In the Netherlands, livestock-associated methicillin-resistant Staphylococcus aureus
(LA-MRSA) has been found in pigs, veal calves, horses and poultry. However, little
is known about its prevalence in healthy dairy cattle. Recently, a new mec gene, called
mecC, has been found in methicillin-resistant S. aureus (MRSA) isolates from humans
and animals in several countries. The objective of our pilot study was to investigate
the prevalence of MRSA (mecA and mecC) in dairy cows at a large slaughterhouse. Samples
from the skin between the udder and hind leg were taken from 411 cows. The samples
were incubated in Mueller-Hinton enrichment broth with 6.5% NaCl, followed by selective
enrichment and plated onto Columbia agar with 5% sheep blood, Brilliance MRSA 2 agar
and Baird-Parker agar. Suspected colonies were tested by PCR for a S. aureus specific
DNA fragment, the mecA and mecC genes and the Panton-Valentine leucotoxin (PVL) genes.
All MRSA isolates and methicillin-susceptible S. aureus (MSSA) isolates were typed
by spa typing and MLVA typing. Sixteen of 411 (3.9%) cows, all originating from different
farms, were found to be MRSA positive and this prevalence is lower than in Dutch pigs,
veal calves and broilers. All MRSA isolates belonging to livestock-associated MLVA
complex 398, were PVL-negative and spa type t011 predominated. MSSA isolates (n=39)
were of many different MLVA types and spa type t543 was found most often. Four MSSA
isolates belonging to MLVA clonal complex 398 and spa types t011 (n=2), t108 and t034
were isolated from different MRSA-negative animals. In conclusion, the prevalence
of MRSA in dairy cows was low and isolates carrying the mecC gene were not found,
indicating that it is absent or has a low prevalence (<0.73%) in Dutch dairy cows.