Case Report of Treatment of Polymicrobial Bacteremia Caused by Carbapenem-Resistant Klebsiella pneumoniae , and Bacillus Species in an Immunocompetent Patient With Meropenem-Vaborbactam.
Zoey Zagoria, John Cerenzio, Justin Andrade
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Case in brief
A 74-year-old immunocompetent woman with a prolonged hospital stay and multiple prior courses of intravenous antimicrobials developed polymicrobial bacteremia due to CTX-M- and KPC-producing multidrug-resistant Klebsiella pneumoniae and Bacillus species. Treatment included cefiderocol, then vancomycin with meropenem-vaborbactam, followed by meropenem-vaborbactam alone. The Bacillus isolate was susceptible to meropenem-vaborbactam (0.023 mcg/mL), interpreted using a meropenem breakpoint of 4 mcg/mL. The bloodstream infection was successfully treated with meropenem-vaborbactam.
What made this case unusual
The patient was immunocompetent despite invasive Bacillus bacteremia, which is more typically reported in immunocompromised hosts. The Bacillus isolate was susceptible to meropenem-vaborbactam, enabling treatment of both organisms with monotherapy.
Diagnostic / clinical pearl
In polymicrobial bacteremia involving Bacillus species, request susceptibility testing when available; isolate-specific results may help identify an agent that covers both pathogens and permits therapy consolidation.