Biomedical subjects

Françoise Portaels

Publications and source records attributed to Françoise Portaels.

At least 19 recordsLinked to original sources

PubMed2006

Epidemiology of antituberculosis drug resistance (the Global Project on Anti-tuberculosis Drug Resistance Surveillance): an updated analysis.

BACKGROUND: The burden of tuberculosis is compounded by drug-resistant forms of the disease. This study aimed to analyse data on antituberculosis drug resistance gathered by the WHO and International Union Against Tuberculosis and Lung Disease Global Project on Anti-tuberculosis Drug Resistance Surveillance. METHODS: Data on drug susceptibility testing for four antituberculosis drugs--isoniazid, rifampicin, ethambutol, and streptomycin--were gathered in the third round of the Global Project (1999-2002) from surveys or ongoing surveillance in 79 countries or geographical settings. These data were combined with those from the first two rounds of the project and analyses were done. Countries that participated followed a standardised set of guidelines to ensure comparability both between and within countries. FINDINGS: The median prevalence of resistance to any of the four antituberculosis drugs in new cases of tuberculosis identified in 76 countries or geographical settings was 10.2% (range 0.0-57.1). The median prevalence of multidrug resistance in new cases was 1.0% (range 0.0-14.2). Kazakhstan, Tomsk Oblast (Russia), Karakalpakstan (Uzbekistan), Estonia, Israel, the Chinese provinces Liaoning and Henan, Lithuania, and Latvia reported prevalence of multidrug resistance above 6.5%. Trend analysis showed a significant increase in the prevalence of multidrug resistance in new cases in Tomsk Oblast (p<0.0001). Hong Kong (p=0.01) and the USA (p=0.0002) reported significant decreasing trends in multidrug resistance in new cases of tuberculosis. INTERPRETATION: Multidrug resistance represents a serious challenge for tuberculosis control in countries of the former Soviet Union and in some provinces of China. Gaps in coverage of the Global Project are substantial, and baseline information is urgently required from several countries with high tuberculosis burden to develop appropriate control interventions.

Antitubercular Agents↗

PubMed2006

Evolution of Mycobacterium ulcerans and other mycolactone-producing mycobacteria from a common Mycobacterium marinum progenitor.

It had been assumed that production of the cytotoxic polyketide mycolactone was strictly associated with Mycobacterium ulcerans, the causative agent of Buruli ulcer. However, a recent study has uncovered a broader distribution of mycolactone-producing mycobacteria (MPM) that includes mycobacteria cultured from diseased fish and frogs in the United States and from diseased fish in the Red and Mediterranean Seas. All of these mycobacteria contain versions of the M. ulcerans pMUM plasmid, produce mycolactones, and show a high degree of genetic relatedness to both M. ulcerans and Mycobacterium marinum. Here, we show by multiple genetic methods, including multilocus sequence analysis and DNA-DNA hybridization, that all MPM have evolved from a common M. marinum progenitor to form a genetically cohesive group among a more diverse assemblage of M. marinum strains. Like M. ulcerans, the fish and frog MPM show multiple copies of the insertion sequence IS2404. Comparisons of pMUM and chromosomal gene sequences demonstrate that plasmid acquisition and the subsequent ability to produce mycolactone were probably the key drivers of speciation. Ongoing evolution among MPM has since produced at least two genetically distinct ecotypes that can be broadly divided into those typically causing disease in ectotherms (but also having a high zoonotic potential) and those causing disease in endotherms, such as humans.

Bacterial Toxins↗

PubMed2006

Evidence for an intramacrophage growth phase of Mycobacterium ulcerans.

Mycobacterium ulcerans is the etiologic agent of Buruli ulcer (BU), an emerging tropical skin disease. Virulent M. ulcerans secretes mycolactone, a cytotoxic exotoxin with a key pathogenic role. M. ulcerans in biopsy specimens has been described as an extracellular bacillus. In vitro assays have suggested a mycolactone-induced inhibition of M. ulcerans uptake by macrophages in which its proliferation has not been demonstrated. Therefore, and uniquely for a mycobacterium, M. ulcerans has been classified as an extracellular pathogen. In specimens from patients and in mouse footpad lesions, extracellular bacilli were concentrated in central necrotic acellular areas; however, we found bacilli within macrophages in surrounding inflammatory infiltrates. We demonstrated that mycolactone-producing M. ulcerans isolates are efficiently phagocytosed by murine macrophages, indicating that the extracellular location of M. ulcerans is not a result of inhibition of phagocytosis. Additionally, we found that M. ulcerans multiplies inside cultured mouse macrophages when low multiplicities of infection are used to prevent early mycolactone-associated cytotoxicity. Following the proliferation phase within macrophages, M. ulcerans induces the lysis of the infected host cells, becoming extracellular. Our data show that M. ulcerans, like M. tuberculosis, is an intracellular parasite with phases of intramacrophage and extracellular multiplication. The occurrence of an intramacrophage phase is in accordance with the development of cell-mediated and delayed-type hypersensitivity responses in BU patients.

