The Relationship between Post-Traumatic Stress Disorder Due to Brain Injury and Glutamate Intake: A Systematic Review.

There is a growing body of evidence that suggests a connection between traumatic brain injury (TBI) and subsequent post-traumatic stress disorder (PTSD). While the exact mechanism is unknown, we hypothesize that chronic glutamate neurotoxicity may play a role. The consumption of dietary glutamate is a modifiable factor influencing glutamate levels in the blood and, therefore, in the brain. In this systematic review, we explored the relationship between dietary glutamate and the development of post-TBI PTSD. Of the 1748 articles identified, 44 met the inclusion criteria for analysis in this review. We observed that individuals from countries with diets traditionally high in glutamate had greater odds of developing PTSD after TBI (odds ratio = 15.2, 95% confidence interval 11.69 to 19.76, p < 0.01). These findings may support the hypothesis that chronically elevated blood glutamate concentrations caused by high dietary intake invoke neurodegeneration processes that could ultimately result in PTSD. Further studies will clarify whether lowering glutamate via diet would be an effective strategy in preventing or treating post-TBI PTSD.

Tumor-agnostic plasma assay for circulating tumor DNA detects minimal residual disease and predicts outcome in locally advanced squamous cell carcinoma of the head and neck.

BACKGROUND: Forty to fifty percent of patients with locally advanced squamous cell carcinoma of the head and neck (LA SCCHN) relapse despite multimodal treatment. Circulating tumor DNA (ctDNA) has the potential to detect minimal residual disease (MRD) after curative-intent therapy and to identify earlier which patients will progress. We developed a tumor-agnostic plasma ctDNA assay to detect MRD in unselected LA SCCHN with the aim of predicting progression-free survival (PFS) and overall survival without the need for tumor sequencing. PATIENTS AND METHODS: A 26-gene next-generation sequencing panel was constructed that included the most frequently mutated genes in SCCHN and two HPV-16 genes. MRD was assessed in each patient through an in-house informatic workflow informed by somatic mutations identified in the corresponding pre-treatment plasma sample. The presence of MRD was defined as the detection of ctDNA in one plasma sample collected within 1-12 weeks of the end of curative treatment. The primary endpoint was the PFS rate at 2 years. At least 32 patients were planned for inclusion with the hypothesis that PFS at 2 years was >80% in MRD-negative patients and <30% in MRD-positive patients (α = 0.05, ß = 0.9). RESULTS: We sequenced DNA from 116 plasma samples derived from 53 LA SCCHN patients who underwent curative-intent treatment. ctDNA was detected in 41/53 (77%) patients in the pre-treatment samples. Out of these 41 patients, 17 (41%) were MRD positive after treatment. The 2-year PFS rate was 23.53% (9.9% to 55.4%) and 86.6% (73.4% to 100%) in MRD-positive and MRD-negative patients, respectively (P < 0.05). Median survival was 28.37 months (14.30 months-not estimable) for MRD-positive patients and was not reached for the MRD-negative cohort (P = 0.011). CONCLUSIONS: Our ctDNA assay detects MRD in LA SCCHN and predicts disease progression and survival without the need for tumor sequencing, making this approach easily applicable in daily practice.

A Complex Diving-For-Food Task to Investigate Social Organization and Interactions in Rats.

For many species, where status is a vital motivator that can affect health, social hierarchies influence behavior. Social hierarchies that include dominant-submissive relationships are common in both animal and human societies. These relationships can be affected by interactions with others and with their environment, making them difficult to analyze in a controlled study. Rather than a simple dominance hierarchy, this formation has a complicated presentation that allows rats to avoid aggression. Status can be stagnant or mutable, and results in complex societal stratifications. Here we describe a complex diving-for-food task to investigate rodent social hierarchy and behavioral interactions. This animal model may allow us to assess the relationship between a wide range of mental illnesses and social organization, as well as to study the effectiveness of therapy on social dysfunction.

Safety of systemic anti-cancer treatment in oncology patients with non-severe COVID-19: a cohort study.

