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

Global and Regional Burden of Isoniazid-Resistant Tuberculosis

BACKGROUND

Isoniazid has been the backbone of tuberculosis chemotherapy for 6 decades. Resistance to isoniazid threatens the efficacy of treatment of tuberculosis disease and infection. To inform policies around treatment of tuberculosis disease and infection in children, we sought to estimate both the proportion of child tuberculosis cases with isoniazid resistance and the number of incident isoniazid-resistant tuberculosis cases in children, by region.

METHODS

We determined the relationship between rates of isoniazid resistance among child cases and among treatment-naive adult cases through a systematic literature review. We applied this relationship to regional isoniazid resistance estimates to estimate proportions of childhood tuberculosis cases with isoniazid resistance. We applied these proportions to childhood tuberculosis incidence estimates to estimate numbers of children with isoniazid-resistant tuberculosis.

RESULTS

We estimated 12.1% (95% confidence interval [CI] 9.8% to 14.8%) of all children with tuberculosis had isoniazid-resistant disease, representing 120,872 (95% CI 96,628 to 149,059) incident cases of isoniazid-resistant tuberculosis in children in 2010. The majority of these occurred in the Western Pacific and Southeast Asia regions; the European region had the highest proportion of child tuberculosis cases with isoniazid resistance, 26.1% (95% CI: 20.0% to 33.6%).

CONCLUSIONS

The burden of isoniazid-resistant tuberculosis in children is substantial, and risk varies considerably by setting. The large number of child cases signals extensive ongoing transmission from adults with isoniazid-resistant tuberculosis. The risk of isoniazid resistance must be considered when evaluating treatment options for children with disease or latent infection to avoid inadequate treatment and consequent poor outcomes.

Incidence of multidrug-resistant tuberculosis disease in children: systematic review and global estimates

BACKGROUND

Multidrug-resistant tuberculosis threatens to reverse recent reductions in global tuberculosis incidence. Although children younger than 15 years constitute more than 25% of the worldwide population, the global incidence of multidrug-resistant tuberculosis disease in children has never been quantified. We aimed to estimate the regional and global annual incidence of multidrug-resistant tuberculosis in children.

METHODS

We developed two models: one to estimate the setting-specific risk of multidrug-resistant tuberculosis among child cases of tuberculosis, and a second to estimate the setting-specific incidence of tuberculosis disease in children. The model for risk of multidrug-resistant tuberculosis among children with tuberculosis needed a systematic literature review. We multiplied the setting-specific estimates of multidrug-resistant tuberculosis risk and tuberculosis incidence to estimate regional and global incidence of multidrug-resistant tuberculosis disease in children in 2010.

FINDINGS

We identified 3403 papers, of which 97 studies met inclusion criteria for the systematic review of risk of multidrug-resistant tuberculosis. 31 studies reported the risk of multidrug-resistant tuberculosis in both children and treatment-naive adults with tuberculosis and were used for evaluation of the linear association between multidrug-resistant disease risk in these two patient groups. We identified that the setting-specific risk of multidrug-resistant tuberculosis was nearly identical in children and treatment-naive adults with tuberculosis, consistent with the assertion that multidrug-resistant disease in both groups reflects the local risk of transmitted multidrug-resistant tuberculosis. After application of these calculated risks, we estimated that around 999,792 (95% CI 937,877-1,055,414) children developed tuberculosis disease in 2010, of whom 31,948 (25,594-38,663) had multidrug-resistant disease.

INTERPRETATION

Our estimates underscore that many cases of tuberculosis and multidrug-resistant tuberculosis disease are not being detected in children. Future estimates can be refined as more and better tuberculosis data and new diagnostic instruments become available.

FUNDING

US National Institutes of Health, the Helmut Wolfgang Schumann Fellowship in Preventive Medicine at Harvard Medical School, the Norman E Zinberg Fellowship at Harvard Medical School, and the Doris and Howard Hiatt Residency in Global Health Equity and Internal Medicine at the Brigham and Women's Hospital.

Isoniazid-resistant tuberculosis in children: a systematic review

BACKGROUND

Isoniazid resistance is an obstacle to the treatment of tuberculosis disease and latent tuberculosis infection in children. We aim to summarize the literature describing the risk of isoniazid-resistant tuberculosis among children with tuberculosis disease.

