Salmonella Gallinarum is one of the most important bacterial pathogens associated with diminished egg production in poultry. The aim of this study was to understand the occurrence, molecular traits and antimicrobial resistance patterns of
Salmonella Gallinarum strains isolated from small-scale commercial layer flocks with low level biosecurity standards in Bangladesh. A total of 765 samples, including cloacal swabs (535), visceral organs (50), and droppings (180), were collected from chickens of 12 layer flocks in 11 districts.
Salmonella Gallinarum was isolated and characterized through culture-based method, followed by biochemical tests, sero-grouping, PCR assays, sequencing, and antibiogram. The identity of biochemically detected isolates of
Salmonella Gallinarum was confirmed via genus-specific 16S rRNA gene based PCR, followed by
invA and
spvC genes based PCR assays. Occurrence of
Salmonella Gallinarum was detected in overall 25.75% (197/765) samples, with a significantly (
p < 0.05) higher incidence in visceral organs (42%) in comparison to cloacal swab (24%) and droppings (26%). Sequencing and subsequent phylogenetic analysis of
invA and
spvC genes in representative strains of
Salmonella Gallinarum revealed a close genetic lineage, with a sequence similarity of 98.05–99.21% and 97.51–99.45%, respectively, to previously published sequences of the corresponding genes from the same serogroup strains. Remarkably, 66.5% (131/197) of the isolated strains of
Salmonella Gallinarum were found to be resistant to 3 to 6 antimicrobial agents, and interpreted as multidrug resistant (MDR). The findings of this study underscore an inherent need of appropriate control measures to curb the widespread incidence of MDR
Salmonella Gallinarum in small-scale commercial layer flocks, thereby, facilitating enhanced egg production and further support to the food security and safety in low resource settings.
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