[Susceptibility of M. tuberculosis to antituberculosis drugs as determined by two methods, in Sucre state, Venezuela]

The objective of this study was to evaluate the resistance to isoniazid (INH), rifampicin (RIF), streptomycin (STR) and ethambutol (EMB), with the Canetti's proportions method (PM) and the nitrate reductase assay (NRA) of 59 clinical strains of Mycobacterium tuberculosis, isolated in the period of august 2005 to december 2006, in Sucre state, Venezuela. Primary and acquired drug resistance was 6.3% and 14.3%, respectively. Only one strain was found to be multidrug resistant (MDR). The overall agreement between the NRA and PM was 100% for INH, RIF and EMB, and 96% for STR. The time to obtain results was 10 to 14 days for the NRA, compared to 42 days for the PM. The NRA was easy to perform and therefore represents a useful tool for rapid and accurate determination of drug-resistant M. tuberculosis. The sequence of the rpoB gene of the RIF resistant strain demonstrated a never described mutation (change in the codon 456; TCG > CAG) in the hypervariable region of 81 base pairs where most of the mutations of the RIF resistant strains have been reported. Comparison of our results with those of the last resistance prevalence study carried out in the years 1998-1999, shows a decrease in the studied area.

Detection and characterization of waterborne gastroenteritis viruses in urban sewage and sewage-polluted river waters in Caracas, Venezuela

The detection and molecular characterization of pathogenic human viruses in urban sewage have been used extensively to derive information on circulating viruses in given populations throughout the world. In this study, a similar approach was applied to provide an overview of the epidemiology of waterborne gastroenteritis viruses circulating in urban areas of Caracas, the capital city of Venezuela in South America. Dry season sampling was conducted in sewers and in a major river severely polluted with urban sewage discharges. Nested PCR was used for detection of human adenoviruses (HAds), while reverse transcription plus nested or seminested PCR was used for detection of enteroviruses (HuEVs), rotaviruses (HRVs), noroviruses (HuNoVs), and astroviruses (HAstVs). HRVs were fully characterized with genotype-specific primers for VP4 (genotype P), VP7 (genotype G), and the rotavirus nonstructural protein 4 (NSP4). HuNoVs and HAstVs were characterized by sequencing and phylogenetic analysis. The detection rates of all viruses were >or=50%, and all sampling events were positive for at least one of the pathogenic viruses studied. The predominant HRV types found were G1, P[8], P[4], and NSP4A and -B. Genogroup II of HuNoVs and HAstV type 8 were frequently detected in sewage and sewage-polluted river waters. This study reveals relevant epidemiological data on the distribution and persistence of human pathogenic viruses in sewage-polluted waters and addresses the potential health risks associated with transmission of these viruses through water-related environmental routes.

[Mycobacterium tuberculosis: spoligotypes in the Carabobo state, Venezuela]

In order to study the genetic variability of Mycobacterium tuberculosis circulating in the Carabobo State at Venezuela, 317 strains of M. tuberculosis isolated from patients living in different health districts whose acid fast smears were positive, were included. Each strain was characterized by spoligotyping and the pattern compared with the national and worldwide SpolDB4.0 databases; 220 isolates (69.4%) were grouped in 24 clusters, being LAM the most common family (34%). In contrast to other Venezuelan regions, the most common Carabobo spoligotype was number 605, with 46 isolates (14.5%). In addition, there were 97 (30.6%) orphan spoligotypes, 19 of which are found in SpolDB4.0, and 78 non described. Co-infection with human immunodeficiency virus was detected in 11 patients (3.5%). These results show high genotypic variability of M. tuberculosis in the region, contributing with new information for a better understanding of tuberculosis transmission in Venezuela.

