In vitro and ex vivo activity of the fluoroquinolone DC-159a against mycobacteria.

Antimicrobial resistance is a global health problem. In 2021, it was estimated almost half a million of multidrug-resistant tuberculosis (MDR-TB) cases. Besides, non-tuberculous mycobacteria (NTM) are highly resistant to several drugs and the emergence of fluoroquinolone (FQ) resistant M. tuberculosis (Mtb) is also a global concern making treatments difficult and with variable outcome. The aim of this study was to evaluate the activity of the FQ, DC-159a, against Mtb and NTM and to explore the cross-resistance with the currently used FQs.A total of 12 pre-extensively drug-resistant (XDR) Mtb, 2 XDR, 36 fully drug susceptible strains and 41 NTM isolates were included to estimate the in vitro activity of DC-159a, moxifloxacin (MOX) and levofloxacin (LX), using minimal inhibitory and bactericidal concentration (MIC and MBC). The activity inside the human macrophages and pulmonary epithelial cells were also determined.DC-159a was active in vitro and ex vivo against mycobacteria. Besides, it was more active than MOX/LX. Moreover, no cross-resistance was evidenced between DC-159a and LX/MOX as DC-159a could inhibit Mtb and MAC strains that were already resistant to LX/MOX.DC-159a could be a possible candidate in new therapeutic regimens for MDR/ XDR-TB and mycobacterioses cases.

Effect of the deletion of lprG and p55 genes in the K10 strain of Mycobacterium avium subspecies paratuberculosis.

The lprG-p55 operon of Mycobacterium tuberculosis, M. bovis and M. avium strain D4ER has been identified as a virulence factor involved in the transport of toxic compounds. LprG is a lipoprotein that modulates the host immune response against mycobacteria, whereas P55 is an efflux pump that provides resistance to several drugs. In the present study we search for, and characterize, lprg and p55, putative virulence genes in Mycobacterium avium subsp. paratuberculosis (MAP) to generate a live-attenuated strain of MAP that may be useful in the future as live-attenuated vaccine. For this purpose, we generated and evaluated two mutants of MAP strain K10: one mutant lacking the lprG gene (ΔlprG) and the other lacking both genes lprG and p55 (ΔlprG-p55). None of the mutant strains showed altered susceptibility to first-line and second-line antituberculosis drugs or ethidium bromide, only the double mutant had two-fold increase in clarithromycin susceptibility compared with the wild-type strain. The deletion of lprG and of lprG-p55 reduced the replication of MAP in bovine macrophages; however, only the mutant in lprG-p55 grew faster in liquid media and showed reduced viability in macrophages and in a mouse model. Considering that the deletion of both genes lprG-p55, but not that of lprG alone, showed a reduced replication in vivo, we can speculate that p55 contributes to the survival of MAP in this animal model.

Surveillance and characterization of drug-resistant Mycobacterium tuberculosis isolated in a reference hospital from Argentina during 8 years' period.

Background: Argentina is considered a country with a middle tuberculosis (TB) incidence. However, according to the last national epidemiological report released in 2018, since 2013, the trends are steadily increasing. The aims of this study were to determine the drug-resistance (DR), multi-DR and extensively DR (MDR/XDR-TB), and rifampicin resistance (RIF-R) burden as a part of the local TB diagnosis (June 2010-August 2018); to detect the mutations associated to isoniazid (INH) and RIF-R and their geographical distribution; and to analyze the lineage relationship among the genetic patterns of the isolates circulating in the community. Methods: Respiratory and extrapulmonary specimens were processed by Ziehl-Neelsen stain and cultured on specific media. Drug-susceptibility testing of isolates was performed by the MGIT 960 and a colorimetric micro-method. Mutations conferring DR were detected by Genotype and DNA sequencing. Results: The study showed a DR-TB prevalence of approximately 20% of the isolated strains, while M/XDR-TB-and particularly RIF-R-affected more than 5.0% of the total amount of cases. DR geographical distribution revealed isolates carrying mutations in the inhA gene promoter region only constrained to three districts where it was also registered two same family relatives' cases with the infrequent rpoB S522 L/Q mutation. The fact that most DR/MDR-TB isolates were not grouped in genetic clusters suggested that these cases may mostly have occurred due to endogenous reactivation rather than recently transmission. Conclusion: According to the obtained results, it would be convenient, in highly MDR-TB suspected individuals, to confirm phenotypically, the INH and RIF susceptibility detected by molecular tests.

Exploring the "Latin American Mediterranean" family and the RDRio lineage in Mycobacterium tuberculosis isolates from Paraguay, Argentina and Venezuela.

