Project description:Infection caused by bacteria from environmental reservoirs such as E. coli and S. uberis have not decreased in prevalence. Lack of success in controlling bovine mastitis due to S. uberis is associated with the route of infection which is not well understood and there is inadequate information on pathogenesis of S. uberis. Therefore, this study was to investigate the virulence factors of S. uberis using comparative genome analyses using isolates from cows with clinical mastitis and isolates from cows with a low cell count in their milk using a Subtracted Diversity Array (SDA). This study also reports the construction and validation of a microarray capable of fingerprinting the virulent and non-virulent isolates using the SDA technique.
Project description:Streptococcus uberis is one of the principal causative agents of bovine mastitis. The organism is typically considered an environmental pathogen, however, recent studies also suggest possible host adaptation. In this study, two multilocus sequence typing (MLST) schemes and whole genome DNA microarrays were used to evaluate the degree and nature of genome flexibility between S. uberis strains. The 21 isolates examined in this study arise from a collection of 232 international isolates for which previous epidemiological and preliminary genotyping data existed. The microarray analysis resulted in an estimate of the core genome for S. uberis, consisting of 1530 ORFs, among 1855 tested, representing 82.5% of the S. uberis 0140J genome. The remaining ORFs were variable in gene content across the 21 tested strains. A total of 26 regions of difference (RDs), consisting of three or more contiguous ORFs, were identified among the variable genes. Core genes mainly encoded housekeeping functions, while the variable genes primarily fell within categories such as protection responses, degradation of small molecules, laterally acquired elements, and two component systems. Recombination detection procedures involving the MLST loci suggested S. uberis is a highly recombinant species, precluding accurate phylogenetic reconstructions involving these data. On the other hand, the microarray data did provide limited support for an association of gene content with strains found in multiple cows and/or multiple herds, suggesting the possibility of genes related to bovine transmissibility or host-adaptation. Keywords: comparative genomic hybridization
