Avinash Singh1, Kashi Nath Prasad2, Mohibur Rahman3, Ravi Prakash Rai3, Satyendra Kumar Singh3, Janmejai Kumar Srivastava4. 1. Department of Microbiology, Sanjay Gandhi Postgraduate Institute of Medical Sciences, Lucknow 226 014, India; Amity Institute of Biotechnology, Amity University, Lucknow, Uttar Pradesh, India. 2. Department of Microbiology, Sanjay Gandhi Postgraduate Institute of Medical Sciences, Lucknow 226 014, India. Electronic address: kashinprasad@gmail.com. 3. Department of Microbiology, Sanjay Gandhi Postgraduate Institute of Medical Sciences, Lucknow 226 014, India. 4. Amity Institute of Biotechnology, Amity University, Lucknow, Uttar Pradesh, India.
Abstract
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.
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.