Active Surveillance and Decolonization Without Isolation Is Effective in Preventing Methicillin-Resistant Staphylococcus aureus Transmission in the Psychiatry Units

Abstract

Background: Control of methicillin-resistant Staphylococcus aureus (MRSA) is difficult in select populations. We used molecular typing to study the effect of universal surveillance and decolonization of carriers, without isolation, on MRSA transmission in a specialized unit.

Methods: Patients admitted to the unit were screened for nasal MRSA at admission and discharge. Those who acquired MRSA during their stay were identified and linked to carriers with shared time in unit. Molecular typing of isolates was performed to identify transmission.

Results: Of 3285 admissions, 82% were tested for MRSA nasal carriage; the discharge screening compliance was 64.7%. Admission prevalence was 2.3% among patients screened, and 7 (0.42%) acquired nasal MRSA during their stay. All patients who acquired MRSA shared time in the unit with a colonized patient. There were 3.9 MRSA acquisitions per 1000 at-risk days. Isolates from 5 patients that acquired MRSA during their stay as well as their potential donors (11 donor: recipient patient pairs) were available for typing. Pulsed-field gel electrophoresis matched 1 acquisition isolate to a colonized patient isolate. There were no MRSA infections during the study period.

Conclusions: Despite less than perfect nasal screening compliance and exemption from traditional isolation precautions, acquisition of MRSA was 0.42% in this patient population over a course of 4.75 years, including a single case of acquisition, genetically similar to a known potential donor source. Screening for MRSA colonization and decolonizing of carriers was sufficient in reducing transmission in this vulnerable population.

Keywords: molecular typing; nosocomial MRSA; psychiatry units; transmission.

Figure 1.

Algorithm of nasal methicillin-resistant Staphylococcus aureus screen for patients admitted to the mental health unit, and allocation of patients to different epidemiologic groups. The investigation did not monitor potential transmission from colonized healthcare workers or the environment.

Figure 2.

Molecular characterization of “donor” and corresponding “recipient(s)” isolates. The pulsed-field gel electrophoresis (PFGE) dendogram compares fingerprint patterns of each recipient isolate (indicated by a letter) and their matching putative donor isolate(s) (indicated by the corresponding letter followed by numbers). Columns marked mupA and PVL (Panton-Valentine leukocidin) indicate the results for genetic tests performed to detect the mupA and PVL gene, respectively. Percentage relatedness to the recipient isolate and PFGE-type strains are indicated.