Animals↗

PubMed2006

Colorimetric redox-indicator methods for the rapid detection of multidrug resistance in Mycobacterium tuberculosis: a systematic review and meta-analysis.

OBJECTIVES: With the spread of multidrug-resistant tuberculosis (MDR-TB) there is increasing demand for new accurate and cost-effective tools for rapid drug susceptibility testing (DST), particularly for developing countries. The reference standard method used today for DST is very slow and cumbersome. Colorimetric assays using redox indicators have been proposed to be used in low-resource countries as rapid alternative culture methods for the detection of resistance especially to rifampicin and isoniazid. These methods appear as promising new tools but their accuracy has not been systematically evaluated. METHODS: We did a meta-analysis to evaluate the accuracy of the colorimetric assays for the detection of rifampicin and isoniazid-resistant tuberculosis among clinical isolates. We searched Medline, PubMed (NCBI), Global health-CAB, EJS-E (EbscoHost), ISI Web, Web of Science and IFCC databases and contacted authors if additional information was needed. RESULTS: Eighteen studies met our inclusion criteria for rifampicin resistance detection and 16 for isoniazid. We used a summary receiver operating characteristic (SROC) curve to perform meta-analysis and summarize diagnostic accuracy. For both drugs, all studies had a sensitivity and specificity that ranged between 89% and 100%. CONCLUSIONS: There is evidence that colorimetric methods are highly sensitive and specific for the rapid detection of MDR-TB. These new tools could offer affordable technologies for TB laboratories especially in places where resources are limited and where the prevalence of MDR-TB is important and make TB control efforts more effective. Additional studies are needed in high MDR prevalence countries and cost-effectiveness analysis to have more evidence on the utility of these methods. Future developments to detect resistance directly from smear-positive sputum specimens should be taken into consideration to speed up the process.

Antitubercular Agents↗

PubMed2006

Newly developed primers for comprehensive amplification of the rpoB gene and detection of rifampin resistance in Mycobacterium tuberculosis.

New rpoB gene primers for detecting Rif(r) in Mycobacterium tuberculosis complex bacteria achieved 100% specificity and 88% (fresh sputa) and 92% (ethanol-preserved sputa) diagnostic sensitivity and detected up to 4 CFU/sample. Of the 99 Rif(r) isolates examined, 97% had mutations within cluster I, 2% at codon 176, and 1% at codon 497.

Antibiotics, Antitubercular↗

PubMed2006

Direct detection of Mycobacterium tuberculosis complex DNA and rifampin resistance in clinical specimens from tuberculosis patients by line probe assay.

The INNO-LiPA.Rif TB test (LiPA) has only been applied to a limited number of clinical specimens. To assess the utility of this test for detecting Mycobacterium tuberculosis complex DNA and rifampin (RMP) resistance, 420 sputum samples comprising specimens from untreated (n=160) and previously treated (n=260) patients from 11 countries in Asia, Africa, Europe, and Latin America were tested. DNA was extracted from sputum samples by using a modification of the Boom's method, while the rpoB core region was amplified by nested PCR. The results were analyzed in conjunction with those obtained by Ziehl-Neelsen (ZN) microscopy and by culture on solid media. The LiPA test was positive for M. tuberculosis complex DNA in 389 (92.9%) specimens, including 92.0% (286 of 311) ZN-positive and 94.5% (103 of 109) ZN-negative specimens. Of these, 30.6% were RMP resistant. In contrast, 74.3% of the specimens were positive for M. tuberculosis by culture, and 30.8% of them were RMP resistant. LiPA detected M. tuberculosis complex DNA in 92.4% (110 of 119) of the culture-positive and 100.0% (41 of 41) of the culture-negative specimens from untreated patients. There was a 99.6% concordance between the RMP resistance as determined by culture and by the LiPA test. With an optimal DNA extraction method, LiPA allows rapid detection of M. tuberculosis complex DNA and RMP resistance directly from sputum specimens. LiPA can still provide useful information when culture fails for various reasons. The rapid availability of this information is necessary to adjust patient treatment and avoid the risk of amplification of drug resistance.

