Objective: To investigate the antimicrobial resistance among non-fermenting gramnegative bacilli, particularly, non-aeruginosa Pseudomonas species. Significance: Surveillance of this pathogens, because the antimicrobial resistance among nonfermenting gram-negative bacilli has increased significantly in Venezuela in recent years. Study: We evaluated non-aeruginosa Pseudomonas species strains isolates collected from patients with suspected infections in a hospital of Caracas, Venezuela (West General Hospital) between 1997–2003. Study population: For the studied period, 146 clinical strains of non-aeruginosa Pseudomonas species were isolated, we consider also in this analysis related species: Burkholderia, Stenotrophomonas, Flavimonas, Sphingomonas, Ralstonia and Comamonas. Methodology: Clinical samples were processed and identified with standard cultures and biochemical tests. In vitro antimicrobial susceptibility of the isolates was assessed by an agar disk diffusion method using Mueller-Hinton agar as recommended by the National Committee for Clinical Laboratory Standards (NCCLS). Isolates were tested against 15 drugs: imipenem, meropenem, aztreonam, piperacillin, tobramycin, amikacin, gentamicin, ceftazidime, cefepime, netilmicin, cefoperazone, ciprofloxacin, levofloxacin, lomefloxacin, ofloxacin. Epi Info v.6.0 was used in statistical analysis. Results: From total isolated strains, 50.7% corresponded to Stenotrophomonas maltophilia, 21.2% to Burkholderia cepacia, 17.8% to P. fluorescens, 4.1% to P. putida, 1.4% to P. stutzeri, 1.4% to Flavimonas oryzihabitans, 1.4% to Sphingomonas paucimobilis, 1.4% to Ralstonia pickettii, 0.7% to P. mendocina, 0.7% to Comamonas testosteroni. S. maltophilia showed high resistance to carbapenemes (100% of resistance to imipenem and meropenem), and a considerable susceptibility to certain quinolones (63.6% of susceptibility to ciprofloxacin and 95.% to levofloxacin). B. cepacia displayed higher resistance to gentamicin (58.3%) and high susceptibility levels to carbapenems (80.0% to meropenem and 88.5% to imipenem). P. fluorescens showed high resistance to piperacillin and gentamicin (55.6% and 47.8% respectively) and high susceptibility to quinolones (72.7% for ofloxacin, 73.9% for ciprofloxacin and 80.0% to lomefloxacin). P. putida showed higher resistance for amikacin and ciprofloxacin (50%, both). Conclusions: The high rates of antimicrobial resistance among these bacterial pathogens in this hospital are important. Judicious use of antimicrobial agents can never be overemphasized. Continued surveillance of the changes of resistance patterns over time is necessary.ajrodriguezm_md@hotmail.comsemestralEl objetivo del presente estudio fue evaluar la resistencia antimicrobiana de bacilos gram-negativos no fermentadores, particularmente especies de Pseudomonas no aeruginosa. Esto tiene gran relevancia dado el incremento de la resistencia de dichos patógenos en el país. El estudio se realizo con muestras tomadas de pacientes con infecciones del Hospital General del Oeste, de Caracas, Venezuela entre 1997–2003. En dicho período, 146 cepas clínicas de especies de Pseudomonas no aeruginosa fueron aisladas, en el análisis se incluyeron: Burkholderia, Stenotrophomonas, Flavimonas, Sphingomonas, Ralstonia y Comamonas. Las muestras fueron evaluadas por el método de difusion de discos en agar de Mueller-Hinton por la técnica de Kirby- Bauer, de acuerdo a las pautas de la NCCLS. Las cepas fueron probadas contra 30 drogas. Del total de cepas aisladas, 50.7% fueron Stenotrophomonas maltophilia, 21,2% Burkholderia cepacia, 17,8% P. fluorescens, 4,1% P. putida, 1,4% P. stutzeri, 1,4% Flavimonas oryzihabitans, 1,4% Sphingomonas paucimobilis, 1,4% Ralstonia pickettii, 0,7% P. mendocina, 0,7% Comamonas testosteroni. S. maltophilia mostró alta resistencia a los carbapenems (100% de resistencia a imipenem y meropenem), y una considerable sensibilidad a ciertas quinolonas (63,6% a ciprofloxacina y 95.% a levofloxacina). B. cepacia mostró alta resistencia a gentamicina (58,3%) pero alta sensibilidad a carbapenems (80,0% meropenem y 88,5% imipenem). P. fluorescens mostró alta resistencia piperacilina y gentamicina (55,6% y 47,8% respectivamente) y alta sensibilidad a quinolonas (72,7% ofloxacina, 73,9% ciprofloxacina y 80,0% lomefloxacina). Las altas tasas de resistencia antimicrobiana entre los aislados evaluados en este hospital son relevantes. Uso juicioso de antimicrobianos, por ende, debe ser sobre - enfatizado. Así mismo, la vigilancia continua en los cambios de patrones de resistencia en el tiempo es necesaria.