BACKGROUND: The Latin American & Mediterranean (LAM) spoligotype family is one of the most successful genotype of Mycobacterium tuberculosis worldwide and particularly prevalent in South-America. Within this family, a sublineage named Region of Difference Rio (RDRio) was reported initially in Brazil and is characterized by a genomic deletion of about 26.3 kb. This lineage seems to show a specific adaptation to the Euro-Latin American population. In this context, we sought to evaluate the LAM family and the presence of the RDRio genotype in samples from three Latin American countries including Paraguay, Venezuela and Argentina. To detect LAM strains reliably we applied a typing scheme using spoligotyping, 12 loci MIRU-VNTR, the Ag85C103 SNP and the regions of difference RDRio and RD174. IS6110-RFLP results were also used when available. RESULTS: Genotyping of 413 M. tuberculosis isolates from three Latin-American countries detected LAM (46%) and the ill-defined T clade (16%) as the most frequent families. The highest clustering rate was detected in the sample population from the city of Caracas in Venezuela. We observed considerable differences in the presence of the RDRio lineage, with high frequency in Caracas-Venezuela (55%) and low frequency in Buenos Aires-Argentina (11%) and Paraguay (10%). The molecular markers (RD174, Ag85C103, MIRU02-MIRU40 signature) of the RDRio lineage were essentially confirmed. For the LAM family, the most polymorphic loci were MIRU40, MIRU31, MIRU10, MIRU26, MIRU16 and the least polymorphic MIRU24, MIRU20, MIRU04, MIRU23. CONCLUSIONS: Our results suggest a differential adaptation of LAM-sublineages in neighboring populations and that RDRio strains spread regionally with different rates of distribution. The Ag85C SNP and RDs (RD174, RDRio) tested in this study can in fact facilitate molecular epidemiological studies of LAM strains in endemic settings and low-income countries.

Crystal violet decolorization assay for rapid detection of multidrug-resistant Mycobacterium tuberculosis isolates: A multicenter study.

Background: Effective control of tuberculosis is achieved by early diagnosis and drug susceptibility testing for initiation of appropriate treatment. The performance of crystal violet decolorization assay (CVDA) for susceptibility testing of Mycobacterium tuberculosis to isoniazid (INH) and rifampicin (RIF) was compared in a multicenter study. Methods: Seventy-two M. tuberculosis isolates were tested in two phases by CVDA. Results: In Phase I, the specificity, sensitivity, positive predictive value (PPV), negative predictive value (NPV), and agreement for INH were 100%, respectively. Specificity, sensitivity, PPV, NPV, and agreement for RIF were 98.2%, 100%, 94.1%, 100%, and 98.6%, respectively. In Phase II, specificity, sensitivity, PPV, NPV, and agreement were 98%, 100%, 95.4%, 100%, and 98.6% for INH, respectively. Specificity, sensitivity, PPV, NPV, and agreement for RIF were 96.3%, 88.2%, 88.2%, 96.3%, and 94.4%, respectively. Results in the study were obtained on average 10.9 ± 3.1 days in Phase I and 9.8 ± 2.2 days in Phase II. Conclusion: CVDA can be performed for drug susceptibility testing in developed and developing countries. In addition, further studies with larger sample size are needed for evaluation of this method.

String test: A new tool for tuberculosis diagnosis and drug-resistance detection in children.

Background: There is a critical need to improve the diagnostic accuracy of tuberculosis (TB) in children. Several techniques have been developed to improve the quality of sputum samples; however, these procedures are very unpleasant and invasive and require hospitalization and trained personnel. This study aims to explore the potential use of a new and noninvasive tool, "string test," for TB diagnosis in children and in adults not able to render sputum samples and at risk of developing multidrug-resistant TB (MDR-TB). Methods: Children with clinical suspicion of TB attending the pediatric consultation at the Cetrangolo or Cordero Hospitals and adults suspected of MDR-TB and unable to produce sputum attending the Infectious Disease Unit of Cetrangolo Hospital were included in this study. Subjects and Methods: The "string test" is a string that is swallowed by the patients and exposed to gastrointestinal secretions that were late analyzed for TB diagnosis and drug-resistance detection by GenoType MTBDRplus. MedCalc software was used to perform statistical analysis. Results: This technique could be applied on 62.1% of selected children. About 11 (30.6%) children were diagnosed as TB cases, 8 (22.2%) from gastric aspirate and using the "string test." Six out of 19 adults were also diagnosed. Genotype directly on the string specimen detected two MDR-TB in adults and two isoniazid-resistant cases before obtaining the isolate. Conclusion: This test was safe, cheap, and easily implemented without requiring hospitalization. This research could represent a significant step forward to diagnose and rapidly detect drug-resistant TB in children.

