Transferable resistance to gentamicin and other antibiotics in Enterobacteriaceae isolates from municipal wastewater

In two sets of Enterobacteriaceae and Pseudomonas bacteria resistant to at least two antibiotics a distinctly upward trend was found in the incidence of strains resistant to gentamicin. The strains examined were either routine isolates from three municipal wastewater treatment facilities or from the Danube river samples collected near the outlet of municipal sewerage. The resistance to gentamicin points to the representation of strains originating from hospitalized patients and its incidence among wastewater strains is recordable since the summer of 1981. Gentamicin resistance transfer could be demonstrated in a sewage sludge strain of Klebsiella pneumoniae resistant to seven antibiotics and in two multiresistant isolates from the river Danube. Resistance transfers in the case of other antibiotics, especially those susceptible to beta-lactamase (ampicillin, carbenicillin), were demonstrated in 10 out of the 24 di- and multiresistant strains tested. These findings show that both municipal wastewater and water in streams may function as the reservoirs of strains bearing the determinants of transferable resistance. Such strains may play an important role not only in the ecology and epidemiology of R plasmids, but also in the accidental spread of the so-called DNA recombinants that might escape during gene manipulations.