A MRSA screening is a process whose purpose is to detect the presence of the MRSA bacteria in patients. MRSA screenings are used primarily on colonised patients and on infected patients after they have been treated, to determine whether any resistant bacteria remains.

At a community level, MRSA screening may help to identify the source of a MRSA outbreak, and at a national level it can help to identify genetic characteristics of a MRSA strain.

MRSA Culture

The most commonly used test to identify MRSA colonisation is the culture. A swab is taken from the patient and is then cultured. Swabs are usually taken from the nose, though they can also be collected from wound sites or skin lesions on people with known MRSA infections. The culture is a definitive test and usually takes one to two days to complete.

When Are MRSA Screenings Performed?

A MRSA screening may be requested when a doctor, health department, researcher or hospital wants to evaluate MRSA colonisation in a patient, family member or group of people within the community. Certain populations in a community whose members have close contact may be tested for MRSA when an increased number of infections occur within their group. Example of these populations include football teams, residents of nursing homes and health care workers. Sometimes patients who have previously been treated for MRSA will be screened to determine whether the bacteria is still present.

MRSA Screening On Admission To Hospital

To cut down the number of hospital acquired MRSA infections, some hospitals have introduced a screening process that takes place when patients are admitted. Additionally, healthcare workers and family members of carriers may also be screened for MRSA.

Testing For MRSA

A Methicillin-resistant Staphylococcus aureus (MRSA) screen is conducted to identify the presence of MRSA and no other pathogens. MRSA may be present in a colonised patient or in the wound site of a patient already treated for an MRSA infection.

The Culture

The culture is the most widely used form of testing to identify MRSA colonisation. A nasal swab is collected from the nostrils of an asymptomatic person and cultured. This means it is either put into a special nutrient broth or spread onto a nutrient gel. It is then incubated and examined for the growth of MRSA colonies. It is also possible to collect a swab from a wound site of a person previously treated for MRSA. That too would be cultured. Testing in this way can take up to two days but the results are definitive.

MRSA Testing – Results

A patient is a carrier of MRSA if the screen is positive.

MRSA remains if a wound site culture take from a person previously treated for MRSA is positive.

MRSA is either not present or not significantly present if the nasal screen or wound site culture is negative.

Testing High Risk Groups For MRSA

Currently universal testing for MRSA is not practised. Some hospitals have identified high-risk patients, who may be potential MRSA carriers and conducted MRSA screening in a bid to control the spread of MRSA. Healthcare workers and family members of carriers may be screened for MRSA. In nursing homes, for example, many people may be tested for MRSA so as to understand the extent of the spread of colonisation.

Screening for MRSA alone, however, cannot prevent its spreading. In a study conducted by Geneva University, 22,000 patients took part. Some patients were subject to testing for MRSA and some were not. Those patients found to be colonised by MRSA in the screening group were exposed to a range of measures such as isolation and decontamination. Interestingly, no significant difference between the numbers contracting MRSA, during their hospital stay, were found. So what is the solution to this?

Testing More Effectively

Testing for MRSA could be targeted better:

1. Surgical patients who undergo elective procedures, with a particularly high risk of MRSA infection, could be targeted. A patient could be screened for MRSA if undergoing a surgical procedure such as a prosthetic implant.
2. Transplantation, cardiothoracic, orthopaedic, intensive care, burns, trauma, vascular surgery and renal and referral centres are all areas with a high proportion of MRSA infection among colonised patients. If testing is specifically directed into these areas, screening will become increasingly effective.
3. Where there is a high risk of MRSA carriage, MRSA testing should be directed.

Patients having experienced a previous MRSA infection or colonisation should be screened.

Patients frequently readmitted to healthcare facilities and patients who were recently inpatients or residents at a hospital or healthcare facility, with a likely high prevalence of MRSA, should be screened.

It is argued that because the contamination of the hospital environment is a greater cause of infections than patients arriving at the hospital with MRSA, the targeting of screening is particularly important. So where are we currently in respect of testing for MRSA?

MRSA Testing – The Present Situation

In the UK, the Labour government has called on NHS hospitals to introduce screening for routine operations. However, this is just one part of its anti-infection strategy. The recruitment of additional infection control nurses and the deep cleaning of hospitals are included in the government’s approach. This task is made much more difficult when considering that the number of cleaners in the NHS has fallen from 100,000 in 1984 to 55,000 in 2004. A reversal in this trend is certainly expected if any ground is to be made in combating MRSA. The government is right, however, to be adopting a multi-faceted strategy because testing alone will not control MRSA.

Testing for MRSA plays an instrumental role in beginning to control its spread. Screening for MRSA can be made more effective by directing it towards higher risk groups; however, this must be done in conjunction with other measures. Whether this will significantly reduce the spread in the long-term, we do not know for sure, but certainly, it is a positive move in the right direction.