21. Principles of Disease

Explain why Staphylococcus epidermidis is rarely pathogenic while the similar S. aureus is more commonly virulent.

Why is mycolic acid a virulence factor for mycobacteria?

Compare and contrast mycoplasmas and viruses.

Match the genera of pathogens to their appearance in stained smears: Actinomyces, Bacillus, Clostridium, Mycobacterium, Staphylococcus, Streptococcus.

(a) Methenamine silver <IMAGE>

(b) Gram <IMAGE>

(c) Gram <IMAGE>

(d) Acid fast <IMAGE>

(e) Gram <IMAGE>

(f) Gram <IMAGE>

The presence of lipid A in the outer membranes of Gram-negative bacteria.

a. affects the formation of blood clots in the host

b. causes these bacteria to be oxidase positive

c. triggers the secretion of a protease enzyme to cleave IgA in mucus

d. enables enteric bacteria to ferment glucose anaerobically

The only genus of Gram-negative cocci that causes significant disease in humans is

a. Pasteurella

b. Salmonella

c. Klebsiella

d. Neisseria

Which of the following bacterial cells is most likely to be virulent?

a. a cell with fimbriae and LOS

b. a cell with a polysaccharide capsule and lipooligosaccharide

c. a cell with fimbriae, lipooligosaccharide, and a polysaccharide capsule

d. a cell with fimbriae but no capsule

Which of the following statements is true?

a. PID is a severe type of diarrhea in which infection spreads from the intestines to

the bloodstream.

b. PID can result from Neisseria infection.

c. PID is more common in men than women.

d. Members of the family Enterobacteriaceae usually cause PID.

A coliform bacterium that likely contaminates dairy products is

a. Bartonella

b. Serratia

c. Enterobacter

d. Proteus

Capsules of pathogenic enteric bacteria are virulence factors because they

a. capture iron from hemoglobin and store it in the bacteria

b. release hemolysins that destroy red blood cells

c. produce fimbriae that enable the bacteria to attach to human cells

d. protect the bacteria from phagocytosis and from some antibodies

The pathogen Haemophilus influenzae b causes.

a. meningitis in children

b. upper respiratory flu

c. endocarditis

d. genital chancroid

Which of the following diseases is typically mild?

a. Brazilian purpuric fever

b. bartonellosis

c. pediatric meningitis

d. cat scratch disease

Which bacterium causes infections in many burn victims?

a. Moraxella catarrhalis

b. Pseudomonas aeruginosa

c. Escherichia coli

d. Bartonella bacilliformis

Which of the following statements is true of Q fever?

a. For many years its cause was questionable.

b. It was first described in 1976 during an outbreak in Quincy, Massachusetts.

c. Researchers found it could be effectively treated with quinine.

d. The sharp spikes of fever on patients' temperature charts resemble porcupine quills.

Which of the following is a bile-tolerant anaerobe?

a. Bacteroides

b. Escherichia

c. Shigella

d. Prevotella