EFSA Evaluates Risk of MRSA in Food and Animals

Various types of MRSA, including CC398, can be found in slaughterhouses and on raw meat, but the Panel stated that, based on current data, the risk of infection for slaughterhouse workers and persons handling meat appears to be low.

30/03/09 The European Food Safety Authority (EFSA) has published an opinion on the public health significance of meticillin-resistant Staphylococcus aureus (MRSA) in animals and foods. EFSA’s Panel on Biological Hazards (BIOHAZ) found that while food may be contaminated by MRSA, there is currently no evidence that eating or handling contaminated food may lead to an increased risk of humans becoming healthy carriers or infected with this bacterium. The Panel also concluded that where MRSA prevalence in food-producing animals is high, people in contact with live animals, especially farmers, veterinarians and their families, are at greater risk than the general population.

In the case of food-producing animals, a specific type of MRSA, called CC398, has emerged and is most often carried without symptoms by intensively reared animals. The Panel noted that this strain represents a small proportion of the overall cases of MRSA in the European Union. Various types of MRSA, including CC398, can be found in slaughterhouses and on raw meat, but the Panel stated that, based on current data, the risk of infection for slaughterhouse workers and persons handling meat appears to be low.

Professor Dan Collins, chair of the BIOHAZ Panel, said: “There’s no evidence to date that humans can become infected with the CC398 strain of MRSA from eating contaminated food. Neither is there evidence that this strain has caused food poisoning.”

The Panel further noted that the occurrence of CC398 varies widely throughout Europe. A risk for people in contact with live food-producing animals has been identified and veterinarians and farmers, as well as their families, are at greater risk of becoming carriers or infected than the general population. In affected countries, the CC398 strain is mostly detected in pigs, veal calves, and broiler chickens.

Animal pets can also become infected with MRSA, but almost in all cases the bacteria is passed from humans to pets and then back to humans. The Panel noted that there are no specific studies available which examined the relative risk of different small animals and horses as sources of infection in humans.

Regarding control options, the Panel said that animal movement and contact between animals are each likely to be an important factor for the transmission of CC398. The Panel said that since the most important routes of transmission to humans are through direct contact with live animals and their environments, the most effective control measures are likely to be at farm level.

The BIOHAZ Panel also said that systematic monitoring of MRSA should be carried out to evaluate trends in the development of MRSA in food-producing animals in all Member States. Further work should be performed on harmonising methods for sampling, detecting and quantifying MRSA in humans and animals, and for detecting MRSA as a contaminant in food, and in the environment. The Panel also recommended that guidelines for screening of patients admitted to hospitals should be expanded to include professional categories exposed to intensively reared livestock.

The Staphylococcus aureus is a bacterium that can be persistently or intermittently carried by healthy humans and it is a very common cause of minor skin infections that usually do not require treatment. In patients in hospitals, Staphylococcus aureus is a common cause of hospital-acquired infections. Its variant, meticillin-resistant S. aureus (MRSA) first emerged in the 1970s, and is now often found in hospitals in many European Member States. In recent years, clones of MRSA have evolved outside the hospitals, causing infections among people who have no connection with hospitals.

The Scientific Opinion of EFSA’s BIOHAZ Panel, to which the European Centre for Disease Control and Prevention (ECDC) also contributed, was carried out in parallel with the work of the European Medicines Agency (EMEA) on other aspects of MRSA. EMEA has published a reflection paper on the use of antimicrobials in livestock and companion animals in relation to the risk of MRSA infection in animals. (EMEA reflection paper). A summary paper bringing together the findings on the topic of MRSA by the three EU agencies is scheduled to be published later in the year.