Journal Articles

Permanent URI for this collectionhttps://mro.massey.ac.nz/handle/10179/7915

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Author: search.filters.author.French NPSubject: search.filters.subject.Staphylococcus aureus

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    Zoonotic transmission of asymptomatic carriage Staphylococcus aureus on dairy farms in Canterbury, New Zealand.
    (Microbiology Society, 2024-12-04) Straub C; Taylor W; French NP; Murdoch DR; Priest P; Anderson T; Scott P
    Zoonotic pathogen transmission is of growing concern globally, with agricultural intensification facilitating interactions between humans, livestock and wild animals. Staphylococcus aureus is a major human pathogen, but it also causes mastitis in dairy cattle, leading to an economic burden on the dairy industry. Here, we investigated transmission within and between cattle and humans, including potential zoonotic transmission of S. aureus isolated from cattle and humans from three dairy farms and an associated primary school in New Zealand. Nasal swabs (N=170) were taken from healthy humans. Inguinal and combined nasal/inguinal swabs were taken from healthy cattle (N=1163). Whole-genome sequencing was performed for 96 S. aureus isolates (44 human and 52 cattle). Multilocus sequence typing and assessments of antimicrobial resistance and virulence were carried out. Potential within- and across-species transmission events were determined based on single nucleotide polymorphisms (SNPs). Thirteen potential transmission clusters were detected, with 12 clusters restricted to within-species and one potential zoonotic transmission cluster (ST5). Potential transmission among cattle was mostly limited to single age groups, likely because different age groups are managed separately on farms. While the prevalence of antimicrobial resistance (AMR) was low among both bovine and human isolates, the discovery of an extended-spectrum beta-lactamase gene (bla TEM-116) in a bovine isolate was concerning. This study provides evidence around frequency and patterns of potential transmission of S. aureus on dairy farms and highlights the AMR and virulence profile of asymptomatic carriage S. aureus isolates.
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    The Genetic Relatedness and Antimicrobial Resistance Patterns of Mastitis-Causing Staphylococcus aureus Strains Isolated from New Zealand Dairy Cattle
    (MDPI (Basel, Switzerland), 2021-11-22) Greening SS; Zhang J; Midwinter AC; Wilkinson DA; McDougall S; Gates MC; French NP; Butaye P
    Staphylococcus aureus is one of the leading causes of bovine mastitis worldwide and is a common indication for use of antimicrobials on dairy farms. This study aims to investigate the association between on-farm antimicrobial usage and the antimicrobial resistance (AMR) profiles of mastitis-causing S. aureus. Whole-genome sequencing was performed on 57 S. aureus isolates derived from cows with either clinical or subclinical mastitis from 17 dairy herds in New Zealand. The genetic relatedness between isolates was examined using the core single nucleotide polymorphism alignment whilst AMR and virulence genes were identified in-silico. The association between gene presence-absence and sequence type (ST), antimicrobial susceptibility and dry cow therapy treatment was investigated using Scoary. Altogether, eight STs were identified with 61.4% (35/57) belonging to ST-1. Furthermore, 14 AMR-associated genes and 76 virulence-associated genes were identified, with little genetic diversity between isolates belonging to the same ST. Several genes including merR1 which is thought to play a role in ciprofloxacin-resistance were found to be significantly overrepresented in isolates sampled from herds using ampicillin/cloxacillin dry cow therapy. Overall, the presence of resistance genes remains low and current antimicrobial usage patterns do not appear to be driving AMR in S. aureus associated with bovine mastitis.