METHODS

We did a systematic review of published reports of children with tuberculosis disease who had isolates tested for susceptibility to isoniazid. We searched PubMed, Embase and LILACS online databases up to January 12, 2012.

RESULTS

Our search identified 3403 citations, of which 95 studies met inclusion criteria. These studies evaluated 8351 children with tuberculosis disease for resistance to isoniazid. The median proportion of children found to have isoniazid-resistant strains was 8%; the distribution was right-skewed (25th percentile: 0% and 75th percentile: 18%).

CONCLUSIONS

High proportions of isoniazid resistance among pediatric tuberculosis patients have been reported in many settings suggesting that diagnostics detecting only rifampin resistance are insufficient to guide appropriate treatment in this population. Many children are likely receiving substandard tuberculosis treatment with empirical isoniazid-based regimens, and treating latent tuberculosis infection with isoniazid may not be effective in large numbers of children. Work is needed urgently to identify effective regimens for the treatment of children sick with or exposed to isoniazid-resistant tuberculosis and to better understand the scope of this problem.

Tuberculosis treatment adherence and fatality in Spain

BACKGROUND

The adherence to long tuberculosis (TB) treatment is a key factor in TB control programs. Always some patients abandon the treatment or die. The objective of this study is to identify factors associated with defaulting from or dying during antituberculosis treatment.

METHODS

Prospective study of a large cohort of TB cases diagnosed during 2006-2007 by 61 members of the Spanish Society of Pneumology and Thoracic Surgery (SEPAR). Predictive factors of completion outcome (cured plus completed treatment vs. defaulters plus lost to follow-up) and fatality (died vs. the rest of patients) were based on logistic regression, calculating odds ratios (OR) and 95% confidence intervals (CI).

RESULTS

Of the 1490 patients included, 29.7% were foreign-born. The treatment outcomes were: cured 792 (53.2%), completed treatment 540 (36.2%), failure 2 (0.1%), transfer-out 33 (2.2%), default 27 (1.8%), death 27 (1.8%), lost to follow-up 65 (4.4%), other 4 (0.3%). Completion outcome reached 93.5% and poor adherence was associated with: being an immigrant (OR = 2.03; CI:1.06-3.88), living alone (OR = 2.35; CI:1.05-5.26), residents of confined institutions (OR = 4.79; CI:1.74-13.14), previous treatment (OR = 2.93; CI:1.44-5.98), being an injecting drug user (IDU) (OR = 9.51; CI:2.70-33.47) and treatment comprehension difficulties (OR = 2.93; CI:1.44-5.98). Case fatality was 1.8% and it was associated with the following variables: age 50 or over (OR = 10.88; CI:1.12-105.01), retired (OR = 12.26;CI:1.74-86.04), HIV-infected (OR = 9.93; CI:1.48-66.34), comprehension difficulties (OR = 4.07; CI:1.24-13.29), IDU (OR = 23.59; CI:2.46-225.99) and Directly Observed Therapy (DOT) (OR = 3.54; CI:1.07-11.77).

CONCLUSION

Immigrants, those living alone, residents of confined institutions, patients treated previously, those with treatment comprehension difficulties, and IDU patients have poor adherence and should be targeted for DOT. To reduce fatality rates, stricter monitoring is required for patients who are retired, HIV-infected, IDU, and those with treatment comprehension difficulties.

[Multidrug-resistant tuberculosis]

The emergence and spread of Mycobacterium tuberculosis strains resistant to multiple drugs represent a threat for global tuberculosis control. The World Health Organization (WHO) estimates that almost 500,000 cases of M. tuberculosis resistant to isoniazid and rifampicin (multidrug-resistant, or MDR-TB), at least, emerged in 2006. In addition, new cases of extensively drug-resistant tuberculosis (XDR-TB), defined as MDR-TB with resistance to a fluoroquinolone and at least one second line injectable agent, have been reported in 45 countries in all five continents. Multidrug-resistant tuberculosis is an emerging problem in Spain but the impact of this disease is limited: the WHO estimates that 0.1% of new cases of tuberculosis and 4.3% of previously treated cases are MDR-TB. Treatment of MDR-TB is especially complicated, since this disease requires the use of drugs that are less effective and more toxic, requiring treatment to be administered over longer periods and severely reducing the probability of success. This situation poses a serious problem for low income countries, especially those with a high prevalence of human immunodeficiency virus type 1 (HIV-1) infection. MDR-TB and XDR-TB are also of special concern in wealthy countries, due to mass immigration. Therefore, tuberculosis resistant to multiple drugs should be given high priority in global public health and biomedical research.

