Abstract
Increase in prevalence of MRSA worldwide and hence the need for rapid detection, have led to use of molecular methods for confirmation of the species and also MRSA. Species specific markers like fem or nuc along with the methicillin-resistance determinant, mecA, have been used by several investigators worldwide for the identification of MRSA. In the current study, we have screened 54 microbiologically confirmed (MRSA, MSSA and CoNS) isolates for the presence of mecA, 16S rRNA, femA and nuc markers. While mecAPCR and 16S rRNAPCR results were consistent with other studies, femA and nuc showed dramatic variation in detection rate (sensitivity) of S. aureus 29.6% and 53.7% respectively. Evidences are presented to demonstrate the absence of femA. Our attempt to amplify the complete femA gene using sequences flanking femA further confirmed these results and also indicated that variations exist even in the genomic sequences around femA. Our data reveals the need for exercising care while using primers designed on sequences of constitutive genes like femA and nuc for PCR based identification of S. aureus species. Though geographic variations in the genome of S. aureus have previously been reported from around the world, we present here evidence for the first time from India for absence of femA and also for probable variations in the sequences around the femA gene in clinical isolates of S. aureus.
Highlights
Staphylococcus aureus is one of the major causes of wide spread gram positive bacterial nosocomial infections, especially the post-surgical wound infections [1]
In this study, during our screening for methicillin resistance markers in clinical isolates, we observed that the femA species specific marker failed to amplify in several isolates
We present evidence to show that femA cannot be used as a reliable marker for S. aureus in this geographical region
Summary
Staphylococcus aureus is one of the major causes of wide spread gram positive bacterial nosocomial infections, especially the post-surgical wound infections [1]. The discovery of penicillin proved to be a major breakthrough in treating these infections, with it had emerged a major concern; the notorious ability of Staphylococcus aureus to develop resistance to antibiotics and remain nonresponsive to treatment [3]. After the introduction of methicillin, reports of Methicillin-resistant Staphylococcus aureus (MRSA) had begun to surface within hospitals in the early 1960s, which are increasingly prevalent worldwide [4,5]. Such endemic MRSA infections are difficult to eradicate and remain active reservoirs of infection thereby increasing the hospital costs, length of hospital stays, morbidity and mortality
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