Incidence of antibiotic resistance and transmissible R factors in the gram-negative bowel flora of hospital patients on admission.

Stool specimens obtained on admission of 95 patients to a male urological ward were examined quantitatively for antibiotic-resistant gram-negative aerobic bacteria. All patients excreted resistant strains of some kind; 67% resistant Escherichia coli strains. Organisms resistant to sulphonamides, tetracyclines, and streptomycin occurred at a frequency of 10(-3)-10(-4). Ampicillin resistance was encountered most frequently, i.e. greater than 10(-2), whereas organisms resistant to chloramphenicol were found less often (10(-6)). Transmissible R factors were demonstrated in 53/121 (44%) resistant E. coli strains. A connection between tetracycline resistance and ability to transfer resistance was demonstrated. Resistance to chloramphenicol did not occur as a single resistance trait but was transferred from all strains resistant to this antibiotic.