title: Tuberculosis transmission among immigrants and autochthonous populations of the eastern province of Saudi Arabia.
abstract: BACKGROUND
  Eastern province of Saudi Arabia is an industrial zone with large immigrant population and high level of tuberculosis case notification among immigrants. The impact of immigration and current trends of tuberculosis transmission among immigrants and autochthonous population in the region had not been investigated so far using molecular tools.
  
  
  METHODS
  During 2009- 2011, a total of 524 Mycobacterium tuberculosis isolates were collected from the central tuberculosis reference laboratory, representing an estimated 79.2% of the culture-positive tuberculosis cases over the study period in the province. These isolates were genotyped by using 24 locus-based MIRU-VNTR typing and spoligotyping followed by first line drug susceptibility testing. The molecular clustering profiles and phylogenetic diversity of isolates were determined and compared to the geographical origins of the patients.
  
  
  RESULTS
  Genotyping showed an overall predominance of Delhi/CAS (29.4%), EAI (23.8%) and Ghana (13.3%) lineages, with slightly higher proportions of Delhi/CAS among autochthonous population (33.3 %) and EAI (30.9%) among immigrants. Rate of any drug resistance was 20.2% with 2.5% of multi-drug resistance. Strain cluster analysis indicated 42 clusters comprising 210 isolates, resulting in a calculated recent transmission index of 32.1%. Overall shared cluster ratio was 78.6% while 75.8% were shared between autochthonous population and immigrant population with a predominance of immigrants from South east Asia (40.7%). In contrast, cross national transmission within the immigrant population was limited (24.2%). Younger age (15-30- p value-0.043, 16-45, p value 0.030), Saudi nationality (p value-0.004) and South East Asian origin (p value-0.011) were identified as significant predisposing factors for molecular strain clustering.
  
  
  CONCLUSIONS
  The high proportion of molecular clusters shared among the autochthonous and immigrant populations suggests a high permeability of tuberculosis transmission between both populations in the province. These results prompt for the need to strengthen the current tuberculosis control strategies and surveillance programs.
authors.affiliation: Department of Infection and Immunity, King Faisal Specialist Hospital and Research Centre, Riyadh, Saudi Arabia.
authors.forename: Bright
authors.initials: B
authors.lastname: Varghese
authors.forename: Philip
authors.initials: P
authors.lastname: Supply
authors.forename: Mohammed
authors.initials: M
authors.lastname: Shoukri
authors.forename: Caroline
authors.initials: C
authors.lastname: Allix-Beguec
authors.forename: Ziad
authors.initials: Z
authors.lastname: Memish
authors.forename: Naila
authors.initials: N
authors.lastname: Abuljadayel
authors.forename: Raafat
authors.initials: R
authors.lastname: Al-Hakeem
authors.forename: Fahad
authors.initials: F
authors.lastname: AlRabiah
authors.forename: Sahal
authors.initials: S
authors.lastname: Al-Hajoj
mesh_terms: D000293:Adolescent; D000328:Adult; D002648:Child; D002675:Child, Preschool; D054242:Emigrants and Immigrants / Q000706:statistics & numerical data; D005260:Female; D005843:Geography; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D008297:Male; D008875:Middle Aged; D012307:Risk Factors; D012529:Saudi Arabia; D014376:Tuberculosis / Q000453:epidemiology / Q000635:transmission*; D055815:Young Adult