Outbreak of infection with multidrug-resistant Klebsiella pneumoniae carrying bla(IMP-8) in a university medical center in Taiwan

Klebsiella pneumoniae strains with the transferable carbapenem-hydrolyzing metallo-beta -lactamases, which include IMP- and VIM-type enzymes, remain e xtremely rare. To investigate whether IMP- or VIM-producing K. pneumoniae i solates had spread at a university medical center in Taiwan, a total of 3,4 58 clinical isolates of K. pneumoniae consecutively collected in 1999 and 2 000 were tested by the agar diffusion method, colony hybridization, PCR, an d nucleotide sequencing. A total of 40 isolates (1.2%), or 17 nonrepetitive isolates, from 16 patients were found to carry bla(IMP-8) a metallo-beta - lactamase gene recently identified from a K. pneumoniae strain in Taiwan. C arriage of bla(VIM) or other bla(IMP) genes was detected in none of the rem aining isolates. Of the 17 nonrepetitive bla(IMP-8)-positive isolates, 15 i solates (88.2%) appeared susceptible to imipenem (MICs, less than or equal to4 mug/ml) and meropenem (MICs, less than or equal to1 mug/ml), indicating the difficulty in detecting bla(IMP-8) in K. pneumoniae by routine suscept ibility tests; 14 isolates (82.4%) produced SHV-12 as well; and 14 isolates (82.4%) were also resistant to fluoroquinolones. The organisms caused woun d infections in eight patients and bloodstream infections in three patients . They were not directly associated with the death of nine patients. Before the recovery of the bia(IMP-8)-positive isolates, all 16 patients had unde rgone various surgical procedures, and 15 patients had been admitted to the surgical intensive care unit, suggesting a nosocomial outbreak. Two major patterns were observed by pulsed-field gel electrophoresis for 14 of the 17 nonrepetitive isolates, indicating that the clonal spread was mainly respo nsible for the outbreak.