title: Phenotypic and molecular characteristics of methicillin-resistant Staphylococcus aureus isolates from Ekiti State, Nigeria.
abstract: BACKGROUND
  The characteristics and antimicrobial resistance profiles of Staphylococcus aureus differs according to geographical regions and in relation to antibiotic usage. The aim of this study was to determine the biochemical characteristics of the prevalent S. aureus from Ekiti State, Nigeria, and to evaluate three commonly used disk diffusion methods (cefoxitin, oxacillin, and methicillin) for the detection of methicillin resistance in comparison with mecA gene detection by polymerase chain reaction.
  
  
  METHODS
  A total of 208 isolates of S. aureus recovered from clinical specimens were included in this study. Standard microbiological procedures were employed in isolating the strains. Susceptibility of each isolate to methicillin (5 μg), oxacillin (1 μg), and cefoxitin (30 μg) was carried out using the modified Kirby-Bauer/Clinical and Laboratory Standard Institute disk diffusion technique. They were also tested against panels of antibiotics including vancomycin. The conventional polymerase chain reaction method was used to detect the presence of the mecA gene.
  
  
  RESULTS
  Phenotypic resistance to methicillin, oxacillin, and cefoxitin were 32.7%, 40.3%, and 46.5%, respectively. The mecA gene was detected in 40 isolates, giving a methicillin-resistant S. aureus (MRSA) prevalence of 19.2%. The S. aureus isolates were resistant to penicillin (82.7%) and tetracycline (65.4%), but largely susceptible to erythromycin (78.8% sensitive), pefloxacin (82.7%), and gentamicin (88.5%). When compared to the mecA gene as the gold standard for MRSA detection, methicillin, oxacillin, and cefoxitin gave sensitivity rates of 70%, 80%, and 100%, and specificity rates of 76.2%, 69.1%, and 78.5% respectively.
  
  
  CONCLUSIONS
  When compared with previous studies employing mecA polymerase chain reaction for MRSA detection, the prevalence of 19.2% reported in Ekiti State, Nigeria in this study is an indication of gradual rise in the prevalence of MRSA in Nigeria. A cefoxitin (30 μg) disk diffusion test is recommended above methicillin and oxacillin for the phenotypic detection of MRSA in clinical laboratories.
authors.affiliation: Department of Medical Microbiology and Parasitology, College of Health Sciences, Ladoke Akintola University of Technology, Ogbomoso, Nigeria.
authors.forename: Olugbenga Adekunle
authors.initials: OA
authors.lastname: Olowe
authors.forename: Olayinka Oluwatoyin
authors.initials: OO
authors.lastname: Kukoyi
authors.forename: Samuel Sunday
authors.initials: SS
authors.lastname: Taiwo
authors.forename: Olusola
authors.initials: O
authors.lastname: Ojurongbe
authors.forename: Oluyinka Oladele
authors.initials: OO
authors.lastname: Opaleye
authors.forename: Oloyede Samuel
authors.initials: OS
authors.lastname: Bolaji
authors.forename: Abiodun Adebimpe
authors.initials: AA
authors.lastname: Adegoke
authors.forename: Olufunmilola Bamidele
authors.initials: OB
authors.lastname: Makanjuola
authors.forename: David Olusoga
authors.initials: DO
authors.lastname: Ogbolu
authors.forename: Oyebode Terry
authors.initials: OT
authors.lastname: Alli
keywords: MRSA; Nigeria; disk diffusion; evaluation; mecA gene