Abstract
Data are scarce on demographical factors related to the population structure of Mycobacterium tuberculosis in Saudi Arabia. A study was conducted on 902 clinical isolates to explore current trends in the phylogeography and associated demographical factors of tuberculosis by using spoligotyping and 24 loci based MIRU-VNTR typing. Young male patients (aged 16-29 and 30-44) were predominant in this cohort. The phylogenetic diversity among M. tuberculosis isolates was found high, as almost all known genetic lineages were identified. Delhi/CAS (26.4%), EAI (13.7%) and Haarlem (11.3%) were the most common lineages observed, particularly among the low age groups (16-29 and 30-44 years), whereas elderly patients (>60 years) showed a predominance in the lineages S, Ghana, TUR and Uganda-I. A statistically significant association was observed between gender of the patients and lineages of EAI (p value 0.026) and LAM (p value 0.005). Overall, molecular strain cluster rate was 34.4% with an elevated rate among patients aged below 15 years (43.1%), while cases among the elderly (>60 years) showed the lowest degree of clustering (12.5%). The largest level of clustering was noticed among cases caused by strains of the lineages Haarlem (59.8%), Beijing (55.8%) and LAM (42.8%). The current population structure of M. tuberculosis in Saudi Arabia is highly diverse with significant associations to demography, transmission dynamics and origin of the patients. The difference in genotype distributions among low and high aged patients reflects the ongoing change in the strain population structure in the country.
