In this case report, we present case reports for two nurses, both working in departments of respiratory medicine, who developed tuberculosis (TB). For each individual case, whole genome sequencing revealed only one specific match within a genomic distance of <6 single-nucleotide polymorphisms. The subsequent epidemiological investigations confirmed that both nurses had relevant exposures to their corresponding match at 1139 and 1704 days before presenting with TB symptoms, respectively. Twenty-two studies were identified that reported on the use of genotyping to identify occupational transmission of Mycobacterium tuberculosis to healthcare workers. Only two studies applied whole genome sequencing (WGS), both conducted in resource-rich countries, comparable to the present Danish investigation. When comparing the two WGS studies to the other studies that used older genotyping techniques, WGS provided a higher resolution and much more detailed information. Consequently, the epidemiological investigations were more straightforward. In conclusion, WGS is a powerful tool for determining whether M. tuberculosis transmission is occupational as demonstrated for the two cases in this study.
Keywords: Tuberculosis; healthcare workers; occupational transmission; whole genome sequencing.
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