Abstract
BackgroundBovine mastitis is an important cause of economic loss in dairy farms. Streptococcus uberis is among the most frequently isolated bacterial species isolated from cows with mastitis. The aim of this study was to perform an in-depth genetic assessment of S. uberis strains isolated from bovine clinical mastitis (CM) and to perform a phylogenetic analysis to represent the evolutionary relationship among S. uberis sequences.ResultsA total of 159 isolates was genetically characterized using whole genome sequencing. According to the virulence determinants, all strains harbored the hasC, leuS, perR, purH, and purN virulence genes. Thirty-four resistance genes were identified in at least one strain. In terms of acquired genes, we observed that 152 (95.6 %) strains had a resistance gene to lincosamine (lnuD), 48 (30.2 %) to tetracycline (tetM), 4 (2.51 %) to tobramicine (ant6), and 1 to lincosamide (lsa(E)). MLST detected the Sequence Type (ST)797 (n = 23), while 85.5 % of the strains did not match to known STs.ConclusionsThen, eleven distinct ST were identified after we submitted the new alleles to assign new STs. The other prevalent STs observed were ST1215 (n = 58), ST1219 (n = 35), and ST1213 (n = 15). And it was not possible to identify the MLST of four strains. Phylogenetic lineages indicated a high genomic diversity of S. uberis in our collection, confirming that most strains isolated from bovine mastitis have different reservoirs, typical of environmental pathogens.
Highlights
Bovine mastitis is an important cause of economic loss in dairy farms
The aim of this study was to perform an in-depth genetic assessment of S. uberis isolated from bovine clinical mastitis (CM) and to perform a phylogenetic analysis to represent the evolutionary relationship between S. uberis sequences
83 % of the isolates (n = 132) were recovered from mild cases of clinical mastitis, while 17 % where either moderate or severe
Summary
Bovine mastitis is an important cause of economic loss in dairy farms. Streptococcus uberis is among the most frequently isolated bacterial species isolated from cows with mastitis. Bovine mastitis is one of the major concerns for the dairy industry being associated with direct and indirect economic losses. Many microbial species were described as the cause of bovine mastitis and among them, Streptococcus spp. is among the most isolated genera in dairy herds, being associated with both clinical and subclinical forms of the disease [3, 4]. S. uberis is a Gram-positive pathogen inducing both clinical and subclinical mastitis, causing reduction of milk production, changes in milk composition and increase of somatic cell count (SCC) in dairy. The advance of knowledge about the genetic features associated with S. uberis causing mastitis associated with clinical outcomes such as cure after antimicrobial treatment, death/culling due mastitis, mammary quarter loss and disease reoccurrence, can contribute to the developing of efficient strategies for prevention and control of this pathogen in dairy herds
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