title: Mix-infection of S. Typhi and ParaTyphi A in Typhoid Fever and Chronic Typhoid Carriers: A Nested PCR Based Study in North India.
abstract: BACKGROUND
  Enteric fever is a systemic disease caused by Salmonella organism such as serotypes Typhi and ParaTyphi A, B, C. Salmonella ParaTyphi A contributes more than 50% of all the enteric fever cases and it has recently been projected as an emerging pathogen.
  
  
  METHODS
  The present study was aimed to detect Salmonella Typhi and ParaTyphi A in urine, blood and stool specimens collected from cases of enteric fever (110), chronic typhoid carriers (46) and healthy controls (75) to explore the possibility of mixed infection by nested PCR. A new nested PCR primer was designed targeting putative fimbrial protein (stkG) gene which is one of the fimbrial gene families to Salmonella ParaTyphi A and for S. Typhi already reported primers targeting flagellin (fliC) gene.
  
  
  RESULTS
  Large volume of urine specimens (15 ml) was found to be the best for detection of Salmonella serotypes. The urine sample was found to have mixed-infection by both the serotypes in 40.9% of the cases but lower in blood (27.3%) and stool (13.6%).
  
  
  CONCLUSIONS
  The present study concludes that occurrence of mixed infection may be quite frequent in typhoid and chronic typhoid carriers' individuals, although the reported recent rise in ParaTyphi A incidence may not be real.
authors.affiliation: PhD Student, Department of Microbiology, Institute of Medical Sciences, Banaras Hindu University , Varanasi, India .
authors.forename: Chandra Bhan
authors.initials: CB
authors.lastname: Pratap
authors.affiliation: Senior Resident, Department of Microbiology, Institute of Medical Sciences, Banaras Hindu University , Varanasi, India .
authors.forename: Gopal
authors.initials: G
authors.lastname: Kumar
authors.affiliation: PhD Student, Department of Microbiology, Institute of Medical Sciences, Banaras Hindu University , Varanasi, India .
authors.forename: Saurabh Kumar
authors.initials: SK
authors.lastname: Patel
authors.affiliation: Professor, Department of General Surgery, Institute of Medical Sciences, Banaras Hindu University , Varanasi, India .
authors.forename: Vijay K
authors.initials: VK
authors.lastname: Shukla
authors.affiliation: Professor, Department of Medicine, Institute of Medical Sciences, Banaras Hindu University , Varanasi, India .
authors.forename: Kailash
authors.initials: K
authors.lastname: Kumar
authors.affiliation: Professor, Department of Community Medicine, Institute of Medical Sciences, Banaras Hindu University , Varanasi, India .
authors.forename: Tej Bali
authors.initials: TB
authors.lastname: Singh
authors.affiliation: Professor, Department of Microbiology, Institute of Medical Sciences, Banaras Hindu University , Varanasi, India .
authors.forename: Gopal
authors.initials: G
authors.lastname: Nath
keywords: Enteric fever; Fimbrial protein (stkG) gene; Mix-infection; Multiplex PCR; Nested PCR; S. ParaTyphi A; S. Typhi