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Best Practice: Exploring the evidence for screening staff for MRSA

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Author Christine Perry, MSc, RN, is assistant chief nurse and director of infection prevention and control at University Hospitals of Bristol NHS Foundation Trust.

Abstract Perry, C. (2008) Exploring the evidence for screening staff for MRSA. Nursing Times; 104: 36, 34–36.

Christine Perry reviews the current evidence for screening staff for MRSA and the issues to be considered when screening identifies positive members of staff.

Screening staff for MRSA and restricting those found positive from duty are hotly debated in the popular and medical press (Brady, 2008; Simpson et al, 2007). UK guidelines for the control of MRSA (Coia et al, 2006) do not recommend mass staff screening but the adoption of a risk-based approach. Understanding the rationale for staff MRSA screening protocols requires an appreciation of the extent to which staff carry MRSA and the role this plays in MRSA transmission, the purpose of screening programmes and associated employment issues.

Background information on MRSA can be found in Box 1.

Box 1. Facts about MRSA

The bacterium MRSA was first identified in 1961. It is a gram-positive cocci that colonises the skin and mucuous membranes. Healthcare-associated strains commonly cause wound, invasive device and lower respiratory tract infections. If it is spread within a healthcare environment, it occurs through direct contact, for example from healthcare workers hands, from contaminated equipment, or in some circumstances airborne spread may occur. In recent years cases of MRSA have been seen in fit healthy people who have had no contact with healthcare, particularly in the US. These community-associated strains cause skin and soft tissue infections, for example, recurrent boils. Prevention and control of MRSA relies on a high standard of infection control precautions at all times (including single-room isolation or cohorting), appropriate screening policies and good compliance with topical therapies aimed at reducing or removing carriage of the organism.

Staff carriage of MRSA

Staphylococcus aureus is an inhabitant of the skin or nose in 20–30% of the general population (Hawker et al, 2001) and some may carry meticillin-resistant strains. In a recent UK study, 6.6% of patients admitted to a medical admission unit were found to be MRSA positive and 21.1% of patients visited by district nursing staff were tested as positive (Thomas et al, 2007).

MRSA carriage rates among healthcare workers have generally been reported as low (Nulens et al, 2005; Scarnato et al, 2003). However, in one UK study, 7.7% of GPs were found to have MRSA nasal carriage (Mulqueen et al, 2007). Levels of staff MRSA carriage in published studies are difficult to interpret. This is because staff are exposed to MRSA during the course of their work and may acquire transient carriage of the organisms that is lost when they leave the healthcare environment (Dawson et al, 1997).

Albrich and Harbath (2008) propose three distinct states of MRSA carriage in healthcare workers:

  • Non-carriers;
  • Persistent carriers who have long-term carriage with the same strain;
  • Intermittent or transient carriers who have carriage with varying strains for short periods of time.

Outbreaks of MRSA have frequently been attributed to poor staff hand hygiene (Farrell et al, 1998) or to contaminated equipment (Schultsz et al, 2003; Rampling et al, 2001).

The role of staff in the transmission of MRSA to patients is still considered to be controversial (Simpson et al, 2007). However, a recent extensive review of published studies (Albrich and Harbrath, 2008) has concluded that transmission from staff to patients may be greater than previously thought.

Where staff have persistent carriage of MRSA, their role in transmission to and infection of patients is still questionable. Of 23 healthcare workers who tested positive for MRSA over a two-year period, only one was identified as a source of infection to patients (Lessing et al, 1996).

Where staff are epidemiologically linked to MRSA infections in patients, it is often where they have not responded to a programme of MRSA eradication therapy, where they are increased dispersers of skin scale (Sherertz et al, 2001), or where they have ongoing episodes of infection (Bertin et al, 2006).

In a hospital outbreak of a community-associated MRSA, two healthcare workers who were positive for the outbreak strain had recurrent eye infections or skin abscesses (CDR Weekly, 2006). Evidence that healthcare worker screening and MRSA eradication have been necessary to arrest outbreaks where other infection control interventions have been unsuccessful (Ben-David et al, 2008), supports the current emphasis in the UK guidelines on incremental staff screening.

When and how should staff be screened for MRSA?

Current UK guidance does not support mass staff screening. However, it indicates that, where new cases of MRSA occur among patients on a ward, staff with skin lesions should be referred to an occupational health department for screening and treatment of any dermatological or other long-term condition. In addition, staff screening is indicated where:

  • Other active control measures (for example, isolation) have not been successful in preventing an outbreak;
  • Where there are unusual epidemiological issues, for example, a day-case centre where MRSA-positive patients have not overlapped;
  • Where carriage by staff is suspected, for example, surgical wound infections where the same member of the scrub team has been involved in all cases.

Pre-employment screening is advocated by Albrich and Harbath (2008) but is not included in recommendations for health clearance (Department of Health, 2007a). The procedure for screening is outlined in Box 2.

