Molecular Epidemiology and Population Structure of Bovine Streptococcus uberis

Abstract

The molecular epidemiology and population structure of 30 bovine subclinical mastitis field isolates of Streptococcus uberis, collected from 6 Portuguese herds (among 12 farms screened) during 2002 and 2003, were examined by using pulsed-field gel electrophoresis (PFGE) for clustering of the isolates and multilocus sequence typing (MLST) to assess the relationship between PFGE patterns and to identify genetic lineages. The 30 isolates were clustered into 18 PFGE types, using a similarity cutoff of 80%, and 3 PFGE types accounted for almost half of the isolates (46.6%). These major types were herd specific, suggesting either cow-to-cow transmission or infection with isolates from the same environmental reservoirs. The remaining unrelated PFGE types of isolates were from different herds strongly suggesting environmental sources of Strep. uberis infection. All 30 isolates were analyzed by MLST and clustered into 14 sequence types (ST). These ST were found to be novel, either with 10 new alleles of 6 housekeeping genes or with different combinations of previously assigned alleles. Five of these ST were clustered into 3 clonal complexes (lineages), ST-143, ST-86, and ST-5, known to include bovine isolates from several geographic locations (Australia, New Zealand, United Kingdom, Sweden, and Denmark) and 9 singletons. To our knowledge, this is the first report that documents molecular typing studies of bovine isolates of Strep. uberis from Portugal, which were shown to represent novel genomic backgrounds of this pathogen.

Genetic diversity and virulence genes in Streptococcus uberis strains isolated from bovine mastitis

“…PFGE demonstrated a high discriminatory index (0.9889) in accordance with previous studies (DOUGLAS et al, 2000;LASAGNO et al, 2011;PHUEKTES et al, 2001;RATO et al, 2008RATO et al, , 2013. Four pulse-types found by PFGE (VI, VII-a, VIII, and IX) showed two strains with similar patterns that were classified as having identical restriction patterns (Figure 1).…”

“…Our findings suggest that the transmission may also occur during milking, beyond the environmental transmission, according Rato et al (2008). transmission, according Rato et al (2008). In our study, strains of clinical and subclinical mastitis cases were used; however, the small sample size makes it impossible to make inferences about the relationship between the severity of the disease that can be related to several conditions pertaining to the host, such as udder health, nutrition, genetic diseases, and lactation stage (JAYARAO et al, 1991).…”

“…Several molecular methods based on genotyping have been used to study the population diversity of S. uberis (LASAGNO et al, 2011;RATO et al, 2008;WANG et al, 2013;ZADOKS et al, 2003). These approaches may permit the development of more effective control measures for this microorganism.…”

“…These approaches may permit the development of more effective control measures for this microorganism. Among the different molecular typing methods, the Pulsed Field Gel Electrophoresis (PFGE) technique has been used to study pathogens involved in the etiology of bovine mastitis because it is highly discriminatory and highly reproducible (BASEGGIO et al, 1997;DOUGLAS et al, 2000;LASAGNO et al, 2011;PHUEKTES et al, 2001;RATO et al, 2008RATO et al, , 2013. According to Shome et al (2012), PFGE is the technique of choice for short-term or local epidemiological analyses.…”

Genetic diversity and virulence genes in Streptococcus uberis strains isolated from bovine mastitis

“…Additionally, three other different subtypes were found in these herds, amounting to five subtypes infective in seven cows, pointed the high diversity of S. uberis. Our findings suggest that the transmission may also occur during milking, beyond the environmental transmission, according Rato et al (2008). transmission, according Rato et al (2008).…”