[Combination effect of teicoplanin and beta-lactams on MRSA]

In vitro combination effect of teicoplanin and beta-lactams was investigated against 109 MRSA strains isolated from a variety of clinical specimens at the Social Health Insurance Medical Center during the period from January 1994 through February 2000. TEIC + panipenem (PAPM) was revealed by microbroth dilution method-based checkerboard method, to exhibit synergistic effect of min. FIC index < or = 0.5 against all the 109 strains. The combination of TEIC and flomoxef (FMOX) was shown to have synergistic effect on 108 strains (99.1%). The combination of TEIC and cefepime (CFPM) was shown to have synergistic effect on 96 strains (88.1%). The combination of TEIC and cefmetazole (CMZ) was shown to have synergistic effect on all the 109 strains (100%). The mean value of min. FIC indices obtained from each of the combinations was 0.1259 as to TEIC + PAPM, 0.2019 as to TEIC + FMOX, 0.3257 as to TEIC + CFPM and 0.1995 as to TEIC + CMZ, in other words, the combination of TEIC + PAPM showed the lowest value of all the combinations. While MIC80 was 2.0 micrograms/ml when TEIC was used alone, it was < or = 0.06 microgram/ml when used together with PAPM, and 0.13 microgram/ml when used together with FMOX, respectively. While MIC80 was 3.2 micrograms/ml when PAPM was used alone, it was 0.5 microgram/ml when used together with TEIC. Meanwhile, the value for FMOX was changed from > or = 128 micrograms/ml to 4.0 micrograms/ml. When TEIC was used in combination with CFPM, MIC80 was found to be 0.5 microgram/ml. Similar to the case of the concurrent use with FMOX, the value obtained by combination with CMZ was 0.13 microgram/ml. While MIC80 was 128 micrograms/ml when CFPM was used alone, it was 8.0 micrograms/ml when used together with TEIC, whereas the value for CMZ was decreased from 64 micrograms/ml to 2.0 micrograms/ml. In conclusion, TEIC's antibacterial activity was shown to be accentuated by any of the combinations.