title: Purification and antigenic detection of O-specific polysaccharides ofSalmonella entericaserovar Paratyphi A isolate from Pakistan: an emerging threat.
abstract: BACKGROUND
  Paratyphoid fever caused bySalmonella entericaserovar Paratyphi A is becoming a serious health problem in Asian countries particularly Pakistan, China and India and situation is aggravated by current unavailability of a licensed vaccine. This study was designed to purify the O-specific polysaccharides (OSP) produced by an isolate ofSalmonellaParatyphi A from Pakistan and detect antigenicity of extracted lipopolysaccharide (LPS) and purified OSP pioneerly in South Asian region as candidate for conjugate vaccine preparation.
  
  
  RESULTS
  S. Paratyphi A isolates were identified through PCR using primers offliC-agene (329 bp) and confirmed via nested PCR usingfliC-nested primers (289 bp). Yield of the LPS ofS. Paratyphi A isolate was 40 mg/L of the bacterial culture using hot phenol method. The purified LPS revealed the characteristic ladder like pattern ofS. Paratyphi A LPS on SDS-PAGE with silver staining. Purified OSP obtained by acid hydrolysis yielded 23 mg/L of culture broth and was not detected by silver staining. Antigenic interaction of the purified LPS and OSP with hyper immune mice sera was confirmed by single precipitin line evaluated through immunodiffusion assay. The antigenicity was found well intact.
  
  
  CONCLUSIONS
  The purified antigenic OSP fromS.Paratyphi A may have the potential to be coupled with a carrier protein to develop low cost conjugate vaccine candidates againstS.Paratyphi A in paratyphoid endemic regions.
authors.affiliation: National Institute for Biotechnology and Genetic Engineering (NIBGE), Faisalabad, Pakistan.
authors.forename: Zainab
authors.initials: Z
authors.lastname: Rahmat
authors.affiliation: National Institute for Biotechnology and Genetic Engineering (NIBGE), Faisalabad, Pakistan.
authors.forename: Aamir
authors.initials: A
authors.lastname: Ali
authors.affiliation: National Institute for Biotechnology and Genetic Engineering (NIBGE), Faisalabad, Pakistan.
authors.forename: Yasra
authors.initials: Y
authors.lastname: Sarwar
authors.affiliation: Department of Biotechnology, Abdul Wali Khan University, Mardan, Pakistan.
authors.forename: Muhammad
authors.initials: M
authors.lastname: Salman
authors.affiliation: Department of Pathology, The University of Faisalabad, Sargodha Road, Faisalabad, Pakistan.
authors.forename: Abdul
authors.initials: A
authors.lastname: Haque
keywords: Antigenicity; Conjugate vaccines; Lipopolysacchrides; OSP; Salmonella Paratyphi A