Ticarcillin/clavulanic acid: determination of minimal inhibitory concentrations against bacterial strains isolated from patients in intensive care units. Comparison with other agents.

A total of 303 bacterial strains isolated from bronchoaspirates of Intensive Care Unit (ICU) patients, collected through June and December 1993, were tested for susceptibility to ticarcillin/clavulanic acid, imipenem, amikacin, ceftazidime, ciprofloxacin and piperacillin. The minimal inhibitory concentration (MIC) for each antibiotic was determined according to the NCCLS, by means of serial dilution on microplates. The isolates, 80.8% of which were beta-lactamase producing strains, belonged to Pseudomonas aeruginosa (79 strains), Pseudomonas fluorescens (8 strains), Xanthomonas maltophila (25 strains), Escherichia coli (16 strains), Klebsiella-Enterobacter-Serratia (KES) (62 strains), Proteus spp. (15 strains), Acinetobacter spp. (22 strains), Moraxella spp. (15 strains), Bacteroides catarrhalis (8 strains), Haemophilus spp. (11 strains), Staphylococcus aureus (32 strains), Enterococcus faecalis (10 strains). The highest rate of susceptibility to ticarcillin/clavulanic acid (100%) was detected among E. faecalis (MIC 2-16 micrograms/ml), B. catarrhalis (MIC 1-4 micrograms/ml) and Haemophilus spp. (MIC 1-4 micrograms/ml). Among the non-fermenting microorganisms ticarcillin/-clavulanic acid showed good activity toward P. aeruginosa and P. fluorescens (86% and 75% respectively). It was also very active against X. maltophilia with a susceptibility of 96%. Susceptibility to the other antibiotics tested was within the range of 16% and 28%.