High throughput phenotypic selection of Mycobacterium tuberculosis mutants with impaired resistance to reactive oxygen species identifies genes important for intracellular growth.

Mycobacterium tuberculosis has the remarkable capacity to survive within the hostile environment of the macrophage, and to resist potent antibacterial molecules such as reactive oxygen species (ROS). Thus, understanding mycobacterial resistance mechanisms against ROS may contribute to the development of new anti-tuberculosis therapies. Here we identified genes involved in such mechanisms by screening a high-density transposon mutant library, and we show that several of them are involved in the intracellular lifestyle of the pathogen.

Different antibiotic resistance and sporulation properties within multiclonal Clostridium difficile PCR ribotypes 078, 126, and 033 in a single calf farm.

Clostridium difficile strains were sampled periodically from 50 animals at a single veal calf farm over a period of 6 months. At arrival, 10% of animals were C. difficile positive, and the peak incidence was determined to occur at the age of 18 days (16%).

Phylogeny of Mycobacterium tuberculosis Beijing strains constructed from polymorphisms in genes involved in DNA replication, recombination and repair.

Background: The Beijing family is a successful group of M. tuberculosis strains, often associated with drug resistance and widely distributed throughout the world. Polymorphic genetic markers have been used to type particular M.

Resolving lineage assignation on Mycobacterium tuberculosis clinical isolates classified by spoligotyping with a new high-throughput 3R SNPs based method.

We developed a new multiplexed-PCR assay to accurately classify Mycobacterium tuberculosis complex (MTC) isolates at the sublineage level by single nucleotide polymorphisms (SNPs). This method relies on 7 SNPs located in different genes of the MTC strains (recC, rec0, recR, ligB, ligC, alkA, and mgtC). Most of these genes are involved in replication, repair and recombination (3R) functions of M.

DNA repair in Mycobacterium tuberculosis revisited.

Our understanding of Mycobacterium tuberculosis DNA repair mechanisms is still poor compared with that of other bacterial organisms. However, the publication of the first complete M. tuberculosis genome sequence 10 years ago boosted the study of DNA repair systems in this organism.

Evolution and diversity of clonal bacteria: the paradigm of Mycobacterium tuberculosis.

Background: Mycobacterium tuberculosis complex species display relatively static genomes and 99.9% nucleotide sequence identity. Studying the evolutionary history of such monomorphic bacteria is a difficult and challenging task.

Isoxyl activation is required for bacteriostatic activity against Mycobacterium tuberculosis.

Isoxyl (ISO), a thiourea derivative that was successfully used for the clinical treatment of tuberculosis during the 1960s, is an inhibitor of the synthesis of oleic and mycolic acids in Mycobacterium tuberculosis. Its effect on oleic acid synthesis has been shown to be attributable to its inhibitory activity on the stearoyl-coenzyme A desaturase DesA3, but its enzymatic target(s) in the mycolic acid pathway remains to be identified. With the goal of elucidating the mode of action of ISO, we have isolated a number of spontaneous ISO-resistant mutants of M.

A non-sense mutation in the putative anti-mutator gene ada/alkA of Mycobacterium tuberculosis and M. bovis isolates suggests convergent evolution.

Background: Previous studies have suggested that variations in DNA repair genes of W-Beijing strains may have led to transient mutator phenotypes which in turn may have contributed to host adaptation of this strain family. Single nucleotide polymorphism (SNP) in the DNA repair gene mutT1 was identified in MDR-prone strains from the Central African Republic. A Mycobacteriumtuberculosis H37Rv mutant inactivated in two DNA repair genes, namely ada/alkA and ogt, was shown to display a hypermutator phenotype.

Modification of the mycobacteriophage Ms6 attP core allows the integration of multiple vectors into different tRNAala T-loops in slow- and fast-growing mycobacteria.

Background: Mycobacteriophage Ms6 integrates into Mycobacterium smegmatis and M. bovis BCG chromosome at the 3' end of tRNAala genes. Homologous recombination occurs between the phage attP core and the attB site located in the T-loop.

Multidrug-resistant Mycobacterium tuberculosis, Bangui, Central African Republic.

We investigated multidrug-resistant (MDR) Mycobacterium tuberculosis strains in Bangui, Central African Republic. We found 39.6% with the same spoligotype and synonymous single nucleotide polymorphism in the mutT1 gene.