Prevalence of seg, seh and sei Genes among Clinical and Nasal Staphylococcus aureus Isolates in Palestine

Aims: To investigate the presence of the staphylococcal enterotoxin genes seg, seh and sei among clinical and nasal isolates.
Place and Duration of Study: Department of Biology and Biotechnology, An-Najah N. University, Palestine, in 2011.
Methodology: A total 124 S. aureus isolates were collected, forty three were nasal and 81 were clinical isolates. PCR technique was used to detect enterotoxin genes seg, seh and sei, mecA gene and analysis of SCCmec types. Enterotoxigenic strains were also typed using coagulase typing kit.
Results: Fifty two (41.9%) isolates were positive for one or more of these enterotoxin genes. The prevalence of toxin genes among S. aureus isolated from nasal swabs 25/43 (58.1%) was higher than those isolated from clinical samples 27/81 (33.3%). Combination of the toxin genes was noted only in MSSA isolate from both nasal swabs and clinical samples. Distribution of toxin genes in MSSA isolates was higher (49.5%) than those in MRSA isolates (21.2%). SCCmec typing showed that the MRSA enterotoxigenic strain were belonged to types II, III and IVa. MRSA strains were found to belong to coagulase serotypes II, III and VII, while MSSA strains were belonged to serotypes II-VII. In nasal samples, 16/25 (64.0%) of enterotoxigenic strains showed the genotype seg+/sei+, while in clinical samples 1/27 (3.7%), 1/27 (3.7%) and 3/27 (11.1%) of enterotoxigenic strains showed the genotypes seg+/seh+, seg+/sei+ and seg+/seh+/sei+, respectively. This study showed that the majority of the isolates 42/124 (33.9%) were seg+, while none of nasal strains harbored seh gene.
Conclusion: The prevalence of seg, seh and sei genes in the S. aureus isolated from nasal swabs differed significantly from those obtained from clinical samples, as well as the prevalence of the same genes in MSSA differed significantly from those in MRSA. In addition, S. aureus isolates from clinical and nasal swabs could serve as a possible reservoir of newly described seg, seh and sei genes.