Klebsiella pneumoniae with multiple antimicrobial resistance

A Klebsiella pneumoniae strain was isolated from the urine of a patient at one of the centers participating in the 2001 edition of the MYSTIC program in Brazil. The initial phenotypic findings of the isolated K. pneumoniae presented an unusual MIC of 8 microg/mL to meropenem, 2 microg/mL to imipenem, elevated MICs to broad spectrum cephalosporins (ceftazidime/cefotaxime/cefepime MIC > 256 microg/mL), aminoglycosides (gentamycin > 256 microg/mL and tobramycin = 48 microg/mL), piperacillin/tazobactam (MIC > 256 microg/mL) and susceptibility to ciprofloxacin (MIC = 0.25 microg/mL). The strain also tested positive for ESBL production with double-disk and E-test methodologies. More detailed investigation revealed that the strain produced a SHV-4 type enzyme and also lacked a 36 kDa outer membrane porin.