Occurrence of extended Spectrum Beta-Lactamase producing Enterobacteriaceae in wastewater and receiving water bodies.

Abstract

Antimicrobial resistance is taking center-stage in increasing morbidity and mortality, especially in Low- and middle-income countries like Uganda. WHO drew a roadmap to increase antimicrobial resistance surveillance using the One-Health approach so as to attain information about this silent pandemic in an all-encompassing manner. This is because resistance determinants circulate within humans, animals and the environment. The environment acts as a reservoir for antibiotic resistance genes, however, information about antimicrobial resistance in the environment in Uganda is still lacking. Resistance to third-generation cephalosporins is a key priority as they are among the most effective and safest antimicrobials. Therefore, this study set out to determine the presence of ESBL-producing Enterobacteriaceae and carriage of ESBL genes blaCTX-M, blaTEM and blaSHV in wastewater and receiving water bodies. This was a longitudinal study carried out between October 2022 and April 2023, from Mbarara and Gulu city. Wastewater samples were collected from wastewater treatment plants (WWTPs) of Kizungu, Katete and Kakoba of Mbarara City, Gulu City wastewater treatment plant, hospital effluent of Mbarara Regional Referral Hospital and Gulu Regional Referral Hospital. Water samples of receiving waterbodies were collected from river Rwizi and Pece stream upstream and downstream WWTPs. Water samples were also picked from R. Aswa which does not receive wastewater directly from any treatment plant. Samples were filtered, enriched and inoculated on ChromESBL agar plates.The inoculated plates were then incubated 37°C for 24hrs.All pink and blue colonies were subjected to VITEK automated identification system to confirm ESBL-positive E. coli and K. pneumoniae. DNA was extracted from all positive isolates using the ZymoBiomics Kit and conventional PCR was done.All wastewater and receiving water samples from Mbarara study site had at least E. coli or K. pneumoniae isolated. For samples from Gulu study site, all wastewater samples and receiving grew K. pneumoniae but no E. coli. All the four samples from R. Aswa had no E. coli or K. pneumoniae isolated. All the thirty isolates (20 E. coli and 10 K. pneumoniae) carried the blaCTX-M gene while 22 of these also carried the blaTem gene and only 8 carried the blaSHV gene. Findings of this study reveal that ESBL producing Enterobacteriaceae were present in wastewater and its receiving water bodies but not in waterbodies that do not receive wastewater directly. The study recommends improved wastewater treatment that aims at disinfection before discharge. It also recommends further research on genomic relatedness of isolates to track the source in relation to clinical isolates.