High frequency of SCCmec type V and agr type I among heterogeneous vancomycin-intermediate Staphylococcus aureus (hVISA) in north India. (March 2017) - Singh, Avinash
Highlights: The molecular epidemiology of hVISA and VS-MRSA differs in this geographical region. The distinction between CA-MRSA and HA-MRSA is increasingly becoming blurred. CA-MRSA markers such as SCC mec V and PVL are common in hVISA isolates in this centre. Whether such strains are community-acquired or due to genetic resortment of CA- and HA-MRSA needs further study. Majority of hVISA isolates belonged to agr type I, suggesting its role in reduced vancomycin susceptibility. 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 (SCC mec ) 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 SCC mec 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 SCC mec type II, 17/50 (34.0%) were type III, 3/50 (6.0%) were type IVa and 10/50 (20.0%) were type V. SCC mec type V was significantly associated with hVISA, whereas SCC mec 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.