Abstract
Streptococcus uberis is one of the leading causes worldwide of mastitis in the dairy industry, with the most likely sources of infection attributed to environmental reservoirs such as contaminated bedding materials. Early detection of those cases most likely to progress to clinical disease would lead to improved animal welfare, a critical component of overall health and productivity. A multiplex PCR-based diagnostic test was developed for detection of S. uberis directly from milk and targeting two genes previously identified as important for intramammary colonisation and persistence in dairy cattle. Results indicated the threshold for detection directly from milk was 20,000 CFU/ml and this was achieved without the need for preenrichment. In addition, S. uberis could be identified from milk samples collected during intramammary challenge studies, prior to clinical signs of infection and at much lower detection limits. The PCR test developed for confirmation of the presence of S. uberis directly from infected milk has potential value as a diagnostic test to identify early infection and/or to confirm that antibiotic therapy has been successful.
Highlights
Bovine mastitis is one of the most prevalent diseases within the dairy industry, resulting in significant economic and production losses, and is a considerable welfare issue for affected cows [1,2,3]. e current rate of clinical mastitis in the UK has been reported at 47 cases per 100 cows per year [4] with associated costs estimated to vary between £110 and £340 per cow [5,6,7,8]. ere are an estimated 2.73 million dairy cows in the UK [9], and approximately 1.28 million cases of clinical mastitis with financial losses attributed to vary between £141 and £436 million per annum in the UK alone
Clinical mastitis due to S. uberis typically corresponds with high bacterial numbers between 106 and cfu/ml of milk [15, 16] bacterial concentrations may peak as high as cfu/ml
S. uberis strain 0140 J, originally isolated from a clinical case of bovine mastitis in the UK, and 12 other previously characterised clinical strains [35] were used throughout this study. e Escherichia coli strain P4 and Staphylococcus aureus strain M60 were both isolated from clinical cases of bovine mastitis [36, 37]
Summary
Bovine mastitis is one of the most prevalent diseases within the dairy industry, resulting in significant economic and production losses, and is a considerable welfare issue for affected cows [1,2,3]. e current rate of clinical mastitis in the UK has been reported at 47 cases per 100 cows per year [4] with associated costs estimated to vary between £110 and £340 per cow [5,6,7,8]. ere are an estimated 2.73 million dairy cows in the UK [9], and approximately 1.28 million cases of clinical mastitis with financial losses attributed to vary between £141 and £436 million per annum in the UK alone. The multiplex PCR was performed using genomic DNA from a number of bacterial pathogens previously associated with mastitis including E. coli, S. aureus, S. agalactiae, S. dysgalactiae, and L. garvieae and a number of related species from the Streptococcaceae family (E. faecium and S. pneumoniae), all of which were negative (Figure 1(b)), with 16 S rDNA PCR performed to confirm the presence of genomic DNA in these samples (Figure 1(c)).
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