Pilot study of seasonal occurrence and distribution of antibiotics and drug resistant bacteria in wastewater treatment plants in Slovakia.

This work presents environmental and quality-control data from the analyses of 33 antibiotics in influent and effluent water from two waste water treatment plants (WWTPs) in the capital and the biggest city of Slovakia. Seeing that consumption of antibiotics depends on epidemiological season, samples were collected during February and August. Among assessed antibiotics ciprofloxacin and clarithromycin were detected in highest concentrations in influent water. Seasonal changes were observed only in plant A when antibiotic concentrations decreased. On the other hand an increase in some cases was observed in plant B. Insufficient degradation of some macrolides, sulfonamides and trimethoprim was detected according to their higher concentrations in effluent water. Contact of antibiotics in subinhibitory concentrations and sludge bacteria in WWTPs represent the base for the development of significant levels of microbial resistance. Simultaneously, antibiotic resistance of fecal coliforms and fecal streptococci from sewage sludge was evaluated. Majority of coliform bacteria were found to be resistant to ampicillin and gentamicin. A significant seasonal difference was determined only in case of high-level resistance. In summer samples, an increase in the strains resistant to concentrations higher than the resistance breakpoints established by EUCAST and NCCLS was observed. No antibiotic resistance in streptococci was observed. However, as a part of sewage sludge is mixed with compost and utilized in agriculture, better processing of sludge should be considered.