Molecular characterization of clonal lineage and Staphylococcal toxin genes from S. aureus in Southern Nigeria

Background. The pathogenic role of S. aureus as causative agent of serious infections and food poisoning is on the increase. However, there are few reports on comprehensive analyses of toxins and staphylococcal enterotoxin (SE) genes in S. aureus in Africa. This study analyzed spa types and toxin genes in S. aureus obtained from our previous studies in Southern Nigeria.

Methods. Forty-seven non-duplicate S. aureus isolates were obtained from humans (n = 34) and poultry (n = 13) from previous studies in Southern Nigeria. The strains were analyzed for mecA, selected toxins genes (sea, seb, sec, sed, see, seg, seh, sei, sej, sek, sel, sem, sen, seo, sep, seq, ser, seu), TSST and lukS-PV/lukF-PV by PCR. Population structures of the strains were detected by Staphylococcal protein A (spa) typing.

Results. Twenty three percent of all isolates (47) carried the Panton-Valentine leukocidin (PVl) gene. Two MRSA were detected. Twenty different spa types were obtained, with the highest percentages, 17% belonging to spa type t091 was observed in 4 states from clinical, nasal and poultry samples while t069 is the most prevalent type in poultry. Eighty-nine percent of the all tested isolates harbored at least one staphylococcus enterotoxin. Seo was the most prevalent SE (34%) followed by seg (30%) and sea (21%), while toxic shock syndrome toxin (TSST), seb,sec,,see, sej, sel, sem, and ser, seu were absent in all strains. Spa type t355 was associated with the PVl and complete absence of all studied SE. Sea, seq, seb, sek were associated with spa type 069; t127 was associated with sea while sep was associated with spa type t091. There was coexistence of seo/seg and sei/seg.

Conclusions. We detected a high incidence of enterotoxins and PVl encoding genes in these potential staphylococcal reservoir. Specific toxin genes were observed in particular spa types.