Staphylococcus aureus Isolated from Ruminants with Mastitis in Northern Greece Dairy Herds: Genetic Relatedness and Phenotypic and Genotypic Characterization.

Charalampos Kotzamanidis,Antonios Zdragas,Andigoni Malousi,Sofia Anastasiadou,Stavros Mygdalias,Sergelidis Daniel,Ekateriniadou Loukia,George Vafeas,Virginia Giantzi

doi:10.3390/toxins13030176

Charalampos Kotzamanidis, Antonios Zdragas + Show 7 more

Open Access

https://doi.org/10.3390/toxins13030176

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Abstract

Staphylococcus aureus is the most common mastitis-related pathogen in dairy cattle, goats, and sheep worldwide. However, the population structure and genomic characteristics of mastitis-associated S. aureus in small ruminants are limited. Furthermore, the genotypic and phenotypic characteristics involved in the pathogenicity of S. aureus have been thoroughly defined, yet their association with the severity of mastitis is not fully established. Here, we performed genotyping by pulsed-field gel electrophoresis (PFGE) and spa analyses to assess the genetic diversity and relatedness of 162 S. aureus strains recovered from clinical mastitis (CM) and subclinical mastitis (SCM) cases from goats, sheep, and bovines. PFGE analysis revealed 108 distinguishable pulsotypes and 3 main clusters that comprised isolates from the three host species, while according to spa typing, 32 different spa types were identified. Genotypic analysis revealed a spreading of genetically related or indistinguishable S. aureus strains among ovine, caprine, and bovine farms of distant geographical regions. In total, 28 different staphylococcal enterotoxin (SE) gene profiles were observed, revealing a diverse range of SE genes among isolates. By evaluating the antimicrobial resistance, we found low phenotypic antimicrobial resistance among all ruminant isolates. We also performed multiple correspondence analysis, which indicated that the presence of the sec gene, biofilm production, and high autoaggregation ability are associated with CM cases.

Highlights

Mammary infection of ruminants leading to subclinical and clinical mastitis is associated with severe economic losses due to the reduction in milk yield and milk quality and the cost of treatment [1] and has an impact on animal welfare [2]
Key Contribution: This study demonstrates that sheep, goats, and bovines are exposed to a broad range of genetically diverse S. aureus strains that do not represent host-specific genetic populations and that the outcome of mastitis in ruminants is associated with specific genotypic and phenotypic traits of S. aureus
Staphylococcal enterotoxins are considered to play an important role in the development of mastitis, since S. aureus isolates from cases of mastitis had a higher prevalence of enterotoxin genes than isolates from milk of cows without mastitis [9], and in addition, staphylococcal enterotoxin (SE) genes were found to be related with the severity of bovine mastitis [10]

Summary

Introduction

Mammary infection of ruminants leading to subclinical and clinical mastitis is associated with severe economic losses due to the reduction in milk yield and milk quality and the cost of treatment [1] and has an impact on animal welfare [2]. Staphylococcus aureus is the most common mastitis-related pathogen in dairy cattle, goats, and sheep [3,4], with infected animals frequently shedding the bacterium into their milk [5]. Intramammary infection in animals is caused by S. aureus strains with the capacity to produce a variety of virulence factors such as antigens, toxins, and various resistance proteins [8]. Staphylococcal enterotoxins are considered to play an important role in the development of mastitis, since S. aureus isolates from cases of mastitis had a higher prevalence of enterotoxin genes than isolates from milk of cows without mastitis [9], and in addition, SE genes were found to be related with the severity of bovine mastitis [10]. The ability of S. aureus to form biofilm is considered a crucial virulence trait [11], while the S. aureus property of autoaggregation is often associated with pathogenicity [12]

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