MRSA Carriage Among Hospital Employees and Their Families

Abstract & Commentary

Synopsis: A total of 6.2% of hospital employees were nasal carriers of MRSA, with the rate highest among workers in long-term care (36%). In 4 of 10 families surveyed, family members were colonized by the same MRSA as the employee.

Source: Eveillard M, et al. Carriage of methicillin-resistant Staphylococcus aureus among hospital employees: Prevalence, duration, and transmission to households. Infect Control Hosp Epidemiol. 2004;25(2):114-120.

Eveillard and colleagues performed nasal surveillance swabs on 965 employees of a French tertiary care teaching hospital; the enrollment rate was 75%. At the same time, they conducted a point prevalence survey of hospitalized patients. A total of 262 employees (27.2%) were carriers of methicillin-susceptible Staphylococcus aureus, and 6.2% were carriers of methicillin-resistant S aureus (MRSA). MRSA carriage rates varied by occupation and hospital location. The prevalence was 9.0% among workers on clinical wards compared to 2.1% for nonclinical employees (P < .0001). Nurses and nursing assistants had the highest prevalence of carriage (9.6%), and administrative personnel had the lowest (0.8%). MRSA carriage rates among patients and employees varied by hospital location.

Comparing patient and employee strains by pulsed-field gel electrophoresis, employee strains were identical to patient strains for 25% of isolates from medical wards and 100% of isolates from long-term care wards.

In a second study of 72 volunteer health care workers, 14 (19%) were MRSA carriers. There was a statistically significant association between length of service in the hospital and MRSA carriage. Ten volunteer families underwent screening for MRSA carriage; 6 family members (3 spouses and 3 children) were MRSA carriers in 4 families. All strains isolated from family members were identical to the heath care worker’s strain by PFGE analysis.

Comment by Robert Muder, MD, Hospital Epidemiologist, Pittsburgh Medical Center, Pittsburgh, Section Editor, Hospital Epidemiology and Associate Edtior of Infectious Disease Alert.

Most information on MRSA carriage by health care personnel derives from studies of nosocomial MRSA outbreaks. The reported rates of carriage have varied widely, and an association between staff carriage of MRSA and patient infection is not always clear. There are few data on the prevalence of endemic MRSA carriage among health care workers.

The prevalence of MRSA carriage among employees working in acute care units ranged from 0% to 12.5%, which is comparable to the range reported in prior studies. It was lowest in the maternity unit, which is not surprising, as patients there had a low rate of MRSA colonization, due, no doubt, to their low burden of underlying disease.

It was surprising that the rate of MRSA carriage among long-term care staff was 36%; this was no doubt related to the fact that 67% of long-term patients were colonized. All of the long-term care staff isolates were identical to patient isolates. This is certainly due in part to the high prevalence of MRSA carriage by patients but may also relate to the long duration of residence by the patients, allowing ample opportunity for transmission among patients and between patients and staff.

What is not clear from this study is the role played by staff MRSA carriage in the transmission of MRSA to patients. Are the staff reservoirs of MRSA that enable colonization and infection of patients, or are they innocent bystanders? This question cannot be answered by point-prevalence studies.

However, this study has some important implications for health care workers. This study confirms prior studies showing that health care workers are at risk of acquiring MRSA during the course of work.1 These workers are at risk of developing clinical MRSA infection.2 In addition, this study clearly demonstrates that colonized health care workers can transmit MRSA to family members.

It is premature to recommend that all health care workers be screened for MRSA. More detailed studies of MRSA acquisition and transmission between patients and staff are needed. However, acquisition of MRSA by health care workers is potentially preventable by practicing good hand hygiene and observing the principles of contact isolation. Health care workers should already be doing this out of concern for patient safety; concern for their own well-being and that of their families should provide still more incentive.

References

1. Goetz A, et al. Methicillin-resistant Staphylococcus aureus: A hospital-based study. Infect Control Hosp Epidemiol. 1999;20:689-691.

2. Muder RR, et al. Infection with methicillin-resistant Staphylococcus aureus among hospital employees. Infect Control Hosp Epidemiol. 1993;14:576-578.