Molecular characterization and epidemiology of methicillin-resistant Staphylococcus aureus isolated from clinical samples in Sokoto, Nigeria

Abstract

Objectives: Methicillin-resistant Staphylococcus aureus (MRSA) is a major public health threat and a cause of hospital-acquired and community-acquired infections. This study was undertaken to investigate antimicrobial resistance pattern, the genetic lineage, presence of S. aureus protein A (SPA) gene, and staphylococcal chromosomal cassette mec (SCC mec) types of MRSA isolated from clinical samples sent for microbiological test in major government hospitals in Sokoto. Material and Methods: A total of 90 S. aureus MRSA isolates were collected and confirmed using standard microbiological techniques. Antibiotic susceptibility testing was done using the disk diffusion method; mecA detection and sequencing were carried out. Phylogenetic reconstruction was also done using the molecular evolutionary genetics analysis X software and phylogeny tree constructed by Neighbor-Joining method. SCC mec typing and SPA detection were also done. Results: Of the 90 S. aureus isolates, 42 were found to be MRSA using the cefoxitin disk diffusion, the most potent antibiotic against them was quinupristin/dalfopristin with 83.3% followed by rifampicin with 81.0% and 6 clindamycin with a 71.4%. With 78.6% of the isolates showing resistance to the fluoroquinolone antibiotic ciprofloxacin, tetracycline and gentamicin came in second and third, with 64.3% and 61.9% of isolates showing resistance, respectively. Most of the MRSA isolates were resistant to more than three antibiotics. Polymerase chain reaction showed 36 (85.7%) harbored the mecA gene and of the 36 mecA positive isolates, phylogenetic reconstruction of representative MRSA sequences showed that MRSA sequences in this study clustered in two closest clades suggesting a possible horizontal transfer. Of the 36 isolates, 23 were SCC mec type I, ten were type IV, and three were non-typeable, while the SPA gene was detected in all the isolates amplified. Conclusion: The use of phenotypic and molecular methods in this study provided useful information on antibiotic resistance profile, epidemiology, and molecular characteristics of MRSA isolates in Sokoto Nigeria. The information provided could help in monitoring the evolution of MRSA strains in Nigeria over time.