Bacteria (Part III) Flashcards
how can the enterobacteriaceae be largely separated?
into organisms that cause gastrointestinal disease and those that cause nosocomial infections
what are the enterobacteriaceae organisms that cause gastrointestinal disease?
escherichia coli, shigella, salmonella, and yersinia enterocolitica
what are the enterobacteriaceae organisms that cause nosocomial infections?
proteus mirabilis, klebsiella pneumoniae, enterobacteria, serratia
What are 5 examples of lactose fermenters?
E. coli and many nosocomial enterobacteriaceae (Klebsiella, enterobacter, citrobacter, and serratia)
what do lactose fermenters create on the agar plate?
they create a vibrant pink color change on MacConkey agar and appear dark black with a metallic sheen on EMB agar
what is escherichia coli?
a gram negative rod, lactose fermenter, normal flora of GI tract; a protypical enteric bacteria of the enterobacteriaceae family
how does E. coli pick up virulence factors?
through plasmids either through horizontal gene transfer or via bacteriophages
what is the most common cause of urinary tract infection?
E. coli
What diseases can E. coli cause? (4)
1) diarrhea 2) meningitis (especially neonatal) 3) urinary tract infection 4) PNA
what virulence factor does E. coli have?
pili
What causes enterotoxigenic E. coli?
consumption of fecally contaminated food or water; it is the most common cause of so called traveler’s diarrhea
what are the high risk areas of acquiring enterotoxiogenic E. coli?
mexico, south america, africa, the middle east, and asia
what does enterotoxiogenic E. coli cause?
watery diarrhea
what are the toxins released from enterotoxiogenic E. coli that cause watery diarrhea?
Heat labile (LT) and heat stabile (ST) toxins
how do the LT and ST toxins released by enterotoxiogenic E. coli cause watery diarrhea?
they cause an osmotic pull of water out of cells by causing failure of reabsorption of ions (Na or Cl) or secretion of ions (Cl or HCO3)
what virulence factor does enteroinvasive E. coli have?
a virulence plasmid which allows it to invade the bowel wall–> the result is bloody diarrhea
what strain of E. coli has been known to contaminate a wide variety of foods including undercooked meat and spinach as well as lettuce?
enterohemorrhagic E. coli
what toxin does enterohemorrhagic E coli produce? (EHEC)
shiga-like toxin 1 or 2
what is the effect of shiga-like toxin 1 or 2?
it causes cell death through ribosomal inhibition. The result is bloody diarrhea
What is the subtype of enterohemorrhagic E. coli?
E. coli 0157
what is the effect of E. coli 0157?
it causes hemolytic uremic syndrome
what is hemolytic uremic syndrome?
a disease characterized by anemia, thrombocytopenia, and kidney damage
what does E. coli 0157 produce?
a specific toxin- Stx2 toxin- which can cause endothelial damage to small blood vessels
what does damage to endothelial cells caused by Stx2 cause?
microthrombi–> ultimately causes thrombocytopenia and anemia; the Stx2 toxin also causes kidney damage
what is shigella?
a gram negative rod, non-motile, always pathogenic
how is shigella transmitted?
through fecal oral transmission
where are shigella outbreaks common?
in preschool, daycare centers, nursing homes
what is the action of shigella?
it invades the intestine producing high fever with bloody diarrhea and abdominal cramps
what are the four species of shigella?
S. sonnei, S. dysenteriae, S. flexneri, and S. boydii
what is the most common species of Shigella in the US?
S. sonnei
which species of shigella is the most virulent and why?
Shigella dysenteriae is the most virulent in that strains of it produce a shiga toxin that causes more widespread cell death by inhibiting protein synthesis at the 60 S ribosomal unit
What is Salmonella?
a gram negative rod, motile, encapsulated
how does salmonella spread?
fecal-oral transmission- unwashed contaminated food like chicken eggs or spinach
what is salmonella typhi?
an exclusively human pathogen
what is salmonella typhi associated with?
it can develop chronic carriage in the gallbladder; it is associated with gallbladder adenocarcinoma
what is associated with non-typhoidal salmonella outbreaks?
zootonic reservoir- handling of pets such as turtles or hedgehogs
What are the diseases associated with Salmonella?
typhoid fever, sepsis/bacteremia, gastroenteritis/diarrhea
what specifically causes typhoid fever?
salmonella typhi
what is the incubation period for typhoid fever?
7-14 day incubation period
what type of fever is associated with typhoid fever?
a “stepwise fever”- rises during the day, drops each morning, troughs and peaks over time
what are the symptoms/presentations of typhoid fever?
diffuse and colicky right upper quadrant abdominal pain, headache, malaise, hepatosplenomegaly, delirium “typhoid encephalopathy”, fever peaks (104 F); development of “rose spots”= bacterial embolli; overwhelming toxemia can lead to death
where can chronic carriage of Salmonella typhi occur?
in the gallbladder
what diseases can the non-typhi salmonella cause?
localized infection of the bone, brain, and lung
who is at risk for salmonella poisoning and why?
salmonella species are encapsulated so those without a spleen are more at risk for infection
what can non-typhoidal salmonella species cause?
febrile watery diarrhea with or without some associated trace blood