BACKGROUND: The viral pandemic coronavirus disease 2019 (COVID-19) has disrupted cancer patient management around the world. Most reported data relate to incidence, risk factors, and outcome of severe COVID-19. The safety of systemic anti-cancer therapy in oncology patients with non-severe COVID-19 is an important matter in daily practice. METHODS: ONCOSARS-1 was a single-center, academic observational study. Adult patients with solid tumors treated in the oncology day unit with systemic anti-cancer therapy during the initial phase of the COVID-19 pandemic in Belgium were prospectively included. All patients (n = 363) underwent severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) serological testing after the first peak of the pandemic in Belgium. Additionally, 141 of these patients also had a SARS-CoV-2 RT-PCR test during the pandemic. The main objective was to retrospectively determine the safety of systemic cancer treatment, measured by the rate of adverse events according to the Common Terminology Criteria for Adverse Events, in SARS-CoV-2-positive patients compared with SARS-CoV-2-negative patients. RESULTS: Twenty-two (6%) of the 363 eligible patients were positive for SARS-CoV-2 by RT-PCR and/or serology. Of these, three required transient oxygen supplementation, but none required admission to the intensive care unit. Hematotoxicity was the only adverse event more frequently observed in SARS-CoV-2 -positive patients than in SARS-CoV-2-negative patients: 73% vs 35% (P < 0.001). This association remained significant (odds ratio (OR) 4.1, P = 0.009) even after adjusting for performance status and type of systemic treatment. Hematological adverse events led to more treatment delays for the SARS-CoV-2-positive group: 55% vs 20% (P < 0.001). Median duration of treatment interruption was similar between the two groups: 14 and 11 days, respectively. Febrile neutropenia, infections unrelated to COVID-19, and bleeding events occurred at a low rate in the SARS-CoV-2-positive patients. CONCLUSION: Systemic anti-cancer therapy appeared safe in ambulatory oncology patients treated during the COVID-19 pandemic. There were, however, more treatment delays in the SARS-CoV-2-positive population, mainly due to a higher rate of hematological adverse events.

Laser-Induced Brain Injury in the Motor Cortex of Rats.

A common technique for inducing stroke in experimental rodent models involves the transient (often denoted as MCAO-t) or permanent (designated as MCAO-p) occlusion of the middle cerebral artery (MCA) using a catheter. This generally accepted technique, however, has some limitations, thereby limiting its extensive use. Stroke induction by this method is often characterized by high variability in the localization and size of the ischemic area, periodical occurrences of hemorrhage, and high death rates. Also, the successful completion of any of the transient or permanent procedures requires expertise and often lasts for about 30 minutes. In this protocol, a laser irradiation technique is presented that can serve as an alternative method for inducing and studying brain injury in rodent models. When compared to rats in the control and MCAO groups, the brain injury by laser induction showed reduced variability in body temperature, infarct volume, brain edema, intracranial hemorrhage, and mortality. Furthermore, the use of a laser-induced injury caused damage to the brain tissues only in the motor cortex unlike in the MCAO experiments where destruction of both the motor cortex and striatal tissues is observed. Findings from this investigation suggest that laser irradiation could serve as an alternative and effective technique for inducing brain injury in the motor cortex. The method also shortens the time for completing the procedure and does not require expert handlers.

A Middle Cerebral Artery Occlusion Technique for Inducing Post-stroke Depression in Rats.

Post-stroke depression (PSD) is the most recurrent of all psychiatric complications resulting from an ischemic stroke. A greater majority (about 60%) of all ischemic stroke patients suffer from PSD, a disorder considered to be an ischemic stroke-related precursor for increased death and degradation in health. The pathophysiology of PSD is still obscure. To study the mechanism of development and occurrence of PSD further, and to find out a therapy, we attempted to develop a new protocol that requires occluding the middle cerebral artery (MCA) via the internal carotid artery (ICA) in rats. This protocol describes a model of PSD induced in rats through the middle cerebral artery occlusion (MCAO). Also used in the experiment are the Porsolt forced swim test and the sucrose preference test to confirm and evaluate the depressive mood of the rats under investigation. Rather than inserting the catheter through the external carotid artery (ECA), as stipulated for the original procedure, this MCAO technique has the monofilament passing directly through the ICA. This MCAO technique was developed a few years ago and leads to a reduction in mortality and variability. It is generally accepted that the criteria used are preferred in the selection of biological models. The data obtained with this protocol show that this model of MCAO could be a way of inducing PSD in rats and could potentially lead to the understanding of the pathophysiology and the future development of new drugs and other neuroprotective agents.

Establishment of novel technical methods for evaluating brain edema and lesion volume in stroked rats: A standardization of measurement procedures.

