Biology subjects

Sloan, D. J.

Publications and source records attributed to Sloan, D. J..

3 recordsLinked to original sources

bioRxiv2020

Understanding the diversity of DNA methylation in Mycobacterium tuberculosis

Although Mycobacterium tuberculosis (Mtb) strains exhibit genomic homology of >99%, there is considerable variation in the phenotype. The underlying mechanisms of phenotypic heterogeneity in Mtb are not well understood but epigenetic variation is thought to contribute. At present the methylome of Mtb has not been completely characterized. We completed methylomes of 18 Mycobacterium tuberculosis (Mtb) clinical isolates from Malawi representing the largest number of Mtb genomes to be completed in a single study using Single Molecule Real Time (SMRT) sequencing to date. We replicate and confirm four methylation disrupting mutations in lineages of Mtb. For the first time we report complete loss of methylation courtesy of C758T (S253L) mutation in the MamB gene of Indo-oceanic lineage of Mtb. We also conducted a genomic and methylome comparison of the Malawian samples against a global sample. We confirm that methylation in Mtb is lineage specific although some unresolved issues still remain.

genomics↗

bioRxiv2019

Improving diagnosis and monitoring of treatment response in pulmonary tuberculosis using the molecular bacterial load assay (MBLA)

ObjectivesBetter outcomes in tuberculosis require new diagnostic and treatment monitoring tools. In this paper we evaluated the utility of a marker of M. tuberculosis viable count, the Molecular Bacterial Load assay (MBLA) for diagnosis and treatment monitoring of tuberculosis in a high burden setting. MethodsPatients with smear positive pulmonary tuberculosis from two sites in Tanzania and one each in Malawi and Mozambique. Sputum samples were taken weekly for the first 12 weeks of treatment and evaluated by MBLA and mycobacterial growth indicator tube method (MGIT). ResultsThe results of high and low positive control samples confirmed inter site reproducibility. Over the 12 weeks of treatment there was a steady decline in the viable bacterial load as measured by the MBLA that corresponds to rise in time to a positive result (TTP) in the Mycobacterial Growth Indicator Tube. Both MBLA and MGIT provided similar time to test negativity. Importantly, as treatment progressed samples in MGIT were increasingly likely to be contaminated, which compromised the acquisition of results but did not affect MBLA samples. ConclusionsMBLA produces a reproducible measure of Mtb viable count comparable to that of MGIT that is not compromised by contamination in a real-world setting. As a molecular test, the results can be available in as little as four hours and could allow health care professionals to identify rapidly patients who are failing therapy.

microbiology↗

bioRxiv2019

Association of variants within the GST and other genes with anti-tubercular agents related toxicity: a systematic review and meta-analysis

BackgroundIndividuals receiving treatment with anti-tuberculosis (TB) drugs may experience serious side-effects, such as anti-TB drug-induced hepatotoxicity (ATDH). Genetic variants, such as polymorphisms of the GST gene and other genes, may increase the risk of experiencing such toxicity events. This systematic review and meta-analysis provides a comprehensive evaluation of the evidence base for associations between variants of the GST gene and other genes and toxicity outcomes related to anti-TB drugs.\n\nMethodsWe searched for relevant studies in MEDLINE, PubMed, EMBASE, BIOSIS and Web of Science. We pooled effect estimates for each genotype on each outcome, and stratified all analyses by country. We qualitatively assessed the methodological quality of the included studies.\n\nResultsWe included data from 28 distinct cohorts of patients in the review. The methodological quality of included studies was variable, with several important areas of concern. For GSTM1, patients with the homozygous null genotype were significantly more likely to experience hepatotoxicity than patients with heterozygous or homozygous present genotype (odds ratio [OR]=1.44, 95% confidence interval [CI] 1.15, 1.82). Moderate heterogeneity was observed in this analysis (I2=51.2%). No significant difference was observed for the GSTT1 null polymorphism. For the rs3814057 polymorphism of the PXR gene, both heterozygous genotype and homozygous mutant-type significantly increased hepatotoxicity risk compared with homozygous wild-type (heterozygous versus homozygous wild-type: OR=1.98, 95% CI 1.06, 3.69; I2=0%; homozygous mutant-type versus homozygous wild-type: OR=2.18, 95% CI 1.07, 4.44; I2=0%).\n\nConclusionsWe found that it is challenging to perform robust synthesis of the evidence base for associations between GST and other genetic variants and toxicity related to anti-TB drugs. We identified significant associations between the GSTM1 null and PXR rs3814057 polymorphisms and ATDH. To the best of our knowledge, no meta-analyses on genetic variants other than variants of the NAT2, CYP2E1, GSTM1 and GSTT1 genes have been published. Our results therefore add to the existing understanding of the association between genetic variants and hepatotoxicity.

genetics↗