ANTIBACTERIAL ACTIVITIES OF NEW QUINOLONES AGAINST FRESH CLINICAL ISOLATES

In order to investigate antibacterial activities of new quinolones (NQs) against a number of clinical isolates obtained in our laboratory during a period from February, 1993 to January, 1994, minimum inhibitory concentrations (MICs) were determined using most of the NQs available in the market as of December, 1993. The obtained results are summarized as follows: 1. Noticeable differences were observed among the antibacterial activities of 8 different NQs tested against Gram-positive bacteria, i. e., there were large differences in their MIC distributions. Some differences were also observed among different NQs in ratios of NQ-resistant strains among Staphylococcus spp. From these results, it seems necessary to further study tolerance mechanisms of these Gram-positive bacteria toward different NQs and also to examine possible differences in antibacterial activities among different NQs against Gram-positive bacteria in clinical settings. 2. MIC distributions against Gram-negative bacteria were also different among the 8 NQs tested. Though elevated MICs were observed against NQ-resistant Gram-negative bacteria in many cases, and somewhat higher, though not exceedingly high, MIC values than those against NQsensitive bacteria were found in other cases, patterns of MIC values against different NQ-resistant Gram-negative bacteria were similar for all of the 8 NQs tested. This may explain the fact that most of NQ-resistant Gram-negative bacteria showed similar resistant patterns to the 8 NQs tested. 3. Among the NQ-resistant bacteria, were found Haemophilus influenzae and Neisseria gonorrhoeae strains. Ratios of resistant strains were approximately 10% or lower for the former and approximately 20% for the latter. 4. With MICs of ampicillin and cefaclor used as control, it appears that benzylpenicillin (PCG)-insensitive or PCG-resistant Streptococcus pneumoniae (PISP or PRSP) and CEPs-resistant Escherichia coli are increasing.