Transferable drug resistance associated with coliforms isolated from hospital and domestic sewage.

The incidence of antibiotic-resistant fecal coliforms in raw and treated hospital and municipal wastes was investigated to determine whether such wastes may serve as reservoirs for the spread of resistant bacteria and resistance transfer factors. Multiple resistance occurred in 87.8% of isolates from hospital and 42.6% of isolates from municipal wastes. Antibiotic resistance was transferable to Escherichia coli and Salmonella cholerae-suis recipient strains from 62.3% of resistant isolates from hospital and 90.9% of resistant isolates from municipal wastes, and from 56.2% of all isolates from hospital and 45.9% of all isolates from municipal wastes. Numbers of multiply-resistant fecal coliforms decreased during passage through a sewage treatment plant, but their proportion did not change appreciably, although proportions exhibiting resistance to 3, 4, 5, 6, and 7 drugs decreased. A study of transfer in sewage indicated that transfer of resistance from donors present in sewage to pathogenic Salmonella strains can occur under appropriate conditions. The data suggest that both raw and treated wastes, and especially those from hospitals, may serve as reservoirs for the spread of antibiotic-resistant bacteria and transferable resistance in the environment.