Sex- and age-dependent association of SLC11A1 polymorphisms with tuberculosis in Chinese: a case control study.

BACKGROUND: Host genetic factors are important determinants in tuberculosis (TB). The SLC11A1 (or NRAMP1) gene has been studied extensively for genetic association with TB, but with inconsistent findings. In addition, no study has yet looked into the effect of sex and age on the relationship between SLC11A1 polymorphisms and TB. METHODS: A case-control study was conducted. In total, 278 pulmonary TB patients and 282 sex- and age-matched controls without TB were recruited. All subjects were ethnic Chinese. On the basis of linkage disequilibrium pattern, three genetic markers from SLC11A1 and one from the nearby IL8RB locus were selected and examined for association with TB susceptibility. These markers were genotyped using single strand conformation polymorphism analysis or fragment analysis of amplified products. RESULTS: Statistically significant differences in allele (P = 0.0165, OR = 1.51) and genotype (P = 0.0163, OR = 1.59) frequencies of the linked markers SLC6a/b (classically called D543N and 3'UTR) of the SLC11A1 locus were found between patients and controls. With stratification by sex, positive associations were identified in the female group for both allele (P = 0.0049, OR = 2.54) and genotype (P = 0.0075, OR = 2.74) frequencies. With stratification by age, positive associations were demonstrated in the young age group (age < or =65 years) for both allele (P = 0.0047, OR = 2.52) and genotype (P = 0.0031, OR = 2.92) frequencies. All positive findings remained significant even after correction for multiple comparisons. No significant differences were noted in either the male group or the older age group. No significant differences were found for the other markers (one SLC11A1 marker and one IL8RB marker) either. CONCLUSION: This study confirmed the association between SLC11A1 and TB susceptibility and demonstrated for the first time that the association was restricted to females and the young age group.

Diagnostic application of genotypic identification of mycobacteria.

This study evaluated conventional methods, GLC and three molecular tests, including 16S rRNA sequencing, for the identification of mycobacteria, and the experiences of the authors with the integration of these methods into a diagnostic clinical laboratory were also recorded. Of 1067 clinical isolates of mycobacteria identified by conventional tests, 365 were tested by Accuprobe hybridization assays and PCRs specific for Mycobacterium tuberculosis (MTB) complex or Mycobacterium avium complex (MAC), 202 were tested by 16S rRNA sequencing, and 142 were tested by GLC. Three runs of all tests were performed on a weekly basis. The identifications for 209 MTB complex and 118 MAC isolates obtained by species-specific PCR were in complete agreement with AccuProbe hybridization and conventional test results. The 16S rRNA sequence-based identification, at a similarity of > or =99 %, for 132 of 142 isolates was concordant with the identifications made by the biochemical methods, and for 134 isolates was concordant with the identifications made by GLC at species, group or complex level. 16S rRNA sequencing resulted in fewer incorrectly identified or unidentified organisms than GLC or conventional tests. For the slowly growing non-tuberculous mycobacteria, the mean turnaround times for identification were 4-5 days for 16S rRNA sequencing, 14-29 days for GLC and 22-23 days for conventional methods. Considering the large proportion of some species among clinical isolates, a strategy of initial screening with species-specific PCR (or AccuProbe assays) for the MTB complex and MAC, followed by direct sequencing of the strains that yield negative results, should make 16S rRNA sequencing more affordable for routine application in diagnostic laboratories.