Evaluation of the VersaTREK system compared to the Bactec MGIT 960 system for first-line drug susceptibility testing of Mycobacterium tuberculosis.

The aim of this study was to evaluate the reliability of the VersaTREK system for Mycobacterium tuberculosis drug susceptibility testing compared with results obtained with the Bactec MGIT 960 system. A total of 67 strains were evaluated. Overall agreement was at 98.5%. Kappa indexes were 1.0 for isoniazid, rifampin, and ethambutol, 0.937 for pyrazinamide, and 0.907 for streptomycin. The VersaTREK system is validated for M. tuberculosis drug susceptibility testing.

Non-tuberculous mycobacteria in the sputum of HIV-infected patients: infection or colonization?

It can be difficult to establish the clinical significance of the isolation of non-tuberculous mycobacteria (NTM) from the sputum of HIV-infected patients. In this observational study, we have investigated factors associated with having NTM infection. During the period of the study, 10 patients had NTM infection and 14 had NTM colonization. Factors associated with having NTM infections were: CD4 lymphocyte count <50 cells/mL (odds ratio [OR] 10; 95% confidence interval [CI] 1.4-69.3), haemoglobin <11 g/dL (OR 7.2; 95% CI 1.08-47.9), weight loss (OR 9; 95% CI 1.3-63.9), duration of symptoms for more than a month (OR 54; 95% CI 4.2-692.5), the presence of acid fast bacilli (AFB) in sputum (OR 30.3; 95% CI 2.6-348.9) and repeated positive NTM cultures in other sputum samples (OR 4.3; 95% CI 1.6-11.7). In conclusion, we must suspect NTM infection in patients with long-standing symptoms, anaemia, low CD4 lymphocyte count, several positive sputum cultures and when AFB are seen.

Incidence and significance of acid-fast bacilli in sputum smears at the end of antituberculous treatment.

OBJECTIVE: A group of patients with pulmonary tuberculosis (PT) who received and correctly completed antituberculous therapy were studied to determine the incidence and significance of positive acid-fast bacilli (AFB) in sputum smears at the end of this treatment. DESIGN: Retrospective chart review of persons with bacteriologically proved PT. PATIENTS: Of 1,052 patients diagnosed as having PT between 1988 and 1992, 453 who fulfilled the following criteria were included in the study: (1) diagnosis established by positive AFB and positive culture in sputum smears; (2) no previous antituberculous treatment had been received; (3) HIV serologic test results were negative; (4) treatment was correctly completed; (5) they were followed up throughout the period of treatment; and (6) expectoration was still present at the end of treatment and at least two spontaneous sputum samples could be obtained. RESULTS: Positive AFB of sputum smears were found at the end of treatment in 10 (2.2%) of the 453 patients studied. Five patients had only one positive smear, and the other five had more than one. Of these ten cases, sputum culture was negative in eight, which were considered to be unviable bacilli, and positive for nontuberculous mycobacteria in two. Clinical symptoms or worsening on chest radiograph were observed only in one patient with unviable bacilli, but they were caused by a concomitant nonspecific respiratory tract infection. CONCLUSIONS: Positive AFB smear results at the end of completed treatment regimens analyzed in this study have occurred because of unviable bacilli and nontuberculous mycobacteria colonization. The presence of more than one positive smear seems not to increase the probability of treatment failure and is more frequently due to nontuberculous mycobacteria. Results of culture can thus be awaited without the need to prolong or modify antituberculous therapy.

In vitro susceptibility of Mycobacterium kansasii to the difluorinated quinolone sparfloxacin using a broth microdilution and macrodilution MIC system.

OBJECTIVES: To study the minimum inhibitory concentrations (MIC) of the difluorinated quinolone sparfloxacin against 32 clinical isolates of Mycobacterium kansasii from 23 patients, all of whom had clinically significant infections due to M. kansasii, and 11 the acquired immune-deficiency syndrome (AIDS). To study the correlation between the microdilution and macrodilution techniques in M7H9 broth. DESIGN: The MICs were determined by two methods: broth microdilution in microplates and broth macrodilution in tubes. The isolates were inoculated into two-fold drug dilutions (ranging from 0.063 to 8 microg/ml) in Middlebrook 7H9 broth and then incubated at 37 degrees C for 21 days. RESULTS: All 32 strains were susceptible, with identical MIC results in both methods, 96.9% of them showing an MIC of 0.25 microg/ml. CONCLUSION: These MIC studies suggest that sparfloxacin may be useful for drug treatment of slow-growing nontuberculous mycobacteria such as M. kansasii. The microdilution method appears to be a reliable method for routine susceptibility testing of M. kansasii, and is easy to interpret and to carry out.

