title: In vitro susceptibility of 124 Xanthomonas maltophilia (Stenotrophomonas maltophilia) isolates: comparison of the agar dilution method with the E-test and two agar diffusion methods.
abstract: The in vitro susceptibility of 124 Xanthomonas maltophilia isolates was tested by four methods: Agar dilution (reference method), E-test, a disk diffusion and a tablet diffusion method. Trimethoprim-sulfamethoxazole had the highest activity against X. maltophilia, followed by a combination of aztreonam-clavulanic acid at different ratios, the ratio 1:1 being the most active with a susceptibility rate of 85% as compared to 2% for aztreonam alone. Addition of the beta-lactamase inhibitor tazobactam to piperacillin enhanced the rate of susceptible isolates from 31% to 53%, Relatively few isolates were susceptible to ciprofloxacin (27%) and gentamicin (9%). Generally, the disk diffusion method had a considerably higher frequency of "very major" discrepancies when compared with the agar dilution method than with the other methods. The susceptibility of X. maltophilia to trimethoprim-sulfamethoxazole and ciprofloxacin could reliably be determined by all the diffusion methods tested, but otherwise the agar dilution method is to be preferred. A standardized and reliable diffusion method for susceptibility testing of X. maltophilia remains to be found. Trimethoprim-sulfamethoxazole must be considered the drug of choice in the treatment of severe X. maltophilia infections. The combination aztreonam-clavulanic acid is promising, but must be proved in a clinical setting.
authors.affiliation: Department of Clinical Microbiology, Frederiksberg Hospital, Denmark.
authors.forename: M
authors.initials: M
authors.lastname: Arpi
authors.forename: M A
authors.initials: MA
authors.lastname: Victor
authors.forename: I
authors.initials: I
authors.lastname: Mortensen
authors.forename: A
authors.initials: A
authors.lastname: Gottschau
authors.forename: B
authors.initials: B
authors.lastname: Bruun
mesh_terms: D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D002442:Ceftazidime / Q000494:pharmacology; D002939:Ciprofloxacin / Q000494:pharmacology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D004926:Escherichia coli / Q000187:drug effects; D005839:Gentamicins / Q000494:pharmacology; D006801:Humans; D008826:Microbial Sensitivity Tests; D010397:Penicillanic Acid / Q000031:analogs & derivatives / Q000494:pharmacology; D010878:Piperacillin / Q000494:pharmacology; D011550:Pseudomonas aeruginosa / Q000187:drug effects; D013211:Staphylococcus aureus / Q000187:drug effects; D000078142:Tazobactam; D015662:Trimethoprim, Sulfamethoxazole Drug Combination / Q000494:pharmacology; D014974:Xanthomonas / Q000187:drug effects* / Q000302:isolation & purification; D065093:beta-Lactamase Inhibitors
chemical_list: D000900:Anti-Bacterial Agents; D004791:Enzyme Inhibitors; D005839:Gentamicins; D065093:beta-Lactamase Inhibitors; D002939:Ciprofloxacin; D015662:Trimethoprim, Sulfamethoxazole Drug Combination; D010397:Penicillanic Acid; D002442:Ceftazidime; D000078142:Tazobactam; D010878:Piperacillin