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Transmission of MRSA from eating pork unlikely

09/2009, 12.05.2009

BfR and EFSA assess the risks from methicillin-resistant Staphylococcus aureus in livestock

The Federal Institute for Risk Assessment (BfR) has evaluated whether methicillin-resistant Staphylococcus aureus (MRSA) in livestock may constitute a health risk for humans. These "Livestock associated MRSA" (LaMRSA) are mainly found in pig stocks but also in other livestock. "It is unlikely, based on the knowledge currently available, that MRSA can be transmitted to humans from livestock via food like raw meat or raw milk", said Professor Dr. Dr. Andreas Hensel, "as we estimate that the amount of germs in and on food is low". Nevertheless, consumers should observe good kitchen hygiene when handling food in order to reduce any residual risk. People who are frequently in contact with livestock are more at risk of being colonised with MRSA. This group includes in particular farmers and veterinary surgeons but also slaughterhouse staff. Individuals who are colonised with MRSA do not automatically fall sick. Affected individuals should draw the attention of their doctor to possible colonisation with MRSA when being treated for other diseases and during hospital stays. In this way they can prevent MRSA leading to wound infections or triggering other infections because of their weakened immune system. The BfR assessment largely corresponds to the evaluation of the European Food Safety Authority (EFSA).

MRSA are strains of the bacterium Staphylococcus aureus that are resistant to specific antibiotics, the beta-lactam antibiotics. They colonise the skin and mucosa, and normally go unnoticed and do not provoke any effects. According to estimates around 1 to 2 percent of the population are colonised with MRSA. The bacterium can become a problem above all in hospitals. In the case of patients with a weakened immune system or chronic diseases it can lead to wound infections, infections of the respiratory tract and blood poisoning. They are very difficult to treat because of the bacterium’s antibiotic resistance. Since the 1990s there have been increasing reports of MRSA strains that do not come from hospitals.

In recent years it has emerged that the bacterium also plays a role in livestock. There have been more and more reports of positive tests in animals in which one specific type was identified in almost all cases. It is called ST398 and colonises both animals and humans. Up to now, it has only rarely led to diseases. Transmission to humans of this type is so rare that, at the present time, it can be assumed that colonised individuals do not constitute an elevated risk for other people. When it comes to transmission between animals, the use of antibiotics seems to play a role. Based on the latest findings, the bacterium is able to spread rapidly between various animal populations, particularly through trade involving colonised animals.

Thanks to extensive cooperation veterinary and public health bodies have obtained important insight in the space of two years into the spread of the pathogen and the estimation of the associated risk. During discussions and in working groups with experts, BfR has looked at and assessed the results of the ongoing studies. The National Working Group on MRSA in Livestock of the Federal Ministry of Food, Agriculture and Consumer Protection (BMELV) has discussed the possible management options to safeguard consumer health and specified the next steps. Developments are to be closely monitored by means of further research work, also in cooperation with other European countries. Joint steps by the veterinary and public health authorities are to minimise the carry-over of LaMRSA into public health facilities. At the same time, measures to reduce the pathogen in livestock are to be developed.

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