title: Antimicrobial susceptibility and synergy studies of Stenotrophomonas maltophilia isolates from patients with cystic fibrosis.
abstract: Stenotrophomonas maltophilia is a newly emerging pathogen being detected with increasing frequency in patients with cystic fibrosis (CF). The impact of this multidrug-resistant organism on lung function is uncertain. The optimal treatment for S. maltophilia in CF patients is unknown. We studied the in vitro activity of ten antimicrobial agents, and conducted synergy studies by using checkerboard dilutions of eight pairs of antimicrobial agents against strains isolated from 673 CF patients from 1996 to 2001. This represents approximately 7 to 23% of the CF patients in the United States who harbor S. maltophilia annually. Doxycycline was the most active agent and inhibited 80% of 673 initial patient isolates, while trimethoprim-sulfamethoxazole inhibited only 16%. High concentrations of colistin proved more active than high concentrations of tobramycin and gentamicin. Serial isolates (n = 151) from individual patients over time (median, 290 days) showed minimal changes in resistance. Synergistic or additive activity was demonstrated by trimethoprim-sulfamethoxazole paired with ticarcillin-clavulanate (65% of strains), ciprofloxacin paired with ticarcillin-clavulanate (64% of strains), ciprofloxacin paired with piperacillin-tazobactam (59% of strains), trimethoprim-sulfamethoxazole paired with piperacillin-tazobactam (55% of strains), and doxycycline paired with ticarcillin-clavulanate (49% of strains). In all, 522 (78%) isolates were multidrug resistant (i.e., resistant to all agents in two or more antimicrobial classes) but 473 (91%) of these were inhibited by at least one antimicrobial combination (median, four; range, one to eight). To determine appropriate treatment for patients with CF, it is important to monitor the prevalence, antimicrobial susceptibility, and clinical impact of S. maltophilia in this patient population.
authors.affiliation: Department of Pediatrics, Columbia University, New York, New York 10032, USA.
authors.forename: Pablo
authors.initials: P
authors.lastname: San Gabriel
authors.forename: Juyan
authors.initials: J
authors.lastname: Zhou
authors.forename: Setareh
authors.initials: S
authors.lastname: Tabibi
authors.forename: Yunhua
authors.initials: Y
authors.lastname: Chen
authors.forename: Marco
authors.initials: M
authors.lastname: Trauzzi
authors.forename: Lisa
authors.initials: L
authors.lastname: Saiman
mesh_terms: D000900:Anti-Bacterial Agents; D000890:Anti-Infective Agents / Q000494:pharmacology*; D003550:Cystic Fibrosis / Q000382:microbiology*; D024881:Drug Resistance, Bacterial; D004357:Drug Synergism; D004359:Drug Therapy, Combination / Q000494:pharmacology; D006801:Humans; D008826:Microbial Sensitivity Tests; D020615:Stenotrophomonas maltophilia / Q000187:drug effects*
chemical_list: D000900:Anti-Bacterial Agents; D000890:Anti-Infective Agents