Statistical analysis

In the first stage, the distributions of RdxA inactivation and FrxA inactivation in both metronidazole-resistant and metronidazole-susceptible strains were analysed using the Fisher’s exact test. A P-value of less than 0.05 was considered significant. In the second stage, involving strains with full-length RdxA, for each gene in the core genomes, the association of each variable site in a protein sequence alignment with a metronidazole-resistant phenotype was statistically examined using Fisher’s exact test with a Bonferroni correction. This involved multiplying the acquired P-value by the number of variable sites in the gene being tested. An adjusted P-value of less than 0.05 was regarded as statistically significant.