Antitubercular Agents↗

PubMed2006

Mixed infection and clonal representativeness of a single sputum sample in tuberculosis patients from a penitentiary hospital in Georgia.

BACKGROUND: Studies on recurrent tuberculosis (TB), TB molecular epidemiology and drug susceptibility testing rely on the analysis of one Mycobacterium tuberculosis isolate from a single sputum sample collected at different disease episodes. This scheme rests on the postulate that a culture of one sputum sample is homogeneous and representative of the total bacillary population in a patient. METHODS: We systematically analysed several pre-treatment isolates from each of 199 smear-positive male adult inmates admitted to a prison TB hospital by standard IS6110 DNA fingerprinting, followed by PCR typing based on multiple loci containing variable number of tandem repeats (VNTRs) on a subset of isolates. Drug susceptibility testing (DST) was performed on all isolates for isoniazid, rifampicin, streptomycin and ethambutol. RESULTS: We found mixed infection in 26 (13.1%) cases. In contrast, analysis of a single pre-treatment isolate per patient would have led to missed mixed infections in all or 14 of these 26 cases by using only standard DNA fingerprinting or the PCR multilocus-based method, respectively. Differences in DST among isolates from the same patient were observed in 10 cases, of which 6 were from patients with mixed infection. CONCLUSION: These results suggest that the actual heterogeneity of the bacillary population in patients, especially in high TB incidence settings, may be frequently underestimated using current analytical schemes. These findings have therefore important implications for correct interpretation and evaluation of molecular epidemiology data and in treatment evaluations.

Adult↗

PubMed2006

A new rapid and simple colorimetric method to detect pyrazinamide resistance in Mycobacterium tuberculosis using nicotinamide.

OBJECTIVES: The purpose of this study was to develop and assess a rapid method for pyrazinamide resistance detection in Mycobacterium tuberculosis using nicotinamide in a colorimetric resazurin assay. METHODS: We have tested M. tuberculosis isolates using nicotinamide in a 96-well format with the redox indicator resazurin (REMA) and compared results using the BACTEC 460-TB system with two concentrations of pyrazinamide (100 and 300 mg/L), as well as the Wayne method for detecting pyrazinamidase activity. Mutations in the pncA gene were detected by DNA sequencing of the pyrazinamide-resistant strains. RESULTS: Out of 95 clinical isolates of M. tuberculosis tested, 25 were determined to be resistant by the Wayne, BACTEC (300 mg/L), and the REMA nicotinamide methods. Using a nicotinamide MIC>250 mg/L as the cut-off for defining resistance, only one strain was falsely labelled as resistant. The REMA nicotinamide assay demonstrated a sensitivity of 100% and a specificity of 98%. The BACTEC (100 mg/L) falsely classified 8 strains as resistant. DNA sequencing detected mutations in 18/22 of the pncA genes from pyrazinamide-resistant strains. CONCLUSIONS: The REMA plate using nicotinamide to detect resistance to pyrazinamide is a simple and rapid method that could be useful in limited-resource countries.

Amidohydrolases↗

PubMed2006

Mycobacterium tuberculosis complex genetic diversity: mining the fourth international spoligotyping database (SpolDB4) for classification, population genetics and epidemiology.

BACKGROUND: The Direct Repeat locus of the Mycobacterium tuberculosis complex (MTC) is a member of the CRISPR (Clustered regularly interspaced short palindromic repeats) sequences family. Spoligotyping is the widely used PCR-based reverse-hybridization blotting technique that assays the genetic diversity of this locus and is useful both for clinical laboratory, molecular epidemiology, evolutionary and population genetics. It is easy, robust, cheap, and produces highly diverse portable numerical results, as the result of the combination of (1) Unique Events Polymorphism (UEP) (2) Insertion-Sequence-mediated genetic recombination. Genetic convergence, although rare, was also previously demonstrated. Three previous international spoligotype databases had partly revealed the global and local geographical structures of MTC bacilli populations, however, there was a need for the release of a new, more representative and extended, international spoligotyping database. RESULTS: The fourth international spoligotyping database, SpolDB4, describes 1939 shared-types (STs) representative of a total of 39,295 strains from 122 countries, which are tentatively classified into 62 clades/lineages using a mixed expert-based and bioinformatical approach. The SpolDB4 update adds 26 new potentially phylogeographically-specific MTC genotype families. It provides a clearer picture of the current MTC genomes diversity as well as on the relationships between the genetic attributes investigated (spoligotypes) and the infra-species classification and evolutionary history of the species. Indeed, an independent Naïve-Bayes mixture-model analysis has validated main of the previous supervised SpolDB3 classification results, confirming the usefulness of both supervised and unsupervised models as an approach to understand MTC population structure. Updated results on the epidemiological status of spoligotypes, as well as genetic prevalence maps on six main lineages are also shown. Our results suggests the existence of fine geographical genetic clines within MTC populations, that could mirror the passed and present Homo sapiens sapiens demographical and mycobacterial co-evolutionary history whose structure could be further reconstructed and modelled, thereby providing a large-scale conceptual framework of the global TB Epidemiologic Network. CONCLUSION: Our results broaden the knowledge of the global phylogeography of the MTC complex. SpolDB4 should be a very useful tool to better define the identity of a given MTC clinical isolate, and to better analyze the links between its current spreading and previous evolutionary history. The building and mining of extended MTC polymorphic genetic databases is in progress.

