A scoping review of antimicrobial resistance in the Australian dairy cattle industry

Abstract

Introduction: Quantification of antimicrobial resistance (AMR) is beneficial to inform policies and direct prudent antimicrobial use.

Aim: This study aimed to assess the current published evidence of AMR from passive and active ad hoc surveillance activities within the Australian dairy cattle industry.

Methods: Following a scoping review framework 373 articles published before January 2023 were retrieved using the keyword search function from two online databases (PubMed® and Web of Science™ Core Collection). The duplicate articles were removed and the title, abstract, and full text of the remaining articles were reviewed following the study objectives and inclusion criteria (location, subject/theme, and data). Data from the remaining articles were extracted, summarised, interpreted and the study quality assessed using the Grades of Recommendations, Assessment, Development, and Evaluation guidelines.

Results: A total of 29 articles dating from the 1960 s until 2022 were identified to meet the study criteria (passive: n = 15; active: n = 14). Study characteristics such as sampling type, sampling method, and AMR assessment were all common characteristics from both passive and active surveillance articles, being milk samples, individual sampling, and phenotypic assessment respectively. Passive surveillance articles had a wider range in both the type of bacteria and the number of antimicrobials investigated, while active surveillance articles included a higher number of bacterial isolates and sampling from healthy populations. There was an overall low level of clinical AMR across all articles. Higher prevalence of non-wildtype Escherichia coli, Salmonella spp., and Staphylococcus spp., although limited in data, was suggested for commonly used Australian veterinary antimicrobials for these bacteria. The prevalence of phenotypic AMR varied due to the health and age status of the sampled animals. The articles reviewed in this study suggest the prevalence of AMR genes was higher for commonly used antimicrobials, although genes were not always related to the phenotypic AMR profile.

Conclusions: Published evidence of AMR in the Australian dairy cattle industry is limited as demonstrated by only 29 articles included in this review following selection criteria screening. However, collectively these articles provide insight on industry AMR prevalence. For example, the suggestion of non-wildtype bacteria within the Australian dairy cattle indicating a risk of emerging or increasing industry AMR. Therefore, further surveillance is required to monitor the development of future AMR risk within the industry. Additionally, evidence suggesting that animals varying in health and age differ in prevalence of AMR imply a requirement for further research into animal population demographics to reduce potential bias in data collated in both national and global surveillance activities.

Keywords: Antimicrobial resistance; Australian dairy cattle; Prevalence of AMR.