Download Different CNS species found in milk and cow environment: field

Abstract dMRW 01.12.2009
Veerle Piessens
Different CNS species found in milk and cow environment: field study on six
Flemish dairy herds.
1Veerle
Piessens, 1Els Van Coillie,1Bert Verbist, 2Karlien Supré, 3Gorik Braem, 3Luc De
Vuyst, 1Marc Heyndrickx, 2Sarne De Vliegher
1Institute
for Agricultural and Fisheries Research (ILVO), Food Science and Technology Unit, Melle,
Belgium; 2Dept. Reproduction, Obstetrics, and Herd Health, Faculty of Veterinary Medicine, Ghent
University, Belgium; 3Research Group Industrial Microbiology and Food Biotechnology, VUB, Brussels,
Belgium
In many prevalence studies of mastitis pathogens worldwide, coagulase-negative
staphylococci (CNS) were found to be the predominant group of organisms isolated from
milk samples. Although CNS are considered as mild pathogens, they are also known to
cause clinical mastitis and can persist for long periods in the mammary gland. On the
other hand, in some cases CNS colonization appeared to have a protective effect against
major mastitis pathogens. To understand these various roles of CNS, more research on
the species and strain level is needed. In the present study, epidemiology of different
CNS species was investigated with an emphasis on CNS that are found in the
environment.
A longitudinal study was conducted on six Flemish dairy farms from May 2008 through
May 2009. On each farm, quarter milk samples of a selection of cows and environmental
samples were taken monthly for isolation of CNS. Sixty cows (10 cows/herd) were
followed during this 13 month period to study the persistence of CNS intramammary
infections (IMI). In total, 139 CNS from milk and 649 environmental CNS were isolated
and analyzed by amplification fragment length polymorphism (AFLP) genotyping for
species identification and strain differentiation. In general, Staphylococcus sciuri, S.
equorum and S. haemolyticus were the predominating CNS species in the cow
environment (air in the free-stall, slatted floors, bedding from cubicles and unused
bedding). However, herd-to-herd differences were observed as it relates to most
isolated CNS species. The main species found in the milk samples of the selected cows,
were S. chromogenes, S. haemolyticus, S. epidermidis and S. simulans, which were also the
species that caused chronic IMI. Based on AFLP-type, we found that quarters were often
chronically infected for several months by the same CNS strain. One S. chromogenes
AFLP-type even persisted up to 11 consecutive months in the same quarter. Moreover,
same AFLP-types were found between milk isolates and isolates originating from the
environment, which indicates that possible sources of IMI causing CNS strains exist in
the environment.
We conclude that origin of CNS IMI might differ depending on causative CNS species,
since certain species seem particularly adapted to survival in the udder and were almost
absent in the environment (S. chromogenes and S. epidermidis), while others were both
prevalent in milk and environment (S. haemolyticus and S. simulans). On the other hand,
the species S. equorum and S. sciuri were ubiquitous in the environment, and were rarely
found in milk. These preliminary results emphasize that there is diversity in pathogenic
behavior between CNS species and that herd-dependent factors are probably important.
Further scrutiny of the epidemiology and virulence of different CNS species will help to
gain more knowledge on these important etiological agents for IMI.