Computational Biology↗

PubMed2006

Evaluation of multiple genetic markers for typing drug-resistant Mycobacterium tuberculosis strains from Poland.

In the present study, 77 drug-resistant Mycobacterium tuberculosis strains isolated in Poland in 2000 were characterized by the mycobacterial interspersed repetitive unit-variable number tandem repeat (MIRU-VNTR) typing and our novel method based on PCR amplification of DNA regions between IS6110 and 16-bp GC-rich frequent repeats (designated IS6110-Mtb1/Mtb2 PCR). The results were compared with previous data of the more commonly used methods, IS6110 restriction fragment length polymorphism (RFLP) and spoligotyping. The discriminatory power of IS6110-Mtb1/Mtb2 method was only slightly lower than that of IS6110 RFLP, whereas MIRU-VNTR typing was the least discriminative among the 4 methods used. Clustering of strains by using results of IS6110-Mtb1/Mtb2 PCR correlated well with RFLP-defined clusters, further confirming epidemiologic relationships among patients. These results indicate that the novel genotyping method could be an attractive alternative for other PCR-based typing procedures, such as spoligotyping and MIRU-VNTR typing. Also, it seems to be a valuable adjunct to the reference IS6110 RFLP method for studying the genetic diversity of drug-resistant M. tuberculosis strains in Poland.

Bacterial Typing Techniques↗

PubMed2006

Mycobacterium ulcerans infection: control, diagnosis, and treatment.

The skin disease Buruli ulcer, caused by Mycobacterium ulcerans, is the third most common mycobacterial disease after tuberculosis and leprosy and mainly affects remote rural African communities. Although the disease is known to be linked to contaminated water, the mode of transmission is not yet understood, which makes it difficult to propose control interventions. The disease is usually detected in its later stages, when it has caused substantial damage and disability. Surgery remains the treatment of choice. Although easy and effective in the early stages of the disease, treatment requires extended excisions and long hospitalisation for the advanced forms of the disease. Currently, no antibiotic treatment has proven effective for all forms of M ulcerans infection and research into a new vaccine is urgently needed. While the scientific community works on developing non-invasive and rapid diagnostic tools, the governments of endemic countries should implement active case finding and health education strategies in their affected communities to detect the disease in its early stages. We review the diagnosis, treatment, and control of Buruli ulcer and list priorities for research and development.

Bacterial Vaccines↗

PubMed2006

Application of the resazurin microtitre assay for detection of multidrug resistance in Mycobacterium tuberculosis in Algiers.

This study assessed the performance of a rapid, low-cost, colorimetric method, the resazurin microtitre assay (REMA) plate method, for the detection of resistance to isoniazid and rifampicin in 136 clinical isolates of Mycobacterium tuberculosis from two hospitals in Algiers. MICs were determined and the results were compared with those obtained with the conventional proportion method on Löwenstein-Jensen medium. Excellent results were obtained for the REMA plate method, with a sensitivity of 100 % for both isoniazid and rifampicin and a specificity of 98.3 and 99.2 %, respectively. The REMA plate method appears to be a reliable method for the rapid determination of multidrug-resistant tuberculosis and is a good alternative for use in resource-limited countries such as Algeria.

Algeria↗

PubMed2006

Nitrate reductase assay for detection of drug resistance in Mycobacterium tuberculosis: simple and inexpensive method for low-resource laboratories.

The nitrate reductase assay (NRA) was used as an alternative method for detection of resistance to the first-line antituberculous drugs isoniazid, rifampicin, ethambutol and streptomycin. A total of 320 strains of Mycobacterium tuberculosis were studied and the results compared with the proportion method (PM) on Löwenstein-Jensen medium. The mean time to obtain results was 10 days and the overall agreement between the NRA and PM was 98.8 %. The NRA was easy to perform and represents a useful tool for rapid and accurate determination of drug-resistant M. tuberculosis strains in low-resource countries.

