Virulotyping of Salmonella enterica serovar Typhi isolates from Pakistan: Absence of complete SPI-10 in Vi negative isolates


Sadia Liaquat, Yasra Sarwar, Aamir Ali, Abdul Haque, Muhammad Farooq, Ilargi Martinez-Ballesteros, Lorena Laorden, Javier Garaizar, Joseba Bikandi.


The distribution of virulence factors in S. Typhi can vary in isolates from different geographical regions and can have significant effect on the disease control. In this study, we have checked the distribution of 56 reported virulence associated factors in 35 local isolates of S. Typhi to identify any variations that can help in designing effective control strategies for typhoid.
We have identified four naturally occurring variants which are simultaneously lacking SPI-7 and SPI-10, two adjacently located pathogenicity islands on S. Typhi chromosome. These isolates are not producing Vi capsular antigen hence the Vi based vaccines will not be effective against them. These findings highlight the need to develop typhoid vaccines specifically effective in Pakistan.


Click here to view the article, published in PLoS Neglected Tropical Diseases.