Comparative genomics of Staphylococcus aureus isolates causing mastitis in cows.

JOSÉ MATÍAS IRAZOQUI; CECILIA CAMUSSONE; LUIS CALVINHO; ARIEL AMADIO

Mar del Plata

Congreso; IX Congreso Argentino de Bioinformática y Biología Computacional.; 2018

Asociación Argentina de Bioinformática y Biología Computacional

Staphylococcus aureus can act as a major pathogen in many animal species, and represents one of the leading causes of intramammary infection (IMI) both in lactating cows and periparturient dairy heifers. Presence or absence of specific staphylococcal virulence factors has been associated with IMI severity and persistence in the bovine mammary gland. However, mechanisms associated with these different infections traits are not yet fully understood.In this work, we analyzed 4 bovine S. aureus isolates, using whole genome sequencing. Strains 5011 and 5128, were isolated from lactating cows in Santa Fe province and caused subclinical chronic infections. Strain 117 was isolated from a lactating cow in Córdoba province and caused a clinic infection. Lastly, strain B456 was isolated from a heifer pre-partum mammary secretion in Santa Fe. Regarding capsule genotype, 5128, 117 and B456, were genotyped as CP5, while 5011 was nontypeable. The 4 strains were sequenced using Illumina MiSeq, generating 2x250bp reads. In addition, strains 5128 and 5011 were also sequenced using MinION technology (Oxford Nanopore).By combining sequencing technologies, we manage to circularize the genome and all plasmids of 5128 and 5011 isolates. The assembly of isolates 117 and B456 resulted in 34 and 89 contigs, respectively. An in silico MLST analysis showed that only two strains (5128 and 117) shared the same ST,. Finally, in average, 2500 genes were predicted for each strain, from which 2121 were strictly conserved across all of them (>=99% nucleotide identity). Among the unique genes, resistance to different antibiotics, virulence factors and capsular polysaccharide biosynthesis proteins were found and compared.In conclusion, we were able to reconstruct the complete genome of 4 S. aureus isolates causing different disease patterns. The study and comparison of these genomes would help to explain the differences between the different infection traits, and to identify new targets for the development of experimental mastitis vaccines.