[The occurrence of antibiotic resistant coliforms in the waste water of a water treatment plant].

Colony counts and total coliforms of the investigated biological treatment plant were decreased by more than 90% on average. In activated sludge processes the colony counts increased, whereas total coliforms did not show significant differences between raw sewage and activated sludge processes. With regard to the antibiotics tetracycline, chloramphenicol, kanamycin and gentamicin raw sewage samples contained on average 10(3) antibiotic resistant coliforms/ml. From agar plates supplemented with antibiotics a total of 896 strains were characterized. Single resistant E. coli strains (29.3%) were isolated most frequently from agar plates supplemented with tetracycline. However, coliforms isolated from agar plates which were supplemented with chloramphenicol, kanamycin and gentamicin showed a prevalent resistance to 5 and 6 antibiotics tested. The variety of resistance patterns of gentamicin-resistant coliforms was determined by few plasmids encoding gentamicin resistance only.