Mycobacterium tuberculosis drug resistance, Abkhazia

Extensively drug-resistant tuberculosis in India: Current evidence on diagnosis & management

Emergence of extensively drug-resistant tuberculosis (XDR-TB) has significantly threatened to jeopardize global efforts to control TB, especially in HIV endemic regions. XDR-TB is mainly an iatrogenically created issue, and understanding the epidemiological and risk factors associated with it is of paramount importance in curbing this menace. Emergence of this deadly phenomenon can be prevented by prompt diagnosis and effective treatment with second-line drugs in rifampicin-resistant TB (RR-TB) as well as multidrug-resistant TB (MDR-TB) patients. Optimal treatment of RR-TB, MDR-TB and XDR-TB cases alone will not suffice to reduce the global burden. The TB control programmes need to prioritize on policies focusing on the effective as well as rational use of first-line drugs in every newly diagnosed drug susceptible TB patients so as to prevent the emergence of drug resistance.

Fluoroquinolone resistance in non-multidrug-resistant tuberculosis-a surveillance study in New South Wales, Australia, and a review of global resistance rates

BACKGROUND

Fluoroquinolones (FQs) are used for drug-susceptible tuberculosis (TB) in patients unable to tolerate first-line agents. Current trials are also investigating these drugs in empiric first-line TB therapy, to improve outcomes and allow for shortened treatment regimens. Widespread FQ use in the community has resulted in FQ resistance in many microorganisms, including Mycobacterium tuberculosis. Despite this, FQ drug susceptibility testing (DST) is rarely performed in non-multidrug-resistant TB (non-MDR-TB).

METHODS

We conducted a 1-year surveillance study of FQ resistance on all MTB isolates from New South Wales (NSW), Australia. In addition, we performed a literature review of previous studies assessing FQ resistance in non-MDR-TB to summarize the global extent of this resistance pattern.

RESULTS

Two (0.6%) out of 357 MTB isolates from NSW were found to be FQ-resistant. One isolate was an MDR strain (11% of all MDR-TB). The other was isoniazid-monoresistant (0.3% of all non-MDR-TB). Eleven studies from 10 countries had performed FQ resistance surveillance on non-MDR-TB. In the majority of these studies, FQ resistance was found to be low (mean 1%; 95% confidence interval 0.2-2%).

CONCLUSIONS

FQ resistance in non-MDR-TB is uncommon in NSW, Australia. The existing global evidence suggests that FQ resistance remains largely confined to MDR-TB strains. In the majority of TB endemic regions, however, FQ resistance in non-MDR-TB has not been assessed. Knowledge of the prevalence of FQ resistance in MTB is essential to guide the rational use of these drugs, including their feasibility as first-line agents.

IS6110 restriction fragment length polymorphism typing of drug-resistant Mycobacterium tuberculosis strains from northeast South Africa

Tuberculosis (TB) remains a deadly infectious disease affecting millions of people worldwide; 95% of TB cases, with 98% of death occur in developing countries. The situation in South Africa merits special attention. A total of 21,913 sputum specimens of suspected TB patients from three provinces of South Africa routinely submitted to the TB laboratory of Dr. George Mukhari (DGM) Hospital were assayed for Mycobacterium tuberculosis (MTB) growth and antibiotic susceptibility. The genetic diversity of 338 resistant strains were also studied. DNA isolated from the strains were restricted with Pvu II, transferred on to a nylon membrane and hybridized with a PCR-amplified horseradish peroxidase 245 bp IS6110 probe. Of the 338 resistant strains, 2.09% had less than 5 bands of IS6110, and 98% had 5 or more bands. Unique restriction fragment length polymorphism (RFLP) patterns were observed in 84.3% of the strains, showing their epidemiological independence, and 15.7% were grouped into 22 clusters. Thirty-two strains (61.5%) from the 52 that clustered were from Mpumalanga, 16/52 (30.8%) from Gauteng, and 4/52 (9.6%) from Limpopo province. Clustering was not associated with age. However, strains from male patients in Mpumalanga were more likely to be clustered than strains from male patients in Limpopo and/or Gauteng province. The minimum estimate for the proportion of resistant TB that was due to transmission is 9.06% (52-22 = 30/331). Our results indicate that transmission of drug-resistant strains may contribute substantially to the emergence of drug-resistant tuberculosis in South Africa.

Treatment of tuberculosis in a region with high drug resistance: outcomes, drug resistance amplification and re-infection

Introduction

Emerging antituberculosis drug resistance is a serious threat for tuberculosis (TB) control, especially in Eastern European countries.

Methods

We combined drug susceptibility results and molecular strain typing data with treatment outcome reports to assess the influence of drug resistance on TB treatment outcomes in a prospective cohort of patients from Abkhazia (Georgia). Patients received individualized treatment regimens based on drug susceptibility testing (DST) results. Definitions for antituberculosis drug resistance and treatment outcomes were in line with current WHO recommendations. First and second line DST, and molecular typing were performed in a supranational laboratory for Mycobacterium tuberculosis (MTB) strains from consecutive sputum smear-positive TB patients at baseline and during treatment.

