Review
Health-care workers: source, vector, or victim of MRSA?

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Summary

There is ongoing controversy about the role of health-care workers in transmission of meticillin-resistant Staphylococcus aureus (MRSA). We did a search of the literature from January, 1980, to March, 2006, to determine the likelihood of MRSA colonisation and infection in health-care workers and to assess their role in MRSA transmission. In 127 investigations, the average MRSA carriage rate among 33 318 screened health-care workers was 4·6%; 5·1% had clinical infections. Risk factors included chronic skin diseases, poor hygiene practices, and having worked in countries with endemic MRSA. Both transiently and persistently colonised health-care workers were responsible for several MRSA clusters. Transmission from personnel to patients was likely in 63 (93%) of 68 studies that undertook genotyping. MRSA eradication was achieved in 449 (88%) of 510 health-care workers. Subclinical infections and colonisation of extranasal sites were associated with persistent carriage. We discuss advantages and disadvantages of screening and eradication policies for MRSA control and give recommendations for the management of colonised health-care workers in different settings.

Introduction

Hospitals worldwide are increasingly concerned by meticillin-resistant Staphylococcus aureus (MRSA). Whereas hospital-acquired MRSA (HA-MRSA) has been a concern for inpatients since the 1960s, the threat of community-associated MRSA (CA-MRSA) has recently been associated with young and healthy people without traditional risk factors.1, 2, 3 CA-MRSA has started to spread from the community into hospitals, where outbreaks have occurred.1, 2, 3, 4 Since health-care workers are at the interface between hospitals, long-term care facilities, and nursing homes on the one hand and the community on the other, they may serve as reservoirs, vectors, or victims of MRSA cross-transmission (figure 1).

Although the role of health-care workers in sporadic, epidemic, and endemic MRSA transmission has been extensively described in individual reports, the only previous review was restricted to outbreak investigations.5 Moreover, infection control practitioners and professional societies have reached different conclusions about the implications for daily practice.6, 7, 8, 9, 10, 11 In view of these uncertainties and current changes in the epidemiology of MRSA, more comprehensive approaches to controlling MRSA should be considered. We review the reported prevalence of MRSA colonisation in health-care workers and their role in MRSA transmission. Based on these results, we formulate recommendations for MRSA screening in personnel and for further management of colonised health-care workers.

Section snippets

MRSA and health-care workers

We identified 169 original articles that reported either prevalence, risk factors, or management—including screening, decolonisation, and work-related consequences—of MRSA colonisation or infection in health-care workers from 37 countries. Most reports were from high-income countries, and included 102 outbreak investigations, 29 point prevalence studies, 32 prospective surveillance studies, and six case reports or case series. Notably, we did not identify any controlled intervention studies

Stages of MRSA carriage

Three types of MRSA carrier status can be distinguished for health-care workers:51 non-carriers; persistent carriers, who are chronically colonised with the same strain; and intermittent or transient carriers, who are colonised with varying strains for short time periods.

Cookson and colleagues51 collected nasal swabs from 26 nurses working in a dedicated MRSA ward before and after each shift for 7 weeks. Transient carriage after a shift, which was lost before the next shift, was identified in

MRSA carriage and outbreaks

Several studies have described outbreaks of MRSA among patients associated with colonised health-care workers. From 1992 to 2002 at Utrecht University Hospital (Netherlands), where strict isolation procedures were in place, colonisation with MRSA was identified in less than 1% of health-care workers.31 Spread to other areas of the hospital could usually be prevented if the index case had been identified, but was common when the source remained unknown. Importantly, health-care personnel served

MRSA carriage in settings with endemic MRSA

MRSA carriage of health-care workers was lower during outbreaks (3·9%) compared with endemic settings (8·1%), although heterogeneity between studies prevented direct comparisons. Shorter duration of outbreaks, greater attention to hand hygiene, and attempts to eliminate carriage among patients and health-care workers may contribute to lower rates during outbreaks. By contrast, health-care systems with endemic MRSA are overwhelmed by high numbers of carriers with lower awareness of the threat of

CA-MRSA and health-care workers

The role of health-care workers in CA-MRSA transmission is still poorly studied;75 they may be the source or vectors of cross-infection,132 they may become secondarily colonised or infected from patients,133 or their colonisation may be unrelated to colonisation in patients.134 Although rates of CA-MRSA colonisation appeared to be similar to HA-MRSA in our review, there was a higher proportion of infection, highlighting the direct hazard to medical personnel.133 This finding was confirmed in a