Risk factors for multidrug-resistant tuberculosis in a tuberculosis unit in Madrid, Spain

The setting for this retrospective cohort study was a specialised tuberculosis unit in Madrid, Spain. The objective was to describe the risk factors for multidrug-resistant tuberculosis (MDR-TB). The medical records of all patients admitted to the unit were reviewed retrospectively to identify factors associated with multidrug resistance. Patients with positive culture for M. tuberculosis and with available drug-susceptibility tests were included. The variables assessed were age, gender, country of origin, homelessness, alcohol consumption, intravenous drug use, methadone substitution therapy, contact with a tuberculosis patient, sputum smear, site of disease, previous tuberculosis treatment, HIV infection, history of imprisonment, diabetes mellitus and chronic obstructive pulmonary disease. Thirty patients with MDR-TB and 666 patients with non-MDR-TB were included from the years 1997 to 2006. The only factors associated with MDR-TB in multivariate analysis were previous tuberculosis treatment (OR: 3.44; 95% CI: 1.58-7.50; p = 0.003), age group 45-64 years (OR: 3.24; 95% CI: 1.34-7.81; p = 0.009) and alcohol abuse (OR: 0.12; 95% CI: 0.03 to 0.55; p = 0.003). In our study, patients who had had previous treatment for tuberculosis, who were 45-64 years of age or who had no history of alcohol abuse were more likely to have MDR-TB.

[Resistant Mycobacterium tuberculosis strains from immigrants in the community of Madrid: current assessment]

OBJECTIVE

Immigration to Spain from countries with high rates of tuberculosis infection is increasing. The aim of this study was to describe and analyze resistance to antituberculosis drugs in strains isolated from foreign-born patients in the Community of Madrid.

PATIENTS AND METHODS

A cohort of immigrants was identified at 14 hospitals in the Community of Madrid. To assess the sensitivity of isolated strains, we used the MGIT 960 system and/or the proportion method of Canetti. Clinical and sociodemographic information was recorded for each patient. We compiled descriptive statistics and performed univariate analysis, followed by multiple logistic regression analysis.

RESULTS

From a total of 312 cases, 268 strains were isolated. Sensitivity was tested in 221 strains. The proportion of immigrants with no health care coverage was 19.9%. Thirty-one strains (14.0%) were resistant; 24 (12.6%) were in newly diagnosed cases and 6 (27.3%) were in patients who had been treated previously. Ten strains (4.5%) were multidrug resistant. Resistance to isoniazid was detected in 18 strains (9.5%). Multidrug resistance was associated with a history of prior antituberculosis treatment (odds ratio, 5.94; 95% confidence interval, 1.46-24.18).

CONCLUSIONS

Barriers to health care faced by immigrants with tuberculosis should be removed. Treatment should begin with 4 drugs while the results of sensitivity tests are pending. A history of prior antituberculosis treatment should raise a suspicion of multidrug resistance.

[Anti-tuberculosis drug resistance of Mycobacterium tuberculosis in the area of the Hospital de Sagunto from 1999 to 2004]

OBJECTIVES

This study aimed to know the drug resistance patterns of Mycobacterium tuberculosis, specifically primary drug resistance to isoniazid, in the area of the Hospital de Sagunto and to study the clinical characteristics and the risk factors associated with them.

MATERIAL AND METHODS

Patients included were those who were diagnosed of tuberculosis and whose M. tuberculosis strains were isolated in culture of a clinical sample and in whom a susceptibility test against the first line anti-tuberculosis drugs was performed from January 1999 to December 2004. Risk factors and clinical characteristics of the patients were gathered from the case- history.

RESULTS

The total number of strains isolated was 77 and the global rate of resistance was 14.1%. Rate of primary drug resistance was 12.1%, and acquired 27%. No multidrug resistant case was detected. Primary drug resistance was 3% to isoniazid, 3% to rifampin, 3% to pyrazinamid, 4.5% to ethambutol and 3% to streptomycin. Acquired drug resistance was 9.1% against isoniazid and 27% against streptomicin, no resistance against the other drugs tested being found.

