Deleção de genes codificadores de proteínas anti-inflamatórias em Salmonella Pullorum: impacto sobre a persistência e a virulência em Gallus gallus domesticus

Abstract

Pullorum disease (PD) is a non-zoonotic poultry disease caused by Salmonella Pullorum (SP). This bacterium can be vertically transmitted, resulting in high mortality rates in poultry flocks. One of its characteristics is the induction of persistent infection in part of the flock. Several studies have investigated the persistence of SP in chicks. However, the mechanisms involved in the survival of SP and its evasion from the chick's immune system remains to be clarified. The present study aimed to investigate whether effector proteins with anti-inflammatory properties are related to the persistence and pathogenicity of SP in male layer chickens. For this purpose, deletions were made in the avrA, gtgA, pipA, and sseL genes in a wild strain of SP, resulting in four mutant strains (SPΔavrA, SPΔgtgA, SPΔpipA, and SPΔsseL). Subsequently, PD-susceptible chicks were distributed into the following groups: Group A (chicks inoculated with SPΔavrA), B (with SPΔgtgA), C (with SPΔpipA), D (with SPΔsseL), E (with SP), F (chicks challenged with Salmonella Gallinarum for comparison of possible increased pathogenicity in mutant strains), and G (chicks without inoculation). At 7 days old, the chicks were orally administered a challenge strain and were evaluated over 10 weeks. Samples were collected at 7, 14, 21, 35, 49, and 63 days post-infection (dpi) to assess the presence of Salmonella spp. in spleen and liver, clinical signs, and macroscopic changes in the organs. At 7 dpi, a larger quantity of SP was detected in the spleen and liver than the mutant strains. The detection frequency of SP and the other mutants was similar across the groups throughout the study. Chicks challenged with SPΔavrA showed more intense clinical signs of infection. There was no statistical difference in the frequencies of macroscopic changes among the chicks in the challenged groups. Overall, the results indicated that there were no differences in pathogenicity and persistence between the mutant and wild strains of SP.