Comparación y evaluación de métodos cuantitativos para determinar la susceptibilidad antimicrobiana de cepas del complejo Mycobacterium abscessus / Comparison and Evaluation of Quantitative Methods for Determining Antimicrobial Susceptibility of Complex Mycobacterium Abscessus Strains / Comparação e avaliação de métodos quantitativos para determinar a susceptibilidade antimicrobiana de cepas do complexo Mycobacterium abscessos

Resumen Introducción: el complejo Mycobacterium abscessus incluye especies patógenas emergentes multirresistentes, lo cual limita las opciones terapéuticas para tratar las infecciones causadas por dichos microorganismos. En este estudio se compararon las concentraciones inhibitorias mínimas (CIM) obtenidas mediante dos métodos cuantitativos, se establecieron los puntos de corte empleados en el micrométodo colorimétrico (MMC) y se evaluó la susceptibilidad antimicrobiana. Materiales y métodos: la CIM de nueve antibióticos fue determinada mediante el MMC y la microdilución en caldo (MDC) para 19 cepas del complejo M. abscessus. El test F de Snedecor se utilizó para establecer la diferencia significativa de las CIM entre los dos métodos y se determinaron los puntos de corte mediante la técnica de distribución de la probabilidad para el MMC. Resultados: se encontró una correlación de los resultados de la CIM del 50% entre MMC y MDC para los antibióticos ensayados. Probablemente esta discrepancia en los resultados se deba a diferencias en algunos parámetros técnicos de cada procedimiento. Todas las cepas fueron sensibles a la amikacina y resistentes a meropenem y ampicilina-sulbactam. Independientemente de la especie del complejo M. abscessus, las fluoroquinolonas mostraron una baja actividad inhibitoria (0-25%) sobre los aislados clínicos, resultados que son similares a los reportados por otros autores. Conclusión: Los patrones de multirresistencia observados en las cepas analizadas sugieren la necesidad de utilizar las pruebas de susceptibilidad como herramientas que permitan orientar y optimizar las conductas terapéuticas en infecciones producidas por M. abscessus.

Abstract Introduction: The Mycobacterium abscessus complex includes multidrug resistant emerging pathogens, which limit therapeutic options for treating infections caused by these microorganisms. In this study, the minimum inhibitory concentrations (MICS) obtained by 2 quantitative methods were compared, the cut-off points used in the colorimetric micromethod (CMM) were established and the antimicrobial susceptibility was evaluated. Materials and Methods: The MIC for nine antibiotics was determined by CMM and broth microdilution (BMD) for 19 strains of M. abscessus complex. The Snedecor F test was used to establish the significant difference in the CIM between the methods, cutoff points were determined by the probability distribution method for the CMM. Discussion: A correlation of 50% between CMM and BMD for antibiotics tested was found. Probably, this discrepancy in the results is due to differences in some technical parameters of each procedure. All strains were susceptible to amikacin and were resistant to meropenem and ampicillin-sulbactam. Independently of the species of M. abscessus complex, fluoroquinolones showed a low inhibitory activity (0-25%) on clinical isolates, results that are similar to those reported by other authors. Conclussion: The Multidrug resistance patterns observed in the strains tested suggest the need for susceptibility testing as tools to guide and optimize the therapeutic behavior in infections caused by M. abscessus.

Resumo Introdução: o complexo Mycobacterium abscessus inclui espécies patógenas emergentes multirresistentes, o qual limita as opções terapêuticas para tratar as infeções causadas por estes microrganismos. Neste estudo compararam-se as concentrações inibitórias mínimas (CIMS) obtidas mediante 2 métodos quantitativos, se estabeleceram os pontos de corte empregados no micrométodo colorimétrico (MMC) e se avaliou a susceptibilidade antimicrobiana. Materiais e métodos: a CIM de 9 antibióticos foi determinada mediante o MMC e microdiluição em caldo (MDC) para 19 cepas do complexo M. abscessus. O teste F de Snedecor utilizou-se para estabelecer a diferença significativa das CIMS entre os dois métodos e determinaram-se os pontos de corte mediante a técnica de distribuição da probabilidade para o MMC. Resultados: se encontrou uma correlação dos resultados da CIM do 50% entre MMC e MDC para os antibióticos testados. Provavelmente, esta discrepância nos resultados se deve a diferenças em alguns parâmetros técnicos de cada procedimento. Todas as cepas foram sensíveis à amikacina e resistentes a meropenem e ampicilina-sulbactam. Independentemente da espécie do complexo M. abscessos, as fluoroquinolonas mostraram uma baixa atividade inibitória (0-25%) sobre os isolados clínicos, resultados que são similares aos reportados por outros autores. Conclussão: Os patrões de multirresistência observados nas cepas analisadas, sugerem a necessidade de utilizar as provas de susceptibilidade como ferramentas que permitam orientar e otimizar as condutas terapêuticas em infeções produzidas por M. abscessus.

