Molecular detection of virulence genes and antimicrobial resistance in Salmonella isolates from avian and human sources in northeastern Algeria

Abstract

Products of avian origin are one of the major Salmonella reservoirs, responsible for serious public health concerns. Transmission and pathogenicity are mainly caused by molecular mechanisms, including chromosomal and plasmid-encoded virulence factors. This study aimed to perform phenotypic identification, antibiotic resistance profiling against 15 antibiotics, and characterization of virulence factors of 80 Salmonella strains (30 from human and 50 from poultry), collected in Annaba and Constantine regions in Algeria.Antibiogram analysis and simplex PCR revealed complete resistance to four antibiotics: Ampicillin, Penicillin, Cephalotin and Cephoxetin. In addition, four virulence genes (spvA, spiC, spvC and pefA) were detected. These genes were identified in isolates from both avian and human origins, with variations in their distrubition frequencies. This study highlights the significant role of avian-derived Salmonella as a reservoir of antibiotic resistance and virulence genes, posing a serious threat to public health.Antibiotic resistance profiling revealed that avian isolates exhibited complete resistance (100%) to ampicillin, penicillin and cephalothin, followed by a high resistance rate of 98% to cefalexin and ceftriaxone. Moderate resistance levels, ranging from 76% to 46%, were observed against streptomycin, tetracycline, trimethoprim-sulfamethoxazole, ciprofloxacin, kanamycin and nalidixic acid. In contrast, low resistance rates were reported for gentamicin, amikacin, and chloramphenicol, at 20%, 18%, and 16%, respectively.On the other hand, human isolates showed complete resistance (100%) to ampicillin, penicillin, cephalothin and cefalexin. Moderate resistance (76%-46%) was observed against ceftriaxone, kanamycin, cefotaxime, gentamicin, trimethoprim-sulfamethoxazole, nalidixic acid, streptomycin, and chloramphenicol. Low resistance levels were detected for tetracycline, ciprofloxacin, and amikacin, at 26%, 20%, and 6.6%, respectively.These findings along with the widespread presence of virulence genes (spvA, spiC, spvC, and pefA) in both human and poultry isolates, underscore the potential for cross-species transmission and the urgent need for enhanced surveillance. The regional findings from Annaba and Constantine emphasize the importance of stricter antibiotic use policies in poultry farming.