Abstract
The colonization of patients by Klebsiella and several other gram-negative bacteria was studied in a hospital urological ward over a period of six months. Before and during the survey there was no evidence of an outbreak of nosocomial infection and multi-drug resistant strains of Klebsiella were not isolated. Klebsiella were biotyped by nine biochemical tests, which led to the detection of 66 biotypes spread uniformly throughout the survey period. This method of biotyping proved a useful epidemiological tool. The colonization rate of throats, hands, and faeces of patients increased after admission to the ward, especially when antibiotics were used. The effect of systemic antibiotics was greater than that of urinary antibiotics especially on throat and faeces carrier rates. Carrier rates for Klebsiella increased also after catheterization and operation--relationships which could well be multifactorial. During the first two weeks after admission the proportion of antibiotic resistant strains of Klebsiella in carriers increased. The proportion of resistant strains amongst isolations from clinical infections was always greater than among strains isolated routinely from sites of carriage.