Phylogeny of the Listeria Species Obtained from Dairy Environmental Samples

Abstract

Aims: To establish the phylogeny of the species of Listeria isolated from dairy environmental samples. Study Design: Isolates of Listeria were isolated from dairy environmental samples and subjected for pheno and genotypic identity. Based on genotypic identification, phylogeny of the species of Listeria was created based on neighbour joining method. Place and Duration of Study: The study was conducted in a laboratory (controlled setting) between June 2020 to July 2021. Methodology: Isolation of Listeria species were carried out on PALCAM agar. Isolates were maintained on the same agar slants and working cultures were prepared in the broth medium. The isolates were identified through various biochemical tests and confirmed using rRNA sequencing. The neighbour joining method was adopted to establish the phylogeny of all the Listeria species obtained from dairy environmental samples. Results: A total of 18 numbers of isolates of Listeria were obtained from the dairy environmental samples such as about 3 isolates from soil, dung, chilled milk each followed by 2 from fodder; feed; swab of udder; can milk and one from urine. The pheno and genotypic identity of Listeria revealed as Listeria ivanovii (6 nos; 50.0%), followed by Listeria grayi (5 nos;41.6 %) and Listeria seeligeri (1 no; 8.40%). Phylogenetic analysis through Neighbour joining method revealed that L. ivanovii L18, L8, L16 and L. grayi L9, L10, L12 were having relatedness about 87% while L. ivanovii L15, L7, L17, L. grayi L11, L13 and Listeria seeligeri L14 had about 92% homology. Blasting the obtained sequences in NCBI of the Listeria isolates revealed that there was a significant genetic correlation between Listeria isolate L7, L14, L15, L16 and L17 with NewYork isolate of Listeria, isolates L8 and L12 with Nigerian isolate, L9 and L11 with American isolate, L10 with German isolate, L13 with Himachal Pradesh isolate and L18 with Greece isolate. Conclusion: The Listeria isolates obtained from dairy environmental samples in the current study unravelled the genetic relatedness with the isolates from New York, Nigeria, Germany, Himachal Pradesh and Greece indicating their geographical distribution and divergence.