Mycobacterial Ser/Thr protein kinases and phosphatases: physiological roles and therapeutic potential

Reversible protein phosphorylation is a major regulation mechanism of fundamental biological processes, not only in eukaryotes but also in bacteria. A growing body of evidence suggests that Ser/Thr phosphorylation play important roles in the physiology and virulence of Mycobacterium tuberculosis, the etiological agent of tuberculosis. This pathogen uses 'eukaryotic-like' Ser/Thr protein kinases and phosphatases not only to regulate many intracellular metabolic processes, but also to interfere with signaling pathways of the infected host cell. Disrupting such processes by means of selective inhibitors may thus provide new pharmaceutical weapons to combat the disease. Here we review the current knowledge on Ser/Thr protein kinases and phosphatases in M. tuberculosis, their regulation mechanisms and putative substrates, and we explore their therapeutic potential as possible targets for the development of new anti-mycobacterial compounds.

Mycobacterium bovis cultured from commercially pasteurized cows’ milk: Laboratory cross-contamination

The ability of Mycobacterium paratuberculosis to survive the commercial pasteurization process of raw milk remains controversial. In a study undertaken in Venezuela to culture M. paratuberculosis from commercially pasteurized cows' milk, 83-200 ml containers of milk were processed and cultured on Herrold's egg yolk slants. No M. paratuberculosis was cultured but a total of six colonies of Mycobacterium bovis were isolated from one container each from two different milk providers. Because laboratory cross-contamination was suspected, the laboratory records were reviewed and spoligotyping was carried out on the isolated individual colonies. On the day before these milk specimens were processed, the biological safety cabinet had been used for the isolation of M. bovis from lymph nodes from infected cattle. Spoligotyping showed that that the colonies isolated from the milk all had the same pattern as the strains isolated from the lymph nodes that were processed the previous day. As far as we know, this is the first report of cross-contamination in a veterinary mycobacterial laboratory. False-positive cultures in the mycobacterial laboratory are not rare. In this setting M. bovis was isolated because it is the most common manipulated organism in this laboratory. We believe that reports on the isolation of M. paratuberculosis from commercially pasteurized milk should exclude cross-contamination before reporting, especially when this organism is routinely isolated from animal material in the same lab.

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.

In-house phage amplification assay is a sound alternative for detecting rifampin-resistant Mycobacterium tuberculosis in low-resource settings

An in-house mycobacteriophage amplification assay for detecting rifampin-resistant Mycobacterium tuberculosis showed 100% sensitivity, 97.7% specificity, and 95.2% predictive value for resistance in a test of 129 isolates from a hot spot area of multidrug-resistant M. tuberculosis. The applicability of the test was demonstrated in the routine work flow of a low-resource reference laboratory.

Snapshot of moving and expanding clones of Mycobacterium tuberculosis and their global distribution assessed by spoligotyping in an international study

The present update on the global distribution of Mycobacterium tuberculosis complex spoligotypes provides both the octal and binary descriptions of the spoligotypes for M. tuberculosis complex, including Mycobacterium bovis, from >90 countries (13,008 patterns grouped into 813 shared types containing 11,708 isolates and 1,300 orphan patterns). A number of potential indices were developed to summarize the information on the biogeographical specificity of a given shared type, as well as its geographical spreading (matching code and spreading index, respectively). To facilitate the analysis of hundreds of spoligotypes each made up of a binary succession of 43 bits of information, a number of major and minor visual rules were also defined. A total of six major rules (A to F) with the precise description of the extra missing spacers (minor rules) were used to define 36 major clades (or families) of M. tuberculosis. Some major clades identified were the East African-Indian (EAI) clade, the Beijing clade, the Haarlem clade, the Latin American and Mediterranean (LAM) clade, the Central Asian (CAS) clade, a European clade of IS6110 low banders (X; highly prevalent in the United States and United Kingdom), and a widespread yet poorly defined clade (T). When the visual rules defined above were used for an automated labeling of the 813 shared types to define nine superfamilies of strains (Mycobacterium africanum, Beijing, M. bovis, EAI, CAS, T, Haarlem, X, and LAM), 96.9% of the shared types received a label, showing the potential for automated labeling of M. tuberculosis families in well-defined phylogeographical families. Intercontinental matches of shared types among eight continents and subcontinents (Africa, North America, Central America, South America, Europe, the Middle East and Central Asia, and the Far East) are analyzed and discussed.

