High level resistance to aminoglycosides in enterococci from Riyadh.

Enterococci with high level of aminoglycosides resistance are being reported from different parts of the world with increasing frequency. Treatment of infections caused by such isolates is associated with a high incidence of failure or relapse. This is attributed to the loss of the synergetic effect of aminoglycosides and cell wall active agents against isolates exhibiting this type of resistance. To determine the prevalence of enterococci with high level resistance to aminoglycosides in Riyadh, Saudi Arabia, 241 distinct clinical isolates were examined by disk diffusion method using high content aminoglycosides disks. Seventy-four isolates (30%) were resistant to one or more of the aminoglycosides tested. The most common pattern of resistance was that to streptomycin and kanamycin. Of the 241 isolates tested, 29 (12%) were resistant to high levels of gentamicin, 35 (15%) to tobramycin, 65 (27%) to kanamycin and 53 (22%) to streptomycin. The highest rate of resistance to a high level of gentamicin was found among enterococcal blood isolates (30%). Eighteen of the isolates were identified as Enterococcus faecium, 13 (72%) of these showed high level resistance to two or more of the aminoglycosides tested.