Occurrence of Extended Spectrum β-Lactamase (ESBL)-producing Enterobacterales and blaTEM/blaSHV genes in selected well and river water sources in Adamawa-North, Nigeria

Abstract

Enterobacterales are organisms of public health significance that cause opportunistic and severe infections associated with substantial morbidity and increased mortality. This study examined the occurrence of ESBL-producing organisms in water sources in the Adamawa-North Senatorial Zone, Nigeria. Water samples were screened for bacterial growth, and isolates were identified using standard procedures. Enterobacterales isolates were investigated by phenotypic and molecular methods to assess the prevalence of antibiotic resistance genes associated with Extended Spectrum Beta-Lactamase (ESBL) enzymes. Presumptive ESBL producers were identified by disc diffusion testing and confirmed by the double-disc synergy test. Specific Polymerase Chain Reaction (PCR) assays were used to detect the ESBL genes bla_SHV and bla_TEM. A total of 341 bacterial isolates belonging to the order Enterobacterales were recovered from the water samples. Of these, 153 (44.9%) were resistant to ceftriaxone, ceftazidime, or both. Among the 75 phenotypically confirmed ESBL producers, 62 (82.7%) carried at least one of the two tested genes, whereas 13 (17.3%) had neither bla_TEM nor bla_SHV detected. The bla_TEM gene was detected in 43 (57.3%) isolates and bla_SHV in 47 (62.7%), while 28 (37.3%) carried both genes. Co-detection was most frequent in K. variicola (100%), followed by E. cloacae (80.0%), K. oxytoca (50.0%), C. freundii (50.0%), and M. morgani (50.0%). The odds of detecting bla_TEM relative to bla_SHV were 1.33 times higher among isolates from river water than among those from hand-dug wells, although the association was not statistically significant. These findings indicate the widespread occurrence of ESBLs in Enterobacterales from non-clinical sources. Water sources may therefore serve as reservoirs for the dissemination of antibiotic resistance genes, posing a potential risk to the health and safety of the affected communities.