Partial purification and environmental application of CTX-type ESBL beta-lactamases from wastewater-derived E. coli isolates

BACKGROUND: Extended-spectrum beta-lactamases (ESBLs) of Escherichia coli give rise to resistance to broad-spectrum beta-lactam antibiotics, making treatment difficult clinically and complicating environmental management. Understanding hospital effluent as a reservoir and dissemination route for these resistant enzymes is therefore very vital. METHODS: The crude beta-lactamase enzyme extracts were partially purified by ammonium sulfate precipitation and Sephadex G-100 gel filtration chromatography, enzyme activity was assessed for observed degradation of ceftriaxone by UV spectrophotometry. Protein content was quantified by the Lowry method, and enzyme purity analyzed by SDS-PAGE. The ability of the partially purified enzymes to degrade ceftriaxone in hospital wastewater was also assessed. RESULTS: Crude enzyme extracts showed appreciable ceftriaxone degradation activity. Partial purification enhanced the specific activity of the enzyme while significantly reducing contaminating proteins. SDS-PAGE indicated a reduction in protein bands after purification. Partially purified enzymes showed remarkable ceftriaxone degradation in buffer and remained active, albeit to a lesser degree, in hospital wastewater. CONCLUSION: This study demonstrates the partial purification and characterization of CTX-type ESBL beta-lactamases from E. coli isolates obtained from wastewater. Partially purified enzymes remain active and have potential for application in reducing -beta-lactam antibiotics in hospital wastewater, thus proposing an environmental approach for curbing antibiotic resistance.