Oral Presentation Australian Society for Microbiology Annual Scientific Meeting 2024

Characterisation of a novel Integrative Conjugative Element in multi-drug resistant Pasteurella multocida Sequence Type 394 circulating within feedlot cattle affected with Bovine Respiratory disease in Australia (104554)

Piklu Roy Chowdhury 1 , Tamara Alhamami 2 , Henrietta Venter 3 , Tania Veltman 2 , Mandi Carr 2 , Joanne Mollinger 4 , Darren J Trott 2 , Steven P Djordjevic 1
  1. Australian Institute for Microbiology and Infection, University of Technology Sydney, City Campus,, Sydney, NSW, Australia
  2. Australian Centre for Antimicrobial Resistance Ecology, School of Animal and Veterinary Sciences, University of Adelaide, Roseworthy Campus,, Roseworthy, SA, Australia
  3. Clinical Health Sciences, University of South Australia, Adelaide, SA, Australia
  4. Department of Agriculture and Fisheries, Health and Food Sciences Precinct, Coopers Plains, QLD, Australa

Pasteurella multocida is one of the major bacterial pathogens associated with Bovine respiratory disease (BRD) in feedlot cattle globally and costs the Australian feedlot industry > $40 million annually. Antimicrobial resistance in BRD causing bacterial pathogens is on the rise; and multi-drug resistance is a significant threat in North America due to the widespread dissemination of mobile genetic elements called integrative conjugative elements (ICEs) containing multiple drug resistance genes. Antibiotics used to treat BRD in Australia include tulathromycin, tetracycline, tilmicosin and ceftiofur. In a recent survey (2014-2019) of P. multocida isolated from post-mortem lung swab of cattle from New South Wales, Queensland, South Australia, and Victoria, we identified four isolates which were resistant to tilmicosin, tetracycline and aminopenicillins. Genomic epidemiology revealed clustering of resistance genes in isolates that presented the multi-drug resistant phenotype, all of which were representatives of multi-locus sequence type (ST)394, which currently predominates in Australia. Analysis of the genetic context of the clustered resistance genes in a representative isolate, P. multocida 17BRD-035, and risk assessment of their ability to disperse laterally, led to the identification of novel ICE, ICE-PmuST394. The element houses a resistance module carrying two variants of the blaROB gene, blaROB-1 and blaROB-13, and the recently characterised macrolide esterase gene, estT. The resistance gene combination on ICE-PmuST394 accounted for resistance to ampicillin and tilmicosin, but not to tulathromycin and tildipirosin. ICE-PmuST394 was also identified in three other isolates (two ST394s and a ST125) in Australia and is also likely present in P. multocida ST79 in the USA. Our analysis suggests that ICE-PmuST394 is circulating locally both by clonal expansion and horizontal transfer, but is currently restricted to a single feedlot in Australia. Although ICE-PmuST394 carries a limited number of unusual antimicrobial resistance genes, it carries sites that are known hotspots for genomic recombination. The element has a unique molecular marker, which could be exploited for genomic surveillance purposes.The element is amenable to hosting more resistance genes, and its presence (or dispersal) should be regularly monitored locally and globally.

  1. 1. Roy Chowdhury P, Alhamami T, Venter H et al. Identification and evolution of ICE-PmuST394: a novel integrative conjugative element in Pasteurella multocida ST394. J Antimicrob Chemother 2024. 2. Roy Chowdhury P, Alhamami T, Venter H et al. Complete Genome Sequence of Pasteurella multocida Sequence Type 394, Isolated from a Case of Bovine Respiratory Disease in Australia. Microbiol Resour Announc 2022; 11: e0089021. 3. Alhamami T, Roy Chowdhury P, Venter H et al. Genomic profiling of Pasteurella multocida isolated from feedlot cases of bovine respiratory disease. Vet Microbiol 2023; 283: 109773.