Primary DNA damage but not mutagenicity correlates with ciprofloxacin concentrations in German hospital wastewaters

Recently, we showed for the wastewater of a large Swiss university hospital that primary DNA damage, assessed by a bacterial SOS repair assay (umuC te st), could be largely assigned to a specific class of antibiotics, the fluo roquinolones (FQs) (Hartmann et al. [1998] Environ Toxicol Chem 17:377-382) . Ln an attempt to confirm the significance of FQs for the bacterial DNA da maging effects in native hospital wastewaters, 25 samples from five German clinics were screened in this study by the umuC test. The results were comp ared to HPLC-derived concentrations of ciprofloxacin, an important member o f the FQs. Ten samples (40%) were umuC-positive and ciprofloxacin concentra tions ranged from 0.7 to 124.5 mu g/L (n = 24). Primary DNA damage, as indi cated by the umuC test, correlated strongly with ciprofloxacin concentratio ns in a logistic, dose-dependent manner (r(2) = 0.896), almost irrespective of the use of S9 metabolic activation. The lowest observed effect concentr ation (LOEC) for ciprofloxacin was 5.2 mu g/L (+S9) and 5.9 mu g/L (-S9). S imilar to our previous findings, these results indicate that positive umuC results in hospital wastewater are strongly dependent on the presence of fl uoroquinolone antibiotics. In a second part of the study, previously genera ted Ames and V79 chromosomal aberration data of the same samples (Gartiser and Brinker [1995] in Umweltbundesamt Texte 74/95) were compared with the n ewly generated results. Neither the mutagenic effects detected by the Ames assay (8%, n = 25) nor the positive V79 results (46% n = 13) seemed to be c aused by ciprofloxacin. Therefore, the Ames and V79 results suggest the pre sence of additional mutagens that are yet to be identified.