Isolation, Characterization and In vivo Evaluation of Therapeutic Potential of Bacteriophage Sal11TP against Salmonella enterica Serovar Paratyphi A

Salmonella Paratyphi A, also known as typhoidal Salmonella, is the causative agent of typhoid fever or paratyphoid fever, a threatening, invasive (bacteraemia), and occasionally fatal human disease (also called enteric fever). Even though Salmonella infections can be treated with different antibiotics, developing resistance to many broad-range antibiotics like chloramphenicol, nalidixic acid, ampicillin, and sulfamethoxazole is still a big problem. Therefore, an alternative strategy is needed urgently, which is more effective with minimal systemic side effects for treating diseases caused by Salmonella paratyphi A. In this current study, we describe the isolation, characterization, and in vivo evaluation of Sal11TP, a host-specific bacteriophage with lytic activity against multidrug-resistant Salmonella paratyphi A. Morphological examinations revealed that phage Sal11TP belonged to the order caudovirales of the Siphoviridae family, with an icosahedral head (62.8 nm) and a long tail (104.5 nm in length). Based on the one-step growth curve, Sal11TP has a short latent period (20 min) and burst size (29 PFU/cell). The in vitro stability test showed that it remained stable below 40 °C and pH 6-7 after treatment for 1 h. The ideal multiplicity of infection for phage Sal11TP was 0.001. The therapeutic potential of phage Sal11TP was evaluated using a mouse model. Findings of the study demonstrated a reduction in bacterial loads in the heart and kidney tissues of intraperitoneally infected mice during prophylaxis, as well as a dose-dependent and antibiotic versus phage treatment. The explanation of the characteristics and in vivo research results of phage Sal11TP show that it could be used as an effective bio-control agent to prevent Salmonella paratyphi A infections. Phage Sal11TP’s characteristics and in vivo results suggest it could serve as an effective bio-control agent against Salmonella paratyphi A infections.