Susceptibility of Stenotrophomonas maltophilia Clinical Isolates to Antibiotics and Contact Lens Multipurpose Disinfecting Solutions

PURPOSE. To determine the susceptibility of Stenotrophomonas maltophilia to various antibiotics and contact lens multipurpose disinfecting solutions. METHODS. Forty S. maltophilia strains from contact lens cases, contact lenses, or eye swabs of contact lens wearers including 27 asymptomatic wearers and 13 keratitis patients were examined for their susceptibility to different antibiotics, using a disc diffusion assay, and to multipurpose disinfecting solutions using a broth microdilution method. RESULTS. Certain strains were resistant to aztreonum (15%), imipenem (93%), chroramphenicol (13%), and cefepime (8%). Two of those strains were multidrug resistant. All strains were sensitive to trimethoprim-sulfamethoxazole, tigecycline, ceftazidime, and fluoroquinolones. Overall, the minimum inhibitory concentration (MIC) for all strains was significantly higher (P < 0.05) for AQuify (50% dilution) and OPTI-FREE RepleniSH (25%) than all other multipurpose contact lens disinfecting solutions (MPDS) (3%-14%, except RepleniSH versus MeniCare Soft [14%]). AQuify, OPTI-FREE RepleniSH, and MeniCare Soft had significantly higher minimum bactericidal concentrations (undiluted MPDS) than other disinfecting solutions (P < 0.05). CONCLUSIONS. The Australian ocular isolates of S. maltophilia remain susceptible to trimethoprim-sulfamethozole, tigecycline, and most fluoroquinolones. However, the isolates showed resistance to certain multipurpose disinfecting solutions.