Molecular Identification of Staphylococcus aureus Complex Strains and Evaluation of Methicillin Resistance Among Human Community Isolates from Biological Samples at Angré Hospital University in Abidjan, Côte d’Ivoire
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The Staphylococcus aureus complex is a group of bacterial species that share several biological and pathogenic characteristics. It mainly includes Staphylococcus aureus , as well as closely related species such as Staphylococcus argenteus and Staphylococcus schweitzeri. S. schweitzeri is the only species in this complex that predominantly occurs in African fauna. However, data on a possible transmission of S. schweitzeri to humans are still limited. From a phenotypic perspective, differentiating the species within the S. aureus complex remains challenging, which may obscure the true diversity of the complex. As a result, strains identified as S. aureus might belong to other species. This study aimed to determine the distribution of S. aureus complex species and the methicillin resistance rate among clinical isolates collected in Abidjan. Methods: We analyzed 330 clinical strains previously identified as S. aureus using conventional phenotypic methods. This was supplemented by conventional PCR assays targeting the nuc gene and the NRPS gene, which allows discrimination among members of the complex. Methicillin-resistant S. aureus (MRSA) was detected using the cefoxitin disk diffusion test, and the presence of the mecA gene was assessed by PCR in MRSA-positive isolates. Results: All isolates tested positive for the nuc gene (270 bp), and 96.97% were positive for the NRPS gene (160 bp). S. aureus was confirmed in 317 isolates (>96%). MRSA accounted for 50.30% of all isolates, with a statistically significant increase in MRSA prevalence with age and department hospital (p = 0.00049, P=0.0001857). Conclusion: PCR detection of the nuc and NRPS genes confirmed that nearly all isolates belonged to the S. aureus species. Therefore, our data suggest that S. schweitzeri has not yet been able to cross the species barrier to humans in Côte d’Ivoire. Over half of the biological samples from the university hospital contained methicillin-resistant S. aureus strains, highlighting a significant public health concern.
Author summary
S. aureus belongs to the S. aureus complex, along with, for example, S. schweitzeri and S. argenteus . While much is already known about S. aureus , knowledge about the pathogenicity and spread of S. schweitzeri , which has so far mainly been found in monkeys and fruit bats in sub-Saharan Africa, is still very limited. It is not yet known whether it is a zoonotic pathogen. This is the first study in Côte d’Ivoire in which molecular tools were used to differentiate S. aureus from other closely related species in clinical samples collected from a hospital in Abidjan, the capital city. Two genes, nuc and NRPS, were targeted to determine the species present. We confirmed that almost all of our samples were positive for S. aureus and negative for S. schweitzeri . This suggests that S. schweitzeri has not yet evolved the ability to transmit from animals to humans and cause infection. However, more than half of the bacteria were resistant to the important antibiotic methicillin, posing a real public health problem. These results highlight the need to improve local surveillance of bacterial infections to enable them to be better understood and treated.