Determinants of drug-resistant tuberculosis: analysis of 11 countries.

SETTING: Eleven countries/territories. OBJECTIVES: Global information on the determinants of drug-resistant tuberculosis (TB) based on representative data is not available. We therefore studied the relationship between demographic characteristics, prior TB treatment, and human immunodeficiency virus (HIV) infection with anti-tuberculosis drug resistance. METHODS: Population-based representative data on new and previously treated patients with TB collected within an international drug resistance surveillance network. RESULTS: Of 9,615 patients, 8,222 (85.5%) were new cases of TB and 1,393 (14.5%) were previously treated cases. Compared with new cases, previously treated cases were significantly more likely to have resistance to one (OR = 2.5,95% CI 2.1-3.0; P < 0.001), two (OR = 4.6, 95%CI 3.7-5.6; P < 0.001), three (OR = 11.5, 95%CI 8.6-15.3; P < 0.001), and four (OR = 18.5, 95% CI 12.0-28.5; P < 0.001) drugs. An approximately linear increase in the likelihood of having multidrug-resistant tuberculosis (MDR-TB) was observed as the total time (measured in months) of prior anti-tuberculosis treatment increased (P < 0.001, chi2 for trend). In multivariate analysis, prior TB treatment for 6-11 months (OR = 7.6, 95% CI 2.6, 22.4; P < 0.001) and > or = 12 months (OR 13.7, 95% CI 4.5-41.6; P < 0.001), but not HIV positivity, was associated with MDR-TB. CONCLUSION: This study shows that prior but ineffective treatment is a strong predictor of drug resistance, and that HIV is not an independent risk factor for MDR-TB. The association between length of treatment and drug resistance may reflect longer treatment as a result of treatment failure in patients with drug resistance; it may also reflect irregular prior treatment for TB, leading to drug resistance.

Non-tuberculous mycobacteria: patterns of isolation. A multi-country retrospective survey.

OBJECTIVE: To collect data on non-tuberculous mycobacteria (NTM) isolated from clinical laboratories in different countries to establish: 1) whether the isolation of NTM was increasing, 2) which species were increasing, and 3) whether there was any pattern of geographical distribution. DESIGN: In 1996, the Working Group of the Bacteriology and Immunology Section of the International Union Against Tuberculosis and Lung Disease contacted 50 laboratories in different countries for the necessary information. RESULTS: The number of patients reported with NTM was 36099 from 14 countries. Mycobacterium avium complex, M. gordonae, M. xenopi, M. kansasii and M. fortuitum were the five species most frequently isolated. There was a significant upward trend for M. avium complex and M. xenopi. Pigmented mycobacteria predominated in Belgium, the Czech Republic and the Mediterranean coast of Spain. Non-chromogenic mycobacteria were found to be predominant in the area of the Atlantic coast of Brazil and in Turkey, the United Kingdom, Finland and Denmark. CONCLUSIONS: There was an increase in the number of NTM isolated from clinical samples of patients. Isolation of the most frequent species is constantly changing in most of the geographical areas, and newer species are emerging due to better diagnostic techniques to detect and identify NTM.

[Drug resistance in Mycobacterium tuberculosis. A multicenter study of the Barcelona area. Grupo de Trabajo sobre Resistencias en Tuberculosis]. / Farmacorresistencia de Mycobacterium tuberculosis. Estudio multicéntrico en el area de Barcelona. Grupo de Trabajo sobre Resistencias en Tuberculosis.

