SUSCEPTIBILITY OF ALCALIGENES-DENITRIFICANS SUBSPECIES XYLOS-OXYDANS TO BETA-LACTAM ANTIBIOTICS

The susceptibility of 56 clinical isolates and two reference strains of Alcaligenes denitrificans subsp. xylosoxydans to β-lactam agents was tested and related to β-lactamase activity of the strains. The MICs of 12 β-lactams determined by an agar dilution method showed that all the strains were sensitive to imipenem and moxalactam. Forty-one cloxacillin-sensitive β-lactamase producing strains were highly susceptible to azlocillin, piperacillin and ticarcillin, and less susceptible to several cephalosporins (cefamandole, cefoperazone, ceftazidime). The 17 remaining β-lactamase-producing strains, which were sensitive to clavulanic acid and to a lesser extent cloxacillin, had variable resistance to the penicillins tested and synergy was obtained when these penicillins were combined with clavulanic acid or tazobactam. The choice of agents for treatment of infections with this organism must take into account the susceptibility phenotype of clinical isolates. © 1990 Friedr. Vieweg & Sohn Verlagsgesellschaft mbH.