Enterobacteria I Flashcards
What are the 4 characteristics of Enterobacteria?
Facultative Gram-Neg rods
Ferment glucose
Reduce nitrate to nitrite
Oxidase negative
What are the 5 enterobacteria genera that cause GI disease?
E. coli Shigella spp. Salmonella spp. Edwardsiella spp. Y. enterocolitica
What are the 5 groups of E. coli that cause gastroenteritis?
ETEC EPEC EIEC EHEC and STEC EAggEC
What is ETEC and what does it cause?
Enterotoxigenic
Traveler’s Diarrhea. Profuse watery diarrhea is predominant symptom.
Toxins that do not damage the mucosal epithelium.
What is EPEC and what does it cause?
Enteropathogenic
Usually occurs in infants. Characterized by low-grade fever, malaise, vomiting, and diarrhea, with a prominent amount of mucus, but with NO gross blood.
What is EIEC and what does it cause?
Enteroinvasive
Epithelial cells invaded.
Hallmarks are fever and colitis. Symptoms are urgency and tenesmus; blood, mucus, and many leukocytes in stool.
What is EHEC and STEC and what does it cause?
Enterohemorrhagic
Shiga Toxin Producing
Release of Shiga toxins and is often caused by E. coli O157 and it causes bloody diarrhea without WBCs.
What is EAggEC and what does it cause?
Enteroaggregative
Adhere to epithelial cells in a pattern resembling a pile of stacked bricks. Symptoms include watery diarrhea with blood and mucus.
What is the triad of symptoms with hemolytic uremic syndrome?
- acute renal failure
- thrombocytopenia
- hemolytic anemia
What is the reservoir of STEC?
Healthy dairy cattle - shed in feces
How is STEC acquired in humans?
Eating undercooked ground beef mainly.
Others include: unpasteurized milk, apple cider, lettuce and other produce, petting zoos, state fair show barns, contaminated water
What are the clinical manifestations of STEC infection?
Hemorrhagic Colitis
Hemolytic Uremic Syndrome
What are the 5 clinical manifestations of Salmonella?
A. Carrier
B. GI-itis = typical abd pain & diarrhea
C. Enteric (“Typhoid”) fever - Transmission = S. Typhi in GI (reservoir is humans only - exception)
- Manifestations = rose spots w/ fever & septicemia for first 2 weeks –> diarrhea for last 2 weeks
- Mechanism = mucosa –> macrophages –> Peyer’s patches –> blood
D. Septicemia = w/o GI symptoms, found in immunosuppressed pts
E. Focal Infections = brain, bone, heart
What are the main virulence factors of Enterobacteria?
Endotoxins
Capsule
Antigenic Phase Variation
What color do lactose fermenters stain on MacConkey agar?
Purple
What color do non-lactose fermenters stain on MacConkey agar?
White/Colorless
What are the 7 tribes of Enterobacteria?
Tribe I – Escherichieae Tribe II – Edwardsielleae Tribe III – Salmonelleae Tribe IV – Citrobactereae Tribe V – Klebsielleae Genus Klebsiella Tribe VI – Proteeae Tribe VII – Yersinieae
What is the reservoir of E. coli?
Intestines of humans and animals
What is the presence of E. coli in water indicative of?
Fecal contamination
What is the most common cause of UTIs?
E. coli
A college student returning from a Spring vacation in Puerto Vallarta, Mexico developed a profuse watery diarrhea accompanied by mild abdominal cramps. His diarrhea is so profuse that he is experiencing symptoms of dehydration. While on vacation he was careful not to purchase food from street vendors but did frequent the local bars and had drinks served with ice. Stool exam revealed no blood or WBC’s. What type of diarrheagenic E. coli is most likely to cause the symptoms experienced by this student?
A. E. coli O157 B. Enterotoxigenic E.coli (ETEC) C. Enteroinvasive E.coli (EIEC) D. Enteropathogenic E. coli (EPEC) E. Enterohemorrhagic E. coli (EHEC)
B. Enterotoxigenic E.coli (ETEC)
What is the most common Shiga Toxin producing E. coli?
E. coli O157
What are the symptoms of hemorrhagic colitis - related to E. coli O157?
Abdominal cramps, watery diarrhea, bloody discharge
No significant fever
Absence of WBC in stool
How is hemolytic uremic syndrome caused by E. coli O157 (STEC also known as EHEC)?
E. coli 0157 does not invade plasma but Shiga toxin does
and it attaches to receptors in renal epithelial cell wall and damages the blood vessel walls - fibrin deposits are rough
-> Cause RBCs to start tearing and O2 supply to kidney is
affected leading to acute renal failure.
This leads to hemolytic anemia, renal failure and thrombocytopenia.
What is multiplex PCR used for?
Allows for a single test that can look for MANY targets ranging from EHEC to V. cholera
What is the treatment for STEC?
Oral rehydration (Gatorade, Pedialyte), supportive care, and careful monitoring of kidney function.
Why are antibiotics not given for STEC?
Antibiotics will cause the massive destruction of
E. coli and lead to the singular release of the
endotoxin AND Shiga toxin -> shock and death
A healthy 3-year-old child develops diarrhea that lasts about a week, and that is bloody for a few days. His diarrhea resolves, but he remains lethargic, and passes only a little urine. A blood smear shows fragmented red blood cells and no platelets. What etiologic agent of infection would most likely produce the signs and symptoms displayed in this case?
A. E. coli 0157 B. Campylo bacter jejuni C. Salmonella typhi D. Shigella flexneri E. Yersinia enterocolitica
A. E. coli 0157
