A Comparison of Effects of Broad-Spectrum Antibiotics and Biosurfactants on Established Bacterial Biofilms
Summary (1 min read)
Introduction
- Microbial biofilms have been implicated in recalcitrant healthcare-associated infections [24, 28, 47], the dissemination of community-acquired diseases [43] and hazardous concerns in the nutritional and environmental sectors [23].
- The detrimental consequences of this in the human population and wider environment have prompted a search for alternative solutions.
- Rhamnolipids (Rhs) are a group of biosurfactants produced by Pseudomonas aeruginosa.
- Their characteristic antimicrobial activity (mostly against planktonic bacteria) and biomedical applications have been extensively investigated [3, 4, 7, 13, 37].
- In order to encompass a wide range of biofilm physiologies, this study compared the action of the biosurfactants with broad-spectrum antimicrobials on mixed bacterial biofilms.
Materials and Methods
- All solvents of analytical grade or other purities were supplied by VWR (HiPerSolv, Chromanorm Range, VWR international, Poole, Dorset, UK).
- Bacterial Strains and Culture Conditions Bacterial strains included Escherichia coli (ATTC 11775), Citrobacter freundii (ATTC 8090), Klebsiella pneumoniae (ATTC 13883), Cronobacter sakazkii (ATTC 29544), Micrococcus luteus (ATTC 4698), Bacillus subtilis (ATTC 6051) and Staphylococcus aureus (ATTC 12600).
- Appropriate controls of test substance only and media only were also added to wells in the same plate.
- The biofilm biomass was quantified using the crystal violet adherence assay.
Results and Discussion
- A comparison of solutions to bacterial colonisation cannot be adequately assessed through exclusively planktonic bacterial assays.
- In order to establish a baseline for inhibitory comparisons, the MIC and the MBC of antibiotics and biosurfactant were determined for mid-logarithmic cultures of common, medically relevant organisms: E. coli, M. luteus and S. aureus.
- These observations are supported by research using concentrations of 10–30 mg/ml Single-Species Biofilm Assay.
- The characterisation of the SAMB by cloning revealed a diverse assemblage of bacteria belonging to two phyla, Bacteroidetes and Proteobacteria, and covering as many as eight genera (Fig. 3 and Supplementary Table 1).
- Taking into account the fourfold dilution of the broad-spectrum antibiotics, this result shows a dramatic reversal of the effectiveness of the biosurfactants from the initial planktonic tests to the mixed biofilm assays.
Conclusions
- After establishing a baseline for the comparison of biosurfactants and antimicrobial agents, the data have indicated that the inhibitory effect of biosurfactants increases drastically in comparison to broad-spectrum antibiotics in biofilm-orientated assays.
- Additionally, through the use of the SAMB, it was observed that the biosurfactants inhibited the formation of complex heterogeneous marine biofilms.
- 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 (Grant No. AI060753).
- The authors declare that they have no conflict of interest.
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Citations
195 citations
Cites background from "A Comparison of Effects of Broad-Sp..."
...Rhamnolipids and other plant biosurfactants have also recently been reported to have some role in the inhibition of complex biofilms and as adjuvants to enhance some antibiotics microbial inhibitors.(145)...
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190 citations
Cites background from "A Comparison of Effects of Broad-Sp..."
...Quinn et al. (2013) have shown that Rhamnolipid is effective in inhibiting S. aureus, B. subtilis and M. luteus single-species biofilms and that they were in fact more effective than broad-spectrum antibiotics used in the study....
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185 citations
164 citations
Cites background from "A Comparison of Effects of Broad-Sp..."
...This is illustrated notably by the production of Pseudomonas aeruginosa rhamnolipids, which are able to disrupt the cohesiveness of biofilm formed by Bordetella bronchiseptica (Irie et al., 2005), Bacillus subtilis, S. aureus, and Micrococcus luteus (Quinn et al., 2013)....
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120 citations
References
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Q2. What future works have the authors mentioned in the paper "A comparison of effects of broad- spectrum antibiotics and biosurfactants on established bacterial biofilms" ?
Further research on S. typhimurium biofilms has revealed that concentrations of 100 lg of Rh were required ( mixture of 11 congeners ) to disperse pre-existing biofilms [ 27 ]. Each bacterial species, surface of attachment, temperature variation and nutrient status has the potential to create a different biofilm dynamic. This may be due to the multiplicity of potential bacterial permutations and the difficulties assessing the colonisation and succession patterns in such biofilms. The biofilms were incubated for a further 4 days before quantification of the biofilm biomass by crystal violet adherence assay.