oa Southern African Journal of Epidemiology and Infection - Stability of GES-type extended-spectrum ß-lactamase genes during antibiotic exposure
Selective antibiotic pressure has recently been implicated in possible selection behind point mutations observed in blaGES-type genes. This study subjected two well-characterised clinical isolates with class 1 integron-borne blaGES-type genes to five days incubation in the presence of minimum inhibitory concentrations (MICs) of 15 different antibiotics, including ß-lactams, aminoglycosides and quinolones. Restriction enzyme analysis and DNA sequencing of blaGES-1 and blaGES-2 and their immediate upstream genetic environments failed to demonstrate any changes compared to non-exposed controls. Short-term exposure of resistant pathogens to the MIC of a single antimicrobial agent is thus unlikely to cause significant changes in these ß-lactamase genes or their immediate genetic regulatory mechanisms.
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