Beta-lactamase activity and susceptibilities to antibiotics among some species of bacteria isolated from medical institution between December 1999 and February 2000

We studied the beta-lactamase activity and susceptibilities to antibiotics in 604 strains among 10 species of bacteria isolated from 10 medical institutions in Tottori and Shimane Prefectures between December 1999 and February 2000. beta-Lactamase activity was measured by the nitrocefin test and penicillinase/cephalosporinase activities were measured by acidometry. beta-Lactamase activity was detected in 72.1% of S. aureus, 18.8% of H. influenzae, and 96.3% of M. catarrhalis. Penicillinase/cephalosporinase activities were detected in 17.8%/22.2% of E. coli, 9.7%/0.0% of K. pneumoniae, 18.6%/95.3% of E. cloacae, 12.7%/79.4% of S. marcescens, and 7.1%/31.8% of P. aeruginosa. Three of 72 strains (4.2%) of K. pneumoniae and 5 of 90 strains (5.6%) of E. coli were assessed as ESBL-producing bacteria using the NCCLS proposed screening method based on routine susceptibility testing results. BLNAR were detected in 13 of 69 strains (18.8%) of H. influenzae.