Stroke plays a role in high morbidity and mortality. Deciphering its mechanisms and pathophysiology is critical for the creation of new drugs and therapies. Most of the previous animal models of stroke, aimed at identifying the extent and location of brain injury following stroke, require animal sacrifice, which, besides ethical considerations, also negates the ability for follow up studies with the same rats. Because of these failures, the use of clinical magnetic resonance scanners for evaluating small animal models has been increasing. Magnetic resonance imaging scanners used particularly for small-bore animals are eligible for use in high-resolution magnetic resonance imaging of rodent brains. However, high costs and scarcity factor heavily in the rare availability of these scanners. In our investigation, we sought to establish a unitary magnetic resonance imaging protocol for stroke assessment in rats. We made use of a 3-Tesla magnetic resonance imaging clinical scanner, as well as another clinical equipment, with the purpose of increasing its reproducibility. The results of inquest validated a new magnetic resonance imaging protocol, comparing a magnetic resonance imaging-measured infarcted zone to the "gold standard" of histological examination. We carried out the experimental procedure on a 3 Tesla magnetic resonance imaging clinical scanner using a conventional eight-channel receive-only coil. The two methods produced remarkable quantitative and qualitative correlations between them. Conclusively, we showed the clinical magnetic resonance imaging scanner to be a high-precision and sensitive image analysis instrument for evaluating both the infarct zone and the brain edema in a stroke experimental rat model.

Biological and Behavioral Patterns of Post-Stroke Depression in Rats.

BACKGROUND: Post-stroke depression (PSD) is the most frequent psychiatric complication following ischemic stroke. It affects up to 60% of all patients and is associated with increased morbidity and mortality following ischemic stroke. The pathophysiology of PSD remains elusive and appears to be multifactorial, rather than "purely" biological or psychosocial in origin. Thus, valid animal models of PSD would contribute to the study of the etiology (and treatment) of this disorder. METHODS: The present study depicts a rat model for PSD, using middle cerebral artery occlusion (MCAO). The two-way shuttle avoidance task, Porsolt forced-swim test, and sucrose preference test were employed to assess any depression-like behavior. Localized brain expressions of brain-derived neurotrophic factor (BDNF) protein levels were evaluated to examine the possible involvement of the brain neuronal plasticity in the observed behavioral syndrome. The raw data were subjected to unsupervised fuzzy clustering (UFC) algorithms to assess the sensitivity of bio-behavioral measures indicative of depressive symptoms post MCAO. RESULTS: About 56% of the rats developed significant depressive-like behavioral disruptions as a result of MCAO compared with 4% in the sham-operated control rats. A pattern of a depressive-like behavioral response was common to all affected MCAO animals, characterized by significantly more escape failures and reduced number of total avoidance shuttles, a significant elevation in immobility duration, and reduced sucrose preference. Significant downregulations of BDNF protein levels in the hippocampal sub-regions, frontal cortex, and hypothalamus were observed in all affected MCAO animals. CONCLUSION: The UFC analysis supports the behavioral analysis and thus, lends validity to our results.

A New Method for Inducing a Depression-Like Behavior in Rats.

Contagious depression is a phenomenon that is yet to be fully recognized and this stems from insufficient material on the subject. At the moment, there is no existing format for studying the mechanism of action, prevention, containment, and treatment of contagious depression. The purpose of this study, therefore, was to establish the first animal model of contagious depression. Healthy rats can contract depressive behaviors if exposed to depressed rats. Depression is induced in rats by subjecting them to several manipulations of chronic unpredictable stress (CUS) over 5 weeks, as described in the protocol. A successful sucrose preference test confirmed the development of depression in the rats. The CUS-exposed rats were then caged with naïve rats from the contagion group (1 naïve rat/2 depressed rats in a cage) for an additional 5 weeks. 30 social groups were created from the combination of CUS-exposed rats and naïve rats. This proposed depression-contagion protocol in animals consists mainly of cohabiting CUS-exposed and healthy rats for 5 weeks. To ensure that this method works, a series of tests are carried out - first, the sucrose preference test upon inducing depression to rats, then, the sucrose preference test, alongside the open field and forced-swim tests at the end of the cohabitation period. Throughout the experiment, rats are given tags and are always returned to their cages after each test. A few limitations to this method are the weak differences recorded between the experimental and control groups in the sucrose preference test and the irreversible traumatic outcome of the forced swim test. These may be worth considering for suitability before any future application of the protocol. Nonetheless, following the experiment, naïve rats developed contagion depression after 5 weeks of sharing the same cage with the CUS-exposed rats.