CONCLUSIONS

The low level of primary drug resistance against isoniazid allows us to start treatment with three-drug regimes in new cases of native population. In our hospital area, the risk factors associated with drug resistances were smoking habit and alcoholism. Although all patients with drug resistance presented pulmonary disease, the differences were not statistically significant. However, the higher rate of pleural effusion in patients with drug resistance was statistically significant.

Impacto de la inmigración en las resistencias de Mycobacterium tuberculosis en la provincia de Castellón: 1995-2003

BACKGROUND AND OBJECTIVE

The aim of this study was to know the frequency of resistant Mycobacterium tuberculosis in the province of Castellon (Spain) and to determine whether immigration is associated with resistance.

MATERIAL AND METHOD

All culture-positive cases diagnosed in Castellon from January 1995 to December 2003 were included in this retrospective study. Susceptibility tests were performed using the Canetti's proportion method and the MB/BacT system. Risk factors associated with tuberculosis were investigated in every case.

RESULTS

Six hundred and forty-four cases of tuberculosis were studied: 560 were Spaniards and 84 foreigners. The overall frequency of resistant strains was 5%. The total rate of resistance in Spaniards was 3.7% and in foreigners 13.1%. In Spanish new cases, drug resistance was 3.2% and in foreigners new cases it was 13.9%. In previously treated cases, drug resistance was 6.7% in Spaniards and 0% in immigrants. No acquired drug resistance was detected in immigrants. Of those strains with resistance, 71.9% had resistance to only one drug, 18.7% to two drugs and 9.4% to more than two drugs. Multidrug-resistance was found in 9.4% of the resistant cases, and in 0.5% of all the studied population. The presence of resistant Mycobacterium tuberculosis was associated with the fact of having a foreign nationality (OR = 3.87; p < 0.001).

CONCLUSIONS

Tuberculosis has been diminishing in Spanish patients in Castellon. Nevertheless, there is an important increase in the number of cases in foreigners, which is associated with a major percentage of resistances. Epidemiological vigilance efforts should especially concentrate on this group in order to support the progressive declivity of the disease.

[Effects of HIV status and other variables on the outcome of tuberculosis treatment in Spain]

OBJECTIVE

To analyze the effect of human immunodeficiency virus (HIV) status and other variables on the outcome of tuberculosis treatment in Spain.

PATIENTS AND METHODS

Multicenter retrospective cohort study in 6 autonomous communities of Spain (from May 1996 to April 1997). Data on treatment outcome were collected for new cases of tuberculosis in accordance with European guidelines. Follow up of patients continued for 3 months after scheduled end of treatment.

RESULTS

Of the 4899 patients included, 3417 (69.7%) had a satisfactory outcome, 438 (8.9%) died before or during treatment, and 1044 (21.4%) had a potentially unsatisfactory outcome. On stratification by HIV status, satisfactory outcome, mortality, and potentially unsatisfactory outcome were reported for 43.4%, 21.5%, and 35.1%, respectively, of HIV-positive patients; 71%, 6.2%, and 22.8%, respectively, of HIV-negative patients; and 74.3%, 7.5%, and 18.2%, respectively, of patients with no HIV status available. HIV modified the effect of several variables on the outcome of treatment, and so separate logistic regression models for each HIV category were constructed. Among HIV-positive patients, mortality increased in patients with neoplastic disease and in users of drugs by nonintravenous routes of administration, whereas potentially unsatisfactory outcomes increased in intravenous drug users and in women.

CONCLUSIONS

In Spain, the outcome of tuberculosis treatment is much worse in HIV-positive patients. Drug use and presence of neoplastic disease substantially affect mortality.

Molecular analysis of isoniazid and rifampin resistance in Mycobacterium tuberculosis isolates recovered from Barcelona

