This site is 100% ad supported. Please add an exception to adblock for this site.

Chapter 9: The Enterics 2


undefined, object
copy deck
What are the main groups of enteric bugs?
Enterobacteriaceae, Vibrionaceae, Pseudomonadaceae, and Bacteroidaceae
Which enterics DON'T ferment lactose?
Salmonella, Shigella, and Pseudomonas
Describe three levels of intestinal invasion causing diarrhea?
1. no cell invasion, diarrhea is caused by exotoxin-mediated fluid loss.
2. Invasion of the intestinal epithelial cells - systemic immune response with WBC infiltration and RBC leakage into the stool.
3. Invasion of the lymph nodes and bloodstream - diarrhea and systemic symptoms
What are the diseases caused by E. coli?
1. Diarrhea
2. UTI
3. Neonatal meningitis
4. Gram (-) sepsis, commonly in debilitated patients
What are the three groups of diarrhea-producing E.coli?
1. Enterotoxigenic E.coli (ETEC)
2. Enterohemorrhagic E.coli (EHEC), including E.coli 0157:H7 which causes HUS
3. Enteroinvasive E.coli (EIEC)
Describe the diarrhea caused by ETEC?
Heat stabile and heat labile toxins are like cholera exotoxins - severe watery diarrhea, stool looks like rice water
Describe the diarrhea caused by EHEC?
Shiga-like toxin causes bloody diarrhea
Describe the diarrhea caused by EIEC?
Bloody with WBCs, like shigellosis. Also causes fever.
How can E.coli travel up the urethra?
Acquisition of a pili virulence factor.
What are the three leading causes of neonatal meningitis?
Group B strep, E.coli, and Listeria.
What is the most common cause of gram (-) sepsis?
What is Klebsiella pneumonia?
Encapsulated, nonmotile bug, causing sepsis, UTI, and pneumonia, characterized by a red currant jelly sputum.
Why is Proteus useful for lab tests?
Cross-reacting antigens with some Rickettsia serves as a clinical tool for determining whether someone has been infected with Rickettsia.
Describe characteristic of Shigella. Contrast with E.coli.
Nonmotile, does not ferment lactose and does not produce H2S. Humans are the only host - and Shigella is always a pathogen.
What illness does Shigella cause?
Begins with fever, abdominal pain, and diarrhea, which may contain blood and pus.
Describe characteristics of Salmonella?
Non-lactose fermenter, is motile, and produces H2S.
What are the three clinically significant groups of Salmonella?
S. typhi, S. cholerae-suis, and S. enteritidis
Salmonella causes which 4 disease states in humans?
Typhoid fever, carrier state, sepsis, and gastroenteritis
Describe clinical features of typhoid fever?
Fever, headache, and abd. pain that is often localized to the right lower quadrant. Diarrhea may develop, spleen may enlarge, and rose spots may appear on the abdomen.
What is appropriate therapy for Salmonella typhi?
Ciprofloxacin or ceftriaxone
Salmonella sepsis is usually caused by which bug? Which organs does it primarily infect?
Salmonella choleraesuis. Infects lungs, brain, or bone.
Why are sickle-cell patients particularly prone to Salmonella osteomyelitis and other infections?
Their asplenic state makes it difficult to clear these encapsulated bacteria. (Normally, macrophages and neutrophils in the spleen phagocytose opsonized bacteria)
Salmonella diarrhea is usually caused by⬦? Treatment?
Salmonella enteritidis. Treatment involves fluid and electrolyte replacement.
What is Yersinia enterocolitica? Causes pain where?
Motile gram-negative rod, transferred by the fecal-oral route. Pain in the right lower quadrant of the abdomen.
What is Yersinia enterocolitica’s unique survival feature?
Can survive and grow in the cold.
Vibrio cholera shape?
Curved gram-negative rod with a single polar flagellum.
V. cholera causes a similar (though more severe) disease as which E.coli subtype? Produces what kind of diarrhea?
ETEC. Watery (rice water) diarrhea.
What are the three most common causes of diarrhea in the world?
Campylobacter jejuni, ETEC, and the Rotavirus.
Campylobacter jejuni causes which type of diarrhea?
Bloody, loose diarrhea.
What is the most common cause of duodenal ulcers? Gastric ulcers?
Helicobacter pylori. Aspirin products.
Describe Pseudomonas aeruginosa? Shape, gram, scent, invasive ability, toxins?
Obligate aerobic gram (-) rod. Produces grape-like scent. Weak invasive ability. Exotoxin A, similar mechanism as diphtheria toxin.
List the important Pseudomonas infections?
1. Pneumonia
2. Osteomyelitis
3. Burn-wound infections
4. Sepsis
5. UTIs, pyelonephritis
6. Endocarditis
7. Malignant external otitis
8. Corneal infections
Which patients are at-risk for Pseudomonas pneumonia?
CF patients and immunocompromised patients.
Which patients are at risk for Pseudomonas osteomyelitis?
Diabetics, IV drug abusers, children with puncture wounds to the foot.
What is the general treatment regimen for Pseudomonas?
Anti-pseudomonal penicillin combined with an aminoglycoside for synergy
When do we encounter Bacteroides fragilis infections?
Bullet wounds through the intestine, seat belt lacerations in MVA’s, bowel penetration in abdominal surgery, etc.
Following abdominal surgery, which antibiotics that cover anaerobes are given as prophylaxis?
Clindamycin, metronidazole, chloramphenicol, etc.

Deck Info