Bacterial Infections

Question 1

Tx: C. difficile

Answer 1

Metronidazole

Question 2

Stool samples in the US should routinely be cultured for the presence of ___, ___, and ___

Answer 2

1. Campylobacter
2. Salmonella
3. Shigella

Question 3

Empiric Tx

Answer 3

Ciprofloxacin

Question 4

Tx: Campylobacter jejuni

Answer 4

Azithromycin

Question 5

• Anaerobic
• Autoclaving → sterilization; incineration → decontamination
• Heat-labile enterotoxins A&B → damage epithelial lining
• Antibiotic-associated GI infections
  
  • Diarrhea
  • Pseudomembranous colitis
• Resistance to certain antibiotics → alters flora
  
  • Endogenous overgrowth
  • Exogenous acquisition
• Discontinue antibiotic (mild cases); metronidazole or vancomycin (severe)

Answer 5

Clostridium difficile

Question 6

• Enteric fever
  
  • Dissemination via lymphatics
• LPS endotoxin affects vascular permeability and nerve tissue
  
  • Rash (weakened BV)
  • Fever (compromised thermal reg.)
• Vaccine available
• Chemotherapy indicated

Answer 6

Salmonella enterica Typhi

Question 7

• Oxidase (-); lactose (-)
• 2500 serotypes
• Adhesins allow biofilm formation on small or large intestine mucosa → invasion and toxin extrusion (type III) → intracellular replication within phagosomes (unlike EIEC & Shigella)
• Dairy, poultry, meat
• Low ID₅₀

Answer 7

Salmonella enterica

Question 8

• Microaerophilic
• Most important etiologic agent for gastroenteritis in the US; also causes septicemia
• Undercooked poultry
• Dysentery
• Resolution ~7-10 days

Answer 8

Campylobacter jejuni

Question 9

• Type III secretion system → injects 4 exotoxins → phagosome lysis → cytoplasmic replication → actin filament → cell-to-cell passage
• Water diarrhea or (MC) dysentery
• Toxin possibility causes HUS
• MC in children <5 y/o
• Low ID₅₀

Answer 9

Shigella

Question 10

• Oxidase (-); peritrichous flagella
• Watery diarrhea (traveler’s diarrhea, bacterial gastroenteritis)
• Strain with plasmid-acquired:
  
  • Fimbrial edhesin
  • Heat-labile (cAMP)
  • Heat-stable (cGMP)

Answer 10

Enterotoxigenic E. coli (ETEC)

Question 11

Special culture protocols are necessary for ___, ___, and ___

Answer 11

1. Vibrio
2. C. difficile
3. EHEC

Question 12

• Oxidase (+); polar flagella
• Acid labile
• Halophilic
• Watery diarrhea, vomiting → dehydration, metabolic acidosis, hypovlemic shock
• Hydration therapy

Answer 12

Vibrio cholera

Question 13

• Don’t cause infection, rather intoxications (enterotoxins)
• Foodborne gastroenteritis
• RAPID onset: N/V, diarrhea
• Chemotherapy not indicated

Answer 13

Staphylococcus aureus

Bacillus cereus

Clostridium perfringens

Question 14

Tx: H. pylori

Answer 14

Triple therapy

1. PPI
2. Clarithromycin
3. Amoxicillin (Pen allergy = metronidazole)

Question 15

Tx for all enterics

E. coli

Shigella

Salmonella

Answer 15

Ciprofloxacin

Question 16

• Dysentery with high fever
• Plasmid-mediated adhesion → invasion of colonic epithelium → lyse phagocytic vacuoles → cytoplasmic replication → actin tails → infect adjacent cells
• Small ID₅₀
• Generally self-limiting
• Very similar to Shigellosis

Answer 16

Enteroinvasive E. coli (EIEC)

Question 17

• Oxidase (+); polar flagella
• Microaerophilic
• Urease byproducts + exotoxins → localized tissue damage
• Epithelial cytoskeleton destruction mediated by specific exotoxin inctroduced by type VI secretion
• Growth suppressed by probiotics

Answer 17

H. pylori

Question 18

Tx: Vibrio

Answer 18

Doxycycline

or

Azithromycin