Antimicrobial and antioxidant activities of the extracts and compounds from the leaves of Psorospermum aurantiacum Engl. and Hypericum lanceolatum Lam.

BACKGROUND: Psorospermun aurantiacum and Hypericum lanceolatum are plants locally used in Cameroon and other parts of Africa for the treatment of gastrointestinal and urinary tract infections, skin infections, venereal diseases, gastrointestinal disorder, infertility, epilepsy as well as microbial infections. The present study was designed in order to investigate the in vitro antimicrobial and radical scavenging activities of the extracts and isolated compounds from the leaves of these plants. METHODS: The plant extract was prepared by maceration in ethyl acetate and methanol and fractionated by column chromatography. The structures of isolated compounds were elucidated by spectroscopic analyses in conjunction with literature data. The broth microdilution method was used to evaluate the in vitro antimicrobial activity against bacteria, yeasts and dermatophytes. The antioxidant potentials of the extracts and their isolated compounds were evaluated using the DPPH radical scavenging method. RESULTS: Five known compounds: physcion (1), 1,8-dihydroxy-3-geranyloxy-6-methylanthraquinone (2), kenganthranol B (3), vismiaquinone (4), and octacosanol (5) were isolated from the leaves of P. aurantiacum while six compounds including friedelin (6), betulinic acid (7), 2,2',5,6'-tetrahydroxybenzophenone (8), allanxanthone A (9), 1,3,6- trihydroxyxanthone (10) and isogarcinol (11) were isolated from H. lanceolatum. Compound 8 and 4 exhibited the highest antibacterial and antifungal activities with MIC ranges of 2-8 µg/ml and 4-32 µg/ml respectively. P. aurantiacum crude extract (Rsa50 = 6.359 ± 0.101) showed greater radical scavenging activity compared with H. lanceolatum extract (Rsa50 = 30.996 ± 0.879). Compound 11 showed the highest radical scavenging activity (RSa50 = 1.012 ± 0.247) among the isolated compounds, comparable to that of L-arscobic acid (RSa50 = 0.0809 ± 0.045). CONCLUSIONS: The experimental findings show that the ethyl acetate and methanol extracts and isolated compounds from P. aurantiacum and H. lanceolatum stem bark possess significant antimicrobial and antioxidant activities justifying the use of these plants in traditional medicine, which may be developed as phytomedicines.

[The Mycobacterium leprae genome: from sequence analysis to therapeutic implications]. / Le génome de Mycobacterium leprae: de l'analyse de la séquence aux enjeux thérapeutiques.

The genome of Mycobacterium leprae, the causative agent of leprosy, was analyzed by rapid sequencing of cosmids and plasmids prepared from DNA isolated from one patient's strain. Results showed that the bacillus possesses a single circular chromosome that differs from other known mycobacterium chromosomes with regard to size (3.2 Mb) and G + C content (57.8%). Computer analysis demonstrated that only half of the sequence contains protein-coding genes. The other half contains pseudogenes and non-coding sequences. These findings indicate that M. leprae has undergone a major reductive evolution leaving a minimal set of functional genes for survival. Study of the coding region of the sequence provides evidence accounting for the particular pathogenic properties of M. leprae which is an obligate intracellular parasite. Disappearance of numerous enzymatic pathways in comparison with M. tuberculosis, an intracellular pathogen comparable to M. leprae, could explain the differences observed between the two organisms. Genomic analysis of the leprosy bacillus also provided insight into the molecular basis for resistance to various antibiotics and allowed identification of several potential targets for new drug treatments.

Le genome de Mycobacterium leprae: de lanalyse de la sequence aux enjeux therapeutiques / The Mycobacterium leprae genome: from sequence analysis to therapeutic implications

L'analyse génomique de Mycobacterium leprae, l'agent pathogène de la lèpre, a été réalisée grâce au séquençage à haut débit des cosmides et plasmides préparés à partir de l'ADN d´une souche isolée d'un patient. Elle a montré que ce bacille possède un seul chromosome circulaire, dont la taille (3,2Mb) et la composition en G+C (57,8%) sont réduits par rapport aux austres chromosomes mycobactériens connus. L'analyse informatique de la séquence a mis en évidence que seule la moitié de la séquences est codante. L'autre moitié contient des pseudogènes et des séquences non codantes. Le génome de M. leprae a donc subi une évolution réductive très importante qui ne lui a laissé qu'un set minimun de gènes fonctionnels pour vivre. Les informations déduites de la partie codante de la séquence permettent d'appréhender les propriétés biologiques particulières de cet agent infectieux à développement intra-cellulaire obligatoire. De plus, la disparition de nombreuses voies enzymatiques par rapport à M. tuberculosis, autre pathogène intra-cellulaire en certains points semblable à M. leprae, explique les différences observées entre les deux organismes. Enfin, l'analyse génomique du bacille lépreux permet de comprendre les bases moléculaires de sa résistance à différents antibiotiques et d'identifier des cibles potentielles pour la mise au point de nouveaux traitements.

