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Chapter 44: Tetracyclines, Macrolides, Clindamycin, Chloramphenicol, Streptogramins, & Oxazolidinones

A 4-year-old child is brought to the hospital after ingesting pills that a parent had used for bacterial dysentery when traveling outside the United States. The child has been vomiting for more than 24 h and has had diarrhea with green stools. She is now lethargic with an ashen color. Other signs and symptoms include hypothermia, hypotension, and abdominal distention. The drug most likely to be the cause of this problem is

(A) Ampicillin

(B) Azithromycin

(C) Chloramphenicol

(D) Doxycycline

(E) Erythromycin

Chloramphenicol is commonly used outside the United States for treatment of bacillary dysentery. The drug causes a dose-dependent (reversible) suppression of erythropoiesis. Although the gray baby syndrome was initially described in neonates, a similar syndrome has occurred with overdosage of chloramphenicol in older children and adults, especially those with hepatic dysfunction. The answer is C.

A pathogen commonly responsible for community-acquired pneumonia is S pneumoniae. In which of the following situations would you NOT suggest treating S pneumoniae with a macrolide antibiotic?

(A) The patient has a history of aplastic anemia

(B) The patient is over 65 years of age

(C) The patient is younger than 4 years of age

(D) The patient lives in a region where S pneumoniae is highly resistant to macrolides

(E) The patient takes selective serotonin reuptake inhibitors (SSRIs)

Antimicrobial resistance can vary drastically by geography. For example, approximately 94% of Streptococcus pneumoniae isolates in China were found to be resistant to macrolide antibiotics in 2017, 34% were resistant in the United States, and only 5% were resistant in Sweden. Furthermore, different mechanisms of resistance have been observed in different regions: efflux pump resistance is more common in North America, whereas ribosomal mechanisms are more common in Europe. The answer is D.

Clarithromycin and erythromycin have very similar spectra of antimicrobial activity. The major advantage of clarithromycin is that it

(A) Does not inhibit hepatic drug-metabolizing enzymes

(B) Eradicates mycoplasmal infections in a single dose

(C) Has greater activity against H pylori

(D) Is active against methicillin-resistant strains of staphylococci

(E) Is active against strains of streptococci that are resistant to erythromycin

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