Assessment of Bacteriophage cocktails (Sal-Pak-1 and Sal-Pak-2) Efficacy against Salmonella Gallinarum Infection in Broiler Chickens
Asad Aslam Khan1, Zulquernain Haider1, Hafsa Naseem1, Shafiq Ur Rehman1
Institute of Microbiology and Molecular Genetics (IMMG), University of the Punjab, Lahore, Pakistan
Salmonella Gallinarum (SG) remains a significant pathogen in poultry, causing high morbidity and mortality, which reflects major economic losses worldwide. Bacteriophage therapy is a promising alternative to antibiotics, with potential benefits for both disease control and production efficiency. This study aimed to evaluate the protective efficacy of bacteriophage formulations (Sal-Pak-1 (4 bacteriophages in cocktail) and Sal-Pak-2 (three bacteriophages in cocktail) against SG infection in broiler chickens, with an emphasis on pathological outcomes. A total of 130 broiler birds were allocated to experimental groups, of which five groups were analysed in this study: G-1 (Sal-Pak-1+SG challenge), G-2 (Sal-Pak-2+SG challenge), G-3 (positive control, SG only), G-4 (negative control), and G-5 (Sal-Pak-1 only). Phages (108 Pfu/Kg feed) were administered via feed from day 7 to 28 1 ml per kg of feed, while the challenge was orally given with pathogenic strain of SG (10⁷ CFU/0.1ml/bird) on day 14. Clinical signs, gross lesions, histopathology, FCR, microbiological load and survival were assessed at 7 and 14 days post-infection (DPI). Survival analysis demonstrated that both the bacteriophage cocktails were effective to control the SG infection. The G3 (challenge only) showed a 54% mortality, in contrast, with phage-treated groups G-1 and G-2 exhibited 100% survival, while no mortality was observed in G-4 and G-5, confirming the safety of phage treatment. The observed feed conversion ratios (FCR) (2.35, 2.58, 3.65, 2.26 and 2.26 in G1, G2, G3, G4 and G4 respectively) obserevd at 7DPI, indicates that bacteriophage treatments lead to improved feed conversion compared with non-treated challenge. The histopathological analysis indicates that challenge only group, exhibited severe lesions including hepatitis, enteritis, and splenomegaly, while phage-treated groups showed reduced pathological severity. G-1 demonstrated mild to moderate lesions with improved intestinal architecture and higher crypt depth of 214µm, while G-2 showed crypt depth of 154.903µm with mild hepatic demage and reduced intestinal integrity. The G-5 with crypt depth of 186.67µm and G-4 with crypt depth of 116.73µm maintained minimal-no-pathological alterations, while the crypt depth of G3 was reported as 111µm. Microbiological analysis indicated a reduction in SG load in phage-treated groups, particularly in G-1 and G-2, where no detectable colonies were observed post-challenge, in contrast to sustained bacterial presence in G-3. Bacteriophage therapy, particularly in G-1 and G-2 cocktail formulations, demonstrated protective effects against SG infection in broilers by reducing bacterial load, tissue damage, improved crypts depth and FCR.