In vitro anti-tuberculosis activity of azole drugs against Mycobacterium tuberculosis clinical isolates.

BACKGROUND: Latent tuberculosis has been associated with the persistence of dormant Mycobacterium tuberculosis in the organism of infected individuals, who are reservoirs of the bacilli and the source for spreading the disease in the community. New active anti-TB drugs exerting their metabolic action at different stages and on latent/dormant bacilli are urgently required to avoid endogenous reactivations and to be part of treatments of multi- and extensively-drug resistant tuberculosis (M/XDR-TB). It was previously reported that azole drugs are active against M. tuberculosis. For that reason, the aims of this study were to determine the in vitro activity of azole drugs, imidazole (clotrimazole, CLO and econazole, ECO) and nitroimidazole (metronidazole, MZ and ipronidazole, IPZ), against a collection of MDR M. tuberculosis clinical isolates; and to analyze their potential use in both the LTB and the active forms of M/XDR-TB treatments. METHODS: A total of 55 MDR M. tuberculosis isolates and H37Rv were included. MZ and IPZ activity against M. tuberculosis isolates were tested using anaerobic culture conditions. The activity of ECO and CLO was measured by the minimal inhibitory concentration (MIC) using a microdilution colorimetric method. RESULTS: MZ and IPZ showed bacteriostatic activity against M. tuberculosis strains. MIC50 and MIC90 to ECO was 4.0µg/ml, while MIC50 to CLO was 4.0µg/ml and MIC90 was 8.0µg/ml respectively. CONCLUSION: All azole compounds tested in the study showed inhibitory activity against MDR M. tuberculosis clinical isolates.

Relevancia clínica, diversidad y variabilidad genética de distintas especies del género Mycobacterium / Clinical Relevance, Diversity and Genetic Variability of Different Species within the Genus Mycobacterium

Introducción: El término micobacterias no tuberculosas (MNT) incluye distintas especies ambientales capaces de enfermar humanosy/o animales incluso mediante una probable transmisión zoonótica Objetivos. Determinar: la importancia clínica de varias especies del género Mycobacterium y la diversidad genética del Complejo M. avium (MAC), la sensibilidad bacteriana in vitro yel éxito del tratamiento especifico. Materiales y Métodos: Recolección de datos clínicos, epidemiológicos y aislamientos en el periodo 2009-2016; identificación molecular de los aislamientos; determinación de la sensibilidad bacteriana in vitro y de la diversidad genética del MAC; evaluación del tratamiento. Resultados: Fueron diagnosticados 225 casos de micobacteriosis, con prevalencia estable ≈ 6% por año, y 22 especies recuperadas: 4 de rápido desarrollo aisladas de 66 pacientes y 18 de lento desarrollo. MAC fue aislado en 95 casos, 40 M. avium hominissuis, 51 M. intracellulare, 3 M. chimaera, 1 M. colombiense. Se observó mayor probabilidad de enfermar por M. intracellulare en pacientes tratados previamente por tuberculosis (TB). Los pacientes HIV+ tuvieron riesgo incrementado de enfermedad causada por M. avium hominissuis. Los aminoglucósidos, fluoroquinolonas y macrólidos fueron las drogas más activas frente a la mayoría de las MNT. Aproximadamente la mitad de los casos curaron. Conclusiones: M. intracellulare, M. aviumhominissuis con una gran variabilidad genética, y M. abscessus fueron los patógenos más frecuentemente hallados. Un hallazgo importante fue el de casos de enfermedad mixta TB+MNT. Estos pacientes requirieron una terapia con agregado de drogas de segunda línea al esquema terapéutico para TB habiendo curado la mayoría de ellos.

