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Chapter 46: Sulfonamides, Trimethoprim, & Fluoroquinolones

Trimethoprim-sulfamethoxazole is established to be effective against which of the following opportunistic infections in the AIDS patient?

(A) Cryptococcal meningitis

(B) Herpes simplex

(C) Oral candidiasis

(D) Toxoplasmosis

(E) Tuberculosis

Trimethoprim-sulfamethoxazole is not effective in the treatment of infections caused by viruses, fungi, or mycobacteria. However, the drug combination is active against certain protozoans, including Toxoplasma, and can be used for both prevention and treatment of toxoplasmosis in the severely immunocompromised AIDS patient. The answer is D.

A 65-year-old woman has returned from a vacation abroad suffering from traveler’s diarrhea, and her problem has not responded to antidiarrheal drugs. A pathogenic gram-negative bacillus is suspected. Which drug is most likely to be effective in the treatment of this patient?

(A) Ampicillin

(B) Ofloxacin

(C) Sulfadiazine

(D) Trimethoprim

(E) Vancomycin

The second-generation fluoroquinolones are very effective in diarrhea caused by bacterial gram-negative pathogens, including E coli, Shigella, and Salmonella. None of the other drugs listed would be appropriate. Many coliforms are now resistant to amoxicillin and ampicillin. Although trimethoprim is available as a single drug, resistance emerges rapidly during treatment unless it is used for urinary tract infections, in which high concentrations can be achieved. Vancomycin has no activity against gram-negative bacilli. The answer is B.

Which statement about the clinical use of sulfonamides is false?

(A) Active against C trachomatis and can be used topically for treatment of chlamydial infections of the eye

(B) Are not effective as sole agents in the treatment of prostatitis

(C) Effective in Rocky Mountain spotted fever

(D) In some bacterial strains resistance occurs via increased PABA formation

(E) Reduced intracellular uptake is a mechanism of sulfonamide resistance in some bacterial strains

Sulfonamides have minimal therapeutic actions in rickettsial infections. Chloramphenicol may be used for Rocky Mountain spotted fever in patients with established allergy or other contraindication to tetracyclines. All of the other statements about sulfonamide antimicrobial drugs are accurate. The answer is C.

A 31-year-old man has gonorrhea. He has no drug allergies, but a few years ...

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