The activity of cefpirome and ten other antibacterial agents against 2858 clinical isolates collected from 20 centres.

Two thousand eight hundred and fifty-eight aerobic clinical isolates of Enterobacteriaceae, Pseudomonas species, staphylococci, streptococci and Haemophilus species were collected in 19 geographically separated centres in the UK and one in Ireland. The identity of each isolate was confirmed at Southmead Hospital and the MIC of cefpirome, cefotaxime, ceftazidime, cefuroxime, cephradine, amoxycillin, piperacillin, imipenem, gentamicin, ciprofloxacin and trimethoprim was determined by an agar dilution method. Against species of Enterobacteriaceae not associated with producing an inducible cephalosporinase, cefpirome had a similar degree of activity to cefotaxime and was more active than ceftazidime and earlier cephalosporins. Against species with a high prevalence of inducible beta-lactamase production, cefpirome was superior to other cephalosporins; imipenem was also active against these isolates. Cefpirome was active against Pseudomonas aeruginosa, methicillin-sensitive staphylococci, non-enterococcal streptococci and Haemophilus spp. When the isolates were exposed to 0.1 mg/L of imipenem in agar plus the test agent, cefpirome had superior activity compared with the other cephalosporins tested for the Enterobacteriaceae, except Proteus vulgaris and Proteus penneri. 8.7% of Enterobacter spp., 7% of Citrobacter spp. and 6.7% of Morganella morganii had susceptibilities to beta-lactams suggesting constitutive hyperproduction of chromosomal cephalosporinase; cefpirome, unlike the other cephalosporins tested, was active against these isolates, although to a lesser degree than against the wild-type inducible isolates. No isolates were thought to produce an extended-spectrum beta-lactamase.