91Ó°ÊÓ

A \(\mathrm{Lac}^{+}\), glucose-fermenting, gram-negative rod isolated from a previously healthy child with bloody diarrhea is most likely to be: A. Shigella sonnei. B. Pseudomonas aeruginosa. C. Escherichia coli. D. Salmonella enterica. E. Helicobacter pylori.

A male older adult, hospitalized and recovering from cardiac bypass surgery, develops pneumonia. Sputum culture reveals a gram-negative rod that produces a green pigment but does not ferment carbohydrates. The most likely organism is: A. Klebsiella pneumoniae. B. Serratia species. C. Proteus species. D. Enterobacter species. E. Pseudomonas aeruginosa.

An older, alcoholic male develops severe, necrotizing lobar pneumonia. The organism is \(\mathrm{Lac}^{+}\)and produces a luxuriant capsule. The most likely agent is: A. Klebsiella pneumoniae. B. Serratia species. C. Yersinia pseudotuberculosis. D. Pseudomonas aeruginosa. E. Campylobacter fetus.

A young man returned from a backpacking trip in Mexico suffering from a high fever, pain in the abdomen, and watery diarrhea. The emergency room doctor noted a faint rash on the patient's abdomen and chest. A blood specimen was collected and plated on MacConkey agar, incubated at \(37^{\circ} \mathrm{C}\) in ambient air. Lac \(^{-}\)colonies grew on the plates. The cultured organism was a gram-negative rod that did not produce Shiga or Shiga-like toxins. The most likely etiological agent for this man's disease is: A. Enterohemorrhagic Escherichia coli B. Shigella dysenteriae C. Salmonella typhi D. Helicobacter pylori E. Campylobacter jejuni