Abstract
BackgroundEastern 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.MethodologyDuring 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.Principle FindingsGenotyping 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.ConclusionsThe 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.
Highlights
Tuberculosis (TB) is a reemerging infectious disease and a substantial public health problem globally despite the improvements in treatment and control [1]{Organization, 2012#259;Organization, 2012 #259}
The immigrant population was classified into four sub-groups according to their geographical origin as, African (AFR-Sudan, Eritrea, Somalia, Ethiopia, Egypt, Chad, Nigeria, Senegal, Cameroon), South Asian (SASIndia, Nepal, Sri Lanka, Bangladesh, Pakistan, Myanmar, Afghanistan), South East Asian (SEA- Philippines, Indonesia, Thailand and China) and West Asian (WA-Yemen)
Among the 532 isolates, 8 isolates were removed from the analysis as they were identified as Mycobacterium bovis by the line probe assay and further identified as BCG vaccine strains by the MIRU typing
Summary
Tuberculosis (TB) is a reemerging infectious disease and a substantial public health problem globally despite the improvements in treatment and control [1]{Organization, 2012#259;Organization, 2012 #259}. The impact of such import is difficult to forecast, due to the chronic nature of TB, the long period before reactivation of remote infection and supposedly low levels of TB transmission [2] This impact is problematic to determine because of the difficulty to obtain representative mycobacterial strain collections, especially in a large country. 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
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