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Tech Talk: May 2012
Staphylococcus aureus – The Cowman’s Curse
Protecting your dairy cows from mastitis is easier said than done, particularly when you
consider the difficult nature of some very hard-to-kil bacteria. This is the cowman’s curse.
Mention mastitis-causing bacteria and a few BIG names spring to mind, Staphylococcus
aureus being one of the most prominent in most people’s minds.
Staphylococcus aureus (Staph. aureus) is referred to in mastitis terms as a ‘contagious
bacteria’ in that it is recognised that it lives and multiplies in the udder tissue and milk and
it can easily pass from cow to cow during the milking process. It was first identified in the
pus of an open wound by the surgeon Sir Alexander Ogston in Aberdeen in 1880. Sore
and cracked teats are therefore an ideal source from which it can enter the udder system.
Over the years, Staph. aureus has been treated by the penicil in class antibiotic,
methicil in. However, it has now developed resistance and Methicil in Resistant Staph.
aureus (MRSA) is greatly feared in both the food chain and hospitals. So methicil in has
been superseded by flucloxacil in which is stronger and more effective.
Skin is a great home for Staph. aureus so cross infection from hand to the cow’s teats or
milk liner to teat is easy. Back flushing, cluster dipping and the wearing of nitrile gloves
What makes Staph. aureus particularly difficult to control is the fact it can produce an
enzyme cal ed beta lactase which prevents many penicil in antibiotics from working. In
addition, the bacteria can create a gel-like coat which prevents the cow’s immune system
So there you have it, a very wel known mastitis causing pathogen, with the ability to hide
from the natural immune system (leucocytes) and capable of resisting the effects of
antibiotics. The British Cattle Veterinary Association (BCVA) report that up to 35% of
known ‘Staphs’ are antibiotic resistant. No surprise then that it is the cowman’s curse on a
high percentage of UK and Irish dairy farms.
Strangely, Staph. aureus has been found in heifer colostrum at first milking so no
contagious spread cow to cow in the milking process here! The source here may be flies
It is clear this problem wil never go away but improved hygiene practices around the
Attention to detail in both PRE and POST milking disinfection has been shown to reduce
the spread of this pathogen. Paying close attention to skin and teat end condition is also
vital in removing another perfect hiding and breeding place for Staph. aureus.
But dry cow management is key as, whilst strong post-milking germicidal routines with full
teat coverage can wash away and kil Staph. aureus in the milk film, it cannot reach the
living and breeding bacteria in milk secreting tissue inside the udder. Therefore, targeted
antibiotic treatment and internal/external sealing, which have both been proven to impact
on Staph. aureus, is a must in dry cow protocols.
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