Fusidic-acid use and resistance

Abstract

Sir—E M Brown and P Thomas (March 2, p 803) report locally high or rising rates of fusidic-acid resistance for Staphylococcus aureus in the UK, as do several correspondents on the British Medical Journal website. Particular concern is expressed about resistance in dermatology patients, in whom resistance rates of up to 34% are reported. Publication of national data is desirable to inform this discussion. Since 1989, the UK Public Health Laboratory Service has asked laboratories in England and Wales to report the antibiotic susceptibilities of isolates from bacteraemias. Reporting is voluntary, but more than 90% of laboratories contribute. The number of S aureus bacteraemias reported grew from 4800 in 1990, to higher than 12 000 in 2001, and the proportion of these attributable to meticillin-resistant S aureus (MRSA) rose from 1·3% to 43·6% (table). Dependent on the year, 55–75% of the reports for S aureus bacteraemia include susceptibility data for fusidic acid, suggesting that resistance has risen from 2% in 1990, to 6·8% in 2000 and 6·1% in 2001 (table), with rates currently being roughly equal among MRSA and meticillinsusceptible S aureus (MSSA). Higher fucidin resistance rates among MRSA in the early surveillance years have little importance, since MRSA were then infrequent in bacteraemias and belonged to other clones than the epidemic—(E)MRSA-15 and (E)MRSA-16 lineages that now predominate. These latter lineages are infrequently resistant to fusidic acid, but resistance is characteristic of some less common epidemic strains, such as (E)MRSA-17. Resistance may reflect heavy or increasing use of fusidic-acid preparations in retail and hospital pharmacies. From 1992 to 2001, according to IMS data, fusidic-acid sales have risen around 2·5-fold in the UK. Topical preparations in the community account for a growing proportion of total use (43·2% in 1992, 62·6% in 2001). There is also substantial use of oral preparations in hospitals and the community. Such heavy use—totalling more than 3 tonnes in 2001, nearly two-thirds of which was topical—is compatible with increasing resistance, especially among dermatological isolates. Resistant strains selected in dermatology patients may be later causes of more serious infections, including bacteraemias, in these patients or in others. In any event, it is disturbing that resistance should be increasing to a drug that, if used systemically and in combination, is beneficial even in the most severe staphylococcal infections.