Coagulase negative
Staphylococcus (CNS) sp. are common causes of sub-clinical and
clinical mastitis in sheep used in dairying, however there is limited information
related to their importance in meat and wool sheep production systems. This report details the identification of CNS
species isolated from ewe milk collected from eight meat and wool sheep flocks
across south-eastern Australia from 2012 to 2014, consisting of 5 Merino and
First Cross ewe flocks and 3 Poll Dorset flocks. Over 4000 samples were collected on these
properties over the two-year study. At
the time of weaning, the samples were collected from ewes by hand stripping
after cleaning the ewe’s teat with 80% methylated spirits. A total of 30 mL of
milk was collected for milk somatic cell counts using a Fossomatic
cell-counting method and a further 5 mL of milk was collected and refrigerated,
prior to standard aerobic culture on sheep blood agar within five days of
collection. On Poll Dorset properties, approximately 20% of ewes showed cell
counts indicative of sub-clinical mastitis with half this rate seen in Merino and
First-Cross ewe flocks. Among the most
common bacterial genera isolated from sub-clinically infected sheep were
Streptococcus sp. and coagulase-negative
Staphylococcus sp.. Standard
biochemical tests were used to initially identify CNS, followed by PCR-RFLP
analysis of the glyceraldehyde-3-phosphate dehydrogenase (
gap) gene that enabled reliable identification to species level (
Onni et al., 2010;
Park et al., 2011). The two most common species identified from
these milk samples were
Staphylococcus
simulans and
Staphylococcus chromogenes/intermedius.