BACKGROUND: The aims of this multicenter study was to establish the level of primary and acquired drug resistance of M. Tuberculosis strains isolated in Barcelona and to identify possible risk groups using clinical data. PATIENTS AND METHODS: All tuberculosis patients with isolation and identification of M. tuberculosis strains from October 1995 to September 1997 were included. Susceptibility tests isoniazid, rifampin, ethambutol, streptomycin and pyrazinamide were performed using the Bactec 460 system and the proportions method on solid medium. Logistic progression was used for statistical analysis. RESULTS: The total number of patients included was 1,749 (1,535 non-treated and 214 previously treated). Primary drug resistance was 5.7% (isoniazid 3.8%; rifampin 1.0%, streptomycin 2.1%, ethambutol 0.3% and pyrazinamide 1.0%). Acquired drug resistance was 20.5% (isoniazid 17.3%, rifampin 9.8%, ethambutol 1.9%, streptomycin 4.7% and pyrazinamide 6.5%). Primary drug resistance was associated with people over 60 years old and women. CONCLUSIONS: The low level of drug resistance enables antituberculosis treatment of non-treated patients to start with the standardised three-drug regimes except in the case of foreign people from countries with a high level of drug resistance. Susceptibility tests are recommended on all M. tuberculosis strains isolated, together with controlled studies of drug resistance surveillance.

[Mycobacterial infections: yield of bacillary microscopy in different clinical samples (1975-1988)]. / Infecciones por micobacterias: rendimiento de la baciloscopia en diferentes muestras clínicas (1975-1988).

BACKGROUND: The yield of microscopy examination as a quick diagnostic test in several pulmonary and nonpulmonary samples referred to the mycobacterial laboratory of a general hospital is reviewed. METHODS: During a 14-year period (1975-1988), 113,836 biological products were investigated. In 9,972 a positive culture for mycobacteria was obtained. For the microscopy examination the auramin technique was used; if positive, acid-alcohol resistance was confirmed by overstaining with the Ziehl-Neelsen technique. The culture was used as the reference method. RESULTS: Microscopic examination was positive in 34% of samples with a positive culture, being 39% for Mycobacterium tuberculosis and 10% for environmental mycobacteria. The overall specificity was 99%, the positive predictive value was 91% and the negative predictive value was 94%. In pleuropulmonary samples the sensitivity ranged from 48% in sputum and 2% in pleural biopsy, with specificity higher than 99%. In nonpulmonary samples, sensitivity, specificity and positive and negative predictive values varied with the type of sample. The false positive rate (positive microscopy with negative culture) was 0.3, and it was shown that 80% of these patients had received previous therapy. In organic fluids (pleural, peritoneal, cerebrospinal), the sensitivity was not greater than 13%. CONCLUSIONS: Sputum, bronchoaspirate and bronchoalveolar lavage were better for the diagnosis of tuberculosis than gastric aspirate. Approximately 1 in each positive microscopy examinations corresponded to environmental mycobacteria. In some nonpulmonary samples with high sensitivity the positive predictive value was low. 80% of the false positive results corresponded to previously treated patients.

[Isolation of M. tuberculosis in abdominal specimens]. / Aislamiento de M. tuberculosis en muestras de origen abdominal.

The isolation of mycobacteria in abdominal specimens during a 10 years period is presented. Twenty-three clinical cases have been reviewed; patients were divided in three groups: 1) Peritoneal and intestinal tuberculosis. 2) Pulmonary tuberculosis with isolation of M. tuberculosis in feces, and 3) Miliary tuberculosis. We emphasize the low yielding of bacilloscopy, the low number of colonies in cultures and the importance of the microbiological study of abdominal specimens in the confirmatory diagnosis. The predominant symptoms of peritoneal tuberculosis were abdominal pain and distention and fever. The study of the ascitic fluid showed in most of the cases lymphocytic exudate and the pathological study of biopsies showed granulomas with caseous necrosis. Three patients had another associated abdominal disease. Isolation of M. tuberculosis in feces does not invariably mean the presence of intestinal tuberculosis. We confirm the frequent association of disseminated tuberculosis and HIV1 infection.

Genetic DNA probes for Mycobacterium avium complex identification.

The acridinium ester labelled DNA probe specific for M. avium complex (MAC) was used for testing 30 strains of MAC previously identified by conventional procedures. The hybridization was positive in 26 strains, negative in 3 strains and one strain seemed to be contaminated when subcultured. The specific DNA probes allow to identify even the slow growing mycobacterial strains, in positive samples, within two hours while conventional methods usually take several weeks to show the result. A rapid confirmation of a mycobacterial species is invaluable for selecting an effective treatment as early as possible, which is extremely important e.g. in immunosuppressed patients, children with lymphadenitis, etc. Nevertheless, this method has the disadvantage of being too expensive for some laboratories, though questionable if repeated subcultures, technician's time and the delay in obtaining results are taken into account, and enabling to identify only a limited number of clinically significant mycobacterial species using commercially available probes.

