Question #7 explained:
RM is a 57 year-old female with a past medical history that includes numerous urinary tract infections. In the last 3 years she has received courses of ciprofloxacin, amoxicillin-clavulanic acid, sulfamethoxazole-trimethoprim (SMX-TMP), nitrofurantoin, cefepime, and piperacillin-tazobactam. She recently saw her primary care physician (PCP) three days ago and was complaining of increased urinary frequency as well as possible fever. A urine culture was taken and the PCP decided to “watch and wait” rather than treat at that time, which the patient agreed to. Today the urine culture has come back positive for extended-spectrum beta-lactamase (ESBL) producing E. coli, resistant to ciprofloxacin, SMX-TMP, and nitrofurantoin. RM is in the clinic today, complaining of dysuria and continued increased urinary frequency, but no fever. The provider diagnosis her with a lower UTI and asks for your help picking an oral drug. Which of the following is an acceptable option?
A. Ertapenem
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- While ertapenem is a carbapenem and can be used for ESBL-producing bacteria, it is IV only and thus will not fulfill the provider’s request for an oral drug.
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B. Ciprofloxacin
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- This answer is incorrect because the isolate is resistant to ciprofloxacin.
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C. Fosfomycin CORRECT
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- Fosfomycin sensitivities are not listed, but it in many geographical locations fosfomycin resistance is low. Since the patient does not have a history of fosfomycin exposure and has a non-severe infection, a trial of fosfomycin is an acceptable path. Options for ESBLs are limited, but if it is a UTI, fosfomycin can be a useful drug.
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D. Cephalexin
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- ESBL-producing organisms have increased resistance to beta-lactam antibiotics. As a first-generation cephalosporin and beta-lactam antibiotic, cephalexin (Keflex) would not be an option in this scenario.
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