[Molecular epidemiological analysis of Pseudomonas aeruginosa by pulsed-field gel electrophoresis]

In order to see the nosocomial infection by Pseudomonas aeruginosa (P. aeruginosa) in the Akita University Hospital, we analyzed the serotype and genotype for 150 strains isolated from various clinical specimens from 1994 to 1996. One hundred strains chosen at random were divided into 11 serotypes by serotyping and into 50 genotypes by pulsed-field gel electrophoresis of Spe I-digested P. aeruginosa genomic DNAs. Serotype E strains, most common, gave 17 genome patterns. Fifty strains separated periodically in certain wards had further 7 genome patterns. The strains isolated from one patient with different times or with different serotypes showed the same stable genotype. Genome patterns were inconsistent with susceptibility to antimicrobial agents. Both drug-susceptible and -resistant strains were found in strains with the same genome pattern. The genome pattern was identical, even though the susceptibility was different due to isolation time or storage. This suggested that the multidrug-resistant strains of P. aeruginosa expanded in the hospital were not derived from one original strain.