Seasonal variation of <i>Escherichia coli-</i> harbored <i>bla</i> TEM, <i>bla</i> CTX-M, and <i>bla</i> SHV genes in selected tributaries of Laguna Lake, Philippines

ABSTRACT Water samples from selected Laguna Lake tributaries were collected during the wet and dry seasons. Escherichia coli was isolated from the water samples, and multiplex PCR was performed to detect blaTEM, blaCTX-M, and blaSHV, and assess their seasonal occurrence. Beta-lactamase genes (bla) such as blaTEM, blaCTX-M, and blaSHV are antimicrobial resistance genes (ARGs) of public health concern. These ARGs have been reported to be prevalent in many environments and may vary seasonally. Laguna Lake in the Philippines is fed by its several tributaries with reported failing water qualities. This study reports the seasonal prevalence of E. coli-harbored blaTEM, blaCTX-M, and blaSHV in selected tributaries of Laguna Lake. Water samples were collected during months representing both wet and dry seasons. E. coli isolates were obtained through membrane filtration and selective culturing and confirmed via uidA detection using polymerase chain reaction (PCR). Genotypically confirmed E. coli isolates were subjected to multiplex-PCR to determine the presence of the targeted ARGs. Results showed a higher prevalence of E. coli isolates during the wet season and the overall predominance of blaTEM. These findings confirm the presence of the targeted beta-lactamase genes in E. coli isolates from Laguna Lake tributaries and highlight the importance of continuous monitoring and source tracking of ARGs to enhance environmental management and public health measures.