New insights into Salmonella virulence: Detection of spvB and spvR genes in avian and human isolates from northeastern Algeria

The emergence of highly virulent and multidrug-resistant Salmonella strains continues to pose a major global public health concern. Building on our previous investigation of 80 Salmonella isolates obtained from avian and human sources in northeastern Algeria (Annaba and Constantine) over a three-year period (2017-2019), in which their resistance profiles to 15 antimicrobial agents were assessed, the present study further explores the molecular features of virulence by targeting two additional plasmid-encoded genes, spvB and spvR. All isolates were subjected to polymerase chain reaction (PCR) amplification using gene-specific primers. The results revealed that spvB was detected in 86.25% of isolates, while spvR was identified in 73.75%, suggesting a strong association with strains capable of causing severe systemic infections. When compared with previous reports, notable geographical variations were observed, which may reflect differences in host reservoirs, ecological conditions, and selective pressures arising from antimicrobial use. The coexistence of spv virulence genes and multidrug-resistant (MDR) phenotypes in our isolates underscores the substantial risk of dissemination of highly pathogenic and resistant Salmonella strains between animals and humans. These findings highlight the need to integrate virulence gene surveillance into existing antimicrobial resistance monitoring programs to better understand and manage the zoonotic transmission dynamics of Salmonella in Algeria.