Identification of virulence factors and antibiotic resistance in Salmonella enterica subsp. enterica serovar Javiana (FARPER-220) isolated from broiler chickens

ABSTRACT Genome sequencing of highly virulent Salmonella enterica subsp. enterica serovar Javiana strain FARPER-220 (ST-1674) isolated from broiler chickens in Peru revealed multiple virulence factors, antibiotic resistance genes, and invasion-related subcategories. The results provide insights into the potential importance of this strain in causing infections in various animals.

bacterium that infects various animals, including birds (1).It belongs to the family Enterobacteriaceae and serogroup D1 (O:9) and can cause systemic infections in susceptible individuals.S. Javiana produces cytotoxic distending toxin or typhoid toxin; this toxin plays a crucial role in DNA damage and systemic colonization of the host (2).
The FARPER-220 strain was isolated from a homogenized mixture of liver and spleen of broiler chickens in southern Peru in 2017.The strain was identified as S. enterica through colony morphology and specific PCR (3).Genomic DNA was extracted from an overnight culture grown in Brain Heart Infusion broth at 37°C using a phenol-chloroform protocol (4).Antibiograms were performed by the Kirby-Bauer disk diffusion method (Table 1) following CLSI standards (5).
Whole-genome sequencing of FARPER-220 was performed with a 20-kb SMRTbell library (PacBio DNA/polymerase binding kit P6) on the PacBio RS II platform (PacBio DNA sequencing kit 4.0) using C4 chemistry with eight single-molecule real-time (SMRT) cells.The genome was assembled de novo using RS HGAP v.3.0 (6) on SMRT Portal (v.2.3) by default (Macrogen, Inc., South Korea).The genome circularization was performed manually, aligning the ends of linear complemented genome segments to form the chitinase-encoding gene.
Functional annotation, complemented by RASTtk analysis, predicts numerous subcategories associated with antibiotic and toxic compound resistance.These encompassed the mercury-resistance operon, copper homeostasis, cobalt-zinc-cadmium resistance, fluoroquinolone resistance, copper tolerance, adaptation to d-cysteine, zinc resistance, and mercuric reductase.Furthermore, functional subcategories indicative of invasion and intracellular resistance were identified, notably the Mycobacterium virulence operon implicated in protein synthesis (SSU ribosomal proteins), DNA transcription, and potential involvement in quinolinate biosynthesis.
In conclusion, the complete genome sequence of S. Javiana, isolated from broiler chickens in Peru, has been identified, as well as various virulence factors and antibioticresistance genes.Laboratorio de Bioinformática, Biología Molecular y Desarrollos Tecnológicos.Laborator ios de Investigación y Desarrollo, Facultad de Ciencias, Universidad Peruana Cayetano Heredia, Lima, Peru