Physiological properties of indigenous lytic bacteriophages as monophage suspension and cocktail against poultry-adapted typhoidal Salmonella variants

The emergence and spread of multidrug resistance among pathogens of the agro-food sector is increasing at an alarming rate, which has directed attention to the search for alternative to antibiotic therapy. The present work studied the physiological and population dynamics of lytic bacteriophages against avian-adapted Salmonella. Out of 28 positive samples, four bacteriophage isolates (Salempty set-ABF37, Salempty set-RCMPF12, Salempty set-MCOH26, Salempty set-DNLS42) were selected based on their ability to clearly lyse bacterial test strains. The isolates propagated were active against closely related D1 serotypes, i.e., S. Enteritidis and S. Typhimurium, with no heterologous activity against Escherichia coli ATCC 25922 and Staphylococcus aureus ATCC 23235. Each of the monophage suspension and cocktail efficiently suppressed the bacterial count from exponential increase in comparison to the untreated bacterial control. The bacterial turbidity was recorded as 0.244 at.600 during 400 min of co-incubation, in contrast to bacterial control showing lambda(600) = 0.669. The latent period was recorded to be 25, 35, 25 and 30 for Salempty setABF37, Salempty set-RCMPF12, Salempty set-MCOH26 and Salempty set-DNLS42, with 73.00, 97.00, 132 and 75.00 PFU cell-1, respectively. The highest lytic activity was seen at 37.00 degrees C - 42.00 degrees C, with phage particle count being fairly stable at pH 3.00 - 9.00. Each of the isolates possessed dsDNA by being resistant to RNase A. The current study concludes that lytic phages are promising alternative to combat multidrug resistant superbugs. The physiological characterization and bacterial growth inhibition are important parameters in standardization of phage therapy. (c) 2022 Urmia University. All rights reserved.

Automated summary

This study investigated the physiological and population dynamics of avian-adapted Salmonella lytic bacteriophages and found that these phages exhibited strong lytic activity against Salmonella and Typhimurium strains, while showing no activity against E. coli and S. aureus. The findings suggest that lytic phages may serve as a promising alternative in combating multidrug-resistant superbugs.