Antimicrobial susceptibility and molecular epidemiological analysis of clinical strains of Pseudomonas aeruginosa

Three hundred and seventy-one strains of Pseudomonas aeruginosa were isolated at the laboratory of Kyushu University Hospital in Japan from May 2002 through January 2003. Large proportions of isolated strains were resistant to carbapenems: 37.5% to imipenem, 21.3% to biapenem, and 18.3% to meropenem. A survey of injectable antibacterial agents used in our hospital during the corresponding period showed that carbapenems were most frequently used. Multidrug-resistant P. aeruginosa (MDRP) strains and metallo-β-lactamase producing strains were isolated at frequencies of 1.6% (6 strains) and 0.81% (3 strains), respectively. By molecular epidemiological analysis, neither MDRP nor metallo-β-lactamase producing strains were molecularly related, whereas some imipenem-resistant strains appeared to be epidemic strains, suggesting a possibility that they might spread by nosocomial infection. To control nosocomial infection, it is important to know a trend in drug-resistant P. aeruginosa and to prevent the spread of not only MDRP and metallo-β-lactamase producing strains but also imipenem-resistant P. aeruginosa strains.