Navigation und Service

Frequently Asked Questions about methicillin-resistant Staphylococcus aureus (MRSA)

Methicillin-resistant Staphylococcus aureus - in short MRSA - is a bacterium that causes, amongst other things, wound infections and inflammations of the respiratory tract in humans. It is resistant to certain antibiotics. Up to now, this germ was mainly found in hospitals where it was transmitted from person to person. In recent years there have been increased cases of infections which people have contracted outside hospital. At the same time, it is becoming increasingly clear that MRSA also occurs in animals, mainly in pigs. The Federal Institute for Risk Assessment (BfR) has compiled Frequently Asked Questions about MRSA and possible sources of infection for man.

Up

Fragen

• What is MRSA?
• How frequently do infections with MRSA occur?
• Is MRSA widespread in Germany compared to other countries?
• How can people become infected with methicillin-resistant S. aureus (MRSA)?
• Can animals carry MRSA?
• Can people become infected through contact with animals?
• Can people become infected with MRSA from food?
• Can consumers tell whether a food is contaminated with MRSA?
• Can consumers notice MRSA on the skin?
• What should consumers do when their skin is colonised with MRSA?
• What are public authorities doing to combat MRSA?
• What can consumers do to protect themselves against methicillin-resistant S. aureus?

What is MRSA?

The abbreviation "MRSA" stands for "methicillin resistant Staphylococcus aureus". It is the name given to Staphylococcus (S.) aureus with the specific property of methicillin resistance. Staphylococcus aureus is a widespread bacterium which colonises the skin and mucous membranes of humans and animals. Normally, colonisation goes unnoticed. As S. aureus is found on the skin, it is frequently involved in infections of the skin and mucous membranes. Certain strains of S. aureus are associated with nosocomial infections. These are infections which people develop during in-patient hospital treatment. These strains are called hospitalism germs. They can cause wound infections, inflammation of the respiratory tract and blood poisoning (septicaemia).

Staphylococcus aureus also plays a role as a pathogen in foodborne intoxications. When the pathogen multiplies readily in a food, enterotoxins are formed which may lead, when the food is consumed, to typical intoxication symptoms like vomiting and nausea.

The methicillin-resistant variant of S. aureus is not sensitive to beta-lactam antibiotics, i.e. to penicillins or cephalosporins. These antibiotics are no longer effective when it comes to treating an infection. This constitutes a particular challenge for the attending doctor as these antibiotics are the standard treatment for this group of pathogens.

Up

How frequently do infections with MRSA occur?

Infections with MRSA mainly occur in hospitals (they are called nosocomial infections and also hospital acquired MRSA). Aside from this, a growing number of infections in humans has been observed which were contracted outside hospital ("community acquired MRSA" infections). In recent years there have been more and more reports of MRSA in pigs, other livestock, horses and small animals. Only isolated figures are available on how frequently healthy individuals are colonised with MRSA in Germany. However, it can be assumed that around one percent of the population are MRSA carriers. In hospitals the numbers are higher. The National Reference Centre for Staphylococci of the Robert Koch Institute collects and types the detected MRSA and analyses the available information.

Up

Is MRSA widespread in Germany compared to other countries?

Compared to other European countries, Germany is in the middle range when it comes to the prevalence of MRSA in hospitals. In Scandinavia and the Netherlands, intensive efforts have been undertaken to control and monitor MRSA and hence it is less widespread there. In the United Kingdom and southern European countries the proportion of methicillin-resistant S. aureus in all S. aureus is far higher.

Up

How can people become infected with methicillin-resistant S. aureus (MRSA)?

Hospitals and more particularly intensive care wards are the most frequent source of MRSA infections. Hospital staff go to great lengths to prevent or identify infections of this nature early on. There is a higher risk of MRSA infection in the case of people with chronic diseases, a weakened immune system or who are on antibiotic medication, especially if this is not taken properly. Direct contact with MRSA carriers and indirect contact with jointly used objects like towels or a lack of hygiene are the main transmission pathways for MRSA.

Up

Can animals carry MRSA?

