Staphylococcus aureus is recognized worldwide as one of the major agents of dairy cow intra-mammary infections. This microorganism can express a wide spectrum of pathogenic factors used to attach, colonize, invade and infect the host. The present study evaluated 120 isolates from eight different countries that were genotyped by RS-PCR and investigated for 26 different virulence factors to increase the knowledge on the circulating genetic lineages among the cow population with mastitis. New genotypes were observed for South African strains while for all the other countries new variants of existing genotypes were detected. For each country, a specific genotypic pattern was found. Among the virulence factors, fmtB, cna, clfA and leucocidins genes were the most frequent. The sea and sei genes were present in seven out of eight countries; seh showed high frequency in South American countries (Brazil, Colombia, Argentina), while sel was harboured especially in one Mediterranean country (Tunisia). The etb, seb and see genes were not detected in any of the isolates, while only two isolates were MRSA (Germany and Italy) confirming the low diffusion of methicillin resistance microorganism among bovine mastitis isolates. This work demonstrated the wide variety of S. aureus genotypes found in dairy cattle worldwide. This condition suggests that considering the region of interest might help to formulate strategies for reducing the infection spreading.

Staphylococcus aureus is globally one of the most important pathogens causing contagious mastitis in cattle. Previous studies using ribosomal spacer (RS)-PCR, however, demonstrated in Swiss cows that Staph. aureus isolated from bovine intramammary infections are genetically heterogeneous, with Staph. aureus genotype B (GTB) and GTC being the most prominent genotypes. Furthermore, Staph. aureus GTB was found to be contagious, whereas Staph. aureus GTC and all the remaining genotypes were involved in individual cow disease. In addition to RS-PCR, other methods for subtyping Staph. aureus are known, including spa typing and multilocus sequence typing (MLST). They are based on sequencing the spa and various housekeeping genes, respectively. The aim of the present study was to compare the 3 analytic methods using 456 strains of Staph. aureus isolated from milk of bovine intramammary infections and bulk tanks obtained from 12 European countries. Furthermore, the phylogeny of animal Staph. aureus was inferred and the zoonotic transfer of Staph. aureus between cattle and humans was studied. The analyzed strains could be grouped into 6 genotypic clusters, with CLB, CLC, and CLR being the most prominent ones. Comparing the 3 subtyping methods, RS-PCR showed the highest resolution, followed by spa typing and MLST. We found associations among the methods but in many cases they were unsatisfactory except for CLB and CLC. Cluster CLB was positive for clonal complex (CC)8 in 99% of the cases and typically positive for t2953; it is the cattle-adapted form of CC8. Cluster CLC was always positive for tbl 2645 and typically positive for CC705. For CLR and the remaining subtypes, links among the 3 methods were generally poor. Bovine Staph. aureus is highly clonal and a few clones predominate. Animal Staph. aureus always evolve from human strains, such that every human strain may be the ancestor of a novel animal-adapted strain. The zoonotic transfer of IMI- and milk-associated strains of Staph. aureus between cattle and humans seems to be very limited and different hosts are not considered as a source for mutual, spontaneous infections. Spillover events, however, may happen.

With the rapid increase of available sequencing data on clinically relevant bacterial species such as S. aureus , the genomic basis of clinical phenotypes can be investigated in much more detail, allowing a much deeper understanding of the mechanisms involved in disease. We characterized in detail the S. aureus genomic island v Saβ and defined a superordinate system to categorize S. aureus strains based on their v Saβ type, providing information about the strains’ virulence-associated genes and clinical potential.

Staphylococcus aureus is a highly contagious mastitis-causing pathogen infecting dairy cattle worldwide. Previous studies have shown the presence of different genotypes (GT) on farms. In Switzerland, Staph. aureus genotype B (GTB) is contagious, whereas GTC and other genotypes cause sporadic, noncontagious mastitis. In this study, we evaluated the epidemiological properties of Staph. aureus, together with its genotypes and spa types, on Swiss dairy farms. A total of 21 dairy farms were sampled throughout Switzerland; 10 farms were positive for the contagious Staph. aureus GTB and 11 farms were negative for GTB. Samples were taken from milk, body surfaces of dairy cattle and other animals, milkers, milking equipment, and environmental sites (e.g., parlor, washing room, stall floor, manger, and bedding). The epidemiology of Staph. aureus depended markedly on the genotype. Staphylococcus aureus GTB was associated with mammary gland, intramammary infections (IMI), and milking clusters, whereas GTC and other genotypes were related to cow and other animal surfaces and occasionally to environment. Genotype C was by far the most common subtype in cattle and was found on GTB-negative and GTB-positive farms. Each farm had a predominant genotype, such as GTB, GTC, GTA, or GTF, but a few farms were almost free from Staph. aureus. The genotypes and spa types of Staph. aureus detected in the noses of milkers clearly differed from those found in dairy cattle, other animals, milking equipment, and the environment. Exceptions were GTS (spa type t034) and GTF (t899), which crossed the species barrier. In most cases, however, the species barrier was maintained because Staph. aureus is adapted to a particular host and even to particular body sites. As biological properties differ among the genotypes, new guidelines to prevent IMI caused by different genotypes were established: classical measures to prevent IMI caused by contagious pathogens still hold for GTB but not for Staph. aureus genotypes that are opportunistic colonizers of bovine skin (e.g., GTC and GTA). For those genotypes, protection of the skin from minor lesions and wounds, particularly on the hocks, is essential.

Staphylococcus aureus is globally one of the most important pathogens causing contagious mastitis in cattle. Previous studies, however, have demonstrated in Swiss cows that Staph. aureus isolated from bovine intramammary infection is genetically heterogeneous, with Staph. aureus genotype B (GTB) and GTC being the most prominent genotypes. In addition, Staph. aureus GTB was found to be contagious, whereas Staph. aureus GTC and all the remaining genotypes were involved in individual cow disease. The aim of this study was to subtype strains of Staph. aureus isolated from bovine mastitic milk and bulk tank milk to obtain a unified view of the presence of bovine staphylococcal subtypes in 12 European countries. A total of 456 strains of Staph. aureus were subjected to different typing methods: ribosomal spacer PCR, detection of enterotoxin genes, and detection of gene polymorphisms (lukE, coa). Major genotypes with their variants were combined into genotypic clusters (CL). This study revealed 5 major CL representing 76% of all strains and comprised CLB, CLC, CLF, CLI, and CLR. The clusters were characterized by the same genetic properties as the Swiss isolates, demonstrating high clonality of bovine Staph. aureus. Interestingly, CLB was situated in central Europe whereas the other CL were widely disseminated. The remaining 24% of the strains comprised 41 genotypes and variants, some of which (GTAM, GTBG) were restricted to certain countries; many others, however, were observed only once.