WBR0642

Author	[[PageAuthor::Rim Halaby, M.D. [1]]]
Exam Type	ExamType::USMLE Step 1
Main Category	MainCategory::Microbiology, MainCategory::Pharmacology
Sub Category	SubCategory::Infectious Disease
Prompt	[[Prompt::A pharmaceutical company is trying to develop a new antibiotic to overcome increasing resistance to macrolides. Their rationale is to create an agent that would be co-administered with azithromycin that counteracts the mechanism by which bacteria become resistant to this antibiotic. Which of the following agents would be appropriate to investigate for this purpose?]]
Answer A	AnswerA::RNA methylation inhibitors
Answer A Explanation	AnswerAExp::Inhibition of RNA methylation can in theory help decrease resistance to macrolides since it targets the main resistance mechanism.
Answer B	AnswerB::Drug acetylation inhibitors
Answer B Explanation	AnswerBExp::Acetylation inhibitors would work more for aminoglycoside resistance but not for macrolides
Answer C	AnswerC::Beta-lactamase inhibitors
Answer C Explanation	AnswerCExp::Beta-lactamase inhibitors like tazobactam, clavulanic acid, and sulbactam are used with penicillin antibiotics to inhibit destruction of the beta-lactam ring by beta-lactamase producing bacteria.
Answer D	AnswerD::Drug efflux pump blockers
Answer D Explanation	AnswerDExp::Although drug efflux can be seen as a mechanism of resistance to macrolides, it is minor compared to rRNA methylation.
Answer E	AnswerE::Drug adenylation inhibitors
Answer E Explanation	AnswerEExp::Drug adenylation is also a form of enzymatic modification seen in resistance to aminoglycosides not in macrolides.
Right Answer	RightAnswer::A
Explanation	[[Explanation:: Macrolides are a class of antibiotic agents that act by inhibiting protein synthesis specifically inhibiting translocation. They bind to the 23S rRNA binding site of the 50S subunit. They are commonly used to treat atypical pneumonias, chlamydia, and non-tuberculous mycobacteria among others. The mechanism of resistance to macrolides is by the methylation of the 23S rRNA binding site. A suggested mechanism to inhibit resistance it to administer an agent to inhibit bacterial methylation enzymes. Learning Objective: Resistance to macrolides is by methylation of the 23S rRNA binding site. References: Walsh C. Molecular mechanisms that confer antibacterial drug resistance. Nature. 2000;406(6797):775-81. Educational Objective: References: ]]
Approved	Approved::No
Keyword	WBRKeyword::Antibiotic resistance, WBRKeyword::Macrolides
Linked Question	Linked::
Order in Linked Questions	LinkedOrder::