Coagulase gene polymorphisms of Staphylococcus aureus isolates from patients at Kosti Teaching Hospital, Sudan

Abstract

Background: Staphylococcus aureus is a common cause of nosocomial infections. Epidemiological typing of S. aureus enables control of its spread. The objective of this study was to investigate coagulase gene polymorphisms of S. aureus isolated from patients at Kosti Hospital in Sudan.

Methods: In total, 110 S. aureus isolates were recovered from 110 patients who were enrolled in the study. S. aureus strains were isolated on blood agar and MacConkey agar and then identified by conventional tests. Resistance to methicillin was determined by detection of the mecA gene. Polymorphism in the coagulase gene (coa) was investigated using PCR followed by AluI RFLP analysis.

Results: Methicillin-resistant S. aureus accounted for 62/110 (56 %) of the isolates. PCR of the coa gene showed two different amplicons, one of 680 bp detected in 83/110 (75.5 %) of the isolates and one of 790 bp detected in 27/110 (24.5 %). When digested with the AluI enzyme, the 790 bp amplicon resulted in three restriction fragments of 500, 210 and 80 bp (coa1). Restriction of the 680 bp amplicon gave two patterns; the first (coa2) was found in 22/110 (20 %) of the isolates and showed four fragments of 210, 210, 180 and 80 bp, and the second (coa3) was found in 61/110 (55.5 %) and revealed three fragments of 390, 210 and 80 bp. Most of the coa3 isolates (75.4%) were methicillin-resistant.

Conclusion: Three polymorphic genotypes of S. aureus were identified in patients at Kosti Hospital. The coa3 genotype was the predominant one and was mostly detected in methicillin-resistant isolates.

Keywords: PCR-RFLP; Staphylococcus aureus; coagulase gene polymorphism; methicillin-resistant.

Fig. 1.

PCR-RFLP analysis of the S. aureus coa gene (representative isolates). (a) Coagulase gene PCR product electrophoresis on 1.5 % agarose gel. Lanes 1 and 2, coagulase PCR product of 680 bp; lane 3, coagulase PCR product of 790 bp; lane 4, negative control; lane 5, ladder. (b) Coagulase gene PCR-RFLP restricted by AluI, electrophoresis on 2% agarose gel. Lane 1, coagulase 680 bp fragmented into three (390, 210 and 80 bp); lane 2, coagulase 680 bp fragmented into four (210, 210, 180 and 80 bp); lane 3, cut of 790 bp into three (500, 210 and 80 bp) fragments; lane 4, negative control; lane 5, ladder.