Susceptibility of 100 strains of Stenotrophomonas maltophilia to three beta-lactams and five beta-lactam-beta-lactamase inhibitor combinations.

One hundred clinical strains of Stenotrophomonas maltophilia were investigated for their susceptibility to ticarcillin, piperacillin, ceftazidime and five combinations with beta-lactamase inhibitors (clavulanic acid, tazocillin or sulbactam) at three concentrations; 26% of the strains were susceptible to ticarcillin, 23% to ceftazidime and 12% to piperacillin. Eighty-two percent of the strains were susceptible to ticarcillin/clavulanic acid. In most cases, no synergy was observed with tazobactam or sulbactam. For eight ticarcillin-susceptible strains, antagonism was observed between ticarcillin and clavulanic acid.