Role of OxyS of Mycobacterium tuberculosis in oxidative stress: overexpression confers increased sensitivity to organic hydroperoxides.

Mycobacterial genomics has uncovered a novel regulatory gene, oxyS, belonging to the LysR family. There is extensive similarity in the DNA-binding domain of OxyS with that of OxyR, the oxidative stress response protein of many bacteria. Since the oxyR gene of Mycobacterium tuberculosis has been multiply inactivated during evolution it was conceivable that some of its functions could be effected by OxyS. It is shown here that OxyS is produced at low levels and that there are at least three different oxyS alleles present in clinical isolates of M. tuberculosis that are susceptible or resistant to isoniazid. Overproduction or depletion of OxyS did not affect susceptibility to isoniazid but increasing the concentration of the regulator lowered levels of the alkyl hydroperoxide reductase, AhpC, and rendered the tubercle bacillus more susceptible to organic hydroperoxides.

Role of promyelocytic leukemia (PML) sumolation in nuclear body formation, 11S proteasome recruitment, and As2O3-induced PML or PML/retinoic acid receptor alpha degradation.

Promyelocytic leukemia (PML) is the organizer of nuclear matrix domains, PML nuclear bodies (NBs), with a proposed role in apoptosis control. In acute promyelocytic leukemia, PML/retinoic acid receptor (RAR) alpha expression disrupts NBs, but therapies such as retinoic acid or arsenic trioxide (As2O3) restore them. PML is conjugated by the ubiquitin-related peptide SUMO-1, a process enhanced by As2O3 and proposed to target PML to the nuclear matrix. We demonstrate that As2O3 triggers the proteasome-dependent degradation of PML and PML/RARalpha and that this process requires a specific sumolation site in PML, K160. PML sumolation is dispensable for its As2O3-induced matrix targeting and formation of primary nuclear aggregates, but is required for the formation of secondary shell-like NBs. Interestingly, only these mature NBs harbor 11S proteasome components, which are further recruited upon As2O3 exposure. Proteasome recruitment by sumolated PML only likely accounts for the failure of PML-K160R to be degraded. Therefore, studying the basis of As2O3-induced PML/RARalpha degradation we show that PML sumolation directly or indirectly promotes its catabolism, suggesting that mature NBs could be sites of intranuclear proteolysis and opening new insights into NB alterations found in viral infections or transformation.

Familial outbreak of disseminated multidrug-resistant tuberculosis and meningitis.

Rapidly progressive multidrug-resistant tuberculosis (MDR-TB) is well documented in human immunodeficiency virus (HIV) positive subjects, but it is not fully recognised in HIV-negative subjects in the familial environment. We report three cases of MDR-TB in three young HIV-negative subjects from the same family. All the patients showed signs of meningitis during the course of their disease, and in two cases a resistant strain of Mycobacterium tuberculosis was isolated in cerebrospinal fluid. Two of the three subjects died from neurological complications; the other was successful treated utilising both systemic and intrathecal therapy for tuberculous meningitis. By a retrospective analysis of DNA obtained from Lowenstein-Jensen cultures, the strains were confirmed as M. tuberculosis resistant to rifampicin and isoniazid, and were closely related in the two cases where specimens were available for analysis. The resistance was acquired in two patients initially infected with a susceptible strain; in the other patient, the resistance was present on the first sensitivity test for which results were available. This report demonstrates the high risk of fatality from MDR-TB for HIV-negative subjects in the absence of reliable early diagnostic and preventive tools. It also reinforces the concept that genetic susceptibility to M. tuberculosis may be an important factor in the clinical presentation and outcome of MDR-TB.

Regulation of catalase-peroxidase (KatG) expression, isoniazid sensitivity and virulence by furA of Mycobacterium tuberculosis.