MRSA and household transmission

Both CA-MRSA and HA-MRSA have spread to close contacts of health-care workers.45, 46, 57, 66, 67, 73, 97, 137, 138, 139 Not only does this entail risks for family members,140 but can also lead to further spread of MRSA.39, 43, 97 This may be particularly relevant for easily transmissible strains43 such as EMRSA-1567 or EMRSA-16.97 Moreover, the home environment can become contaminated with MRSA, which may occasionally require commercial cleaning or complete removal of contaminated material.39,

Screening of health-care workers

A recent review of MRSA outbreaks found a strong association between patient and health-care worker carriage and recommended that screening efforts should focus on health-care workers with symptomatic infection.5 However, screening of infected health-care workers only will likely miss a large number of asymptomatic personnel capable of transmitting MRSA to patients, since staphylococcal dispersal is mainly dependent on whether the person is a nasal carrier.141 There was no marked difference in

Eradication of MRSA carriage

Decolonisation of health-care workers as part of a multifactorial approach has contributed to successful termination of nosocomial MRSA outbreaks,89, 90, 91, 92 which appears easier and more cost effective if applied early before MRSA becomes endemic in an institution.143, 144, 145 In a systematic review, nasal mupirocin was found to be safe and effective, leading to eradication of staphylococci in 130 (91%) of 143 health-care workers at 48–96 h post-treatment; 96 (74%) of 130 successfully

Documentation of eradication and follow-up

Although not recommended or specifically mentioned in British and US guidelines,6, 153, 154 Dutch10 and German8 guidelines emphasise removal of nasal carriers from patient care for at least 48 h after initiation of eradication therapy10 or proven eradication.8, 10 Within 2–3 days of starting mupirocin, MRSA is usually eradicated from the nares;66, 89, 144, 155 therefore, some institutions do not require health-care workers to be removed from patient contact.32, 34

The timing and number of

Treatment failure and relapse

Risk factors for eradication failure are mainly colonisation of extranasal sites or subclinical infections.39, 41, 45, 46, 60, 64, 65, 66, 156, 157 In a few instances, health-care workers even underwent tonsillectomy or other surgical interventions to achieve definitive eradication of MRSA carriage.45, 111, 158 Mupirocin resistance, which occurs at increased rates after widespread application of the drug,18 is an additional risk factor for treatment failure and relapse.157, 159

Recommendations

Health-care worker screening should take place irrespective of the presence of risk factors or purulent infections as part of pre-employment examination,55, 130, 160, 161 or even periodically162 and unannounced before a work shift to avoid detecting only transient carriers.5, 11, 111 Recently, similar or higher percentages of pharyngeal than nasal S aureus163, 164 and MRSA carriage163, 165 have been reported, particularly in healthy people.163, 164, 165 By contrast, throat screening for MRSA in

Limitations

We aimed to provide a broad overview of experiences over different time periods and geographical areas, and therefore accepted considerable heterogeneity in the quality of the reviewed literature. Since many of the included publications were case series or outbreak investigations with limited numbers of MRSA-positive health-care workers, the level of evidence is variable, but they are nonetheless of hypothesis-generating or practical importance. Publication bias is conceivable in opposing

Future research

Since the epidemiology of CA-MRSA is still poorly understood in terms of duration of carriage, transmissibility, attack rates, and possible eradication, future investigations will have to clarify the role of health-care workers as reservoirs and vectors of CA-MRSA in health-care facilities.138 We are aware of the funding constraints and shortages in staff and laboratory facilities in resource-poor environments175 in the face of frequently high MRSA prevalence.73, 176 Feasibility of some of our

Conclusions

The reviewed literature supports different roles of health-care workers in association with MRSA. About 5% of health-care workers become colonised with MRSA, of whom approximately 5% develop clinical disease. Based on the published evidence,127, 177 health-care workers are likely to be important in the transmission of MRSA, most frequently acting as vectors and not as the main sources of MRSA transmission. Thus, good hand hygiene practices remain essential to control the spread of MRSA.127, 177

Search strategy and selection criteria

We searched Medline and Current Contents for mainly English, French, and German articles (including English abstracts of other language articles) published between January, 1980, and March, 2006, on the prevalence, risk factors, and management of MRSA colonisation or infection in health-care workers. Combinations of the following terms were used: “MRSA”, “oxacillin”, “methicillin”, “personnel”, “healthcare worker”, and “healthcare workers”. We also searched an internet-based database of

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