OBJECTIVETo investigate the antimicrobial resistance of clinical isolates of Stenotrophomonas matophilia (SMA) and the mechanisms of their drug resistance.

METHODSDisc diffusion method (NCCLS) was used to detect the resistant patterns of 88 initial SMA isolates resistant to 12 antibiotics isolated from a local hospital in the past 4 years. PCR was used to detect the 7 aminoglycosides modifying enzymes genes (AME) against amikacin and gentamicin. Metal-beta-lactamases (MBLs) were screened by synergic method, and extended-spectrum beta-lactamases (ESBLs) were detected by double-disk synergy test.

RESULTSThe resistance rates of the SMA isolates were 0%-9.7% to minocycline, 12.5%-22.6% to ticarcillin-clavulanic acid, 12.5%-28.6% to levofloxacin, 18.8%-33.3% to doxycycline, 18.8%-40% to sulfamethoxazole compound, 50%-65.7% to ciprofloxacin, 50%-66.7% to cehazindme, 54.8%-66.7% to amikacin, 75%-100% to gentamicin, 81.3%-100% to piperacillin, 87.5%-100% to aztreonam and 93.5%-100% to imipenem. Aac(3)-I and ant(4')-II were not detected in these strains. The positive rates of the other 5 AME genes of aac(3)-II, ant(2'')-I, aac(6')-I, aac(3)-III, aac(3)-IV were 2.3%, 5.7%, 8%, 10%, and 10%, respectively. SMA strains producing ESBLs were found at the rate of 38.6%; 25% of the strains were MBL-producing, and 13.6% produced both ESBLs and MBLs.

CONCLUSIONMost of the SMAs we isolated are multidrug-resistant through various mechanisms. The choice of antibiotics should be made according to the susceptibility results.