Mycobacterium tuberculosis has two genes for ferric uptake regulator orthologues, one of which, furA, is situated immediately upstream of katG encoding catalase-peroxidase, a major virulence factor that also activates the prodrug isoniazid. This association suggested that furA might regulate katG and other genes involved in pathogenesis. Transcript mapping showed katG to be expressed from a strong promoter, with consensus -10 and -35 elements, preceding furA. No promoter activity was demonstrated downstream of the furA start codon, using different gene reporter systems, indicating that furA and katG are co-transcribed from a common regulatory region. The respective roles of these two genes in the isoniazid susceptibility and virulence of M. tuberculosis were assessed by combinatorial complementation of a Delta(furA-katG) strain that is heavily attenuated in a mouse model of tuberculosis. In the absence of furA, katG was upregulated, cells became hypersensitive to isoniazid, and full virulence was restored, indicating that furA regulates the transcription of both genes. When furA alone was introduced into the Delta(furA-katG) mutant, survival in mouse lungs was moderately increased, suggesting that FurA could regulate genes, other than katG, that are involved in pathogenesis. These do not include the oxidative stress genes ahpC and sodA, or those for siderophore production.

Massive gene decay in the leprosy bacillus.

Leprosy, a chronic human neurological disease, results from infection with the obligate intracellular pathogen Mycobacterium leprae, a close relative of the tubercle bacillus. Mycobacterium leprae has the longest doubling time of all known bacteria and has thwarted every effort at culture in the laboratory. Comparing the 3.27-megabase (Mb) genome sequence of an armadillo-derived Indian isolate of the leprosy bacillus with that of Mycobacterium tuberculosis (4.41 Mb) provides clear explanations for these properties and reveals an extreme case of reductive evolution. Less than half of the genome contains functional genes but pseudogenes, with intact counterparts in M. tuberculosis, abound. Genome downsizing and the current mosaic arrangement appear to have resulted from extensive recombination events between dispersed repetitive sequences. Gene deletion and decay have eliminated many important metabolic activities including siderophore production, part of the oxidative and most of the microaerophilic and anaerobic respiratory chains, and numerous catabolic systems and their regulatory circuits.

The decaying genome of Mycobacterium leprae.

Everything that we need to know about Mycobacterium leprae, a close relative of the tubercle bacillus, is encrypted in its genome. Inspection of the 3.27 Mb genome sequence of an armadillo-derived Indian isolate of the leprosy bacillus identified 1,605 genes encoding proteins and 50 genes for stable RNA species. Comparison with the genome sequence of Mycobacterium tuberculosis revealed an extreme case of reductive evolution, since less than half of the genome contains functional genes while inactivated or pseudogenes are highly abundant. The level of gene duplication was approximately 34% and, on classification of the proteins into families, the largest functional groups were found to be involved in the metabolism and modification of fatty acids and polyketides, transport of metabolites, cell envelope synthesis and gene regulation. Reductive evolution, gene decay and genome downsizing have eliminated entire metabolic pathways, together with their regulatory circuits and accessory functions, particularly those involved in catabolism. This may explain the unusually long generation time and account for our inability to culture the leprosy bacillus.

A method for rapid detection of rifampicin-resistant isolates of Mycobacterium leprae.

A genotypic method for predicting rifampicin resistance in Mycobacterium leprae has been developed and rigorously tested on mouse footpad-derived and clinical specimens. A series of immobilized oligonucleotide capture probes can discriminate between wild type and mutant rpoB alleles, and positive controls are available for the most frequent mutation affecting Ser425. Two different non-radioactive detection formats have been tested with comparable success in both an industrialized and a developing country. The standardized procedure could now be used in a prospective study of potential rifampicin resistance among multibacillary patients.

Repetitive sequences in Mycobacterium leprae and their impact on genome plasticity.

About 2% of the genome of Mycobacterium leprae is composed of repetitive DNA. There are more than 26 extinct IS elements together with four families of dispersed repeats, present in five copies or more, RLEP (37 copies), REPLEP (15 copies), LEPREP (eight copies), and LEPRPT (five copies). Although there is no sequence similarity to known transposable elements, RLEP occurs predominantly at the 3'-end of genes and, in several cases, within pseudogenes, suggesting that it was capable of dissemination. Strikingly, on comparison of the genome sequences of M. leprae and the closely related tubercle bacillus, Mycobacterium tuberculosis H37Rv, many of these repetitive sequences were found at sites of discontinuity in gene order. Evidence is presented that loss of synteny, inversion and genome downsizing may have resulted from recombination between dispersed copies of these repetitive elements.