Clearance of an epidemic clone of methicillin-resistant Staphylococcus aureus in a drug-use network: a follow-up study in Switzerland.

BACKGROUND

A single clone of methicillin-resistant Staphylococcus aureus (MRSA) was observed in a drug-use network starting in 1994, and was found to persist throughout 2001, with up to 19% MRSA colonization of intravenous drug users (IDUs). Recent clinical observations have shown low prevalences of this endemic drug clone among MRSA isolates. The goal of this study was to assess the evolution of MRSA carriage among IDUs.

METHODS

The survey took place from November 2008 to September 2009. Ten drug dispensary facilities took part. Demographic and clinical data including sex, history of MRSA, past hospitalization, use of antibiotics, and presence of wounds were collected. Screening of the nares, throat, and wounds was done.

RESULTS

Five hundred and fourteen swab specimens were obtained; 497 of them were nose/throat samples and 17 were wound swabs. MRSA was identified in 5 samples (1%). Four MRSA were found in nose/throat samples and 1 in a wound swab. Pulsed-field gel electrophoresis typing of the MRSA isolates revealed 2 different common endemic types: 4 were identified as the Zurich IDU clone and 1 as the Grison clone.

CONCLUSIONS

The study shows a significant decline of MRSA colonization among IDUs. The underlying causes for this decline could not be determined fully, but we hypothesize a bundle of interventions as contributing: enhanced medical care, better wound management, isolation management, teaching IDUs basic hygiene techniques, and the national 'Four Pillars' policy. Hospital epidemiological policies such as pre-emptive isolation, length of isolation time, and screening procedures were adapted accordingly.