Molecular genotyping of Salmonella spp. isolated from cheese samples of local stores in Al-Diwaniyah city, Iraq.

Abstract

Food safety is an important subject that the global cheese industry increases awareness of. This urges these economic sectors to elevate the level of research to minimize cheese contamination with pathogenic bacteria, such as Salmonella. Based on these merits, this study was conducted to genotype Salmonella spp. isolated from cheese samples of local stores in Al-Diwaniyah City, Iraq. The study used 41 samples of local fresh unsalted white cheese in a selective-growth-based isolation of Salmonella. These isolates were confirmed utilizing a slide-agglutination (SA) test and VITEK® 2 system (V2S). Then, the isolates were subjected to conventional PCR and sequencing techniques that both targeted the 16S rRNA gene. For subtyping, the Salmonella isolates were subjected to a random amplified polymorphic DNA (RAPD)-PCR method. The results of both SA and V2S revealed the presence of 14 (34.2%) isolates of Salmonella spp. in the cheese samples. The PCR confirmed 6 (42.9%) of these isolates, which further were defined with close nucleotide similarity (98.03%) and (97.88%) to different world isolates, such as Salmonella enterica subsp. Arizonae and Salmonella enterica subsp. enterica serovar Typhi, respectively. The RAPD-PCR findings showed different fragments for all the tested isolates. The present study indicates that the samples of the local fresh unsalted white cheese contain different Salmonella genotypes, which could be originated from different contamination sources.