To compare the prevalence of Staphylococcus aureus and methicillin-resistant S. aureus (MRSA) carriage among injection drug users (IDUs) treated in an injection heroin maintenance program with that among IDUs treated in an oral methadone program, and to determine predictors of S. aureus carriage.

Survey.

Two opiate maintenance programs at a psychiatrie university clinic.

A volunteer sample consisting of 94 (74%) of 127 IDUs treated in an injection opiate maintenance program with at least twice daily injections of heroin, and 70 (56%) of 125 IDUs treated in an oral methadone program.

Addicts treated in the intravenous heroin substitution program had a significantly lower overall rate of S. aureus carriage (37 of 94 [39.4%] vs 42 of 70 [60%]; P = .009) and a significantly lower rate of nasal carriage (21 of 94 [22.3%] vs 30 of 70 [42.9%]; P = .005) than did addicts treated in the oral methadone program. Being treated in the oral methadone program was the only independent predictor of S. aureus carriage (odds ratio, 2.27; 95% confidence interval, 1.19-4.31; P=.012). All S. aureus isolates were susceptible to oxacillin.

The regular use of needles under aseptic conditions did not increase the rate of S. aureus carriage among IDUs. Further studies are necessary to investigate whether the lower rate of S. aureus carriage among IDUs treated with intravenous heroin leads to a lower incidence of S. aureus infections in these patients.