Oral Presentation Australian Society for Microbiology Annual Scientific Meeting 2021

Rapid prospective strain typing to identify unsuspected nonsocomial transmission of MRSA and VRE (#123)

Jessica Johnson-Mackinnon 1 2 , Rosemarie Sadsad 1 , Marc Ramsperger 1 , Cecilia Li 1 3 , Vijay Errappa 3 , Miechelline Magallanese 4 , Kathryn O'Donnell 4 , Nicole Tollhurst 5 , Jennifer Sealy 4 , Elizabeth White 4 , Kathy Dempsey 6 , Patricia Furguson 1 2 4 , Adrian Ong 2 5 , Vitali Sintchenko 1 2 3 , Matthew O'Sullivan 1 2 3
  1. Centre for Infectious Disease and Microbiology, Westmead, NSW, Australia
  2. University of Sydney, Sydney, NSW, Australia
  3. NSW Health Pathology, Sydney, NSW, Australia
  4. Infection Prevention and Control Department - Westmead Hospital, Sydney, NSW, Australia
  5. Infection Prevention and Control Department - Blacktown Hospital, Sydney, NSW, Australia
  6. Clinical Excellence Commission - NSW Health, Sydney, NSW, Australia

Background: Genotyping can reliably identify transmission of nosocomial pathogens but is rarely available in an actionable timeframe to assist infection control interventions. In addition the cost per sequence for routine surveillance can make it prohibitive, requiring cost effective surveillance methods.  

Method: Assessments of potential linked cases of Methicillin-resistant Staphylococcus aureus (MRSA) and Vancomyacin resistant Enterococcus faecium (VRE) reported by Infection Control Practitioners (ICP) were compared with routine binary type surveillance using multiplex PCR and reverse line blot hybridisation assays. Binary type links were identified and ranked using an automated algorithm that considered 1) Matching binary types 2) Binary type frequency 3) Patient proximity and 4) temporal separation.

Result: Linked cases identified by ICP review correlated poorly with those identified by BT-link detection algorithm. Binary type linkage (BT-Links) using RLB recorded 3969 MRSA links and 3898 VRE links with 424 MRSA and 356 VRE considered likely transmission events. Over the same period ICPs reported a total of 273 MRSA links and 304 VRE links of which only 200 MRSA and 127 VRE links had matching binary types. Further only 6 of the MRSA ICP reports and 31 of the VRE ICP reports overlapped with the BT-Links. The BT assays used in this study are suitable for prospectively screening all isolates of MRSA and VRE and are far more efficient at predicting potential infection links.