INVESTIGATIONS CONCERNING THE EPIDEMIOLOG Y OF MICROBIAL RESISTANCE TO BIOCIDES

In order to estimate the distribution of bacteria and fungi with an el evated level of resistance to antimicrobial substances, we have analyz ed water samples and surveyed institutions presumably concerned with a nalyses of microbial resistance :university institutes for hygiene, he alth authorities) by means of a questionnaire. A total of 41 water sam ples was drawn from various aquatic biotopes in the region of Heidelbe rg. The samples originated from the effluents of a community sewage tr eatment plant, from the Neckar river, from drinking water supplies and from public swimming pools. The following substance groups were inclu ded in a search for bacteria with an elevated resistance to antiseptic s and disinfectants: Aldehydes, biguanides, quaternary ammonium compou nds (QAC), phenols and halogens. Upon determination of the maximal tol erated concentrations to these antimicrobial agents, samples of treate d wastewater effluents showed a considerably higher prevalence of bact eria resistant to formaldehyde, chlorhexidine and QAC. The highest lev els of resistance were found in Pseudomonas aeruginosa, Pseudomonas pu tida, Pseudomonas fluorescens and Enterobacter species. The maximal to lerated level of 0.06 percent formaldehyde by weight was considerably higher than the levels tolerated by the corresponding ATCC reference s trains. The highest levels of resistence to a biguanid/QAC preparation were seen in isolates of Alcaligenes species and Povidencia species, with a maximal tolerated level of 0.5 volume percent. In addition, sev eral isolates of E. coli and Klebsiella species were observed which sh owed a considerably higher level of resistance to the biguanide prepar ation as compared to the corresponding ATCC reference strains. A quest ionnaire was mailed to a series of institutions and companies presumab ly concerned with problems of microbial resistance. Responses were in accordance with our own observations, both with regard to the spectrum of bacteria observed and to the antimicrobial substances concerned.