Impact of type of wastewater treatment process on the antibiotic resistance of bacterial populations

Abstract

Abstract. Antibiotic resistant bacteria reach the environment directly with faeces, and indirectly with sewage discharged from wastewater treatment plants (WWTPs). The aim of the study was to determine the level of removal of bacteria during wastewater treatment. Samples of untreated and treated sewage were collected from 13 WWTPs with different capacity, modification of treatment and type of inflowing wastewater. Microbiological characterization of the samples included determination of the total number of bacteria resistant (ARB) to β-lactams and tetracyclines as well as the number of Escherichia coli resistant to the same drugs. The counts of ARB and E. coli were determined on TSA and mFc media with/without antibiotic supplementation, respectively. The highest percent of reduction in number of ARB (at least 99.9%) and E. coli (above 99.3%) was obtained for WWTPs with A 2 O system. The lowest percentage reduction of ARB and E. coli was observed for WWTPs operating with SBR system. The lowest number of microorganisms resistant to analyzed antibiotics was observed for ARB and E. coli resistant to cefotaxime and doxycycline. The results indicate a large variation in the removal of antibiotic-resistant bacteria in WWTPs depending on modifications of treatment system and type of inflowing wastewater.

Quantitative Occurrence of Antibiotic Resistance Genes among Bacterial Populations from Wastewater Treatment Plants Using Activated Sludge

“…For this reason, monitoring microbiological pollutant removal effectiveness during wastewater treatment is of particular significance. Results of studies on the number of antibiotic resistant bacteria on culture media were published by Osińska et al [29]. Based on these results, the most frequently occurring bacteria were those that were resistant to amoxicillin and oxytetracycline, i.e., older generation antibiotics.…”

“…The physicochemical parameter values of the analysed wastewater samples and the total number of antibiotic-resistant bacteria and antibiotic resistant E. coli were published by Osińska et al [29]. The average BOD values in the untreated wastewater samples ranged from 401 to 606 mg/L and following the wastewater treatment process they were reduced by 97-99.8%.…”

“…XI, XII, XIII) with an increased nutrient removal mechanical and biological system (see Supplementary Material, Table S1). Wastewater samples were collected in the winter (February) to sterile bottles, transported to the laboratory at a temperature of 4 • C, and subjected to analysis on the day of collection [29]. The sample collection period was selected to correspond with an increased morbidity incidence and, thus, with higher antibiotic consumption.…”

“…Physicochemical parameters of the wastewater samples under study, including five-day Biological Oxygen Demand (BOD), Chemical Oxygen Demand (COD), and Total Suspended Solids (TSS), were assessed simultaneously with a microbiological analysis. The total number of bacteria as well as bacteria resistant to β-lactams (amoxicillin, cefotaxime) and tetracyclines (oxytetracycline, doxycycline) and the total number of Escherichia coli and Escherichia coli resistant to the same drugs were determined according to procedures that were described by Osińska et al [29].…”

“…number of copies = (amount of DNA [ng])× 6.022 × 10 23 average size of genome[bp] × 10 9 × 650 (1) where: 650 g/mole means average molecular weight per base pair, 6.222 × 10 23 /mole is Avogadro's number, including molecules, and 10 9 ng/g is the conversion factor [29]. Standard curves for qPCR were obtained within the range from 10 8 to 10 2 gene copies/µL.…”