Global distribution of Mycobacterium tuberculosis spoligotypes

We present a short summary of recent observations on the global distribution of the major clades of the Mycobacterium tuberculosis complex, the causative agent of tuberculosis. This global distribution was defined by data-mining of an international spoligotyping database, SpolDB3. This database contains 11708 patterns from as many clinical isolates originating from more than 90 countries. The 11708 spoligotypes were clustered into 813 shared types. A total of 1300 orphan patterns (clinical isolates showing a unique spoligotype) were also detected.

The molecular epidemiology of tuberculosis in Caracas, Venezuela, with IS6110 DNA fingerprinting

In this retrospective study we asses the molecular epidemiological situation of Tuberculosis of the city of Caracas, Venezuela in the year 1994, applying IS6110 DNA Fingerprinting of clinical isolates. Fingerprinting of Mycobacterium tuberculosis strains of sixty-four patients TB patients from all the 5 districts of the city revealed fifty-one distinct IS6110 patterns. Isolates from 20 patients (30%) had fingerprints that were shared with at least one other patient. Based on this sampling we conclude that at least a third of the tuberculosis cases in Caracas in the year 1994 were the result of recent and ongoing transmission, indicating micro-epidemics in the town.

[The role of human genetic factors in susceptibility to tuberculosis]

Tuberculosis has been one of the most important illnesses in the history of the world, but it was never understood why only some people, and not others, develop the disease. It was assumed that human genetic factors play a role in susceptibility, but until the advent of molecular markers, it was never possible to convincingly separate inheritance from the compounding factors of environment and exposure to the bacillus. In recent years particular polymorphisms of several human genes have been shown to be correlated with susceptibility to TB: NRAMP1, Vitamin D receptor, Interferon gamma receptor, IL-12 and its receptor, several HLA haplotypes and there are probably several others that will be discovered. Nevertheless, no single gene appears to play a dominant role in the total TB burden of any population, and exposure of the individual to the bacillus and the environment and nutritional state of the individual also seem to play an important role in determining who will develop the disease.

[Characterization of the expression and function of SigM an ECF sigma factor in mycobacteria]

The survival of M. tuberculosis within the macrophage depends on its ability to respond to oxidative stress, and the ECF subfamily of sigma factors likely play an important role. We studied SigM, a sigma factor whose gene is located near the origin of DNA replication. In both M. smegmatis and M. bovis BCG, the expression of sigM was induced at high temperature and in stationary phase. Mutants of M. smegmatis without an intact sigM were defective for survival in oxidative stress and also for the induction of thioredoxin reductase activity in oxidative stress. The thioredoxin system reduces disulfide bonds that are formed in oxidative stress. SigM thus appears to regulate thioredoxins and forms part of the bacteria's complex protective responses.

Intrinsic resistance of Mycobacterium smegmatis to fluoroquinolones may be influenced by new pentapeptide protein MfpA

The fluoroquinolones (FQ) are used in the treatment of Mycobacterium tuberculosis, but the development of resistance could limit their effectiveness. FQ resistance (FQ(R)) is a multistep process involving alterations in the type II topoisomerases and perhaps in the regulation of efflux pumps, but several of the steps remain unidentified. Recombinant plasmid pGADIV was selected from a genomic library of wild-type (WT), FQ-sensitive M. smegmatis by its ability to confer low-level resistance to sparfloxacin (SPX). In WT M. smegmatis, pGADIV increased the MICs of ciprofloxacin (CIP) by fourfold and of SPX by eightfold, and in M. bovis BCG it increased the MICs of both CIP and SPX by fourfold. It had no effect on the accumulation of (14)C-labeled CIP or SPX. The open reading frame responsible for the increase in FQ(R), mfpA, encodes a putative protein belonging to the family of pentapeptides, in which almost every fifth amino acid is either leucine or phenylalanine. Very similar proteins are also present in M. tuberculosis and M. avium. The MICs of CIP and SPX were lower for an M. smegmatis mutant strain lacking an intact mfpA gene than for the WT strain, suggesting that, by some unknown mechanism, the gene product plays a role in determining the innate level of FQ(R) in M. smegmatis.

