Proteases (caseinase and elastase), hemolysins, adhesion and susceptibility to antimicrobials of Stenotrophomonas maltophilia isolates obtained from clinical specimens

Forty-six S. maltophilia isolates obtained from hospital clinical specimens were studied for protease (caseinase and elastase) production, hemolytic activity, adhesion to HEp-2 cells, plastic and glass. Susceptibility to antimicrobial agents was also evaluated. The majority of isolates were obtained from respiratory tract secretions of patients using medical devices. All the isolates grown overnight were able to hydrolyze casein at 30degreesC and 37degreesC. After 72h, all the isolates hydrolyzed elastase at 30degreesC and 40 isolates (87%) at 37degreesC. Most of the isolates presented hemolytic activity after 96h of incubation at both temperatures. Rabbit blood showed the hightest hemolytic activity, after 96h 61% and 98% of tested isolates presented beta-hemolysis at 30degreesC and 37degreesC, respectively. All isolates were susceptible to trimethoprim-sulfametoxazole and were resistant to most beta-lactams tested. By the dilution method, S. maltophilia showed a high susceptibility to ticarcillin-clavulanate and a lower susceptibility to ciprofloxacin than the agar diffusion. The isolates showed adhesion to HEp-2 cells, plastic and glass. The proteolytic activities and adhesion to inanimate surfaces detected in S. maltophilia can be related to the pathogenesis of this bacterium and/or medical device colonization which favors the development of nosocomial infections.