Rifampicin fails to eradicate mature biofilm formed by methicillin-resistant Staphylococcus aureus

• Published in: Revista da Sociedade Brasileira de Medicina Tropical
• Main Authors: Keli Cristine Reiter, Gustavo Enck Sambrano, Bárbara Villa, Thiago Galvão da Silva Paim, Caio Fernando de Oliveira, Pedro Alves d'Azevedo
• Format: Article in Journal/Newspaper
• Language: English
• Published: Sociedade Brasileira de Medicina Tropical (SBMT) 2012
• Subjects: Staphylococcus aureus; Rifampicina; Vancomicina; Biofilme; Resistência; Arctic medicine. Tropical medicine; RC955-962; Arctic
• Online Access: https://doi.org/10.1590/S0037-86822012000400011; https://doaj.org/article/6f46dcd6b9bf4ea0a449d62adc1ccc6c

INTRODUCTION: Antimicrobial activity on biofilms depends on their molecular size, positive charges, permeability coefficient, and bactericidal activity. Vancomycin is the primary choice for methicillin-resistant Staphylococcus aureus (MRSA) infection treatment; rifampicin has interesting antibiofilm properties, but its effectivity remains poorly defined. METHODS: Rifampicin activity alone and in combination with vancomycin against biofilm-forming MRSA was investigated, using a twofold serial broth microtiter method, biofilm challenge, and bacterial count recovery. RESULTS: Minimal inhibitory concentration (MIC) and minimal bactericidal concentration for vancomycin and rifampicin ranged from 0.5 to 1mg/l and 0.008 to 4mg/l, and from 1 to 4mg/l and 0.06 to 32mg/l, respectively. Mature biofilms were submitted to rifampicin and vancomycin exposure, and minimum biofilm eradication concentration ranged from 64 to 32,000 folds and from 32 to 512 folds higher than those for planktonic cells, respectively. Vancomycin (15mg/l) in combination with rifampicin at 6 dilutions higher each isolate MIC did not reach in vitro biofilm eradication but showed biofilm inhibitory capacity (1.43 and 0.56log10 CFU/ml reduction for weak and strong biofilm producers, respectively; p<0.05). CONCLUSIONS: In our setting, rifampicin alone failed to effectively kill biofilm-forming MRSA, demonstrating stronger inability to eradicate mature biofilm compared with vancomycin.