The AraC Family Transcriptional Regulator Rv1931c Plays a Role in the Virulence of Mycobacterium tuberculosis

A Mycobacterium tuberculosis strain disrupted in the AraC homologue Rv1931c was isolated. The mutant strain exhibited reduced survival both in macrophages and in a mouse infection model, with survival being restored on complementation with the Rv1931c gene. These results suggest that Rv1931c regulates genes important for virulence of M. tuberculosis

Seropositivity to anti-phenolic glycolipid-I in leprosy cases, contacts and no known contacts of leprosy in an endemic and a non-endemic area in northeast Brazil.

The seroprevalence rates of IgM anti-phenolic glycolipid-I (PGL-I) antibodies in four study groups with differing exposure to Mycobacterium leprae in Ceará, Brazil were investigated between March 2005 and August 2006. The first three groups in a high prevalence area included 144 cases of leprosy, their 380 contacts and 317 participants with no known leprosy contact. The fourth group in a low prevalence area consisted of 87 participants with no known leprosy contact living in an area in which no cases of leprosy had been reported in the previous 6 months. Seropositivity and levels of IgM antibodies to PGL-I were investigated using ELISA. The seropositivity levels of anti-PGL-I among the different clinical forms of leprosy cases were 61% for lepromatous, 25% for tuberculoid and 27% indeterminate. The levels of anti-PGL-I antibodies in the endemic area differentiated leprosy cases from non-cases. However, the seropositivity was similar among contact cases (15.8%) and no known leprosy contact cases from high (15.1%) and low (13.8%) prevalence areas. The seropositivity of both contacts and no known contacts was much higher than previously reported among no known contacts in other endemic areas. The study indicates that anti-PGL-I antibodies are not useful as immunological markers of household leprosy contacts and no known leprosy contacts in endemic areas

Intrapatient comparison of Mycobacterium leprae by VNTR analysis in nasal secretions and skin biopsy in a Brazilian leprosy endemic region.

Background: This study compares the strains of genotypes of M. leprae from nasal secretions (NS) and skin biopsy (SB) in the same patient, supplementing conventional epidemiology to gain insight into the infection of leprosy in Fortaleza, Brazil. Methods: The sample consisted of 38 newly diagnosed leprosy patients attending the National Reference Center of Dermatology Dona Libania (CDERM), in Fortaleza, who tested positive for M. leprae by PCR in DNA extracts of nasal secretions. DNA was also extracted from skin biopsy (SB) scrapings of each patient and used for multiplex PCR amplification of M. leprae VNTR loci. The number of repeats at 15 loci were determined by the fragment length analysis method. Results: Locus VNTR genotypes were achieved in 38 NS, and in 38 SB specimens. M. leprae strains differed in their genotypes in paired specimens in all but two of 38 patients. The genotype similarity in the remainder ranged from 53% to 87%. Conclusion: M. leprae 15 VNTR loci genotypes of paired nasal and biopsy skin samples from five patients were identical, while as many as seven loci differed in the 33 other patients. When the NS and biopsy genotypes were pooled and compared, it was found that there was a great variability among different VNTR markers. It is important to investigate other molecular markers suitable for typing genetic variations of the bacilli

Genotyping of <i>Mycobacterium leprae</i> for better understanding of leprosy transmission in Fortaleza, Northeastern Brazil

<div><p>Leprosy is endemic in large part of Brazil with 28,761 new patients in 2015, the second largest number worldwide and reaches 9/10.000 in highly endemic regions and 2.7/10.000 in the city of Fortaleza, Ceará, Northeast Brazil. For better understanding of risk factors for leprosy transmission, we conducted an epidemiologic study supplemented by 17 locus VNTR and SNP 1–4 typing of <i>Mycobacterium leprae</i> in skin biopsy samples from new multibacillary (MB) patients diagnosed at a reference center in 2009 and 2010. Among the 1,519 new patients detected during the study period, 998 (65.7%) were MB and we performed DNA extraction and genotyping on 160 skin biopsy samples, resulting in 159 (16%) good multilocus VNTR types. Thirty-eight of these patients also provided VNTR types from <i>M</i>. <i>leprae</i> in nasal swabs. The SNP-Type was obtained for 157 patients and 87% were of type 4. Upon consideration all VNTR markers, 156 different genotypes and three pairs with identical genotypes were observed; no epidemiologic relation could be observed between individuals in these pairs. Considerable variability in differentiating index (DI) was observed between the different markers and the four with highest DI [(AT)15, (TA)18, (AT)17 and (GAA)21] frequently demonstrated differences in copy number when comparing genotypes from both type of samples. Excluding these markers from analysis resulted in 83 genotypes, 20 of which included 96 of the patients (60.3%). These clusters were composed of two (n = 8), three (n = 6), four (n = 1), five (n = 2), six (n = 1), 19 (n = 1) and 23 (n = 23) individuals and suggests that recent transmission is contributing to the maintenance of leprosy in Fortaleza. When comparing epidemiological and clinical variables among patients within clustered or with unique <i>M</i>. <i>leprae</i> genotypes, a positive bacterial index in skin biopsies and knowledge of working with someone with the disease were significantly associated with clustering. A tendency to belong to a cluster was observed with later notification of disease (mean value of 3.4 months) and having disability grade 2. A tendency for lack of clustering was observed for patients who reported to have lived with another leprosy case but this might be due to lack of inclusion of household contacts in the study. Although clusters were spread over the city, kernel analysis revealed that some of the patients belonging to the two major clusters were spatially related to some neighborhoods that report poverty and high disease incidence in children. Finally, inclusion of genotypes from nasal swabs might be warranted. A major limitation of the study is that sample size of 160 patients from a two year period represents only 15% of the new patients and this could have weakened statistical outcomes. This is the first molecular epidemiology study of leprosy in Brazil and although the high clustering level suggests that recent transmission is the major cause of disease in Fortaleza; the existence of two large clusters needs further investigation.</p></div

Genotyping of <i>Mycobacterium leprae</i> for better understanding of leprosy transmission in Fortaleza, Northeastern Brazil - Fig 3

<p>Two minimum spanning trees constructed on a UPGMA clustering on a similarity matrix that was calculated using categorical similarity index and allele copy numbers of all 17 microsatellites (A) and SNP-Type or leaving out the four with highest SI (B). The colors represent the SNP-Types as indicated in the indent; dark blue: no sequence available to differentiate type 1 and 2; light blue: no SNP type available. In Figure B, the node size represents the number of patients included.</p