What is MRSA?
MRSA or methicillin-resistant Staphylococcus aureus refers to bacterial strains that differ from other S. aureus strains only in their resistance to antibiotics. Methicillin resistance does not increase the pathogenicity of the bacteria. MRSA strains are resistant to beta-lactam antibiotics such as penicillin and other betalactams. Like other S. aureus bacteria, MRSA may survive in the environment for extended periods of time.
What does it cause?
S. aureus is a common type of bacteria found on the skin and upper respiratory tract and does not cause disease in healthy people or animals. However, it may cause infections in areas of damaged skin or surgical wounds. Unlike on other infections caused by S. aureus, most common antimicrobials are ineffective on MRSA bacteria. Thus, their treatment is more difficult.
A person or animal may be an asymptomatic MRSA carrier either permanently or temporarily.
Has MRSA been found in animals or meat in Finland?
In Finland, MRSA has been detected in animal production among pigs, dairy cattle and horses. The occurrence of MRSA is systematically studied only in pigs. Consequently, numerous MRSA findings in pigs have been made both at pig farms and slaughterhouses. Though, the occurrence of the bacteria is relatively small in fresh pork. In dairy cattle, MRSA findings are uncommon, even though the actual incidence is unknown. MRSA is also rarely found in dogs and cats. On the Zoonosis Centre website, you can find more information on MRSA (in Finnish).
How is MRSA transmitted between people and animals?
MRSA bacteria can be transmitted between people and animals via touch, air and surfaces. Due to this, the incidence of MRSA in pig farms, for example, may cause a risk of infection to people working in close contact with MRSA carrying animals. The use of antibiotics at animal production farms increases the prevalence of resistant bacterial strains and may help sustain the source of infection. Due to this, antibiotics should only be used on justified grounds. On the website of the Finnish Institute of Occupational Health, you can find more information on protection against MRSA (in Finnish).
In households, MRSA can be transmitted from people to pets and vice versa, and it is often difficult to determine the original carrier. Good hygiene both in homes and on the farms, including hand hygiene, is the best way to prevent infection.
Is food safe from MRSA?
The risk to get MRSA through meat or other food is very low. Processing meat or food contaminated with MRSA may in theory lead to the transmission of MRSA. Though, according to current knowledge, MRSA is not contracted by eating or processing foods that contain such bacteria.
Just as other S. aureus bacteria, even MRSA can produce enterotoxins that cause food poisoning. Enterotoxin-producing staphylococci can only cause food poisoning, if the food in questions contained abundantly S. aureus bacteria. Food poisonings caused by MRSA do not differ from other S. aureus caused poisoning in terms of symptoms or gravity. This type of food poisoning is often short-term and runs its course.
Can raw pet food contain MRSA bacteria?
MRSA bacteria have been found in raw pet food in Finland. Raw pet food consists of raw meat as well as animal by-products, such as organ meats and cartilage, from animals approved for human food. Due to the nature of raw pet food products, the meat is not heated in order to destroy possible pathogens.
How to prevent an MRSA infection from foodstuff?
MRSA infections, like other unwanted foodborne bacteria, can be prevented with good food preparation practices and hand hygiene. MRSA is destroyed from food through heating.
Keep these in mind when preparing food:
- Use sufficient heating. Meat should be heated to at least 75° C.
- Handle raw materials properly. For example, prevent cross-contamination from raw meat to cooked food or fresh ingredients such as salads.
- Wash and dry dishes and utensils carefully. When washing by hand, wash utensils used to handle raw meat last in as hot water as tolerable. In machine wash, temperature should be 60° C. In both methods, it is important that dishes are dried completely before their next use.
- Always wash hands before preparing food and between work stages. At home, thorough washing with soap and warm water is usually enough. Use hand sanitiser if there is flu or stomach flu in your household. Remember that preparing food for others when sick is not advised.