • C. fetus: reservoir is cattle, sheep
      • grow at 25 degrees C
      • tends to disseminate
      • fatal to immunocomp.
    • C. enterocolitis
      • complication: Guillain Barre, septic abortion, reactive arthritis
Term
STEC E coli: epidemiology, complications
Definition
  • epidemiology
    • associated with food and water borne outbreaks (ex: ground beef why it is called the "hamburger disease")
  • complications- Hemolygic Uremic syndrome
    • biggest complication- renal failure
Term
STEC E coli VF's
Definition
  • Shiga toxin
    • classic AB5 toxin
    • B subunit attach to receptors on renal glomerular and tubular cells
    • cytotoxic by cleaving rRNA
    • STEC can produce one of two forms of the Shiga toxin
Term
nontyphoidal Salmonella transmission
Definition
contact with exotic pets, especially reptiles
Term
complications of nontyphoidal Salmonella enterocolitis
Definition
  • bacteremia with intestinal seeding
  • leads to going to bones and joings
  • also can cause endovascular infections
Term
Treatment principles of nontyphoidal salmonella enterocolitis
Definition
  • antibiotic treatment can prolong carriage
  • treat elderly, neonates, immunosuppressed, cardiac valve defects, prosthetic valves
    • ones who could disseminate
Term
What groups of people tend to be at risk for being chronic carriers of nontyphoidal Salmonella enterocolitis
Definition
  • elderly
  • those with galstones
  • infection with Schistosoma haematobium
Term
causative agents of enteric fever
Definition
  • Salmonella enterica servoras Typhi and paratyphi
  • Yersinia
Term
Hallmark of Salmonella enterica serovar Typhi and Paratyphi
Definition
prolonged fever and bacteremia
Term
physical exam findings and complications of typhoid fever
Definition
  • phy exam- rose spots are pathomneumoniic of typhoid fever (faint salmon colored rash on trunk)
    • organisms cultured from biopsy of lesion
  • complications- intestinal perforation/ hemorrhage
Term
diagnosis of enteric infection
Definition
  • stool culture for IDing bacterial organsims (golden standard)
  • blood culture
  • light microscopy for fecal leukocytes
  • Ag detection
  • toxin test (C dificile toxins A and B)
  • electron microscopy (viruses)
  • serology usually not useful
Term
Adv. and disadv. of stool culture
Definition
  • disadvantages
    • cost
    • low yield
    • special media for certain organisms
  • advantages
    • aids in outbreak detection and disease survailence
    • rules out any other cause of diarrhea
    • guides appropriate antimcrobial treatment and track resistance patterns
Term
treatment principles of infectious gastroenteritis
Definition
  • rehydration
  • nonspecific symptomatic therapy
  • must report to public health
  • treatment only for specific circumstances
    • severe or persistent diarrhea, choice of antimicrobial governed by causative agent
    • enteric fever
    • certain organisms:
      • C difficile
      • Giardia, E. histolytica
  • in some cases, antibiotics can worsen disease with some organisms
Term
prevention of enteric infection
Definition
  • safe drinking water in developing wourld
  • Salmonella enterica serovar typhi vaccine (not that affective)
    • oral: live attentuated
    • injectable: heat killed
    • only recommeneded for longterm travel to eares of endemic countries
  • exclusive breast feeding
  • child nutrition
  • wash hands, safely dispose of fecdes
  • give food and drink to children who are sick
  • appropriate home treatment

 

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