In recent years there have been increasing reports of MRSA in animals. These reports involve infections in small animals like dogs and cats but also in horses during a stay in animal clinics or veterinary surgeries. They suffered in particular from wound infections. Secondly, a certain type of MRSA has been detected mainly in pigs which seems to be spreading in animal stocks. By contrast, S. aureus has been a recognised pathogen in inflammations of the mammary gland (mastitis) particularly in cattle for some time now. Up to now, methicillin-resistant S. aureus had only been rarely detected in these cases of disease.

Up

Can people become infected through contact with animals?

Contact with colonised animals can lead to human colonisation with MRSA. So far, this has been described the most frequently after direct contact with pigs and calves. As, however, there have been reports of colonisations and infections in almost all types of pets, each of these animal species is a potential source of MRSA colonisation of humans under certain circumstances. People, who have frequent contact with pigs in a work environment, also run a higher risk of colonisation. Cases of disease involving skin and wound infections or respiratory tract infections with MRSA from animals have only been observed rarely up to now. Very little is known about the exact transmission pathway from animals to humans. In farms with MRSA-colonised animals the pathogen can be detected in dust. It is not yet clear whether inhalation of the disturbed dust plays a role in the colonisation of farmers and veterinary surgeons. Pets like dogs and cats are exposed to a higher risk of colonisation when they have to be treated in animal clinics. The same factors are involved here as for humans in hospitals. Wherever many animals with different diseases congregate, the infection pressure is high. Germs that are insensitive to frequently used antibiotics are at an advantage over sensitive germs. They can colonise further animals and, in some cases, make them sick.

Up

Can people become infected with MRSA from food?

So far there have only been few reports of cases in which an MRSA infection in humans could be attributed to food. In the few known cases the foods had been contaminated by infected persons. Many foods do not offer S. aureus favourable living conditions, which means that the germ cannot multiply readily. In principle, all heat-treated foods like pasteurised milk, roasted or cooked meat are safe. However, care must be taken to ensure that the food is not recontaminated after heat treatment. According to studies from the Netherlands, raw meat from all species of animals may contain low levels of methicillin-resistant S. aureus. It is, therefore, important to strictly comply with customary hygiene measures when handling raw meat. This also offers protection against other infection pathogens like Salmonella, Campylobacter and Escherichia coli.

Up

Can consumers tell whether a food is contaminated with MRSA?

No. This can only be established through extensive laboratory studies.

Up

Can consumers notice MRSA on the skin?

No. Colonisation does not normally lead to any ill effects. S. aureus is part of the skin’s normal bacterial flora. Colonisation with MRSA can only be determined by a laboratory examination. This is frequently done by taking of a swab of the nasal mucosa.

Up

What should consumers do when their skin is colonised with MRSA?

Colonisation does not automatically mean the consumer will become ill. Many people are only temporarily colonised with MRSA without noticing it. Colonisation does, however, increase the likelihood of contracting an inflammatory infection through MRSA. In cases like these people are best advised to discuss the steps to be taken with their general practitioner or local health centre.

Up

What are public authorities doing to combat MRSA?

Public health authorities have been endeavouring for years to prevent the spread of MRSA in humans. Despite these efforts MRSA still constitutes a major challenge for health care. Because of reports of MRSA in animals, especially in livestock and foods of animal origin, veterinary and food control authorities are currently examining on the national and international levels the extent to which methicillin-resistant S. aureus is widespread in animals and foods and the importance of this as an additional source of infection for humans. The Federal Institute for Risk Assessment regularly updates its assessment of the risk for consumer health protection on the basis of emerging data. It makes this assessment available to the Federal Government and the veterinary authorities. Under the aegis of the Federal Ministry of Food, Agriculture and Consumer Protection (BMELV) a working group has been established with representatives from the sciences as well as health, veterinary and food control authorities. It is currently researching ways of reducing MRSA levels in the animal population and of minimising as far as possible the threat to human health.

Up

What can consumers do to protect themselves against methicillin-resistant S. aureus?

The normal hygiene recommendations for handling food and animals apply when it comes to protection against MRSA colonisation. After contact with animals as well as before and after preparing raw meat, consumers should wash their hands thoroughly with soap and water. Furthermore, efforts should be made to avoid any direct contact between the mouth and animals or raw meat.

Up