Bovine Staphylococcus aureus: Subtyping, evolution, and zoonotic transfer

Abstract

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 t529 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.

Genotypes of Staphylococcus aureus: On-farm epidemiology and the consequences for prevention of intramammary infections

“…aureus genotypes (GTOG) were rarely present (Fournier et al, 2008). Studies by and Boss et al (2016) confirmed the Swiss results at the European level: Staph. aureus GTB, GTC, and GTR were the most prominent genotypes, followed by GTF, GTI, and a set of 41 genotypes with rare occurrence.…”

“…Analysis of the spa type was performed as described by Boss et al (2016). In brief, the variable X region of the spa gene was amplified in a total volume of 25 μL containing 300 nmol of each spa primer , 12.5 μL of HotStarTaq master Mix (Qiagen), and 2.5 μL of DNA diluted 1:20 in H 2 O.…”

“…In addition, this method is characterized by high resolution and is associated with the virulence gene pattern of bovine strains (Fournier et al, 2008;Graber et al, 2009;Cremonesi et al, 2015;. Besides RS-PCR, other subtyping methods have been used to further characterize staphylococcal IMI isolates such as spa typing (e.g., Boss et al, 2016;Lundberg et al, 2016), multilocus sequence typing (e.g., Hata et al, 2010;Boss et al, 2016), pulsed-field gel electrophoresis (e.g., Capurro et al, 2010;Cremonesi et al, 2015), and amplified fragment length polymorphism (Sakwinska et al, 2011). Their suitability for large clinical investigations, however, is mainly limited by low throughput or high cost.…”

Comparison of Virulence Gene Identification, Ribosomal Spacer PCR, and Pulsed-Field Gel Electrophoresis for Typing of Staphylococcus aureus Strains Isolated from Cases of Subclinical Bovine Mastitis in the United States

“…One was related to the equipment used. The use of a miniaturized electrophoresis system (Agilent Technologies) has been recommended for best resolution, data evaluation, and data management of RS-PCR results (34). The suggested system can be expensive, and it is not necessarily available in all laboratories conducting PCR, which may be considered a limitation pertaining to this technique.…”

Genomic and transcriptomic comparison between Staphylococcus aureus strains associated with high and low within herd prevalence of intra-mammary infection

“…This study and previous data [5, 6] confirmed that particular gene patterns, virulence profiles and specific genotypes could be associated with diverse clinical outcomes. More recently, two large European studies [7, 8], demonstrated that the Repetitive-Sequence PCR RS-PCR genotype B (GTB), belonging to the Sequence Type ST8 [9, 10], a high contagious and diffusive Staph. aureus involved in bovine IMI, was the most frequently detected in several European countries (Austria, Belgium, France, Germany, Italy, Switzerland).…”