Genomic surveillance reveals international circulation and local transmission of Salmonella enterica serovars Typhi and Paratyphi A in Taiwan.

BACKGROUND/PURPOSE: Morbidity and mortality from typhoid and paratyphoid fever remain an important problem for public health authorities in developing countries. In countries with lower incidences, most cases occur in travelers who visit regions in which typhoid and paratyphoid fever are highly endemic. The aim was to evaluate the source and transmission dynamics of typhoid and paratyphoid fever in Taiwan by using genomic analysis.

METHODS

During 2012-2019, 15 clinical isolates of Salmonella Typhi and S. Paratyphi A were collected. Demographic and clinical information of the infections were analyzed. We performed whole genome sequencing and evolutionary analysis on these isolates.

RESULTS

Clinical and microbiological data from 7 S. Typhi and 8 S. Paratyphi A isolates in Taiwan showed epidemiological and bacterial genomic link to the infection in South and Southeast Asia. The Taiwanese typhoidal isolates also share highly similar genomes with those collected from UK, indicating global circulation of the typhoidal clones. Local transmission of the imported but indigenized international clones was observed. Mutations occurring at gyrA 83 aa, including S83Y and S83F, were identified in the ciprofloxacin-resistant strains.

CONCLUSION

Due to the advance of global transportation and communication, the transmission mode of infectious disease has been modified. Domestic typhoid and paratyphoid fever caused by international resistant clones can occur in low-incidence countries. Genome analysis showed that the indigenous clone originally imported from other countries has been circulating in Taiwan for over a decade.