title: Molecular detection identified a type six secretion system in Campylobacter jejuni from various sources but not from human cases.
abstract: OBJECTIVE
  To determine the presence of the T6SS in Campylobacter jejuni from diverse sources.
  
  
  RESULTS
  The recently identified type VI secretion system (T6SS) is a bacterial injection machinery that plays a role in virulence, symbiosis, bacterial interactions and environmental stress responses. This system has been recently discovered in the major enteric pathogen Camp. jejuni. In this study, we used multiplex PCR (mPCR), based on conserved genetic markers of the T6SS, to screen 366 Pakistani Camp. jejuni isolates from humans, poultry, cattle, wildlife or waste-water sources. We identified the T6SS in isolates from all of these sources except humans. The overall prevalence of the T6SS among the isolates was 17/366 (4·6%) and the T6SS positive isolates clustered into four different groups. Transcription of the T6SS genes, determined using RT-PCR, was observed in bacteria cultured at 37 or 42°C but not in 37°C cultures adjusted to pH3.
  
  
  CONCLUSIONS
  Campylobacter jejuni isolates harbouring T6SS markers genes were identified in livestock and non-livestock sources but in this study we did not identify human diarrhoeal isolates which possessed the T6SS. We demonstrated down-regulation of T6SS in an acidic environment.
  
  
  CONCLUSIONS
  This study questions the role of the T6SS in human diarrhoeal disease. Moreover this study did not identify a clear association of Camp. jejuni isolates harbouring T6SS with any of the niches tested. Our study highlights the need to establish the role of the T6SS in environmental survival or virulence.
authors.affiliation: Microbiology Laboratory, Biosciences Department, COMSATS Institute of Information Technology, Islamabad, Pakistan.
authors.forename: F
authors.initials: F
authors.lastname: Siddiqui
authors.forename: O
authors.initials: O
authors.lastname: Champion
authors.forename: M
authors.initials: M
authors.lastname: Akram
authors.forename: D
authors.initials: D
authors.lastname: Studholme
authors.forename: S A M A S
authors.initials: SA
authors.lastname: Eqani
authors.forename: B W
authors.initials: BW
authors.lastname: Wren
authors.forename: R
authors.initials: R
authors.lastname: Titball
authors.forename: H
authors.initials: H
authors.lastname: Bokhari
mesh_terms: D000818:Animals; D000835:Animals, Wild / Q000382:microbiology; D001426:Bacterial Proteins / Q000235:genetics* / Q000378:metabolism; D002169:Campylobacter Infections / Q000382:microbiology* / Q000662:veterinary*; D016123:Campylobacter jejuni / Q000145:classification / Q000235:genetics* / Q000302:isolation & purification / Q000472:pathogenicity; D002417:Cattle; D015536:Down-Regulation; D005819:Genetic Markers; D006801:Humans; D058751:Livestock / Q000382:microbiology; D011200:Poultry / Q000382:microbiology; D000069376:Type VI Secretion Systems / Q000235:genetics* / Q000378:metabolism; D014774:Virulence
chemical_list: D001426:Bacterial Proteins; D005819:Genetic Markers; D000069376:Type VI Secretion Systems
keywords: Campylobacter jejuni; haemolysin coregulated protein; reverse transcriptase PCR; strain cluster; type six secretion system