Overview

Question 1

Bugs causing diarrhea

Answer 1

Campylobacter❌Comma- or S-shaped organisms; growth at 42°C

E histolytica❌Protozoan; amebic dysentery; liver abscess

Enterohemorrhagic E coli❌O157:H7; can cause HUS; makes Shiga-like toxin

Enteroinvasive E coli❌Invades colonic mucosa

Salmonella (non-typhoidal)❌; flagellar motility; has animal reservoir, especially poultry and eggs

Shigella❌Lactose -very low ID50 ; produces Shiga toxin (human reservoir only); bacillary dysentery

Y enterocolitica❌Day care outbreaks; pseudoappendicitis

Question 2

Watery diarrhea

Answer 2

C difficile❌ Pseudomembranous colitis; associated with antibiotics and PPIs; occasionally bloody diarrhea

C perfringens❌ Also causes gas gangrene

Enterotoxigenic E coli❌ Travelers’ diarrhea; produces heat-labile (LT) and heat-stable (ST) toxins

Protozoa❌ Giardia, Cryptosporidium

V cholerae❌ Comma-shaped organisms; rice-water diarrhea; often from infected seafood

Viruses❌ Rotavirus, norovirus, enteric adenovirus

Question 3

Common causes of pneumonia

Answer 3

<4w ❌Group B streptococci E coli

4w-18y ❌Viruses (RSV) Mycoplasma C trachomatis (infants–3 yr) C pneumoniae (school-aged children) S pneumoniae Runts May Cough Chunky Sputum

18-40y ❌Mycoplasma C pneumoniae S pneumoniae Viruses (eg, influenza)

40-6y ❌S pneumoniae H influenzae Anaerobes Viruses Mycoplasma

Elderly ❌S pneumoniae Influenza virus Anaerobes H influenzae Gram ⊝ rods