Molecular Characterization of nfsA and nfsB Genes in Furazolidone-Resistant Salmonella Spp. Isolated from Poultry Eggs

Furazolidone (FZD), a broad-spectrum antibiotic in the nitrofuran class, is banned in many countries due to health concerns. The illegal use of FZD in poultry can lead to drug resistance in bacteria, such as Salmonella spp., which infect both poultry and humans. Contaminated eggs are a primary source of Salmonella infection. This study investigated the resistance of Salmonella isolates from eggs to FZD to gain crucial insights into the prevalence of resistant strains within the population. To this end, the susceptibility of ۲۲ Salmonella enterica isolates from eggshells to FZD was determined using the disk diffusion and minimum inhibitory concentration methods. Then, the mutations in the nfsA and nfsB genes were examined using the polymerase chain reaction method and sequencing. Results were analyzed using GeneRunner software and BLAST online software. It was found that ۲۷.۲۷% and ۹.۰۹% of the isolates had high and medium resistance to FZD, respectively. The minimum inhibitory concentration results were determined to be ۳۲ μg/ml for sensitive isolates, ۲۵۶ μg/ml for intermediate isolates, and ۵۱۲ μg/ml for resistant isolates. Sequencing analysis identified six insertion mutations and one transition mutation in the nfsA gene of resistant isolates, as well as one silent mutation in the nfsB gene of a sensitive isolate. The study highlights substantial resistance to FZD in Salmonella isolates from eggs, associated with mutations in the nfsA gene. These findings underscore the necessity for monitoring and managing resistance in foodborne pathogens. The significant resistance to FZD and the related mutations in the nfsA gene highlight the critical need for continuous surveillance and research to address the growing issue of antimicrobial resistance, especially in food products.

Keywords:

Furazolidone , nfsA , nfsB , resistance , Salmonella