Introduction: The term non-tuberculous mycobacteria (NTM) includes different ambient species capable of sickening humans and/or animals, even by means of a potential zoonotic transmission. Objectives: To determine: The clinical importance of several species within the genus Mycobacterium and the genetic diversity of the M. avium complex (MAC), the in vitro bacterial sensitivity and the success of the specific treatment. Materials and Methods: Collection of clinical and epidemiologic data and information about isolates of the 2009-2016 period; molecular identification of the isolates; determination of the in vitro bacterial sensitivity and genetic diversity of the MAC; treatment evaluation. Results: 225 mycobacteriosis cases were diagnosed, with a stable prevalence of ≈6% per year and 22 recovered species: 4 rapidly growing species isolated from 66 patients and 18 slowly growing species. The MAC was isolated in 95 cases, M. avium hominissuis - 40 cases, M. intracellulare - 51 cases, M. chimaera - 3 cases and M. colombiense - 1 case. We observed a greater probability of getting sick from M. intracellulare in patients previously treated for tuberculosis (TB). HIV-positive patients had a greater risk of falling ill from M. avium hominissuis. Aminoglycosides, fluoroquinolones and macrolides were the most active drugs against most NTM. Approximately half of the cases healed. Conclusions: M. intracellulare, M. aviumhominissuis with great genetic variability and M. abscessus were the most commonly found pathogens. The cases of TB+NTM mixed disease were an important finding. For treating these patients, it was necessary to add second line drugs to the therapeutic regimen for TB; and most of them healed.

Clinical Relevance, Diversity and Genetic Variability of Different Species within the Genus Mycobacterium

Introduction: The term non-tuberculous mycobacteria (NTM) includes different ambient species capable of sickening humans and/or animals, even by means of a potential zoonotic transmission. Objectives: To determine: The clinical importance of several species within the genus Mycobacterium and the genetic diversity of the M. avium complex (MAC), the in vitro bacterial sensitivity and the success of the specific treatment. Materials and Methods: Collection of clinical and epidemiologic data and information about isolates of the 2009-2016 period; molecular identification of the isolates; determination of the in vitro bacterial sensitivity and genetic diversity of the MAC; treatment evaluation. Results: 225 mycobacteriosis cases were diagnosed, with a stable prevalence of ≈6% per year and 22 recovered species: 4 rapidly growing species isolated from 66 patients and 18 slowly growing species. The MAC was isolated in 95 cases, M. avium hominissuis - 40 cases, M. intracellulare - 51 cases, M. chimaera - 3 cases and M. colombiense - 1 case. We observed a greater probability of getting sick from M. intracellulare in patients previously treated for tuberculosis (TB). HIV-positive patients had a greater risk of falling ill from M. avium hominissuis. Aminoglycosides, fluoroquinolones and macrolides were the most active drugs against most NTM. Approximately half of the cases healed. Conclusions: M. intracellulare, M. aviumhominissuis with great genetic variability and M. abscessus were the most commonly found pathogens. The cases of TB+NTM mixed disease were an important finding. For treating these patients, it was necessary to add second line drugs to the therapeutic regimen for TB; and most of them healed

Evolución de la tuberculosis resistente en la Provincia de Buenos Aires en el período 2006 a 2014 / Drug-Resistant Tuberculosis Evolution in Buenos Aires Province During the Period 2016 to 2014

Introducción: En la Argentina la notificación de tuberculosis (TB) mantiene una tendencia descendente, lenta pero sostenida, siendo las formas resistentes las que complican el panorama epidemiológico actual. Objetivo: Describir la incidencia de TB multi y extensivamente resistente (TB M/XDR) en niños y adultos, analizar su transmisión y la relación con los re-tratamientos. Materiales y métodos: En el período 2006-2014 fue notificado un total 41.782 casos totales de TB de los cuales 35.862 (85.8%) eran pulmonares, 24.913 (69,5%) confirmados por bacteriología y, de éstos, 21.842 (87.7%) por examen directo. Un total de 5.712 (13,7%) casos correspondió a menores de 15 años y 35.843 (85,8%) a adultos. Resultados: Fueron registrados 636 casos de TB resistente a los fármacos: 445 (70,0%) con TB MDR, de los cuales 13 (2,9%) fueron niños; 18 (2,6%) casos presentaron TB XDR (2 niños) y 109 (24,5%) eran MDR con resistencia extendida a una fluoroquinolona o un agente inyectable (amicacina, kanamicina, capreomicina, Pre-XDR). Además, 64 casos presentaban mono o poli resistencia. En total 82 (18,4%) pacientes con TB M/XDR cursaban su primer episodio de TB siendo 20 de ellos contactos confirmados de un caso previo de TB. Un total de 19 adultos MDR fueron considerados casos índices de 31 contactos, 13 niños, que desarrollaron la misma forma de TB. Discusión: El contagio desde los casos índices a niños y adultos fue demostrado por epidemiología molecular y clásica. Los genotipos de los aislamientos y la fecha de diagnóstico de la enfermedad permitieron trazar la cadena epidemiológica del contagio.

