Antibiotic susceptibility of Salmonella spp isolated from farm animals and environmental sources in Tripoli, Libya

Nontyphoidal Salmonella (NTS) serovars remain a potential hazard to human and animal health. Food animals with Salmonella infections can either be cured or remain asymptomatic carriers, serving as a potential source of infection to humans and other healthy animals. Salmonella may also be a reservoir of resistance determinants that can be transferred to other commensal organisms, particularly in the gastrointestinal tract.

This article addresses the prevalence of Salmonella serovars in important food animals and their environment. Antibiotics susceptibility profiling of Salmonella serovars against important antibiotics used in human and animal medicines was also investigated.

In total, 125 fecal samples were collected from food animals (n = 100 fecal samples) and from the environment (n = 25). Salmonellae were isolated using standard laboratory procedures, and typical isolates were further confirmed using laboratory biomedical testing and the automated microbial identification system VITEK 2. Confirmed Salmonella isolates were further analyzed for their susceptibility to antimicrobial agents.

A total of 10.4% (13/125) of samples were found positive for Salmonella by conventional isolation, biochemical identification methods, and VITEK 2 system. The prevalence of Salmonella spp. in cattle feces was 8.9% (4/45), whereas the prevalence in poultry samples was 14.5% (8/55). Only one sample from soil was found positive for Salmonella representing 6.7% (1/25). Serologically, only five Salmonella isolates were further confirmed and typed into three serovars: S. Montevideo (n = 2), S. Kentucky (n = 1), and S. Typhimurium (n = 2). All Salmonella isolates displayed minimum inhibitory concentrations values above the susceptibility breakpoint for ampicillin, piperacillin, and second-generation cephalosporins but showed reduced susceptibility to third-generation cephalosporins. All the isolates also displayed different levels of resistance to ciprofloxacin and levofloxacin. Resistance to the aminoglycosides (amikacin, tobramycin, and gentamicin) was also rerecorded.

The current study demonstrated that the high resistance rates to fluoroquinolones can compromise important therapeutic options against salmonellosis posing also public health concerns.