Potentiality of lytic bacteriophages and their virolysins in lysing multi-drug resistant Salmonella typhi

Abstract

Bacteriophage virolysins or lytic enzymes are bacterial peptidoglycan hydrolases responsible for lysing bacterial cells. Consequently, they are used as enzybiotics alongside with bacteriophage therapy to remedy multi-drug resistant Salmonella typhi. The objective of this study was to evaluate the potentiality of lytic bacteriophages and their virolysins in curing multi-drug resistant S. typhi. S. typhi was isolated and identified according to WHO and ISO guidelines. Antibiotics susceptibilities were tested using CLSI recommendations. Correspondingly, bacteriophage-lysing efficiency was assayed by plaques formation using the double-layer agar technique. Virolysins were extracted using ultracentrifugation and purified by dialysis after buffering in ammonium sulfate. Virolysins activity was determined by measuring the reaction mixtures spectrophotometrically (bacteria incubated as substrate in 37°C for 4 h). The phages and virolysins kinetics exponential rates were calculated using specific differential equations. Susceptibility data plotted based on antibiogram criteria confirmed that 33% of S. typhi isolates were multi-drug resistant. For bacteriophage replication and multiplicity of infection, phages were amplified to produce the maximum particles of titers. The phage titration data fit on sonogram revealed exponential decay of S. typhi incubated for 12 h. Meanwhile, the enzyme kinetics exponential decay on double reciprocal plot showed irretrievable relationship of host decay in 4 h. Since phages depend on their lytic cycle in lysing bacterial host, their enzymes have more capability in decaying the host; besides they are safe and time-saving when used in the treatment of antibiotics resistant S. typhi.