Phenotypic and molecular characterisation of efflux pump genes in clinical isolates of Serratia marcescens

Abstract

Objective: This study focuses on identifying and understanding efflux pump genes in Serratia marcescens bacteria collected from clinical samples. We aimed to ascertain how these bacteria resist antibiotics by characterising their outward features and genetic makeup.

Methods: We examined twenty isolates of S. marcescens, from urinary tract infections, diarrheal cases, and  blood infections. To identify these bacteria, we used standard laboratory tests. We then tested whether they had active efflux pumps with a simple dye-based method called the ethidium bromide-agar cartwheel test. After that, we extracted their DNA and used PCR to look for five specific genes linked to efflux activity: SdeXY-Y, SsmE, SdeCDE-D, SdeAB-B, and LUXR. We applied the usual PCR conditions with primers designed for each gene.

Results: Our results showed that nearly half of the isolates (8 out of 20) had active efflux pumps. The LUXR gene was found in all the bacteria, making it the most common. The SdeCDE-D gene was present in 95% of samples, SdeAB-B in 90%, SdeXY-Y in 60%, and SsmE in 45%. The presence of these genes varied depending on the type of sample, with the highest occurrence in blood and urinary tract infections. To review, we confirmed that multiple efflux pump genes are present in clinical S. marcescens isolates. Notably, LUXR, SdeCDE-D, and SdeAB-B are the most widespread.

Conclusion: These findings suggest that efflux pumps could play an important role in antibiotic resistance, emphasising the need for ongoing genetic monitoring for optimal management of multidrug-resistant infections.