Frequently asked questions about MRSA

What is MRSA?

MRSA, i.e. methicillin-resistant Staphylococcus aureus bacteria, differ from regular S. aureus strains only with regard to their sensitivity to antibiotics. Methicillin resistance does not increase the pathogenicity of the bacteria. MRSA strains are resistant to betalactam antibiotics such as penicillins. Similarly to other S. aureus bacteria, MRSA is able to survive for long periods in its environment.

What does MRSA cause?

MRSA is known to cause healthcare-related infections. S. aureus is a common type of bacterium appearing on the skin and the mucous membranes of the nose, and does not normally cause illness in healthy humans or animals. However, S. aureus may cause an infection in a damaged area of skin and surgical wounds, for example. The most common antimicrobial drugs are not effective against MRSA, which makes treatment difficult. A healthy human or animal without any symptoms can also act as a temporary carrier of MRSA.

Does MRSA occur in animals and meat in Finland?

Of all livestock, MRSA bacteria have been detected in pigs, dairy cattle and horses in Finland. MRSA has been found in pigs in many instances and at several pig farms. MRSA findings are rare in dairy cattle. Among dogs and cats, MRSA is found only occasionally.

About 300 samples of pork meat products at retail will be analysed in 2015 to  study the occurrence of MRSA in Finland.

How is MRSA transmitted between humans and animals?

MRSA bacteria can be transmitted between humans and animals. For this reason, the occurrence of MRSA at pig farms may mean that MRSA transmission between pigs and the personnel working at farms or slaughterhouses can occur.  The use of antibiotics at production animal farms favours the proliferation of resistant strains and may maintain the source of the infection. Therefore the use of antibiotics should always be justified. Within families, MRSA transmissions between humans and pets may occur from humans to animals or vice versa. In many cases, it is difficult to say which was the primary source. Good general and hand hygiene is the best way to prevent infection.

Are foods safe with respect to MRSA?

Since MRSA spreads through contact, i.e. via hands, the handling or eating of meat or other foods harbouring MRSA could theoretically result in an MRSA infection. However, according to current knowledge, MRSA bacteria are not easily spread by means of handling or eating foods containing MRSA. Therefore, the risk of getting MRSA through meat or some other food is minor. Similarly to other Staphylococcus aureus bacteria, some MRSA strains may produce enterotoxins, which cause food poisoning. With regard to symptoms or severity, food poisoning caused by MRSA is not different from food poisoning caused by other S. aureus bacteria.

MRSA can be eliminated from food by heating, meaning that MRSA infections can be prevented, similarly to other food bacteria, by means of good food preparation and hand hygiene. Normal hygienic work practices are effective against food bacteria: sufficient heating, appropriate handling of raw materials, and cleaning of hands when preparing food.

Does MRSA pose a risk to people working in the meat industry?

Animals may carry MRSA without exhibiting any symptoms. On Finnish production animal farms, MRSA has been found in pigs, dairy cows and horses. Of these animals, especially pigs are considered to be a reservoir of the MRSA CC398. Personnel in contact with living pigs, such as pig farmers, vets and slaughterhouse workers, are particularly in risk of getting MRSA from pigs.

The spread of MRSA from animals to humans are prevented at every phase of the production chain by complying with good work hygiene standards. Particular attention should be paid to hand hygiene.

To what temperature should food be heated to kill MRSA?

MRSA can be killed in food by heating. This means that MRSA infections can be prevented like other food-borne bacteria through good work and hand hygiene. Normal hygienic practices are enough to kill food bacteria: adequate heating (e.g. Christmas ham should be cooked to a temperature of at least 75 degrees), appropriate handling of raw materials and clean hands when preparing food.