Poster Presentation Australian Society for Microbiology Annual Scientific Meeting 2024

Emergence of ciprofloxacin resistant invasive salmonella chester infections in victoria associated with travel, 2022-2023 (#5)

Jessica Barnden 1 2 , Mary Valcanis 2 , Sally Dougall 2 , Cheryll Sia 2 , Norelle Sherry 2 , Benjamin Howden 2
  1. The Microbiological Diagnostic Unit Public Health Laboratory, Melbourne, VIC, Australia
  2. Microbiological Diagnostic Unit Public Health Laboratory, University of Melbourne at the Peter Doherty Institute for Infection and Immunity, Melbourne, Victoria, Australia

In Australia, Salmonellosis cases are often linked to food-borne outbreaks and travel-related illness. Non-typhoidal Salmonella spp (NTS) cause a range of symptoms, commonly self-limiting gastroenteritis, however, some serovars can cause extraintestinal or invasive disease such as septicemia.

The Microbiological Diagnostic Unit Public Health Laboratory (MDU PHL) in Victoria perform Salmonella characterisation for the purpose of surveillance for the Victorian Department of Health.  Between 2022-2023 an increase in Salmonella enterica serovar Chester cases was observed from travellers to Bali, Indonesia. (Fig 1). In 2021 MDU PHL typed 43 S. Chester isolates which then more than doubled to 97 isolates by 2023. Over this time, 16% and 14% of all S Chester isolates received in 2022 and 2023 respectively originated from blood cultures (Fig 2 and Fig 3).  The proportion of bacteraemia S. Chester cases is higher than the 4.9% previously reported in an Australian study from 1979 to 2015 (1).

Of the 159 S. Chester isolates submitted for whole genome sequencing (WGS) the dominant MLST  was ST1954 and cgMLST (core genome MLST) cgT228: 36 (58%) in 2022 and 70 (72%) in 2023.  Prior to 2020, only one S. Chester ST1954 was identified at MDU PHL.

A high level (82%) of the 2022-2023 S. Chester ST1954 cgT228 isolates carried the qnrB19 gene which confers phenotypic resistance to fluoroquinolones. Among the Victorian S. Chester isolates, the only ST that harboured the qnrB19 was ST1954. The next most common MLST, ST343, did not harbour antimicrobial resistance mechanisms.

The increase in the rate of S. Chester bacteraemia, coupled with fluoroquinolone resistance is a concern for therapy and potential treatment failure. 

In 2014-2015 an outbreak of S. Chester ST1954 was investigated by the European CDC which found a link between travel history to Morocco and several food sources (2). The African isolates also harboured qnrB19 or qnrS1 genes. ST1954 has been previously shown to be geographically distinct to the African region (3).

Our aim is to use the whole genome sequencing results to provide a global context of the Salmonella Chester ST1954 seen in Australian residents who have travelled to Indonesia over the 2022-2023 time frame.66039751ebb5c-Figure+1.jpg66039751ebb5c-Figure+2.jpg66039751ebb5c-Figure+3.jpg

  1. (1) Williamson DA, Lane CR, Easton M, Valcanis M, Strachan J, Veitch MG, Kirk MD, Howden BP. Increasing Antimicrobial Resistance in Nontyphoidal Salmonella Isolates in Australia from 1979 to 2015. Antimicrob Agents Chemother. 2018 Jan 25;62(2):e02012-17. doi: 10.1128/AAC.02012-17. PMID: 29180525; PMCID: PMC5786757.
  2. (2) Fonteneau L, Jourdan Da Silva N, Fabre L, Ashton P, Torpdahl M, Müller L, Bouchrif B, El Boulani A, Valkanou E, Mattheus W, Friesema I, Herrera Leon S, Varela Martínez C, Mossong J, Severi E, Grant K, Weill FX, Gossner CM, Bertrand S, Dallman T, Le Hello S. Multinational outbreak of travel-related Salmonella Chester infections in Europe, summers 2014 and 2015. Euro Surveill. 2017 Feb 16;22(7):30463. doi: 10.2807/1560-7917.ES.2017.22.7.30463. PMID: 28230522; PMCID: PMC5322187.
  3. (3) (2) Siira L, Naseer U, Alfsnes K, Hermansen NO, Lange H, Brandal LT. Whole genome sequencing of Salmonella Chester reveals geographically distinct clusters, Norway, 2000 to 2016. Euro Surveill. 2019 Jan;24(4):1800186. doi: 10.2807/1560-7917.ES.2019.24.4.1800186. PMID: 30696528; PMCID: PMC6352000.