HIGH-LEVEL RESISTANCE TO AMINOGLYCOSIDES IN ENTEROCOCCI FROM RIYADH

Enterococci with high level aminoglycoside resistance are being report ed from different parts of the world with increasing frequency. Treatm ent of infections caused by such isolates is associated with a high in cidence of failure or relapse. This is attributed to the loss of the s ynergetic effect of aminoglycosides and cell wall active agents agains t isolates exhibiting this type of resistance. To determine the preval ence of enterococci with high level resistance to aminoglycosides in R iyadh, Saudi Arabia, 241 distinct clinical isolates were examined by d isk diffusion method using high content aminoglycoside disks. Seventy- four isolates (30%) were resistant to one or more of the aminoglycosid es tested. The most common pattern of resistance was that to streptomy cin and kanamycin. Of the 241 isolates tested, 29 (12%) were resistant to high levels of gentamicin, 35 (15%) to tobramycin, 65 (27%) to kan amycin and 53 (22%) to streptomycin. The highest rate of resistance to a high level of gentamicin was found among enterococcal blood isolate s (30%). Eighteen of the isolates were identified as Enterococcus faec ium, 13 (72%) of these showed high level resistance to two or more of the aminoglycosides tested.