Synergistic Effect of Phage-Antibiotic Combination against Pseudomonas Aeruginosa and Microencapsulation of Bacteriophages to Improve their Stability in Gastronomic Conditions

Abstract

Multidrug-resistant bacterial infections are propagating and escalating in frequency across the globe, jeopardizing practically every aspect of modern medicine and posing a serious challenge to public health. The excessive consumption of existing medications and a scarcity of newer medications due to restrictive legal constraints and diminished business incentives have both been blamed for the antibiotic resistance dilemma. In trials, progressive alternative therapies like phage treatment demonstrated encouraging results, alluding to its potential for use as preventive or adjuvant therapy in the future. The aim of the study was to determine antimicrobial effectiveness of combining sub-inhibitory concentrations of gentamicin, cefepime and meropenem with P. aeruginosa-specific bacteriophages belonging to Siphoviridae family. Phages showed remarkable stability with sub MIC doses of antibiotics with no significant change in plaque size and morphology. Further, the optimal MOI of phages was determined to be employed synergistically with antibiotics. While observing PAS, it was determined that phages PAA, PAM and PAR exhibited excellent synergy with antibiotics at sub MIC values. Moreover the combinatorial effect of these phages as a cocktail with antibiotics displayed remarkable synergy depicting complete bacterial removal. Furthermore, the synergistic effect of phages and antibiotics was tested on P.aeruginosa biofilms. It was observed that the PAS phenomenon proved to be highly effective in eradicating biofilm at sub MIC doses of antibiotics. The successful application of phages as antimicrobials was determined by testing the stability and activity of free phages in contrast to phages encapsulated in combinatorial bio-composite hydrogels of Sodium Alginate with other polymeric substances in the gastrointestinal environment. It was observed that free phages lost their viability significantly at gastric pH, however the encapsulated phages retained stability to further continue their passage to intestinal environment. The intestinal environment was determined to be highly favourable for phages as maximal phage release occurred in simulated intestinal fluid, to efficiently treat the intestinal ailments. Thus, the encapsulation strategy proved to enhance the effectiveness of phage therapy as an alternative to antibiotics.