We analyzed the isolation of enterobacteria at Showa University Hospital in 2001 and compared the site of isolation and its antibiotic resistance with data of 1991-1992 or 1997-1998. The identification and antibiotic susceptibility tests were performed by Microscan Walk Away (Dade Behring, USA) .
Escherichia coli and
Klebsiella pneumoniae were most frequently isolated. Although the number of
Escherichia coli isolates from the respiratory tract increased, the susceptibility pattern was similar to that of 1991-1992. As for
Klebsiella pneumoniae and
Klebsiella oxytoca, the sites of isolation and the susceptibility patterns were similar to those of 1997-1998. It should be noted that 23 strains of ESBL-producing
Escherichia coli, 19 strains of ESBL-producing
Klebsiella pneumoniae and 4 strains of ESBL-producing
Klebsiella oxytoca were isolated. A total of 399 strains of
Serratia marcescens were isolated. The ratio of met allo-β-lactamase-producing
Serratia marcescens was 3% in 1997-1998. In this survey, 42 strains of imipenem resistant
Serratia marcescens, which is considered to be metallo-β-lactam ase producing
Serratia marcescens, were isolated; this accounted for 10% of the
Serratia marcescens. Analysis of the genome digestion pattern using pulsed field gel electrophoresis revealed that 30 of the 42 strains of imipenem-resistant
Serratia marcescens were identical, indicating an outbreak. After containment of the outbreak, the ratio of imipenem-resistant
Serratia marcescens decreased to 3%. We also isolated
Enterobacter cloacae and
Enterobacter aerogenes 417 and 144 strains, respectively; both bacteria were resistant to ampicillin, cefazolin, and cefmetazole. The most alarming finding of the present survey is the emergence of ESBL-producing bacteria.
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