Introduction: During the last years, Argentina has been maintaining slow but progressive decreasing trends of tuberculosis (TB) incidence rates. In sanitary terms, the drug-resistant forms of the disease are complicating the global control of the disease. Objetive: The main objectives of this study were to describe the incidence of multi and extensive drug-resistant TB (M/XDR) in children and adults, to analyze its transmission within contacts and the relationship with previous treatments. Materials and methods: During 2006-2014 it was notifed to the Control Program of Buenos Aires Province 41,782 TB cases, 5.712 (13.7%) children <15 years old, 35.843 (85.8%) adults; 35,862 (85.8%) patients presented a respiratory form of the disease, 24,913 (69.5%) confrmed by bacteriology, 21,842 (87.7%) by microscopy examination. Results: They were diagnosed 636 cases of drug-resistant TB: 445 (70.0%) MDR TB, 13 (2.9%) children; 18 (2.6%) had a XDR pattern; from 109 (24.5%) individuals the bacteria showed a MDR pattern also resistant to fluoroquinolones or an injectable agent (amikacin, kanamicin or capreomicin). Besides, 64 cases suspected of being MDR were resistant to one or more drugs not accomplishing the MDR criterion. Eighty two (18.4%) patients with M/XDR had their first TB episode being 20 of them, 9 children, contacts of previous TB cases; 19 individuals were considered index cases of another 31 contacts that developed also M/XDR TB. Discussion: Transmission from index cases to contacts was demonstrated by molecular and classical epidemiology. The isolates fngerprinting and the diagnosis of TB dates were useful tools to trace the epidemiologic infection route.

Performance of Four Transport and Storage Systems for Molecular Detection of Multidrug-Resistant Tuberculosis.

BACKGROUND: Detection of drug-resistant tuberculosis is essential for the control of the disease but it is often hampered by the limitation of transport and storage of samples from remote locations to the reference laboratory. We performed a retrospective field study to evaluate the performance of four supports enabling the transport and storage of samples to be used for molecular detection of drug resistance using the GenoType MTBDRplus. METHODS: Two hundred Mycobacterium tuberculosis strains were selected and spotted on slides, FTA cards, GenoCards, and in ethanol. GenoType MTBDRplus was subsequently performed with the DNA extracted from these supports. Sensitivity and specificity were calculated and compared to the results obtained by drug susceptibility testing. RESULTS: For all supports, the overall sensitivity and specificity for detection of resistance to RIF was between 95% and 100%, and for INH between 95% and 98%. CONCLUSION: The four transport and storage supports showed a good sensitivity and specificity for the detection of resistance to RIF and INH in M. tuberculosis strains using the GenoType MTBDRplus. These supports can be maintained at room temperature and could represent an important alternative cost-effective method useful for rapid molecular detection of drug-resistant TB in low-resource settings.

Fitness of drug resistant Mycobacterium tuberculosis and the impact on the transmission among household contacts.

There has been an on-going debate on whether the development of drug resistance in Mycobacterium tuberculosis reduces its relative fitness and its ability to cause disease. The aim of this study was to explore this relationship. For this purpose, we evaluated the in vitro growth of clinical isolates and the transmission of the strains within the patients' households. Clinical and epidemiological data from patients in households, drug-susceptibility and genetic patterns of the isolates were collected. BACTEC MGIT 960™ system with the Epicenter™ software was used to perform fitness experiments and calculate the relative fitness (RF) comparing with the H73Rv reference strain. From 39 households, 124 patients and 388 contacts were included. Concerning transmission, 20 Multi drug-resistant (MDR) and 16 drug sensitive (DS) index cases generated 23 and 28 secondary cases, respectively. An average RF drop of 16.7% was found for MDR strains, but only mutations in rpoB codons 531 were associated with reduced fitness. When the strains were transmitted, their RF tended to decrease, and strains with low RF were less frequently transmitted. Within the limitations of this study, the results showed that the decrease in RF was associated to a limited transmission among the households' contacts.

Evaluation of Mycobacterium tuberculosis cross-resistance to isoniazid, rifampicin and levofloxacin with their respective structural analogs.