Epidemiological evidence of the spread of a Mycobacterium tuberculosis strain of the Beijing genotype on Gran Canaria Island

Molecular epidemiological studies suggest that particular Mycobacterium tuberculosis strains have an enhanced capacity to spread within a community. One strain, the Beijing genotype, has been associated with outbreaks in a number of communities throughout the world. IS6110 restriction fragment length polymorphism (RFLP) analysis was performed on M. tuberculosis isolates from 566 of the 721 patients (78.5%) diagnosed with tuberculosis (TB) on Gran Canaria Island from 1993 to 1996, as well as 35% of isolates from 1991-1992 (85 strains). RFLP identification of the family of strains of the Beijing genotype was confirmed by spoligotyping. Medical records of all patients were reviewed and epidemiological links were identified. Of 566 M. tuberculosis isolates from 1993 to 1996 with RFLP available, 72% belonged to clusters. The largest contained 75 cases and was caused by a strain of the Beijing genotype that was introduced to the island in 1993. It was found in 10 patients in 1993 (5.5%), 12 in 1994 (8.1%), 18 in 1995 (16.4%), and 35 in 1996 (27.1%). Epidemiological linkage was confirmed for 68% of cases. This study has demonstrated rapid dissemination of this strain of the Beijing genotype. This genotype might play an important role in the future of the worldwide tuberculosis epidemic.

Overview of some biomedical research projects in tropical medicine conducted at the Instituto Venezolano de Investigaciones Cientificas

The Instituto Venezolano de Investigaciones Cientificas (IVIC) is a government-funded multidisciplinary academic institution dedicated to research, development and technology in many areas of knowledge. Biomedical projects and publications comprise about 40% of the total at IVIC. In this article, we present an overview of some selected research and development projects conducted at IVIC which we believe contain new and important aspects related to malaria, ancylostomiasis, dengue fever, leishmaniasis and tuberculosis. Other projects considered of interest in the general area of tropical medicine are briefly described. This article was prepared as a small contribution to honor and commemorate the centenary of the Instituto Oswaldo Cruz.

Contribution of the multidrug efflux pump LfrA to innate mycobacterial drug resistance

Multidrug resistance (MDR) in bacteria has been associated with efflux pumps that export structurally unrelated compounds and decrease cytoplasmic drug accumulation. To investigate MDR in mycobacteria, we studied the Mycobacterium smegmatis mutant mc(2)11, which is resistant to doxorubicin, tetracycline, rhodamine, ethidium bromide and the hydrophilic fluoroquinolones. A genomic library constructed from this mutant was used to select clones conferring resistance to doxorubicin. Surprisingly, the clone selected encodes the efflux pump LfrA, which has been reported to confer resistance to hydrophilic fluoroquinolones, ethidium bromide, rhodamine, and acriflavine. To define the contribution of LfrA to the innate mycobacterial drug resistance and to the MDR phenotype in mc(2)11, the lfrA gene was disrupted in both the mc(2)11 mutant and the mc(2)155 wild-type parent. LfrA disruption of the wild-type strain decreased resistance to ethidium bromide and acriflavine, and increased accumulation of ethidium bromide. However, disruption of lfrA gene results only in a 2-fold decrease in minimal inhibitory concentrations (MICs) for ciprofloxacin, doxorubicin, rhodamine, and accumulation of [(14)C]ciprofloxacin was unchanged. LfrA disruption of the MDR strain mc(2)11 produced a similar phenotype. Thus, LfrA contributes significantly to the intrinsic MICs of M. smegmatis for ethidium bromide and acriflavine, but not for ciprofloxacin, doxorubicin or rhodamine.

Alpha-1 antitrypsin deficiency and splenic artery aneurysm rupture: an association?

