Vru (Sub0144) controls expression of proven and putative virulence determinants and alters the ability of Streptococcus uberis to cause disease in dairy cattle

Abstract

The regulation and control of gene expression in response to differing environmental stimuli is crucial for successful pathogen adaptation and persistence. The regulatory gene vru of Streptococcus uberis encodes a stand-alone response regulator with similarity to the Mga of group A Streptococcus. Mga controls expression of a number of important virulence determinants. Experimental intramammary challenge of dairy cattle with a mutant of S. uberis carrying an inactivating lesion in vru showed reduced ability to colonize the mammary gland and an inability to induce clinical signs of mastitis compared with the wild-type strain. Analysis of transcriptional differences of gene expression in the mutant, determined by microarray analysis, identified a number of coding sequences with altered expression in the absence of Vru. These consisted of known and putative virulence determinants, including Lbp (Sub0145), SclB (Sub1095), PauA (Sub1785) and hasA (Sub1696).

Role of Streptococcus uberis adhesion molecule in the pathogenesis of Streptococcus uberis mastitis

“…Work conducted by others and our research team showed the expression of virulence factors other than SUAM (Fontaine et al, 2002;Leigh et al, 2010;Eagan et al, 2012). These reports raise the concept that pathogenic events leading to S. uberis IMI cannot be attributed only to SUAM.…”

Virulence related sequences; insights provided by comparative genomics of Streptococcus uberis of differing virulence

“…S. uberis SUB0144 is a homologue of the S. pyogenes virulence regulatory gene mga. SUB0144 ( vru ) of S. uberis has been found to regulate a number of virulent genes including hasA and hasB1 ( SUB1696 and SUB1697 ), Lbp ( SUB0145 ), SclB ( SUB1095 ) and PauA ( SUB1785 ) and inactivation of vru resulted in reduced ability to colonize the mammary gland as well as reduced clinical signs of mastitis compared with the wild-type strain [ 30 ]. Moreover, Flores et al have shown that a 12-bp deletion in the VNTR region of mga promoter at positions -63 to -75 alters GAS virulence, resulting in asymptomatic carrier phenotype [ 31 ].…”

PCR-Based Direct Detection of Streptococcus uberis from Subclinical and Clinical Dairy Cattle Milk Samples

“…DNA was extracted from 1 ml of milk using the phenol: chloroform extraction method from quarter milk samples obtained from 4 cattle challenged in two contralateral quarters with S. uberis 0140 J [ 15 , 44 ]. S. uberis was detected by multiplex PCR in 75% of samples obtained after 16 hours of challenge and 100% after 24 hours of challenge ( Figure 4(a) ).…”

“…Whilst detection at levels of between 10 4 and 10 5 cfu/ml may seem relatively high compared to some of the more sensitive RT-PCR methods, previous experimental challenge studies have indicated that this bacterial concentration in milk results in a “tipping point” where animals are highly likely to progress to clinical mastitis requiring antibiotic therapy [ 15 , 44 , 45 , 59 ]. Given this, detection of S. uberis at a level lower than 1000 cfu/ml may not be clinically relevant and result in overtreatment of animals unlikely to progress to clinical disease.…”

“…Frozen milk samples from previous dairy challenge experiments [ 15 , 44 ] conducted at IAH, Compton Laboratory under PPL 30/2645, were used in this study to determine the detection limits for S. uberis 0140 J within milk. Briefly, 4 Holstein–Friesian cows, 2–10 weeks into their first lactation with no previous history of mastitis, were challenged with approximately 1000 cfu/ml of S. uberis 0140 J in two contralateral quarters.…”