The emergence of drug-resistant, multidrug-resistant and extensively drug-resistant tuberculosis (TB) is of major public health concern in several countries. In this study, the pharmacodynamic relationships among the structural analogs of antibiotics belonging to the same family were taken into consideration. The aim of this study was to compare the susceptibility of Mycobacterium tuberculosis to isoniazid (INH), rifampicin and levofloxacin (LX) to their respective structural analogs, which are frequently used as second-line agents. The microplate colorimetric method was used to determine the MIC to INH, ethionamide (ETH), rifampicin, rifabutin, LX and moxifloxacin (MOX) in clinical isolates previously shown to be drug resistant. Mutations conferring drug resistance were detected by GenoType MTBDR plus and DNA sequencing. INH and ETH cross-resistance was found in 95.12% (39/41) of the INH-resistant isolates harboring a mutation in inhAP or inhA open reading frame, but rifabutin cross-resistance was observed in 90.0% (63/70) of the clinical isolates originally shown to be resistant to rifampicin. Isolates with high LX-resistance levels also showed high MIC to MOX. Fluoroquinolone cross-resistance was verified in isolates containing the gyrA94 and the gyrA90 mutation. In general, isolates with high INH, rifampicin and LX-resistance levels also displayed high MIC values for their structural analogs. These findings suggest the need to test in vitro the second-line drugs before their incorporation in the therapeutic schemes.

Characterization of a Mycobacterium avium subsp. avium operon associated with virulence and drug detoxification.

The lprG-p55 operon of Mycobacterium tuberculosis and Mycobacterium bovis is involved in the transport of toxic compounds. P55 is an efflux pump that provides resistance to several drugs, while LprG is a lipoprotein that modulates the host's immune response against mycobacteria. The knockout mutation of this operon severely reduces the replication of both mycobacterial species during infection in mice and increases susceptibility to toxic compounds. In order to gain insight into the function of LprG in the Mycobacterium avium complex, in this study, we assayed the effect of the deletion of lprG gene in the D4ER strain of Mycobacterium avium subsp. avium. The replacement of lprG gene with a hygromycin cassette caused a polar effect on the expression of p55. Also, a twofold decrease in ethidium bromide susceptibility was observed and the resistance to the antibiotics rifampicin, amikacin, linezolid, and rifabutin was impaired in the mutant strain. In addition, the mutation decreased the virulence of the bacteria in macrophages in vitro and in a mice model in vivo. These findings clearly indicate that functional LprG and P55 are necessary for the correct transport of toxic compounds and for the survival of MAA in vitro and in vivo.

Predictive value of direct nitrate reductase assay and its clinical performance in the detection of multi- and extensively drug-resistant tuberculosis.

Conventional culture and drug susceptibility testing (DST) methods for Mycobacterium tuberculosis are laborious and time consuming. For this reason alternative rapid culture and DST techniques are urgently needed to shorten the time for drug-resistance detection. A total of 222 smear-positive sputum samples were evaluated by the direct nitrate reductase assay (D-NRA) on Lowenstein-Jensen medium, for the rapid and simultaneous detection of resistance to isoniazid, rifampicin, kanamycin and ofloxacin. p-Nitrobenzoic acid was also included for identification of the M. tuberculosis complex. Results were compared with the BACTEC MGIT 960 as gold standard. The general performance of the D-NRA was very good, reaching a global value of 97 %. D-NRA had a turn-around time of 16.9 days to obtain results while that of the indirect MGIT 960 system was 29 days. D-NRA is a low-cost technology, easy to set up in clinical laboratories and suitable to be used for DST of M. tuberculosis in all smear-positive samples.

Prospective multicentre evaluation of the direct nitrate reductase assay for the rapid detection of extensively drug-resistant tuberculosis.

OBJECTIVES: To perform a multicentre study evaluating the performance of the direct nitrate reductase assay (NRA) for the detection of multidrug-resistant (MDR) and extensively drug-resistant (XDR) tuberculosis in sputum samples. METHODS: The study was conducted in six laboratories performing tuberculosis diagnosis that were located in six different countries. The NRA was performed directly on sputum samples in parallel with the reference method used at each site. Detection of resistance was performed for rifampicin, isoniazid, ofloxacin and kanamycin. RESULTS: Excellent agreement was obtained for all drugs tested at the majority of sites. The accuracy was 93.7%-100% for rifampicin, 88.2%-100% for isoniazid, 94.6%-100% for ofloxacin and 100% for kanamycin. The majority of NRA results were available at day 21 for sites 1, 2 and 5. Site 3 had a turnaround time of 13.9 days, at site 4 it was 18.4 days and at site 6 it was 16.2 days. The contamination rate ranged between 2.5% and 12%. CONCLUSIONS: Rapid detection of drug resistance by the direct NRA on sputum smear-positive samples was accurate and easy to implement in clinical diagnostic laboratories, making it a good alternative for rapid screening for MDR and XDR tuberculosis.

