Heterogeneity in femA in the Indian Isolates of Staphylococcus aureus Limits Its Usefulness as a Species Specific Marker

Rosy Chikkala, Nikhil Oommen George, Kamaraju S. Ratnakar, Ranganathan Natarajan Iyer, Venkataraman Sritharan

Department of Clinical Microbiology, Global Hospitals, Hyderabad, India.
Global Hospitals, Hyderabad, India.
Molecular Diagnostics and Biomarkers Laboratory, Department of Laboratory Medicine, Global Hospitals, Hyderabad, India.

DOI: 10.4236/aid.2012.23013                

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.

Keywords

femA; mecA; nuc; PCR; S. aureus

Conflicts of Interest

The authors declare no conflicts of interest.

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