We studied the presence of mutations in the whole katG gene and specific regions of the oxyR-ahpC and mabA-inhA regulatory region in 61 Mycobacterium tuberculosis isoniazid-resistant isolates. An 81-bp region of the rpoB gene was also sequenced in 17 rifampin-resistant strains. Alterations in the katG gene were detected in 55% of the isolates. Mutation in codon 315 was the most prevalent (32%). Strains showed a high level of resistance, and most maintained a substantial catalase-peroxidase activity. Three strains with an isoniazid MIC of >or=32 microg/ml lacked catalase-peroxidase activity. Two of them had deletions in the catalytic domain of the KatG protein. One strain with deletion and three strains with mutations in the C-terminal domain showed low-level resistance and conserved the catalase-peroxidase activity. Mutations in the mabA-inhA regulatory region were identified in 32% of the isolates. All had low-level resistance, and the vast majority conserved catalase-peroxidase activity. Seventeen percent of the isoniazid-resistant isolates had no detectable alterations at the studied loci. Resistance to rifampin was associated with mutations in the 81-bp of the rpoB gene in all cases. IS6110 analysis indicated that recent transmission contributed substantially to the emergence of isoniazid- resistant tuberculosis in Barcelona through short transmission chains. A rapid genotypic assay, including the 315-katG codon and the -15 nucleotide of the mabA-inhA regulatory region, may cover 62% of isoniazid- resistant strains in Barcelona. In contrast, the targeting of the 81-bp region of rpoB would detect all our rifampin-resistant isolates.

Direct detection in clinical samples of multiple gene mutations causing resistance of Mycobacterium tuberculosis to isoniazid and rifampicin using fluorogenic probes

BACKGROUND

This study evaluates a method based on real-time PCR for direct detection in clinical samples of the common mutations responsible for isoniazid and rifampicin resistance of Mycobacterium tuberculosis.

METHODS

Six pairs of fluorogenic 5' exonuclease probes (Taqman), mutated and wild-type, were designed for six targets: codon 315 of katG, substitution C209T in the regulatory region of inhA, and codons 513, 516, 526 and 531 of rpoB.

RESULTS

A total of 98 clinical samples harbouring resistant bacilli from 55 patients and 126 samples harbouring susceptible bacilli from 126 patients were processed. The isolates from samples were tested for drug susceptibility with the radiometric method and sequenced for the same genetic targets. Among the samples, 93 harboured isoniazid-resistant bacilli. According to the sequencing results, 30 had mutations in katG, 30 in inhA and 33 (35.4%) had no mutations in these targets. All 27 clinical specimens harbouring rifampicin-resistant bacilli showed mutations in rpoB. The detection threshold of this method in detecting target genes in serial dilutions of artificial samples was 1.5 x 10(3) cfu/mL. In clinical samples, the sensitivity ranged from 30.4 to 35.3% for smear-negative samples and from 95.1 to 99.2% for smear-positive samples, with a specificity of 100%. In this study, the overall sensitivity in detecting patients having the target mutations was 74.3%.

CONCLUSIONS

The main advantage of the described method is the possibility of detecting rifampicin and isoniazid resistance within 48-72 h after sample collection, with a sensitivity of nearly 100% in smear-positive samples if the chosen target is responsible for the resistance.

[Drugs with activity against Mycobacterium tuberculosis]

Treatment for Mycobacterium tuberculosis has to be lengthy, since populations of this bacillus differ in metabolic activity, and it has to consist of various associated drugs, since spontaneous chromosome mutations can give rise to drug resistance. The multiresistant phenotype emerges with sequential acquisition of mutations in several loci of separate genes. Knowledge of the mechanisms of resistance permits the development of molecular techniques for the early detection of resistant strains, thereby making proper control possible. Tuberculosis treatment includes isoniazid, rifampicin and pyrazinamide during the first two months and isoniazid and rifampicin to complete six months of treatment. In specific situations, a fourth drug is added, ethambutol for adults and streptomycin for children in whom visual acuity cannot be monitored. This review describes the characteristics, activity, resistance mechanisms and side effects associated with the various antituberculosis drugs.

[Imported tuberculosis: an emerging disease in industrialised countries]

BACKGROUND

The aim of this study was to describe the characteristics of imported tuberculosis (TB) in Barcelona during 1999 and 2000.

MATERIAL AND METHOD

Epidemiological surveillance questionnaire.

RESULTS

During 1999 and 2000, a 7.9% decrease in TB cases was observed among the native population in Barcelona, whereas cases among immigrants grew up to 47.2%. In 2000, 449 TB cases were detected among the native population (incidence, 29.5/100,000) and 121 among immigrants (incidence, 555.9/100,000). Three outbreaks were identified, involving one Indian community (11 cases), two Dominican families (4 cases) and one city school (2 cases) whose index case was a cooperant. Isolated strains of Mycobacterium tuberculosis at the first, second and third outbreak were multisensitive, multidrug-resistant and isoniazid-resistant, respectively.

CONCLUSIONS

The emergence of imported TB cases in Barcelona over 1999 and 2000 suggests that current preventive guidelines must be reviewed.