Tolerability of Biofilm-Forming Trimethoprim-/Sulfamethoxazole-Resistant Small Colony Variants of Against Various Antimicrobial Agents.

Trimethoprim-/sulfamethoxazole-resistant small colony variants (SCVs) of , which are selected by use of trimethoprim/sulfamethoxazole, are involved in intractable biofilm-forming infection. This study aimed to determine the biofilm formation ability in trimethoprim-/sulfamethoxazole-resistant SCVs of and investigate the bactericidal activity of differential antimicrobial agents to its biofilm-forming . Between 32 wild type (WT) and 32 SCVs selected from its WT, the amount of formed biofilm was compared. Vancomycin, daptomycin, rifampicin, and minocycline were exposed to biofilm-forming to determine viable bacterial counts and its susceptibility. The biofilm-producing quantify of SCVs was approximately twice that formed by its WT. Vancomycin and daptomycin reduce 4 logs the bacterial counts of biofilm-forming WT at 24 hours, but did not affect SCVs. Rifampicin and minocycline considerably decreased both WT and SCVs; however, both bacterial counts recovered to an initial number 48 hours later. These survival strains showed resistance to each drug, and mutation or mRNA overexpression was confirmed.