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Chapter 21: Infections Caused by Anaerobic Bacteria

A 55-year-old man visits his physician complaining of a severe cough and production of purulent sputum. His breath has a very unpleasant fetid odor. Chest radiography shows a large amount of fluid in the left pleural space and a 5-cm lung cavity with an air-fluid level. A needle is inserted through the chest wall, and some of the fluid in the pleural space is removed; it is thick, yellow-gray in color, and malodorous. Which of the following organisms or sets of organisms are most likely to be cultured from the pleural fluid?

(A) Bacteroides fragilis, Escherichia coli, and enterococci

(B) Prevotella bivia, peptostreptococci, and Staphylococcus epidermidis

(C) Prevotella melaninogenica, Fusobacterium species, and viridans streptococci

(D) Propionibacterium species, peptostreptococci, and Staphylococcus aureus

(E) Streptococcus pneumoniae

An 18-year-old man develops fever with pain in the right lower quadrant of his abdomen. After initial evaluation, he is taken to the operating room. During surgery, a ruptured appendix with an abscess is found. Bacteroides fragilis is cultured from the abscess fluid. Which of the following factors promote abscess formation by B fragilis?

(A) Lipopolysaccharide

(B) Capsule

(C) Superoxide dismutase

(D) Pili

(E) Leukocidin toxin

Infections caused by Bacteroides species can be treated with all of the following antibiotics except

(A) Ampicillin–sulbactam

(B) Clindamycin

(C) Metronidazole

(D) Penicillin

(E) Cefoxitin

A 17-year-old high school senior develops infectious mononucleosis. About 2 weeks later, he develops a significantly higher fever, a worsening sore throat, an inability to swallow, and severe neck and chest pain. Upon admission, he has signs of sepsis and respiratory distress. What is the most likely organism causing this complication?

(A) Fusobacterium necrophorum

(B) Bacteroides ovatus

(C) Prevotella melaninogenica

(D) Clostridium tetani

(E) Actinomyces israelii

The drug of choice for treatment of infections caused by Actinomyces species is

(A) Tigecycline


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