Correspondence 703

K. aerogenes strains had a 0-lactamase resem-bling the SHV-type enzyme. It is well docu-mented (Jacobs et al., 1986; Acar, Gutmann & Kitzis, 1988) that sulbactam is much less active than clavulanic acid against such /J-lactamases. In its combinations with ampicillin, ticarcillin, azlocillin, mezlociltin, piperaciUin and apal-cillin, sulbactam caused practically no decrease in the MICs for the strains producing TEM-type and SHV-1-type /Mactamases (Jacobs et at., 1986). Combinations of these /J-lactams with clavulanic acid produced a four-fold or greater reduction in MIC. Arisawa & Then (1982) found that the concentrations of clavu-lanic acid required to reduce the activity of TEM-type /Mactamases by 50 % are much less than the corresponding concentrations of sulbactam. Efforts were earlier made to combine cefoperazone with a fixed amount of sulbactam to extend its antibacterial activity against certain /Mactamase-producing Bacter-oides spp. Using the MIC determination method, Crosby & Gump (1982) showed that the combination of cefoperazone with 2 mg/1 clavulanic acid caused a synergistic effect in 72-4 % of the tested Bacteroides strains, whereas the combination of cefoperazone with 10 mg/1 sulbactam did so only in 65-5 % of the strains. The results we report here support the earlier observations that sulbactam is less active than clavulanic acid against certain /?-lactamases of the family Enterobacteriaceae