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Clinical Bacteriology

The main reason why some bacteria are anaerobes (i.e., they cannot grow in the presence of oxygen) is because:

(A) they do not have sufficient catalase and superoxide dismutase.

(B) they have too much ferrous ion that is oxidized to ferric ion in the presence of oxygen.

(C) they have unusual mitochondria that cannot function in the presence of oxygen.

(D) transcription of the gene for the pilus protein is repressed in the presence of oxygen.

Which one of the following sets consists of bacteria that are both anaerobes?

(A) Actinomyces israeli and Serratia marcescens

(B) Campylobacter jejuni and Vibrio cholerae

(C) Clostridium perfringens and Bacteroides fragilis

(D) Mycobacterium tuberculosis and Pseudomonas aeruginosa

(E) Mycoplasma pneumoniae and Corynebacterium diphtheriae

You’re in the clinical lab looking at a Gram stain when the laboratory technician comes up to you and says, “I think your patient has Staph epi [short for Staphylococcus epidermidis] bacteremia.” Which one of the following sets of results did the tech find with the organism recovered from the blood culture?

(A) Gram-positive cocci in chains, catalase-positive, coagulase-positive

(B) Gram-positive cocci in chains, catalase-negative, coagulase-negative

(C) Gram-positive cocci in clusters, catalase-positive, coagulase-negative

(D) Gram-positive cocci in clusters, catalase-negative, coagulase-positive

(E) Gram-positive diplococci, catalase-negative, coagulase-positive

Superantigen production by Staphylococcus aureus is involved in the pathogenesis of which one of the following diseases?

(A) Impetigo

(B) Osteomyelitis

(C) Scalded skin syndrome

(D) Septicemia

(E) Toxic shock syndrome

Which one of the following is the virulence factor produced by Staphylococcus aureus that prevents the activation of complement and thereby reduces opsonization by C3b?

(A) Catalase

(B) Coagulase

(C) Endotoxin

(D) Protein A

(E) Teichoic acid

The main reason why methicillin-resistant Staphylococcus aureus (MRSA) ...

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