Nosocomial outbreak of cross-infection due to multiple-antibiotic-resistant Klebsiella pneumoniae: characterization of the strain and antibiotic susceptibility studies.

A multiple-antibiotic-resistant (MAR) strain of Klebsiella pneumoniae was introduced into a pediatric ward and subsequently colonized neonates of two wards with several cases of systemic infection. This strain produced an extended-spectrum beta-lactamase and was resistant to cefotaxime, ceftazidime, and, among others, all aminoglycosides including amikacin. The majority of representative isolates examined with macrorestriction analysis of genomic DNA (pulsed-field gel electrophoresis) were identical. The strain was susceptible to the innate antibacterial systems operative in fresh defibrinated blood from two adults. Combined human blood/antimicrobial drug assays documented the in vitro bactericidal activity of carbapenems (meropenem was slightly more effective than imipenem), fluoroquinolones (ciprofloxacin and trovafloxacin), and polymyxin B against this MAR strain of K. pneumoniae.