FACTORS INFLUENCING COLONISATION AND ANTIBIOTIC-RESISTANCE PATTERNS OF GRAM-NEGATIVE BACTERIA IN HOSPITAL PATIENTS

A total of 300 cultures were obtained from the hands and throats of fifty-six patients admitted to a medical ward. Gram-negative organisms were found in 51% of hand-cultures and 35% of throat-cultures. Klebsiella species were the most commonly isolated organisms (20% of hand and 19% of throat cultures). Compared with colonisation-rates on admission, serial cultures showed an almost fourfold increase in the percentage of hands and more than a twofold increase in the percentage of throats which were positive for klebsiella after two weeks in hospital. This increase in colonisation with klebsiella occurred almost entirely in those patients receiving antibiotics. A quarter of the klebsiella strains were resistant to multiple antibiotics. Of these 15 resistant strains, 14 were isolated from patients receiving antibiotics, and more than a half contained episomal-resistance-transfer factors (R factors). The frequency of R factors was greatest among klebsiella, less among enterobacter, and least among Escherichia coli strains. This study demonstrated the acquisition of resistant gram-negative organisms by patients receiving antibiotics within a hospital environment, and implicates transferable episomes as mediators of antibiotic resistance in a significant proportion of these organisms.