Salmonella Enterica Isolated from Different Poultry Species in Eastern Algeria: Serotype Diversity and Antibiotic Resistance Profile

Abstract

Salmonella enterica remains a major pathogen causing severe economic losses in the poultry sector and posing significant public health risks globally. This study aimed to determine the prevalence, serotypic diversity, and antimicrobial resistance profiles of Salmonella enterica isolated from various commercial poultry production lines across eastern Algeria.

A multi-center survey was conducted between April 2013 and May 2025 across 137 poultry farms located in eight provinces of eastern Algeria (Sétif, Bordj Bou Arreridj, M'sila, Batna, Constantine, Mila, Skikda, and Oum El-Bouaghi). A total of 321 biological organ samples (liver, heart, and oviducts) were collected from birds exhibiting clinical signs or suspicious necropsy lesions. Isolation and identification were carried out in accordance with ISO 6579-1:2017 guidelines and the API 20E system. Serotyping was performed per ISO/TR 6579-3 recommendations. Antibiotic susceptibility testing against 12 molecules was conducted using the disk diffusion method following CLSI/CA-SFM guidelines.

An overall farm prevalence of 51.82% (71/137) was observed, with marked variation across production lines. The highest prevalence occurred in layer breeders (100%, 3/3) and laying hens (80.00%, 44/55), followed by turkeys (40.00%, 4/10), broilers (29.82%, 17/57), and broiler breeders (25.00%, 3/12). Among the 71 isolated strains, five serotypes were identified, dominated by Salmonella Gallinarum (56.34%, n = 40) and Salmonella Enteritidis (35.21%, n = 25), alongside Salmonella Pullorum (4.22%, n = 3), partially serotyped strains (2.82%, n = 2; S. spp. O:6,7 and S. spp. O:1,2), and one non-typeable isolate (1.41%). Antimicrobial profiling demonstrated total susceptibility (100%) to cefotaxime, gentamicin, colistin, and chloramphenicol, as well as high efficacy for amoxicillin-clavulanic acid (90.14% susceptible), trimethoprim-sulfamethoxazole (90.14%), and enrofloxacin (97.08%). Conversely, alarmingly high resistance was detected against nalidixic acid (98.54%), followed by moderate resistance to tetracycline (23.94%), nitrofuran (22.53%), and ampicillin (15.44%). Multidrug resistance (MDR, ge 3 classes) was observed in 14.08% (n = 10) of isolates, yielding a Multiple Antibiotic Resistance Index (MARI) of 0.27. Statistical analysis revealed a highly significant association between poultry species and serotype distribution (p < 0.01), whereas MDR profiles were uniformly distributed across species (p > 0.05).

The elevated prevalence of host-adapted (S. Gallinarum) and zoonotic (S. Enteritidis) serotypes, coupled with high quinolone resistance and a elevated MAR index, underscores critical gaps in biosecurity and antimicrobial stewardship in Algerian poultry production. Stricter hygiene measures and prudent antibiotic monitoring are urgently needed.