[Disappearance of Streptococcus pyogenes macrolide resistance in an area of northeastern Italy: a possible link with rational long-acting macrolide consumption].

Many studies have shown a correlation between higher consumption of long-acting macrolides and the development of resistance of S. pyogenes but, to our knowledge, no studies have reported the disappearance of S. pyogenes macrolide resistance. We evaluated the possible relationship between the rational use of long-acting macrolide consumption and the disappearance of S. pyogenes erythromycin resistance in an area of northeastern Italy, the district of Pordenone (approximately 300,000 inhabitants). The emerging use of new long-acting macrolides, especially since 1993, has caused a great increase in total macrolide consumption (expressed as defined daily doses per 1,000 inhabitants per day; DDDs), followed by a steady increase in the percentage of S. pyogenes resistant to erythromycin (from 4% in 1994 to 56.3% in 2000). Subsequently, from 2000 to 2007, the maintenance of steady-high DDDs of clarithromycin but low DDDs of azithromycin resulted in a sharp decrease in the percentage of S. pyogenes resistance to erythromycin (from 33.3% in 2001 to 0.2% in 2008). Disappearance of S. pyogenes erythromycin resistance in the last few years, compared with data of long-acting macrolide consumption from 2000 to 2007, suggests that S. pyogenes resistance to erythromycin is more likely associated with the specific type of compound used rather than with total consumption of long-acting macrolides.