Box 2. Screening process

  • Sites recommended for sampling in staff include the nose, the throat and any areas of abnormal or broken skin (Coia et al, 2006).
  • When sampling the nose, throat and skin, swabs can be moistened in sterile 0.9% saline before use, as this aids the transfer of bacteria from the sampling site to the swab (Perry, 2007), increasing the chances of detecting MRSA carriage.
  • The request form should state clearly that the specimens are for MRSA screening, to ensure the correct tests are carried out.
  • The request form should indicate this is a staff member for confidentiality purposes.
  • Screening of the hairline and groin/perineum in staff may be useful in guiding which treatment is used to eradicate MRSA and in determining whether ongoing exclusion from work is required (Coia et al, 2006).

Methods of MRSA testing

  • Rapid PCR testing, where the result is available after two hours – however, this method is licensed only for nose swabs;
  • Direct plating onto selective growth agar plates where an initial result can be available after 24 hours;
  • Broth culture and selective plating, where a negative result can be provisionally reported after 24 hours but a confirmed positive result may take 48 hours or more.

To avoid possible detection of transient carriage, staff should not be screened while they are on duty (Cookson et al, 1989). It should be carried out before the healthcare worker enters an environment where they will potentially be exposed to MRSA.

While nursing and medical staff are likely to have the most extensive patient contact, other groups of staff including allied health professionals and support workers should also be considered for inclusion in screening programmes.

Before a member of staff can be declared free of MRSA carriage, UK guidance recommends that a minimum of three MRSA screens, at weekly intervals, should be carried out once MRSA therapies have been completed. All of them should be negative.

The UK guidelines do not state specifically the sites to be sampled for clearance screens. It is prudent to sample the sites used at first screen (nose, throat and abnormal/broken skin) and any other areas found to be positive on sampling, for example, the hairline or groin.

Dealing with specific strains

For specific strains of MRSA the advice on staff screening is modified. For patients with an MRSA that has lowered resistance to glycopeptides, including vancomycin, screening of all staff contacts may be necessary, including weekly screening for those staff who have ongoing contact with patients (Coia et al, 2006).

If patients have an MRSA infection with the Panton-Valentine Leukocidin (PVL) toxin, screening swabs may be taken from all staff contacts, and samples taken from the following sites: nose; throat; perineum; axilla; skin lesions (DH, 2007b).

Staff should only be screened on the advice of the local infection control or health protection team. As staff screening for MRSA can have personal and employment implications, it should always be carried out in collaboration with an occupational health department or, where this is not available, with the support of the healthcare worker’s GP.

Management of MRSA positive staff

As an MRSA positive status can have ongoing implications for staff and healthcare organisations should have clear plans for management of staff who are found to be positive.

UK guidance on this issue is limited to the principle that only staff with colonised or infected hand lesions should be off work while receiving therapy for MRSA carriage (Coia et al, 2006). Local policies guide post-clearance sampling once the person has been declared free of infection and returned to work. The development of these local policies can lead to inconsistencies in management of staff and discrepancies in restrictions on staff activity and follow up (Hargreaves, 2006).

The RCN (2005) suggests that nurses with persistent MRSA colonisation should be considered to have occupationally acquired the condition and should be treated free of charge. It also recommends that the condition is reported under the Reporting of Injuries Diseases and Dangerous Occurrences Regulations (RIDDOR). In addition, staff should be suspended for medical reasons as opposed to taking sickness absence and should continue to be paid at normal pay levels.

Failure to clear MRSA carriage in staff can have major implications in terms of redeployment if the member of staff works in a high-risk area, for example, as a member of an operating room scrub team or with high-risk patients, for example, those requiring critical care. Before redeployment is considered, extensive efforts to clear carriage should be undertaken. Reports have indicated that extensive cleaning and soft furnishing replacement in the healthcare worker’s home (Allen et al, 1997) and screening and treatment of family members (Kniehl et al, 2005) may be necessary to clear ongoing carriage in some healthcare workers.

In the absence of prescriptive guidelines for the process of managing staff who are MRSA positive, adopting the approach for managing staff with hepatitis B (DH, 2007c), could aid in maintaining confidentiality and provide continuity for the affected healthcare worker.

This includes a formal individual risk assessment of the need to exclude the staff member from work and the appointment of a case manager (usually an occupational health physician) to liaise with the affected worker and relevant advisers over treatments and exclusions.

Conclusion

Although staff screening in the UK is not in line with other European countries with low MRSA rates, it is still based on current evidence and level of risk.

Staff screening should follow a strict protocol to ensure only persistent MRSA carriage is detected.

Workers who are found to be positive should be managed equitably and fairly and, with the same level of confidentiality afforded to patients.

Key Points

  • UK guidelines for the control of MRSA do not recommend mass staff screening (Coia et al, 2006).
  • Staff screening is indicated where:
    • Active infection control measures (for example isolation) have not been successful in stopping an outbreak;
    • There are unusual epidemiological issues, for example, a day-case centre where MRSA positive patients have not overlapped.
  • Carriage by staff is suspected, for example, infection of surgical wounds where the same member of the scrub team has been involved in all cases.
  • In the absence of prescriptive guidelines for managing staff who are MRSA positive, adopting the approach for managing staff with hepatitis B (Department of Health, 2007b), could help to maintain confidentiality and provide continuity for the affected healthcare worker.

 

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