Antitubercular Agents↗

PubMed2006

Genetic diversity in Mycobacterium ulcerans isolates from Ghana revealed by a newly identified locus containing a variable number of tandem repeats.

The molecular typing methods used so far for Mycobacterium ulcerans isolates have not been able to identify genetic differences among isolates from Africa. This apparent lack of genetic diversity among M. ulcerans isolates is indicative of a clonal population structure. We analyzed the genetic diversity of 72 African isolates, including 57 strains from Ghana, by variable number of tandem repeat (VNTR) typing based on a newly identified polymorphic locus designated ST1 and the previously described locus MIRU 1. Three different genotypes were found in Ghana, demonstrating for the first time the genetic diversity of M. ulcerans in an African country. While the ST1/MIRU 1 allele combination BD/BAA seems to dominate in Africa, it was only rarely found in isolates from Ghana, where the combination BD/B was dominant and observed in all districts studied. A third variant genotype (C/BAA) was found only in the Amansie-West district. The results indicate that new genetic variants of M. ulcerans emerged and spread within Ghana and support the potential of VNTR-based typing for genotyping of M. ulcerans.

Africa↗

PubMed2006

Heterogeneity among Mycobacterium ulcerans isolates from Africa.

Mycobacterium ulcerans causes Buruli ulcer, an ulcerative skin disease in tropical and subtropical areas. Despite restricted genetic diversity, mycobacterial interspersed repetitive unit-variable-number tandem repeat analysis on M. ulcerans revealed 3 genotypes from different African countries. It is the first time this typing method succeeded directly on patient samples.

Africa↗

PubMed2006

Mycobacterium ulcerans disease (Buruli ulcer) in a rural hospital in Bas-Congo, Democratic Republic of Congo, 2002-2004.

Buruli ulcer (BU), which is caused by Mycobacterium ulcerans, is an important disabling skin disease. Its prevalence is highest in west and central Africa. We report an apparent resurgence of BU in the Bas-Congo Province, Democratic Republic of Congo. During a 28-month period in 2002-2004, the rural hospital of the Institut Médical Evangélique at Kimpese admitted 51 patients suspected of having BU. Bacteriologic, molecular biologic, and histopathologic studies confirmed BU in 36 of these patients. Extensive clinical data, treatment outcomes, and socioeconomic correlations are summarized. Osteomyelitis was an important complication. A multidisciplinary approach to BU control in the Bas-Congo is proposed, aimed primarily at active case detection.

Adolescent↗

PubMed2006

Preliminary observations on Mycobacterium spp. in dairy cattle in Ecuador.

This study evaluated bovine tuberculosis in Mejia canton, a major dairy cattle production region in Ecuador. Randomly selected cattle (1,012 from 59 farms) classified according to herd size were tested by the single tuberculin test (STT). Sixty days later, positive reactors were tested again by the comparative tuberculin test (CTT). In addition, tissue samples from two STT-CTT-positive reactors detected on a farm were obtained in a local slaughterhouse and analyzed bacteriologically. A total of 4.24% of the cattle were positive in the STT and 3.85% were positive in the CTT, with the highest number (7.95%) in large herds versus 3.4% in medium herds and 0.3% in small herds. Mycobacterium bovis was isolated from mesenteric lymph nodes and lungs of one animal. A 16S ribosomal RNA-based polymerase chain reaction confirmed culture results and differentiated mycobacteria other than M. tuberculosis. This study confirms the zoonotic importance of tuberculosis in Ecuadorian dairy cattle with herd size likely to be a crucial parameter in the prevalence of the disease. The implementation of a national control program is necessary and should be based on the detection of positive cattle by STT in combination with CTT.

Animals↗

PubMed2006

BCG vaccine effectiveness against Buruli ulcer: a case-control study in Benin.

BCG remains the only possible prophylactic intervention against Buruli ulcer (BU). Estimating its public health impact on BU control is an important issue. We conducted a case-control study to investigate the vaccine effectiveness of routine BCG vaccine against BU in southern Benin. From August 2002 to August 2003, BCG vaccination status was obtained for 279 clinically diagnosed BU cases and 988 age- and sex-matched neighborhood controls. BCG coverage, which was estimated by the presence of a scar or a vaccination record, was 64.5% in cases and 67.2% in controls. There was no evidence of a protective effect of routine BCG vaccination against BU in southern Benin (vaccine effectiveness adjusted for socioeconomic status = 12%, 95% confidence interval = -24% to 37%).

Adolescent↗