Mycobacterium africanum, an emerging disease in high-income countries?

BACKGROUND: Mycobacterium africanum is a cause of tuberculosis (TB) that has mainly been described in Africa, but immigration and travel patterns have contributed to the spread of the disease to other countries. METHODS: We retrospectively reviewed TB cases due to M. africanum during 2000-2010 in seven Spanish hospitals. Selected clinical charts were reviewed using a predefined protocol that included demographical, clinical and microbiological data and outcome. RESULTS: Although 57 cases were diagnosed, only 36 clinical charts were available for review: 82.8% were men and the mean age was 31.6 years (range 12-81). Forty-four cases were from Africa, 1 from the Philippines, 1 from India, and 4 from Spain, while the country of origin was unknown in 7 cases. The most frequent site of infection was the lung (58.3%). Four cases (6.9%) were resistant to at least one first-line anti-tuberculosis drug. CONCLUSIONS: Disease due to M. africanum in industrialised countries is mainly associated with immigration from endemic areas, although some cases also occur among native-born populations.

Rifampicin-resistant Mycobacterium tuberculosis: susceptibility to isoniazid and other anti-tuberculosis drugs.

Based on data from 14 Supranational Tuberculosis (TB) Reference Laboratories worldwide, the proportion of rifampicin (RMP) resistant isolates that were isoniazid (INH) susceptible by phenotypic drug susceptibility testing varied widely (0.5-11.6%). RMP-resistant isolates that were INH-susceptible had significantly lower rates of resistance to other first- and second-line anti-tuberculosis drugs (except rifabutin) compared to multidrug-resistant isolates. RMP resistance is not always a good proxy for a presumptive diagnosis of multidrug-resistant TB, which has implications for use of molecular assays that identify only RMP resistance-associated DNA mutations.

Resistance to anti-tuberculosis medications in the Horn of Africa.

We performed drug susceptibility testing among chronic patients hospitalised in the tuberculosis (TB) referral centre of the capital of Djibouti. Among 36 patients tested, 27 had multidrug-resistant TB and four had extensively drug-resistant TB. National guidelines must be revised urgently and the administration of second-line TB medications strictly controlled.

Tuberculosis transmission patterns among Spanish-born and foreign-born populations in the city of Barcelona.

During a 2-year period (2003-2004), tuberculosis (TB) transmission in Barcelona and the factors related to transmission among the Spanish- and foreign-born populations were studied by molecular epidemiology. Data were obtained from TB cases and Conventional Contact Tracing registries and genotyping was performed using restriction fragment length polymorphism (RFLP)-IS6110 and MIRU12 as a secondary typing method. Of the 892 TB cases reported, 583 (65.3%) corresponded to Spanish-born and 309 (34.6%) to foreign-born. Six hundred and eighty-seven cases (77%) were confirmed by culture. RFLP typing of 463/687 (67.4%) isolates was performed, revealing 280 (60.5%) unique and 183 (39.5%) shared patterns, which were grouped into 65 clusters. Spanish-born individuals were significantly more clustered than foreign-born individuals (44.6% vs. 28.8%; p 0.016). Clustering in foreign-born individuals was associated with HIV (p 0.051, odds ratio = 3.1, 95% confidence interval 1-10.9) and alcohol abuse (p 0.022), whereas, in the Spanish-born individuals, clustering was associated with age in the range 21-50 years, (p 0.024). Of the total clusters, 36/65 (55.3%) included only Spanish-born patients, whereas 22/65 (33.8%) included individuals from both populations. In mixed clusters, the index case was Spanish-born in 53% and foreign-born in 47%. Among the foreign-born, 2.8% were ill on arrival, 30% developed TB within the first year and 50.3% developed TB within the first 2 years; 58.3% were from South America. In conclusion, half of the foreign-born TB patients developed the disease during the first 2 years after arrival, which, in most cases, was the result of endogenous reactivation. Recent TB transmission among Spanish-born and foreign-born populations, as well as bidirectional transmission between communities, contributed significantly to the burden of TB in Barcelona, suggesting the need to improve Public Health interventions in both populations.