International Journal of Antimicrobial Agents 37 (2011) 324–331 Contents lists available at ScienceDirect International Journal of Antimicrobial Agents journal homepage: http://www.elsevier.com/locate/ijantimicag Synergistic effect of lipopeptide biosurfactant with antibiotics against Escherichia coli CFT073 biofilm Fabrizio Rivardo a,b,c , Maria Giovanna Martinotti a , Raymond Joseph Turner b,c , Howard Ceri b,c,∗ a Department of Chemical, Food, Pharmaceutical and Pharmacological Sciences (DiSCAFF), Drug and Food Biotechnology Centre, University of Eastern Piedmont, Via Bovio 6, 28100 Novara, Italy b Department of Biological Sciences, Faculty of Science, University of Calgary, 2500 University Drive N.W., Calgary, AB, Canada T2N 1N4 c Biofilm Research Group, Faculty of Science University of Calgary, 2500 University Drive N.W., Calgary, AB, Canada T2N 1N4 article info Article history: Received 4 August 2010 Accepted 13 December 2010 Keywords: Lipopeptide Biosurfactant Synergy Biofilm Eradication Uropathogenic Escherichia coli abstract Biofilms are microcolonies of microbes adherent to biotic and abiotic surfaces, often responsible for chronic infections and medical device contamination. Escherichia coli is one of the prevalent pathogens involved in uropathogenic infections and contamination of catheters. A biosurfactant produced by Bacillus licheniformis V9T14 was tested alone and in association with various antibiotics against a mature 24- h uropathogenic E. coli CFT073 biofilm. Biofilm was grown on polystyrene pegs of a Calgary Biofilm Device, providing a tool to evaluate the efficacy of antimicrobial agents. Antibiotics tested were ampicillin, cefazolin, ceftriaxone, ciprofloxacin, piperacillin, tobramycin and trimethoprim/sulfamethoxazole (19:1). Biosurfactant alone at the concentrations tested was not able to remove the adherent cells of the pre- formed biofilm. However, the difference between the effect of antibiotic alone and in combination with the biosurfactant was significant and exceeded 1 log 10 (90%) reduction in most cases. Results of this study indicate that V9T14 biosurfactant in association with antibiotics leads to a synergistic increase in the efficacy of antibiotics in biofilm killing, and in some combinations leads to total eradication of E. coli CFT073 biofilm. © 2011 Elsevier B.V. and the International Society of Chemotherapy. All rights reserved. 1. Introduction A biofilm is a community of microorganisms attached to a sur- face, surrounded by an extracellular polymeric substance (EPS) made of polysaccharides, DNA and proteins able to aid microbes in their defence from environmental assaults [1]. Bacterial attach- ment to surfaces and consequent biofilm formation are well-known phenomena particularly associated with medical and food indus- try devices. Biofilms are an important cause of catheter-associated urinary tract infections (UTIs) that can lead to nosocomial infec- tions and are a frequent cause of implant rejection, with significant morbidity, mortality and additional hospital costs [2]. Host defence systems typically eliminate transient bacterial contamination, however the presence of foreign bodies such as catheters and orthopaedic implants generates local immunosuppression [3] and thereby lowers the threshold for sustainable bacterial infection [4]. Talpur et al. [5] demonstrated how catheterisation signifi- cantly increases the frequency of intraprostatic tissue infection and ∗ Corresponding author at: Department of Biological Sciences, Faculty of Science, University of Calgary, 2500 University Drive N.W., Calgary, AB, Canada T2N 1N4. Tel.: +1 403 220 6960; fax: +1 403 289 9311. E-mail address: ceri@ucalgary.ca (H. Ceri). bacteriuria. Approximately 80% of nosocomial UTIs are associ- ated with the use of indwelling urinary catheters [6], and UTIs are responsible for 40–60% of all hospital-acquired infections [7]. Escherichia coli is one of the most prevalent pathogens in UTIs [8]. As frequent replacement of a prosthesis due to bacterial infec- tion is uncomfortable, costly, time consuming and may lead to damage of the cellular tissue in patients, alternative approaches to the treatment of catheter infections must be found. Resistance of bacterial infections to antibiotics is increasing worldwide and some older antimicrobial agents are no longer recommended because of high levels of resistance [9]. Several attempts have been made to prevent biofilm formation by incorporation of biocides into sur- face materials or coating surfaces with biocides, especially in the medical field [2]. Biosurfactants are amphiphilic metabolites pro- duced by a wide group of bacteria and can be a useful approach to challenge bacteria growing as a biofilm. Lipopeptides are par- ticularly interesting because of their high surface activity and antibiotic potential [10]. We previously demonstrated that bio- surfactants from Bacillus spp. can reduce surface colonisation by E. coli and Staphylococcus aureus biofilm [11]. Organisms within a biofilm are difficult to eradicate by conventional antimicrobial therapy and can cause indolent infections, providing a signifi- cant challenge as they tend to be more tolerant to antimicrobial treatments than their planktonic counterparts [12,13]. It has been 0924-8579/$ – see front matter © 2011 Elsevier B.V. and the International Society of Chemotherapy. All rights reserved. doi:10.1016/j.ijantimicag.2010.12.011