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Updated: Mar 8, 2026
Multiplex PCR Assay for Typing of Staphylococcal Cassette Chromosome Mec Types I to V in Methicillin-resistant Staphylococcus aureus
Published on: September 5, 2013
High frequency of SCCmec type V and agr type I among heterogeneous vancomycin-intermediate Staphylococcus aureus
Avinash Singh1, Kashi Nath Prasad2, Mohibur Rahman2
1Department of Microbiology, Sanjay Gandhi Postgraduate Institute of Medical Sciences, Lucknow 226 014, India; Amity Institute of Biotechnology, Amity University, Lucknow, Uttar Pradesh, India.
Objectives:
The objective of this study was to compare the genetic features of heterogeneous vancomycin-intermediate Staphylococcus aureus (hVISA) and vancomycin-sensitive methicillin-resistant S. aureus (VS-MRSA) isolates.
Methods:
The presence of staphylococcal cassette chromosome mec (SCCmec) types, Panton-Valentine leukocidin (PVL), accessory gene regulator (agr) types, and vanA and vanB genes in hVISA and VS-MRSA isolates was evaluated by PCR. Genetic relatedness was studied by pulsed-field gel electrophoresis (PFGE).
Results:
The distribution of SCCmec types in hVISA was as follows: 13/29 (44.8%) each of types II and V, 1/29 (3.4%) type III and 2/29 (6.9%) type IVa. Among VS-MRSA isolates, 20/50 (40.0%) were SCCmec type II, 17/50 (34.0%) were type III, 3/50 (6.0%) were type IVa and 10/50 (20.0%) were type V. SCCmec type V was significantly associated with hVISA, whereas SCCmec type III showed an association with VS-MRSA (P=0.020 and P=0.001, respectively). The PVL gene was detected in 9/29 hVISA (31.0%) and 13/50 VS-MRSA (26.0%). By PFGE analyses, both hVISA and VS-MRSA strains were found to be clonally unrelated. In hVISA isolates, 24/29 (82.8%) were agr type I, 3/29 (10.3%) were type III and 2/29 (6.9%) were non-typeable. However, in VS-MRSA isolates, 25/50 (50.0%) were type II, 15/50 (30.0%) were type I, 7/50 (14.0%) were type III and 3/50 (6.0%) were non-typeable.
Conclusions:
The study shows that healthcare-associated MRSA strains may harbour community-acquired MRSA genetic markers. The changing molecular epidemiology and role of agr I in reduced vancomycin susceptibility in hVISA requires further investigation.
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