Status of Vi gene, its expression and Salmonella Pathogenicity Island (SPI-7) in Salmonella Typhi in India.

Salmonella enterica serotype Typhi (S. Typhi) is a causative organism of typhoid fever. A number of Salmonella serovars express a capsular polysaccharide antigen known as Vi, the biosynthetic and export proteins of which are encoded within the viaB locus of Salmonella Pathogenicity Island -7 (SPI-7). SPI-7 is inserted between two partially duplicated copies of tRNA -pheU gene. We have investigated the frequency of viaB operon deletion and loss of SPI-7 due to storage of strains collected during the period 1987-2006 by PCR amplification of fliC (for confirmation of serotype Typhi), tviB (for status of viaB operon) and tRNA -pheU (for absence of SPI-7). All 111 isolates were observed with positive amplification of 495 bp amplicon for fliC. A total of 36 isolates were negative for Vi by agglutination while 39 were negative for viaB operon. Interestingly, 106 isolates were found to have SPI-7. The 5 SPI-7 negative isolates were isolated during recent years. Long-term storage and repeated culture had little or no effect on SPI-7, as none of the 18 isolates recovered from blood before 1997 lacked SPI-7. On the other hand, loss of viaB operon was directly proportional to duration of storage. Thus, it is proposed that stability of Vi gene is dependent on the presence of selection pressure.

Maurya P ，Gulati AK ，Nath G 《SOUTHEAST ASIAN JOURNAL OF TROPICAL MEDICINE AND PUBLIC HEALTH》

Detection of Vi-negative Salmonella enterica serovar typhi in the peripheral blood of patients with typhoid fever in the Faisalabad region of Pakistan.

Baker S ，Sarwar Y ，Aziz H ，Haque A ，Ali A ，Dougan G ，Wain J ，Haque A ... -  《-》

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

Liaquat S ，Sarwar Y ，Ali A ，Haque A ，Farooq M ，Martinez-Ballesteros I ，Laorden L ，Garaizar J ，Bikandi J ... -  《PLoS Neglected Tropical Diseases》

Composition, acquisition, and distribution of the Vi exopolysaccharide-encoding Salmonella enterica pathogenicity island SPI-7.

Pickard D ，Wain J ，Baker S ，Line A ，Chohan S ，Fookes M ，Barron A ，Gaora PO ，Chabalgoity JA ，Thanky N ，Scholes C ，Thomson N ，Quail M ，Parkhill J ，Dougan G ... -  《-》

The capsule encoding the viaB locus reduces interleukin-17 expression and mucosal innate responses in the bovine intestinal mucosa during infection with Salmonella enterica serotype Typhi.

Raffatellu M ，Santos RL ，Chessa D ，Wilson RP ，Winter SE ，Rossetti CA ，Lawhon SD ，Chu H ，Lau T ，Bevins CL ，Adams LG ，Bäumler AJ ... -  《-》