Generalizing from the results from this study, reducing the consumption of one antibiotic might delay the development of antibiotic resistance but not reverse it. This is in line with the earlier, retrospective, studies on E. coli from Great Britain where trimethoprim- sulphamethoxazole was used until 1991 when its pop- ularity gradually declined because of its adverse effects. Formal prescribing restrictions were implemented in 1995, and in the period up to 1999 there was a 97% decrease in the consumption of trimethoprim-sulpha- methoxazole. Despite this, the frequency of resistance to sulphamethoxazole among E. coli was virtually unchanged in 2004 (62,63). Partly using the same set of isolates, it was later shown that streptomycin resis- tance remained stable although the use in Great Britain had been very low for the last 30 years (63,64). In this perspective it is important to highlight that after the intervention in Kronoberg county trimethoprim resis- tance has increased dramatically from 11%–13% in 2008 to a level around 19% in E. coli in 2013 (personal communication G. Kahlmeter).
Two more recent studies have, however, shown that a reduction in antibiotic use could result in decreased resistance frequencies in E. coli (65,66). Butler and co- workers followed the antibiotic prescriptions and resis- tance rates in a large number of Primary Health care centers (PHCCs) in Wales and could show that the PHCCs having the largest reduction in ampicillin (AMP) and trimethoprim (TMP) prescriptions during 7 years also experienced a decrease in the correspond- ing resistance in E. coli in their communities. The decrease was 58.7% to 53.5% for AMP and 29.1% to 25.7% for TMP resistance (65). No data were pre- sented giving the reader a chance to evaluate whether