Assessment of the Role of Mutation in Genetic Variations and Speciation among the Strains of Klebsiella pneumoniae and Escherichia coli Associated with Subclinical Mastitis from the Pastoral Herds in Nigeria

This study was conducted to evaluate the evolutionary relationship and clonal relatedness of Klebsiella pneu-moniae and Escherichia coli strains isolated from subclinical mastitis cases in pastoral herds in Nigeria.Phylogenetic analysis of gene sequences, performed using Bioedit and FigTree software, was employed todetermine the evolutionary relationships among the strains. The analysis revealed that all strains of K. pneu-moniae and E. coli shared a common ancestral origin, with E. coli strains evolving earlier than K. pneumoniaestrains. Among the E. coli strains, E1 and E3 exhibited the highest clonal relatedness, while K6 and K1 werethe most genotypically identical among the K. pneumoniae strains. The observed evolutionary relationshipsand clonal relatedness were primarily driven by continuous nucleotide sequence changes resulting from variousmutations. These mutations led to speciation and genotypic divergence from the ancestral genomes of theinvestigated K. pneumoniae and E. coli strains.