The geographic diversity of nontuberculous mycobacteria isolated from pulmonary samples: an NTM-NET collaborative study.

A significant knowledge gap exists concerning the geographical distribution of nontuberculous mycobacteria (NTM) isolation worldwide. To provide a snapshot of NTM species distribution, global partners in the NTM-Network European Trials Group (NET) framework (www.ntm-net.org), a branch of the Tuberculosis Network European Trials Group (TB-NET), provided identification results of the total number of patients in 2008 in whom NTM were isolated from pulmonary samples. From these data, we visualised the relative distribution of the different NTM found per continent and per country. We received species identification data for 20 182 patients, from 62 laboratories in 30 countries across six continents. 91 different NTM species were isolated. Mycobacterium avium complex (MAC) bacteria predominated in most countries, followed by M. gordonae and M. xenopi. Important differences in geographical distribution of MAC species as well as M. xenopi, M. kansasii and rapid-growing mycobacteria were observed. This snapshot demonstrates that the species distribution among NTM isolates from pulmonary specimens in the year 2008 differed by continent and differed by country within these continents. These differences in species distribution may partly determine the frequency and manifestations of pulmonary NTM disease in each geographical location.

[Zoonotic tuberculosis in Argentina]. / La tuberculosis zoonótica en la Argentina.

There are significant achievements in the control of animal tuberculosis (tB) in Argentina. the percentage of bovines with apparent tB lesions at the slaughterhouse inspection decreased from 6.7% to 0.6% between 1969 and 2011. on the other hand, the mean percentage of human tB cases due to M. bovis among all those bacteriologically confirmed, was in Santa Fe, an agro-industrial province, 2.3% in the period 1977-2001. It fell to 1.6% by 2011. In the Cetrángolo Hospital (Buenos Aires), it was 0.34% in the period 2001-2005, and 0.36% in 2006-2011. At the Muñiz Hospital, these percentages decreased from 1.75% in 1971 to 0.22% in 2006. Frequency of HIV infection among M. bovis cases varied from 5.9% in santa Fe to 11.1% and 20.5% respectively, in Cetrángolo and Muñiz Hospitals (a reference institution for aids) in Buenos Aires. According to these data M. bovis infection predominates in agro-industrial/ rural areas, showing a slow decrease there as well as in Buenos Aires. Co-infection with HIV is more frequent among patients with M. bovis that in all cases of tB. The situation of M. bovis in Argentina is here compared with that in USA and in several European and Latin American countries. Trends followed by tB in cattle, in humans, and the percentages of M. bovis among them, are not always closely related to move towards the common goal of eradicating tB; the employment of appropriate strategies and the strengthening of control measures are critical in both programs.

First evaluation in Argentina of the GenoType® MTBDRplus assay for multidrug-resistant Mycobacterium tuberculosis detection from clinical isolates and specimens.

Tuberculosis (tB) and multidrug and extensively drug-resistant (dR) tB are important public health problems that are spreading worldwide. The aims of this study were to determine the sensitivity and specificity of the genotype® mtBdRplus assay from smear-positive clinical specimens and isolates and to explore its possible application in routine work. Clinical samples were previously decontaminated using naoH-n-acetyl-l-cystein or naoH-Clna hypertonic solution for Ziehl-neelsen staining and cultures. The leftover sediments of smear-positive samples were stored at -20 °C, 70 of which were selected to be included in this study according to their dR profile. thirty dR Mycobacterium tuberculosis isolates were also assessed. Sequencing was used as gold standard to detect mutations conferring isoniazid (InH) and rifampicin (RIF) resistance. Valid results were obtained in 94.0 % of the samples and 85.5 % (53/62) of the InH-R samples were properly identified. mutations in the katGS315t gene and inhA C-15t gene promoter region were present in 59.7 % (37/62) and 25.8 % (16/62) of the InH-R samples, respectively. the system could also identify 97.7 % (41/42) of the RIF-R samples; the mutations found were rpoBS531l (66.7 %, 28/42), d516V (19.0 %, 8/42), H526Y and S531p/W (4.8 %, 2/42 each one), and S522l/Q (2.4 %, 1/42). a 98.8 % concordance between the genotype assay and sequencing was obtained. genotype® mtBdRplus has demonstrated to be easy to implement and to perform in clinical laboratories and useful for a rapid detection of dR M. tuberculosis from decontaminated sputa and clinical isolates. Therefore, this assay could be applied as a rapid tool to predict InH-R and/or RIF-R in dR risk cases.