Mupirocin and Staphylococcus aureus:: a recent paradigm of emerging antibiotic resistance

Objectives: To describe trends in mupirocin resistance among Staphylococcus aureus in New Zealand (NZ), following the availability of mupirocin in 1986. Patients and methods: Data from a variety of sources were used for this study: susceptibility data collected annually from diagnostic laboratories throughout NZ; a local survey of mupirocin-resistant S. aureus in the Auckland area in 1997; a national survey of S. aureus antimicrobial susceptibility in 1999; and the national methicillin-resistant S. aureus (MRSA) surveillance programme. Results: All data sources show that there was a steady increase in mupirocin resistance among S. aureus throughout the 1990s, and rates in NZ are now markedly higher than those reported in most other comparable countries. By 1999, resistance averaged 28%, with higher rates among community-acquired compared with hospital-acquired isolates, and with a wide geographical variation in resistance. Resistance was more common among S. aureus generally than MRSA. Conclusion: We postulate that the steady rise in mupirocin resistance among S. aureus in NZ throughout the 1990s may be due, at least in part, to the over the counter availability of mupirocin from 1991 to 2000. The current patterns of mupirocin consumption need to be reviewed and its use rationalized to maximize the chances of this antibiotic retaining beneficial antistaphylococcal activity.