Association between decreased susceptibility to a new antibiotic for treatment of human diseases, everninomicin (SCH 27899), and resistance to an antibiotic used for growth promotion in animals, avilamycin.

The emergence of multiresistant bacteria has increased the need for new antibiotics or modifications of older antibiotics. One promising agent might be the everninomicin SCH 27899, an oligosaccharide antibiotic recently developed by Schering Plough. However, another oligosaccharide, avilamycin, that is structurally very similar has been used as a growth promoter for food animals in the EU for several years, and a very frequent occurrence of resistance to avilamycin has been found among Enterococcus faecium isolates from broilers in Denmark. This study was conducted to investigate whether the resistance to avilamycin was associated with decreased susceptibility to everninomicin. From broilers, a total of 31 avilamycin susceptible and 55 avilamycin resistant (MIC >16 microg/mL) E. faecium isolates were selected. From pigs, 21 avilamycin-susceptible and eight avilamycin-resistant Enterococcus faecalis and 50 avilamycin-susceptible and two avilamycin-resistant E. faecium isolates were selected. All isolates were tested for susceptibility to everninomicin by E-test. The avilamycin-susceptible enterococci isolates had MICs to everninomicin from 0.064 to 0.75 microg/mL (MIC50 = 0.38 microg/mL) and the avilamycin-resistant isolates had MICs from 1.5 to 16 microg/mL (MIC50 = 3 microg/mL). Complete agreement between decreased susceptibility to avilamycin and everninomicin was found. This study showed that the use of avilamycin as a growth promoter for broilers and pigs has created a reservoir of E. faecium and E. faecalis isolates with decreased susceptibility to everninomicin among food animals already before this antibiotic have been finally developed for human use.