Effects of clofazimine on planktonic and biofilm growth of Mycobacterium tuberculosis and Mycobacterium smegmatis

Mycobacteria form lipid-rich biofilms that restrict the efficacy of antimicrobial chemotherapy, possibly necessitating the use of lipophilic antibiotics. In the current study, the activity of one such agent, clofazimine, against Mycobacterium tuberculosis and Mycobacterium smegmatis planktonic cells and biofilms was investigated. Minimum inhibitory concentrations (MICs) of clofazimine were determined for planktonic cultures, whilst minimum bactericidal concentrations (MBCs) were determined for planktonic, biofilm-producing and biofilm-encased organisms using standard bacteriological proce- dures. The effects of clofazimine on biofilm formation and the stability of pre-formed biofilm were measured using a crystal violet-based spectrophotometric procedure. In the case of M. smegmatis, clofazimine was found to be active against planktonic phase (MICs and MBCs of 2.5 mg/L and >20 mg/L, respectively) and biofilm-producing organisms (MBC of 2.5 mg/L); clofazimine demonstrated greater activity against M. tuberculosis, corresponding values of 0.06, 5 and 0.3 mg/L. Although clofazimine inhibited biofilm production both by M. tuberculosis and M. smegmatis (P < 0.05 at 0.07 mg/L and 0.3 mg/L, respectively) and appeared to reduce the pre-formed M. tuberculosis biofilm, addition of antimicrobial agent to pre-existing biofilm matrices failed to kill biofilm-encased organisms. In conclusion, clofazimine is more effective against M. tuberculosis than against M. smegmatis, exhibiting bactericidal activity both for actively growing and slowly replicating bacilli but not for non-replicating organisms of both species.South African Medical Research Council.http://www.elsevier.com/locate/jgar2016-05-31hb201

The effects of clofazimine on mycobacterium smegmatis biofilm formation

Chemotherapy of tuberculosis (TB), a disease caused by Mycobacterium tuberculosis (M. tuberculosis), is successful against actively-growing bacilli but ineffective against dormant/persistent organisms, found mainly in a protective lipid-laden granuloma, possibly necessitating the use of lipophilic antibiotics. In vitro, these bacilli are encased in lipid-rich biofilms. In this study, the antimycobacterial activity of one such agent, clofazimine, and its nanoparticle formulation, have been investigated against Mycobacterium smegmatis (M. smegmatis), as a surrogate for M. tuberculosis, by determining the bacteriostatic and bactericidal activities of the native (NC) and spray-dried (SDC) preparations of this agent on planktonic and biofilm populations, as well as their effects on biofilm formation and its lipid compositions, specifically free mycolic acid (FM) content. Both preparations were comparable, being bacteriostatic for rapidly-proliferating bacilli, bactericidal for slow-growing, biofilm-producing sessile bacteria, but ineffective against non-replicating, biofilm-encased M. smegmatis organisms. However, similar studies in M. tuberculosis are required.Dissertation (MSc)--University of Pretoria, 2013.ImmunologyUnrestricte