Increasing incidence of multidrug-resistant tuberculosis (MDR-TB) is hampering efforts to control TB. Kuwait is a low (25/100,000) TB incidence country and ~1% of Mycobacterium tuberculosis strains are resistant to rifampin, RIF and isoniazid, INH (MDR-TB). Analysis of resistance conferring mutations in seven genes was combined with spoligotyping for detecting local transmission of MDR-TB in Kuwait.
MDR-TB strains (n=131) from 88 TB patients and 50 susceptible strains were used. Susceptibility testing was done by MGIT 960 system, gMTBDRplus assay and PCR-sequencing of three regions of rpoB, katG codon 315 (katG315) + inhA regulatory region, embB (embB306/embB406/embB497 regions), rpsL + rrs-500-900 regions and pncA for RIF, INH, ethambutol (EMB), streptomycin (SM) and pyrazinamide (PZA), respectively. Sequencing data were used to construct phylogenetic tree by MEGA7 software. Spoligotypes were identified by SITVIT2 and phylogenetic tree was made by MIRU-VNTRplus software.
Mutations were detected in most isolates in rpoB, katG+inhA, embB, rpsL+rrs and pncA which confer resistance to RIF, INH, EMB, SM and PZA, respectively. Phylogenetic analysis of multi-locus concatenated sequences showed unique patterns for 51 patient’s isolates while 37 patient’s isolates grouped in 14 clusters. Spoligotyping identified 35 patterns (19 unique patterns and 69 patients’s isolates in 16 patterns) including 11 orphan patterns. Sixteen isolates yielded 6 clusters (each containing 2-5 isolates) by both fingerprinting methods.
Our study provides the first insight into molecular epidemiology of MDR-TB in Kuwait and identified six potential cases of local transmission of MDR-TB involving 2-5 subjects (including 5 Kuwaiti patients) which had escaped detection by routine surveillance studies. Prospective detection of resistance conferring mutations thus identifies possible cases of local transmission of MDR-TB in low TB incidence countries.
N. Al-Mutairi, None