Occurrence of variants with temperature-dependent susceptibility (TDS) to antibiotics among Stenotrophomonas maltophilia clinical strains

Susceptibility to 20 antibiotics was tested in 104Stenotrophomonas maltophilia strains at 37 and 30°C by means of a dilution micromethod to verity the phenomenon of temperature-dependent susceptibility (TDS). Trimethoprim-sulfamethoxazole, pefloxacin and ofloxacin were the most active preparations at 37°C (93, 90, and 86% of susceptible strains, respectively), whilst trimethoprim-sulfamethoxazole, cefoperazone-sulbactam and pefloxacin performed best at 30°C (94, 94, and 76% of susceptible strains, respectively). Variants 37TDS (minimum inhibitory concentration, MIC, of tested antibiotics at least 4-times lower at 37 than at 30°C) occurred in 60%. Variants 30TDS (at least 4-times lower value of MIC at 30 than at 37°C) were found in 7.7%. Both variants in susceptibility to tested antibiotics appeared in 23.1%, whilst neither of them was observed in 9.6%. The 37TDS phenomenon was recorded most of all with gentamicin (51% of strains), amikacin (47), colistin (44) and tetracycline (34). The 30TDS phenomenon was found particularly with cefoperazone-sulbactam (16.0% of strains) and colistin (10.0%). The above phenomena may be due to changes in membrane permeability, temperature-dependent ribosomal changes, and insufficient adaptation to higher temperatures of some strains of the originally environmental speciesS. maltophilia. Presented at the10th European Congress of Clinical Microbiology and Infectious Diseases, Stockholm (Sweden), 28–31 May 2000.