Genotypic detection of β-lactamase-producing Escherichia coli isolates obtained from Seven Crater Lakes of San Pablo, Laguna, Philippines.

The extended-spectrum β-lactamase (ESBL)-producing Escherichia coli is becoming a global public health concern. More comprehensive surveillance of β-lactam resistance in E. coli would improve monitoring strategies and control resistance transmission in contaminated environments. This study investigated the prevalence of β-lactamase genes in E. coli isolated from the Seven Crater Lakes in San Pablo, Laguna, Philippines. Water samples from lakes were collected for the isolation of E. coli (n = 846) and molecular characterization by detecting the presence of the uidA gene. The isolates were then tested for the presence of β-lactamase genes using PCR. Among the screened genes, bla_AmpC was the most dominant (91%). Other β-lactamase genes such as bla_TEM, bla_SHV, and bla_CTXM were also detected with percentage occurrence of 34, 5, and 1%, respectively. Multiple genes within individual isolates were also observed, wherein bla_TEM/AmpC was the most prevalent gene combination. Moreover, a significant negative correlation between bla_AmpC with bla_SHV and bla_CTXM was depicted in this study. Overall, these findings demonstrate the presence of β-lactamase genes in E. coli in the Seven Crater Lakes of San Pablo and can be used in developing effective strategies to control antibiotic resistance in environmental waters.