In vitro sensitivity of hospital strains of Serratia marcescens to chemotherapeutic agents.

The susceptibility of 83 non-pigmented Serratia marcescens strains was determined by an agar dilution technique. They originated from miscellaneous pathological specimens submitted to the diagnostic laboratory during a nosocomial infection outbreak in 1974. All strains were completely resistant to 128 mug/ml of cephalothin, colistin sulphomethate, lincomycin and penicillin G. They were also resistant to clinically attainable concentrations of ampicillin, chloramphenicol, erythromycin, novobiocin and tetracycline. With regard to drugs with some activity 84% of the strains were susceptible to nalidixic acid, 48% to sulphamethoxazole, 57% to streptomycin, 60% to kanamycin, 61% to gentamicin, 85% to co-trimoxazole and 100% to amikacin. Environmental strains isolated from the infected units were strikingly more sensitive than the patient strains.

Pseudomonas putrefaciens as a cause of infection in humans.

Pseudomonas putrefaciens, a strongly H2S-producing pseudomonad, was isolated from 10 human infections over a two-year period. In one patient the organism was repeatedly isolated from a phlegmone developing in the depth of a varicose leg ulcer. This is the first report on the occurrence of Ps. putrefaciens in humans outside the USA and the first to provide the detailed account of a clinical observation where the opportunistic pathogenic role of this unfamiliar organism has been sufficiently documented. Data are presented on the bacteriological properties and on the antibiotic sensitivity of Ps. putrefaciens.