Abstract
Chronic skin wounds represent a major burn both economically and socially. Pseudomonas aeruginosa and Escherichia coli are among the most common colonizers of infected wounds and are prolific biofilm formers. Biofilms are a major problem in infections due to their increasingly difficult control and eradication, and tolerance to multiple prescribed drugs. As so, alternative methods are necessary. Bacteriophages (phages) and honey are both seen as a promising approach for biofilm related infections. Phages have specificity toward a bacterial genus, species or even strain, self-replicating nature, and avoid dysbiosis. Honey has gained acknowledgment due to its antibacterial, antioxidant and anti-inflammatory and wound healing properties. In this work, the effect of E. coli and P. aeruginosa phages vB_EcoS_CEB_EC3a and vB_PaeP_PAO1-D and chestnut honey, alone and combined, were tested using in vitro (polystyrene) and ex vivo (porcine skin) models and against mono and dual-species biofilms of these bacteria. In general, colonization was higher in the porcine skins and the presence of a second microorganism in a consortium of species did not affect the effectiveness of the treatments. The antibacterial effect of combined therapy against dual-species biofilms led to bacterial reductions that were greater for biofilms formed on polystyrene than on skin. Monospecies biofilms of E. coli were better destroyed with phages and honey than P. aeruginosa monospecies biofilms. Overall, the combined phage-honey formulations resulted in higher efficacies possibly due to honey's capacity to damage the bacterial cell membrane and also to its ability to penetrate the biofilm matrix, promoting and enhancing the subsequent phage infection.
Highlights
Chronic wounds are defined as wounds which failed the sequential reparative process responsible to repair the anatomic and functional integrity of the damaged tissue in a period of 4-8 weeks (Lazarus et al, 1994; Mustoe et al, 2006)
Bacterial growth occurs in biofilms, sessile communities organized in a three-dimensional structure, embedded in a self-produced matrix containing extracellular polymeric substances (EPS) such as polysaccharides, proteins, extracellular DNA, membrane vesicles, and other polymers
PAO1-D, isolated from the Sextaphage preparation, is a Podovirus showing a 56 nm × 64 nm icosahedral capsid, and a 12 nm non-contractile tail (Figure 1). This phage was selected for all further experiments based on its lytic spectra toward the clinical isolates (Table S1) and on the dimension of its large halo (Table S2, Figure S1) that may suggest the presence of enzymes with higher efficiency to degrade the EPS matrix of biofilms
Summary
Chronic wounds are defined as wounds which failed the sequential reparative process responsible to repair the anatomic and functional integrity of the damaged tissue in a period of 4-8 weeks (Lazarus et al, 1994; Mustoe et al, 2006). These wounds lead to considerable morbidity and high costs associated with treatment, which represents an increasing burden on public and health systems worldwide. The biofilm tolerance to several antibiotics and host defenses (Flemming and Wingender, 2010) is promoted by numerous factors. Efflux pumps have been identified in several biofilm forming pathogens, such as E. coli (Ito et al, 2009), P. aeruginosa (Zhang and Mah, 2008) and S. aureus (Ding et al, 2008) and the production of antibiotic degrading-enzymes, such as β-lactamase, was identified in biofilm forming strains (Hengzhuang et al, 2013)
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