A 69-year-old male with diabetes and neurogenic bladder presented with emphysematous cystitis, initially treated with cefepime based on susceptibility testing. Despite the in vitro susceptibility, the patient's condition worsened, necessitating a change to meropenem and colistin. Further investigation revealed the infecting organism was a KPC-producing Escherichia coli, which explained the cefepime treatment failure due to the carbapenemase activity. This case highlights a critical clinical scenario where standard susceptibility testing may not predict in vivo efficacy, especially with carbapenemase-producing organisms. Definitive diagnosis through molecular testing for resistance mechanisms is crucial for effective treatment.
Key note: In vitro susceptibility to cefepime for KPC-producing organisms does not guarantee clinical success.