Pseudomonas cepacia: the sensitivity of nosocomial strains to new antibiotics

Pseudomonas cepacia, considered a phytopathogenic organism for many years, has been shown recently to be widely distributed geographically. The hospital environment has become an important source of this organism but the resistance of Ps. cepacia to most antibiotics has made the treatment of infections a problem. One hundred per cent of the strains tested have proved to be sensitive to the sulphonamides and to novobiocin, 93.0% to the combination of trimethoprim and sulfamethoxazole (co-trimoxazole); 85.2% to minocycline; 77.8% to chloramphenicol and dibekacin and 44.4% to nalidixic acid. One hundred per cent of the strains exhibit resistance to ampicillin, cephalothin, cefamandole, cefoxitin, colistin, cefuroxime, tetracycline and cefazolin; 88.9% to amikacin, tobramycin and sisomycin; 85.2% to carbenicillin. The new beta-lactams, apalcillin, ceftazidime, N-formimidoyl-thienamycin, piperacillin, cefotaxime and azlocillin proved to be the most potent of the molecules tested, inhibiting 90% of the strains, at concentrations of 4, 8, 8, 8, 32 and 16 mg/l and 100% of the strains at 8, 16, 16, 32, 32 and 64 mg/l, respectively. In contrast to the usual sensitivity patterns of Pseudomonas spp, Ps. cepacia has been shown to be resistant to colistin, cefsulodin and the aminoglycosides. However, unlike Ps. aeruginosa, Ps. cepacia has been shown, by the dilution method, to be sensitive to co-trimoxazole, 92.3% of the strains being inhibited by 16 mg/l.