Accessory gene regulators and virulence genes associated with the pathogenicity of Staphylococcus aureus from clinical and community settings in Lagos, Nigeria

Nkechi V. Enwuru; Solayide A. Adesida; Christian A. Enwuru; Udoma E. Mendie

doi:10.17159/sajs.2023/10901

Authors

Nkechi V. Enwuru Department of Pharmaceutical Microbiology and Biotechnology, Faculty of Pharmacy, College of Medicine, University of Lagos, Lagos, Nigeria https://orcid.org/0000-0003-2285-0682
Solayide A. Adesida Department of Microbiology, Faculty of Science, University of Lagos, Lagos, Nigeria https://orcid.org/0000-0003-4733-9741
Christian A. Enwuru Centre for Infectious Disease Research, Microbiology Department, Nigerian Institute of Medical Research, Lagos, Nigeria https://orcid.org/0000-0002-1672-1078
Udoma E. Mendie Department of Pharmaceutical Microbiology and Biotechnology, Faculty of Pharmacy, College of Medicine, University of Lagos, Lagos, Nigeria https://orcid.org/0000-0001-9565-3853

DOI:

https://doi.org/10.17159/sajs.2023/10901

Keywords:

accessory gene regulators, pathogenesis, Staphylococcus aureus, superantigens

Abstract

Staphylococcus aureus is a prominent pathogen that causes serious community and hospital-acquired infections globally. Its pathogenicity is attributed to a variety of secreted and cell surface associated proteins that are modulated by the quorum-sensing accessory gene regulator (agr) system. In this study, we investigated the presence of toxin genes and agr involved with S. aureus from clinical samples and apparently healthy individuals. Unequivocal identification of the isolates was obtained with the Vitek 2 system. We screened 70 clinical (CL) and 22 community (C) S. aureus strains for the methicillin resistance (mecA) gene, agr and superantigens (SAg) (enterotoxins and toxic shock syndrome toxin-1) using PCR techniques. A total of 12 clinical isolates were classified as methicillin-resistant S. aureus (MRSA); 89 isolates belonged to one of the four agr groups (agr^1-4), and 3 isolates were non-typeable. Of the agr groups, agr¹ was the most prominent and mostly consisted of isolates from pus/wounds. The methicillin-susceptible S. aureus (MSSA) isolates were distributed within the four agr groups while MRSA strains were restricted to agr¹ and agr³. The most common enterotoxin gene, sei, was likewise more prevalent in MSSA strains than in MRSA strains, where sea predominated. The co-existence of two or more enterotoxins was confirmed in 40% of the isolates. sea occurred through all the agr groups except agr³ and sei was not found in agr¹ and agr⁴. The toxic shock toxin (tst) gene was detected in six MSSA. These findings suggest that MSSA may cause more lethal infections than MRSA because of the increased frequency of toxic genotypes seen in MSSA strains.

Significance:

Isolates in the agr^1,3 groups had more SAg toxin genes, whereas isolates in the agr⁴ groups possessed more tst genes.
The MSSA isolates contained higher proportions of virulence genes than MRSA.
The clinical implications of this discovery include that MSSA may cause more lethal infections than MRSA due to the greater number of toxigenic genotypes discovered.