Antibiotic resistance study in wastewater treatment plants. Comparative between molecular biology and culture plate


Duran Mestre, Núria


Antibiotic resistance is a growing concern in our society, a fact that originates in the domestic, medical, and intensive livestock sectors. Once administered, the antibiotics are excreted through urine and faeces to wastewater and directly to wastewater treatment plants (WWTPs). The fact that pathogens and antibiotic resistance are found in high concentration in WWTPs makes it more important to treat and disinfect water in order to reduce contamination in the effluent of the plant. Both antibiotic resistant bacteria (ARB) and antibiotic resistance genes (ARG) play a very important role in monitoring water disinfection.
The objective of this project was to evaluate wastewater antibiotic resistance by comparing influent and effluent from the Sant Celoni WWTP plant using molecular biology and plate cultures. The resistance to the following antibiotics has been evaluated: oxytetracycline (OTC), ampicillin (AMP), trimethoprim (TRIM), sulfamethoxazole (SMX) and ciprofloxacin (CIP). The resistance was evaluated through molecular biology and qPCR for detecting ARG and through microbial growth in plaque cultures for quantifying ARB.
There is more presence of ARG and ARB in the influent than effluent. Microbiological analysis confirms the selectivity of Chromogenic agar against TSA. In both cultures the order of resistance percentage from lower to higher is as follows: OTC, TRIM, AMP, SMX and CIP. In molecular biology analysis, on the other hand, the order of resistance percentage from lower to higher is as follows: OTC, SMX, AMP, CIP and TRIM. It is concluded that on the one hand the disinfection system of the Sant Celoni WWTP in ARG is
satisfactory and that the highest antibiotic resistance bacteria coincides with the oldest antibiotics: CIP, SMX and AMP. On the other hand, the results obtained from ARB and ARG agree in some antibiotics, but not enough to state that both methods can provide similar results.



Auset Vallejo, María


IQS SE - Undergraduate Program in Biotechnology