[Antimicrobial susceptibility and beta-lactamase productivity of recent clinical isolates during the period between December 1999 and February 2000].

: Antimicrobial susceptibility testings of 24 antimicrobial agents against 605 clinical strains belonging to 10 species were carried out according to the micro-broth dilution method of NCCLS M7-A4. The productivity of beta-lactamase was also determined against them isolated at 8 medical facilities in Nagano prefecture, Japan during the period between December 1999 and February 2000. When applied the nitrocefin method, beta-lactamase productivity was demonstrated to be positive for 89.2% of 74 S. aureus, 4.3% of 94 H. influenzae, and 100% of 69 M. (B.) catarrhalis isolates. On the other hand, when used the acidometry method, penicillinase/cephalosporinase were found to be positive for 21.2%/9.6% of 52 E. coli, 29.0%/3.2% of 31 K. pneumoniae, 53.2%/100% of 47 E. cloacae, 0%/11.1% of 99 S. marcescens, and 25.9%/55.6% of 54 P. aeruginosa isolates, respectively. Among the beta-lactamase-producers including P. aeruginosa isolates, only 2 E. coli isolates were found to be ESBL-producers. Besides, 9.6% (9/94) of H. influenzae isolates were proved to be BLNAR strains.