A Comparison of Effects of Broad-Spectrum Antibiotics and Biosurfactants on Established Bacterial Biofilms
- 986 Downloads
Current antibiofilm solutions based on planktonic bacterial physiology have limited efficacy in clinical and occasionally environmental settings. This has prompted a search for suitable alternatives to conventional therapies. This study compares the inhibitory properties of two biological surfactants (rhamnolipids and a plant-derived surfactant) against a selection of broad-spectrum antibiotics (ampicillin, chloramphenicol and kanamycin). Testing was carried out on a range of bacterial physiologies from planktonic and mixed bacterial biofilms. Rhamnolipids (Rhs) have been extensively characterised for their role in the development of biofilms and inhibition of planktonic bacteria. However, there are limited direct comparisons with antimicrobial substances on established biofilms comprising single or mixed bacterial strains. Baseline measurements of inhibitory activity using planktonic bacterial assays established that broad-spectrum antibiotics were 500 times more effective at inhibiting bacterial growth than either Rhs or plant surfactants. Conversely, Rhs and plant biosurfactants reduced biofilm biomass of established single bacterial biofilms by 74–88 and 74–98 %, respectively. Only kanamycin showed activity against biofilms of Bacillus subtilis and Staphylococcus aureus. Broad-spectrum antibiotics were also ineffective against a complex biofilm of marine bacteria; however, Rhs and plant biosurfactants reduced biofilm biomass by 69 and 42 %, respectively. These data suggest that Rhs and plant-derived surfactants may have an important role in the inhibition of complex biofilms.
KeywordsTest Substance Biosurfactants Surfactin Minimum Bactericidal Concentration Rhamnolipids
The authors would like to acknowledge Hendrik Fuß and Gowrishankar Muthukrishnan for their expert technical advice and John Slater and Brian Carney for providing funding. This work was supported partly by the Higher Education Authority (Ireland) (Grant No. AI060753).
Conflict of Interest
The authors declare that they have no conflict of interest.
- 7.Chen ML, Penfold J, Thomas RK, Smyth TJ, Perfumo A, Marchant R, Banat IM, Stevenson P, Parry A, Tucker I, Grillo I (2010) Mixing behavior of the biosurfactant, rhamnolipid, with a conventional anionic surfactant, sodium dodecyl benzene sulfonate. Langmuir 26(23):17958–17968PubMedCrossRefGoogle Scholar
- 24.May TB, Shinabarger D, Maharaj R, Kato J, Chu L, DeVault JD, Roychoudhury S, Zielinski NA, Berry A, Rothmel RK et al (1991) Alginate synthesis by Pseudomonas aeruginosa: a key pathogenic factor in chronic pulmonary infections of cystic fibrosis patients. Clin Microbiol Rev 4(2):191–206PubMedGoogle Scholar
- 29.Nworu C, Esimon C (2006) Comparative evaluation of three in vitro techniques in the interaction of ampicillin and ciprofloxacin against Staphylococcus aureus and Escherichia coli. Trop J Pharm Res 5(2):605–611Google Scholar
- 38.Rodrigues L, Banat IM, Teixeira J, Oliveira R (2007) Strategies for the prevention of microbial biofilm formation on silicone rubber voice prostheses. J Biomed Mater Res B 81(2):358–370Google Scholar