Comparative in-vitro activity of cefsulodin and ceftazidime against ticarcillin-resistant Pseudomonas aeruginosa

The in-vitro antibacterial activity of ceftazidime was compared with that of cefsulodin and ticarcillin against 140 strains of Pseudomonas aeruginosa. Against 123 clinical isolates, geometric mean MICs were 1499mg/l for ticarcillin, 15 mg/l for cefsulodin and 2.1 mg/l for ceftazidime. Against constitutive beta-lactamase producers (93 strains), and according to the type of enzyme (TEM-1, carbenicillinases, oxacillinases), ceftazidime had similar activity but MICs of cefsulodin were particularly affected by highly ticarcillin-resistant (carbenicillinase pIs 53, 5.7 and 575) strains. Against ticarcillin-resistant (constitutive beta-lactamase non-producers) and ticarcillin-susceptible strains, the MICs of ceftazidime were slightly lower than those of cefsulodin.