OBJECTIVE

Theoretically, patients with alpha 1-antitrypsin deficiency may be vulnerable to the development of splenic artery aneurysms. alpha-1 antitrypsin deficiency can induce cirrhosis with portal hypertension, and resulting protease-antiprotease imbalances may exaggerate arterial wall weakness due to proteolysis of arterial structural proteins. A splenic artery aneurysm rupture 7 days after liver transplantation provoked a reassessment of the incidence of this phenomenon in a liver transplant population.

METHODS

Case records from three institutions and the results of a survey sent to 126 liver transplantation programs in the United Network for Organ Sharing database were reviewed. The incidence of splenic artery aneurysm rupture in the peritransplantation period, etiology of liver disease associated with this phenomenon, and recommendations regarding management of splenic artery aneurysms was assessed.

RESULTS

Twenty-one cases of splenic artery aneurysm rupture were identified. alpha-1 antitrypsin deficiency was the most common cause of cirrhosis in the majority of identified patients who presented with splenic artery aneurysm rupture, which was associated with a mortality rate of 57%. Respondents to the survey indicated that a preoperative evaluation was warranted if a splenic artery aneurysm was suspected; however, no consensus regarding management exists.

CONCLUSIONS

The presence and risk of rupture of splenic artery aneurysms may be greater in patients with alpha-1 antitrypsin deficiency. If identified before rupture, an aggressive approach to diagnosing and treating these aneurysms should be initiated. At present, no consensus exists regarding the management of splenic artery aneurysms.

Fluorescence-based detection of lacZ reporter gene expression in intact and viable bacteria including Mycobacterium species

A variety of fluorescein di-beta-D-galactopyranoside (FDG)-based substrates were evaluated for measuring beta-galactosidase expression in bacteria. One substrate, 5-acetylamino-FDG (C2FDG), performed well in all bacteria tested, including the slow growing mycobacterium, Mycobacterium bovis BCG. The sensitivity of C2FDG in intact, viable BCG was similar to that of o-nitrophenyl-beta-D-galactopyranoside in cell lysates when used to measure lacZ reporter gene activity. C2FDG was approximately 70-fold more sensitive than green fluorescent protein (GFP) in BCG when assayed in a fluorescence plate reader, and comparable to GFP when measured by flow cytometry. These assays provide an important new alternative for the rapid measurement of reporter gene expression in viable bacteria.

Hepatic manifestations of familial patent ductus venosus in adults

BACKGROUND

The ductus venosus connects the umbilical vein to the inferior vena cava during fetal life and subsequently closes rapidly after birth. It is known as patent ductus venosus when it remains patent in adulthood.

PATIENTS

A 43 year old man with a history of panhypopituitarism presented with recurrent bouts of pedal oedema associated with fatigue, hypoalbuminaemia, and elevated prothrombin time. An ultrasound examination of his abdomen with Doppler revealed notable attenuation of the main portal vein with diminished intrahepatic branches; a computed tomography scan with angiography revealed a large collateral vein within the liver consistent with a patent ductus venosus. Sequential liver biopsies showed a considerable reduction in the calibre and number of the portal veins. His younger brother, who was diagnosed with alcohol related cirrhosis, suffered from intermittent bouts of encephalopathy and was found to have the same vascular lesion. A third brother was found to have a patent ductus venosus as well as two large hepatic masses consistent with focal nodular hyperplasia.

CONCLUSION

The syndrome of familial patent ductus venosus has only previously been described in three infant brothers who presented with hepatic encephalopathy and fatty degeneration of the liver. This report documents three brothers with a patent ductus venosus presenting in adulthood with different manifestations of liver disease. The presence of the same vascular anomaly in three brothers is highly suggestive of a recessive genetic trait with an anatomical manifestation of patent ductus venosus.

Liver transplantation: perspectives after 250 liver transplants at the Ochsner Clinic

At the Ochsner Clinic we recently performed our 250th liver transplant. Reaching this milestone has led us to reflect back on the history of liver transplant, both at our own institution and nationally, noting the many achievements and improvements in liver transplantation during the relatively brief history of this therapeutic modality. Furthermore, there are a number of issues both medical and political which will likely be affecting how liver transplantation is performed in the future.