Behandlung von Pseudomonas aeruginosa-Biofilmen mithilfe von Bakteriophagen

Beschreibung

"Treatment of Pseudomonas aeruginosa biofilms using bacteriophages" The aim of this study was to analyse if a cocktail of the two bacteriophages vB_Pae-TbilisiM32 and vB_Pa-CS2310 is able to prevent the formation of a P. aeruginosa biofilm as well as to eliminate an already established biofilm. The experiments were carried out at the optimum temperature of P. aeruginosa, 37 °C, and at 12 °C, to represent the conditions in the food processing industry. At first, the host range of both phages was determined, resulting in 53 % of the examined P. aeruginosa wild-type strains in vB_Pae-TbilisiM32 and 80 % in vB_Pae-CS2310. Following this, six of these P. aeruginosa strains were chosen, all of which were sensitive to both phages. With these strains, the influence of the two phages and a cocktail of both was tested in liquid culture at 37 °C. Rapid reduction of the bacterial number was observed, followed by fast cell count recovery. At 12 °C, the cocktail was also able to reduce the cell count, or at least to prohibit an increase of the cell count in some strains. Prevention of P. aeruginosa biofilm formation was successful at both 37 °C and 12 °C. Only two strains weren't affected by the cocktail at 37 °C. However, the elimination of the established biofilms wasn't consistent. After 6 h at 37 °C a distinct reduction of the biofilms could be observed, while after 24 h strong biofilm masses occurred again, with optical densities above the media control. By contrast, the progression at 12 °C showed a stronger reduction of the biofilm masses after 72 h than after 24 h. At the end of the experiments, clones were obtained, and even when they survived in coculture with the bacteriophages, plenty of them remained sensible to the used phages and cocktail. The genetic analyses of the bacterial strains did not result in any evidence of genetic change causing resistances. However, apart from the 31 selected genes, only complete gene deletions were investigated, which means that mutations in other genes remain possible. Further investigations regarding the mutations are necessary. Apart from that, phenotypic resistances may also cause survival of bacteria. A slightly changed genetic expression may result in a different formation or masking of the phage receptors. In this case, in a short period after adding the phages, the cell count increases, but the bacteria remain sensible to the phages. Adding bacteriophages is forcing a heterogeneity of the bacteria, which explains the different resistance patterns. To be applied in vivo, the phage cocktail used in this study should be advanced. Although it is already very promising in the prevention of P. aeruginosa biofilms, the resistances in liquid culture and already established biofilms develop in a concise period. Therefore, the cocktail should be extended by further P. aeruginosa phages and used in combination with other therapeutic agents like chlorine. In further studies, the binding receptor of both phages should be examined, and the causal resistance pattern should be investigated. Furthermore, it would be interesting to investigate, if the resistance against the phage cocktail is reducing the virulence of P. aeruginosa. In that case, despite the resistance, a therapeutical application in medical sections would be achievable.

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Jana Elisabeth Lea Perleth

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Bakteriophagen Biofilme Lebensmittelhygiene Lebensmittelsicherheit Oberflächen bacteriophages biofilms food hygiene food safety pseudomonas aeruginosa public health surfaces öffentliche Gesundheit

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