There is a clear link between heavy antimicrobial use and the emergence of resistant bacteria. Whether a reduction in antimicrobial use can reverse this process is less certain.
Lucinda Hall, and David Livermore, and colleagues from St Bartholomew's and The Royal London School of Medicine and Dentistry, and the Central Public Health Laboratory, England, investigated the effect of the 1995 national restriction of sulphonamide prescribing in the UK on the prevalence of sulphonamide resistance in Escherichia coli.
Over 350 clinical isolates of E. coli were collected in 1991 and 1999, and the presence and locations of sulphonamide-resistance genes were assessed.
|Frequency of E. coli sulphonamide resistance:|
Despite a huge decrease in sulphonamide prescriptions - from 3,208,000 prescriptions in 1991 to 77,000 in 1999 - the frequency of resistance remained high (165/359 [46%] in 1999 compared with 143/360 [40%] in 1991).
The prevalence of one specific resistance gene (SUL II) increased from 27% in 1991 to 36.5% in 1999.
Lucinda Hall comments, "We would like to think that if we stop using an antibiotic so much, resistance will go away, and we'll be able to use it again.
"Our study shows that we can't depend on this happening - once resistance to an antibiotic is common, it is going to be very difficult to get rid of. In part, this is because the genes that cause resistance to disused drugs, like sulphonamides, are linked to those that cause resistance to antibiotics we continue to use."
David Livermore adds, "Nevertheless, using antibiotics more carefully should slow the development of new resistance; and this - coupled with the development of new drugs - is vital if we are to keep ahead of the bacteria".
In an accompanying Commentary, Burke Cunha from Winthrop-University Hospital, Mineola, New York, USA, comments that the antibiotic resistance observed in Hall and colleagues' study is unsurprising. This is because the sulphonamide-restriction programme did not restrict the use of other antibiotics with high resistance potential commonly used in general practice, such as tetracycline and ampicillin.