[Antibiotic susceptibility and beta-lactamase activity of pathogenic microbes isolated in Miyagi Prefecture between December in 1999 and February in 2000].

We determined beta-lactamase activity and antimicrobial susceptibility of 556 strains consisting of 10 species isolated in four medical institutions and one microbiological laboratory of Miyagi Prefecture in Japan between December in 1999 and February in 2000. beta-Lactamase determined by nitrocefin method was positive in 68% of S. aureus, in 15% of H. influenzae and in 100% of M. catarrhalis. Penicillinase/cephalosporinase determined by acidometry was positive in 9%/10% of E. coli, in 17%/2% of K. pneumoniae, in 16%/58% of E. cloacae, in 43%/78% of S. marcescens, and in 4%/32% of P. aeruginosa, respectively. Of a total of 298 strains of Enterobacteriaceae and P. aeruginosa, 25 strains (14 strains of E. coli, 10 strains of K. pneumoniae and one strain of S. marcescens) produced class A beta-lactamase, two strains of E. cloacae produced class B beta-lactamase, and 12 strains (one strain of E. coli, four strains of E. cloacae, six strains of S. marcescens and one strain of P. aeruginosa) produced class C beta-lactamase. According to NCCLS standard, three strains (one strain of E. coli and two strains of K. pneumoniae) of ESBL-positive microbes were detected. beta-Lactamase-negative ampicillin-resistant (BLNAR) strains of H. influenzae were found in 10/40 (25.0%) of the strains tested.