polymorphisms of dtxr gene of corynebacterium diphtheriae isolated from diphtheria outbreak in indonesia

Background: in corynebacterium diphtheriae, the dtxr gene plays a role in regulating diphtheria toxin synthesis. the dtxr gene is often used as a marker for identifying c. diphtheriae by the polymerase chain reaction (pcr)methodbecause it is present in all strains of this bacterium. mutations in the dtxr gene can cause the over-synthesis of diphtheria toxin and reduce pcr assays’ sensitivity. objectives: this study aimed to describe the polymorphisms in the dtxr gene of c. diphtheriae isolated from a diphtheria outbreak in indonesia. methods: forty-eight isolates of c. diphtheriae were obtained from clinical samples (throat/nasopharyngeal swabs) of diphtheria cases and close contacts. the isolates were revived on a blood agar plate (bap), bacterial colonies were harvested, and deoxyribonucleic acid (dna) was extracted. the dna sequencing was carried out using a whole-genome sequencing (wgs) approach. the data were converted and analyzed with u-gene software. the dtxr gene analysis was performed with c. diphtheriae pw8 as references. results: there were 59-point mutation locations in 48 isolates examined. none of these single nucleotide polymorphisms (snps) coded for amino acid changes. based on the mutation pattern, seven clades/groups of the dtxr gene of 48 c. diphtheriae isolates were examined. conclusions: at least seven types of dna sequences and more than 50 snps of the dtxr gene were identified in 48 c. diphtheriae isolates from a diphtheria outbreak in indonesia. although all of them are silent mutations, they must be considered in the design of pcr examination in diphtheria laboratories.