Abstract
BackgroundStaphylococcus aureus is a human colonizer with high potential for virulence, and the spread of the virulent strains from the colonized hosts to non-carriers in the community is on the increase. However, there are few reports on comprehensive analysis of staphylococcal enterotoxin (SE) genes with clonal lineage in S. aureus in Africa. This is essential because of diversity of cultures and habits of the people. This study analyzed spa types and enterotoxin genes in S. aureus strains previously isolated from the human nostrils, poultry and clinical samples in Southern Nigeria.MethodsForty-seven S. aureus isolates were obtained from humans nostrils (n = 13), clinical strains (n = 21) and poultry (n = 13) from previous studies in Southern Nigeria. The strains were analyzed for mecA gene, selected toxins genes (sea, seb, sec, sed, see, seg, seh, sei, sej, sek, sel, sem, sen, seo, sep, seq, ser, seu) and Panton-Valentine leukocidin (PVL) gene (lukS-PV/lukF-PV) by PCR. Population structures of the strains were detected by Staphylococcal protein A (spa) typing.ResultsTwenty different spa types were obtained with the highest percentages, 17% observed in spa type t091 from clinical, nasal and poultry samples while t069 was the most prevalent spa type in poultry. Two MRSA were only detected in human strains. The poultry strains had the highest occurrence of SE genes (18%) followed by nasal strains (15%) and clinical strains (10%). Eighty-nine percent of all tested isolates harbored at least one SE gene; seo was the most prevalent (34%) followed by seg (30%) and sea (21%), while sec, see and sej were absent in all strains. Spa type t355 was associated with lukS-PV/lukF-PV gene and complete absence of all studied SE. Sea, seq, seb, sek were associated with spa type t069; sea was associated with t127 while sep was associated with spa type t091. There were coexistences of seo/seg and sei/seg.ConclusionsThe higher carriage of staphylococci enterotoxin genes by the nasal and poultry S. aureus strains suggests a high potential of spread of staphylococcal food poisoning through poultry and healthy carriers in the community. This is the first report of high occurrence of staphylococcal enterotoxins genes in poultry from Nigeria.
Highlights
Staphylococcus aureus is a human colonizer with high potential for virulence, and the spread of the virulent strains from the colonized hosts to non-carriers in the community is on the increase
The first MRSA strain, FAA014 is a clinical strain with spa type t069 while the second MRSA, FAA044 is a nasal strain with spa type t786 from a healthy carrier in the community (Table 2)
We report predominance of spa type t091 and relatively high occurrence of staphylococcal enterotoxin (SE) genes in S. aureus isolates that had been previously collected in Southern Nigeria
Summary
Staphylococcus aureus is a human colonizer with high potential for virulence, and the spread of the virulent strains from the colonized hosts to non-carriers in the community is on the increase. This study analyzed spa types and enterotoxin genes in S. aureus strains previously isolated from the human nostrils, poultry and clinical samples in Southern Nigeria. The higher carriage of staphylococci enterotoxin genes by the nasal and poultry S. aureus strains suggests a high potential of spread of staphylococcal food poisoning through poultry and healthy carriers in the community. This is the first report of high occurrence of staphylococcal enterotoxins genes in poultry from Nigeria. Colonization of human nares by S. aureus is a risk factor for staphylococcal diseases (Wertheim et al, 2004) and invasive staphylococci infection can have its source in strains occurring naturally in the host. The SE toxins’ genes in S. aureus encode different virulence factors which if expressed, can produce the corresponding enterotoxins
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