Phenotypic and molecular characteristics of methicillin-resistant Staphylococcus aureus isolates from Ekiti State, Nigeria

Abstract

IntroductionThe 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.Materials and methodsA 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.ResultsPhenotypic 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.ConclusionWhen 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.

The Effect of Cu-BPDCA-Ty on Antibacterial Activity and The Expression of mecA Gene in Clinical and Standard Strains of Methicillin-Resistant Staphylococcus aureus

“…Molecular methods are the most accurate diagnostic methods. Detection of mecA gene is a gold standard test for MRSA, which is due to the simplicity and repeatability of the molecular methods such as PCR (23). In the present study, like other similar studies, MRSA was detected using the molecular method of PCR of mecA gene, which confirms the results of previous researchers (24).…”

Assessment of five phenotypic tests for detection of methicillin-resistant staphylococci in Cotonou, Benin

“…We observed that oxacillin disk diffusion tests had the lowest performances. This finding is in agreement with other studies (Boutiba-Ben Boubaker et al, 2004;Majouri et al, 2007;Datta et al, 2011;Olowe et al, 2013). Despite these similar findings, these tests are still in the 2012 recommendations of the French Society of Microbiology and are being used in several laboratories in sub-Saharan African countries like Benin (Seydi et al, 2004;Affolabi et al, 2012).…”

“…In addition, most of these studies were restricted only to S. aureus while non-aureus Staphylococcus species were not included. Furthermore, cost of tests which is an important parameter in developing countries, was not also assessed (Mohanasoundaram et al, 2008;Olowe et al, 2013).…”

Molecular Detection of Methicillin Resistance Genes from Clinical Sources and Hospital Environments

“…Oxacillin and methicilin are hardly used in our setting as compared with the Iranian study which noted the rampant use of oxacillin. Our report is however similar to observations by Olowe et al and Terry et al in Osogbo, Nigeria, where 40.4% of S. aureus clinical isolates were resistant to oxacillin [17][18]. The study also shows that majority of staphylococcal isolates were multidrug resistant, seventy-one to ninety-five percent and 51-72% exhibited multi-drug resistance among clinical samples and hospital environments respectively.…”