Enterobacteriaceae isolates from clinical and household tap water samples: antibiotic resistance, screening for extended-spectrum, metallo- and ampC-beta-lactamases, and detection of blaTEM,blaSHV and blaCTX-M in Uyo, Nigeria.

Introduction: Infections caused by multidrug-resistant (MDR) bacteria, extended spectrum β-lactamase (ESBL), metallo-β-lactamase (MBL) and AmpC-β-lactamase (AmpC-βL)-producers are increasing globally. This study identified bacteria in clinical and tap water samples and determined the prevalence of MDR, and β-lactamase enzymes and genes.

Methods: Isolates were identified by the Vitek 2 (bioMérieux, France) automated system. Antibiotic resistance and screening for β-lactamase enzymes and genes was done using disc diffusion method and Vitek 2 automated system, CHROMagar-ESBL, combined double disc, inhibition-based method and multiplex polymerase chain reaction, respectively.

Results: The Enterobacteriaceae isolates obtained were Escherichia coli, Klebsiella pneumoniae, Citrobacter freundii, Salmonella spp., Proteus mirabilis, Enterobacter aerogenes, Shigella sonnei, Proteus vulgaris, Enterobacter sakazakii, Klebsiella oxytoca, Citrobacter diversus, and Serratia liquefaciens. Of the 674 isolates from clinical samples, 36.5%, 28.5%, and 19.9% were ESBL, MBL, and AmpC-βL producers, respectively. A low prevalence of AmpC-βL and MBL producers were obtained, with no significant difference (p<0.05) between the prevalence of ESBL and non-ESBL producers. Isolates exhibited varied levels of resistance to gentamicin, amoxicillin-clavulanic acid, ciprofloxacin, and tetracycline. The results showed that 54.6% of ESBL producers, 57.9% of MBL producers, and 62.8% of AmpC-βL producers were MDR strains. Of the 141 representative isolates tested, 36.9%, 15.6%, and 20.6% had only bla_TEM, bla_SHV, and bla_CTX-M, respectively; 5.7% possessed both bla_TEM and bla_SHV; 7.1% possessed both bla_TEM and bla_CTX-M and 4.3% had both bla_SHV and bla_CTX-M.

Conclusions: This study found a high prevalence of β-lactamase producers, indicating the need for further research on the molecular epidemiology of β-lactamase producers and their impacts in the region.