Oral Presentation Australian Society for Microbiology Annual Scientific Meeting 2023

Defining the role of community transmission in carbapenemase resistance: a five-year case study of blaIMP and blaNDM   (93975)

Georgia P Lynch 1 2 , John Boyce 3 , Nenad Macesic 4 , David T McCarthy 2 5 , Rebekah Henry 1 2
  1. School of Public Health and Preventive Medicine, Monash University, Melbourne, Victoria, Australia
  2. Civil Engineering, Environmental Public Health Microbiology Lab, Melbourne, Victoria, Australia
  3. Biomedicine Discovery Institute, Infection Theme and Department of Microbiology, Monash University, Melbourne, Victoria, Australia
  4. Department of Infectious Diseases, The Alfred Hospital and Central Clinical School, Monash University, Melbourne, Victoria, Australia
  5. School of Civil and Environmental Engineering, Queensland University of Technology, Brisbane, Queensland, Australia

Antimicrobial resistance (AMR) is a pressing global threat with an increasing number of microorganisms becoming resistant to antibiotics. Some antibiotic-resistant strains have been spread between countries viainternational travel.  In 2020-2021, stringent COVID-19 prevention measures were observed to interrupt some AMR transmission pathways. In Australia, the COVID-19 response included significantly decreased cross-border travel, both internationally and within Australia. However, AMR was still observed in clinical cases which were unrelated to self-reported international travel. Organisms of concern being Acinetobacter baumannii, Pseudomonas Aeruginosa and Enterococci spp. This suggests a role for local community transmission.

Melbourne, Victoria’s largest city, was placed under lockdown restrictions for 246 days between February 2020 and September 2021, representing a unique opportunity to investigate community transmission and acquisition of AMR pathogens, pre-, during- and post-lockdown. A study was initiated by the Alfred Hospital, which identified carbapenemase resistance gene types, blaIMP-1 and blaNDM-4, as consistently presented in clinical cases, despite border closures.While some international studies have reported a role for community transmission of these resistance genes, this has not been previously described in Australia. Therefore, this research aimed to understand community transmission of these carbapenemase resistance genes and any changes in transmission associated with the COVID-19 pandemic response. 

Wastewater screening was undertaken as a surrogate for community faecal contributions. Samples were collated from 2017 to 2022 to cover pre-, during- and post-pandemic periods. DNA corresponding to blaIMP was present in wastewater in Melbourne across all sampling timepoints, suggesting that community acquisition may always have played a role in transmission of this plasmid associated gene. DNA sequencing was undertaken to confirm the variants of blaIMP recovered and the specific bacterial genus or genera carrying the gene. Preliminary data indicate that even though the blaNDM was recovered from wastewater samples, the gene was not distributed as widely as the blaIMP gene. This study demonstrates transmission of blaIMP and blaNDM under conditions in which world events prevented the most commonly understood forms of transmission and strongly suggests that there has been previously undetected community transmission of these genes within Australian bacterial isolates for a number of years.