Ravindra Dotel1, Matthew V N O'Sullivan2, Joshua S Davis3, Peter J Newton4, Gwendolyn L Gilbert2. 1. Centre for Infectious Diseases and Microbiology, Westmead Hospital, University of Sydney, Sydney, NSW, Australia; Infectious Diseases Staff Specialist, Blacktown Hospital, Sydney, Australia. Electronic address: r_dotel@yahoo.com. 2. Centre for Infectious Diseases and Microbiology, Westmead Hospital, University of Sydney, Sydney, NSW, Australia; Marie Bashir Institute for Infectious Disease and Biosecurity, University of Sydney, Sydney, Australia. 3. Menzies School of Health Research, Charles Darwin University, Darwin, Australia; John Hunter Hospital, University of Newcastle, Newcastle, Australia. 4. Clinical Director of Microbiology, and Local Director for NSW Health Pathology, Wollongong Hospital, Wollongong, Australia.
Abstract
BACKGROUND: To better understand the molecular epidemiology of MRSA and to assess the utility of 19-target binary typing we undertook large-scale epidemiological surveillance of MRSA from invasive and non-invasive clinical specimens, and screening swabs. METHODS: Binary typing was performed on clinical MRSA isolates collected in New South Wales (NSW), Australia between 01/01/2012 - 31/12/2017. Binary type (BT) predicted multilocus sequence type (ST) and spa types based on results from isolates which had been characterised by both methods. RESULTS: 7624 MRSA isolates were analysed of which 3581 (47%) were wounds or skin & softtissue isolates (W/SSTI), 2436 (32%) screening swabs, 469 (6%) blood cultures (BC), 780 (10%) others, and 358 (5%) unknown. We identified 731 BTs, 54 spa types, and 31 STs. ST239 was the commonest MRSA clone in 2012 (30%), but it decreased to 7% in 2017 (p <0.001). In contrast, <0.5% of MRSA were ST45 in 2012 compared to 14% in 2017 (p<0.001). An emergence of PVL-positive ST22 was also noted. Of all isolates, 28% (2122/7624) were lukS/PVL positive; the proportion, among prospectively collected isolates increased from 24% (1406/5858) to 33% (1933/5858) between 2012 and 2017 (p <0.0001). 43% (1534/3581) W/SSTI, 20% (95/469) BC and 10% (239/2436) screening swabs were PVL-positive. CONCLUSIONS: A major change in the epidemiology of MRSA was noted with a decline of ST239, an emergence of ST45 and PVL-positive ST22, and a significant increase in PVL-positive isolates. Binary typing can be a useful routine laboratory test for prospective molecular surveillance of MRSA colonisation and infection.
BACKGROUND: To better understand the molecular epidemiology of MRSA and to assess the utility of 19-target binary typing we undertook large-scale epidemiological surveillance of MRSA from invasive and non-invasive clinical specimens, and screening swabs. METHODS: Binary typing was performed on clinical MRSA isolates collected in New South Wales (NSW), Australia between 01/01/2012 - 31/12/2017. Binary type (BT) predicted multilocus sequence type (ST) and spa types based on results from isolates which had been characterised by both methods. RESULTS: 7624 MRSA isolates were analysed of which 3581 (47%) were wounds or skin & softtissue isolates (W/SSTI), 2436 (32%) screening swabs, 469 (6%) blood cultures (BC), 780 (10%) others, and 358 (5%) unknown. We identified 731 BTs, 54 spa types, and 31 STs. ST239 was the commonest MRSA clone in 2012 (30%), but it decreased to 7% in 2017 (p <0.001). In contrast, <0.5% of MRSA were ST45 in 2012 compared to 14% in 2017 (p<0.001). An emergence of PVL-positive ST22 was also noted. Of all isolates, 28% (2122/7624) were lukS/PVL positive; the proportion, among prospectively collected isolates increased from 24% (1406/5858) to 33% (1933/5858) between 2012 and 2017 (p <0.0001). 43% (1534/3581) W/SSTI, 20% (95/469) BC and 10% (239/2436) screening swabs were PVL-positive. CONCLUSIONS: A major change in the epidemiology of MRSA was noted with a decline of ST239, an emergence of ST45 and PVL-positive ST22, and a significant increase in PVL-positive isolates. Binary typing can be a useful routine laboratory test for prospective molecular surveillance of MRSA colonisation and infection.