Antimicrobial Susceptibility of Stenotrophomonas maltophilia Clinical Isolates from Blood Samples in Iran

Stenotrophomonas maltophilia is a gram negative rod shaped bacteria which causes serious nosocomial infections in immuno-deficient populations such as HIV infected ones, patients with cancer, neutropenia and specially cystic fibrosis and stem cell transplantation recipients. This microorganism has a high mortality rate and is one of the most important agents of blood and respiratory tract infections in patients with cancer and venous catheter [1-4]. This bacterium has been recovered from soil, plants, animals, water resources and various wet surfaces in hospitals [5]. S. maltophilia infections can occur in children and adults and community-acquired infections include bacteremia, wound/soft tissue infections and urinary tract infections has been reported [6]. Some inherited molecular mechanisms such as outer membrane decreased permeability, efflux pumps, β-lactamases, integrons and biofilm formation have made this bacterium resistant to a large number of antimicrobials such as β-lactams, quinolones, co-trimoxazole, carbapenems, tetracyclines, chloramphenicol, and disinfectants [1, 5, 7, 8]. Antibiotics that commonly are used for S. maltophilia infections include co-trimoxazole, levofloxacin, ticarcillin/clavullanic acid and minocycline. Co-trimoxazole is the first choice treatment but increasing resistance to that has been reported [9, 10]. Ticarcillin/clavulanic acid has been suggested as an alternative for co-trimoxazole resistant isolates while emerging resistance to this agent also has been reported [10]. Combination of antibiotics is a new strategy and synergistic effect for S. maltophilia infections between cotrimoxazole and ticarcillin/clavulanic acid or ceftazidim was observed [11]. Increasing rate of immunocompromised patients, prolonged consumption of antibiotics in hospitalized patients and some genetic disorders like cystic fibrosis make it essential to monitor S. maltophilia drug resistance status. In this study, our objective was determining the antimicrobial susceptibility of S. maltophilia clinical isolates to different antibiotics.