Meticillin-resistant Staphylococcus aureus (MRSA)

Introduction

Staphylococcus aureus is a common bacterium present on skin and in mucous membranes in 20-30% of healthy people. Most of the time it is harmless, but it can cause infections: ­typically local skin and wound infections, but occasionally more severe infections in the body.

Some strains of S. aureus can develop resistance to beta-lactam antibiotics such as penicillin, which are widely used to treat infections. These strains are known as meticillin-resistant S. aureus (MRSA).

Humans typically acquire MRSA through direct contact with infected people or with contaminated medical devices and equipment. MRSA is especially problematic in hospitals, where patients with weakened immune systems are vulnerable to infection.

A specific MRSA strain (CC398) has been reported in food-producing animals, most commonly in intensively reared pigs, veal calves and chickens, and several strains have also been found in horses and companion animals.

EFSA has concluded that food may be contaminated by CC398, but it has not been commonly associated with foodborne infections. However, in areas where MRSA prevalence in food-producing animals is high, people in contact with live animals are at greater risk of acquiring CC398 than the general population, although infections are rare.

Latest

Two livestock-associated methicillin-resistant S. aureus bacteria found in pigs were reported to be linezolid-resistant, says the annual report on antimicrobial resistance by EFSA and ECDC. Linezolid is one of the last-resort antimicrobials for the treatment of infections caused by highly resistant to meticillin.

Milestones

October 2017 EFSA, ECDC and EMA establish a set of indicators that will assist Member States to assess their progress in reducing the use of antimicrobials and combating antimicrobial resistance. These include the proportion of S. aureus bacteria that are resistant to MRSA.

June 2010 EFSA evaluates factors contributing to the spread of MRSA in pigs, following publication of the first EU-wide survey on the occurrence of the bacteria in pigs. Most infections are transmitted through direct or indirect human-to-human contact. People can also be exposed to MRSA through contact with infected animals; this is particularly the case for farmers, veterinarians and their families. There is currently no evidence that MRSA can be transmitted to humans through the consumption or handling of contaminated food.

November 2009 EFSA, the European Centre for Disease Prevention and Control (ECDC), the European Medicines Agency (EMA)and the European Commission’s Scientific Committee on Emerging and Newly Identified Health Risks (SCENIHR) publish a joint scientific opinion on antimicrobial resistance focused on infections that can be transmitted to humans from animals and food (i.e. zoonotic diseases).

June 2009 EFSA, ECDC and EMA publish a joint scientific report on MRSA in livestock, pets and foods. Experts say that food-producing animals such as pigs, veal calves and broiler chickens often carry without symptoms a specific strain of MRSA called CC398.

March 2009 EFSA publishes an opinion on the public health significance of MRSA in animals and foods. Experts say 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 these bacteria.

Role

EFSA provides independent scientific support and advice to risk managers on the risks to human and animal health related to the possible emergence, spread and transfer of antimicrobial resistance in the food chain and in animal populations. EFSA takes an integrated and multidisciplinary approach to its work on antimicrobial resistance.

In its work, EFSA cooperates closely with other relevant EU agencies such as the European Centre for Disease Prevention and Control (ECDC) and the European Medicines Agency (EMA).

Monitoring and analysis of antimicrobial resistance in the food chain

EFSA monitors and analyses the situation on antimicrobial resistance in food and animals across Europe. EFSA is assisted by the network for zoonoses monitoring data, a pan-European group of national representatives and international organisations that assist EFSA by gathering and sharing information on zoonoses in their respective countries.

Based on data collected by the EU Member States, EFSA produces in cooperation with ECDC annual European Union summary reports on zoonotic infections, foodborne outbreaks and antimicrobial resistance showing the situation in Europe.

EFSA also publishes baseline survey reports on the prevalence of antimicrobial resistance in the EU in specific animals, for instance MRSA in pigs, and provides guidance to national authorities on how to carry out monitoring and reporting activities.

EFSA’s scientific panels review the annual reports and make recommendations on prevention and reduction measures.

Risk assessments and recommendations

EFSA assesses the risks of antimicrobial resistance and provides scientific advice on control options at the request of risk managers or on its own initiative. This includes work on antimicrobial resistance in the food and feed chain and the public health significance of MRSA in animals and food focusing on the specific type of MRSA found in food-producing animals. EFSA also assesses the safety of animal feed additives, including the risks related to antibiotic resistance where micro-organisms are involved.

EU framework

MRSA is part of the EU policy on patient safety. In this legislation, EU actions include recommendations on preventing and controlling these infections and on the prudent use of antibiotics in human medicine.

ECDC monitors the evolution of healthcare-associated infections, including MRSA in Europe.