Mutations in the Quinolones Resistance Determining Regions of gyrA in Nosocomial Staphylococcus aureus and Salmonella typhi

Abstract

In Nigeria, Staphylococcus aureus and Salmonella typhi are common causes of human infections and are also recognized as pathogens of public health significance. This study therefore, sought to determine the incidence and extent of fluoroquinolones resistance of S. typhi and S. aureus isolated from patients in Nigerian Defence Academy Hospital. A total of 60 samples obtained from patients with request for stool microscopy, culture and sensitivity, wound swabs, indoor air of surgical wards and swabbing of working benches were analyzed for the presence of S. aureus and S. typhi. The bacterial isolates were then subjected to antibiotic sensitivity testing using a modified Kirby-Bauer disk diffusion method. The antibiotic susceptibility patterns of S. typhi revealed that some of the isolates were resistant to two or more fluoroquinolones namely: ciprofloxacin, sparfloxacin, ofloxacin and pefloxacin. S. aureus on the other hand, also showed resistance to fluoroquinolones. The isolates that showed resistance to more fluoroquinolones were taken for molecular analysis. The genomic DNA was extracted and amplified using specific primer for gyrA by PCR, visualized using agarose gel electrophoresis and then sequenced. The amplicon sizes were 251bp respectively for each of the isolates. The detection of resistant pattern responsible for fluoroquinolones resistance showed that mutation had occurred. Mutation in nucleotide sequence was detected in gyrA gene of the fluoroquinolone resistant strains.