Results

At baseline, MTB strains were fully drug-susceptible in 189/326 (58.0%) of patients. Resistance to at least H or R (PDR-TB) and multidrug-resistance (MDR-TB) were found in 69/326 (21.2%) and 68/326 (20.9%) of strains, respectively. Three MDR-TB strains were also extensively resistant (XDR-TB). During treatment, 3/189 (1.6%) fully susceptible patients at baseline were re-infected with a MDR-TB strain and 2/58 (3.4%) PDR-TB patients became MDR-TB due to resistance amplification. 5/47 (10.6%) MDR- patients became XDR-TB during treatment. Treatment success was observed in 161/189 (85.2%), 54/69 (78.3%) and 22/68 (32.3%) of patients with fully drug susceptible, PDR- and MDR-TB, respectively. Development of ofloxacin resistance was significantly associated with a negative treatment outcome.

Conclusion

In Abkhazia, a region with high prevalence of drug resistant TB, the use of individualized MDR-TB treatment regimens resulted in poor treatment outcomes and XDR-TB amplification. Nosocomial transmission of MDR-TB emphasizes the importance of infection control in hospitals.

Mycobacterium tuberculosis Beijing lineage favors the spread of multidrug-resistant tuberculosis in the Republic of Georgia

High rates and transmission of multidrug-resistant (MDR) tuberculosis (TB) have been associated with the Mycobacterium tuberculosis complex (MTBC) Beijing lineage, pointing to the importance of pathogen genetic factors for the modulation of infection outcome and epidemiology. We present here an in-depth analysis of the population structure of MTBC strains from the Republic of Georgia, a high-incidence setting at the Black Sea Coast. Phylogenetic lineages were identified based on 24-locus MIRU-VNTR (for mycobacterial interspersed repetitive unit-variable number tandem repeat) and spoligotyping analysis. Clusters of strains with identical genotyping profiles were determined as an indicator for the rate of recent transmission. Among the 183 M. tuberculosis isolates investigated, the most prominent lineage found was Beijing (26%), followed by the LAM (18%), Ural (12%), and Haarlem (5%) strains. A closely related previously undefined phylogenetic group (62 strains) showed a genotyping pattern similar to laboratory strain H37RV and was denominated as "Georgia-H37RV-like." Although isoniazid resistance was found among strains of different lineages, MDR TB was nearly completely restricted to Beijing strains (P < 0.0001). Approximately 50% of the isolates were grouped in clusters, indicating a high rate of recent transmission. Our data indicate that, in addition to the confirmation of the importance of Beijing genotype strains for the TB epidemiology in former Soviet Union countries, a high-population diversity with strains of the LAM, Ural, Haarlem, and a previously undefined lineage represents nearly two-thirds of the strains found in Georgia. Higher rates among previously treated and MDR TB patients point to a higher potential of lineage Beijing to escape therapy and develop MDR TB.

Characteristics of drug-resistant tuberculosis in Abkhazia (Georgia), a high-prevalence area in Eastern Europe

Although multidrug-resistant (MDR) tuberculosis (TB) is a major public health problem in Eastern Europe, the factors contributing to emergence, spread and containment of MDR-TB are not well defined. Here, we analysed the characteristics of drug-resistant TB in a cross-sectional study in Abkhazia (Georgia) between 2003 and 2005, where standard short-course chemotherapy is supplemented with individualized drug-resistance therapy. Drug susceptibility testing (DST) and molecular typing were carried out for Mycobacterium tuberculosis complex strains from consecutive smear-positive TB patients. Out of 366 patients, 60.4% were resistant to any first-line drugs and 21% had MDR-TB. Overall, 25% of all strains belong to the Beijing genotype, which was found to be strongly associated with the risk of MDR-TB (OR 25.9, 95% CI 10.2-66.0) and transmission (OR 2.8, 95% CI 1.6-5.0). One dominant MDR Beijing clone represents 23% of all MDR-TB cases. The level of MDR-TB did not decline during the study period, coinciding with increasing levels of MDR Beijing strains among previously treated cases. Standard chemotherapy plus individualized drug-resistance therapy, guided by conventional DST, might be not sufficient to control MDR-TB in Eastern Europe in light of the spread of "highly transmissible" MDR Beijing strains circulating in the community.

High prevalence of multidrug-resistant tuberculosis in Georgia

BACKGROUND

Tuberculosis (TB) has emerged as a serious public health problem in the country of Georgia. However, little or no data exist on rates and risk factors for drug-resistant TB, including multidrug-resistant (MDR)-TB, in Georgia.

OBJECTIVE

To assess the prevalence and risk factors for drug-resistant TB.

METHODS

A cross-sectional prospective survey of patients with suspected pulmonary TB was carried out at four sentinel sites (Tbilisi, Zugdidi, Kutaisi, and Batumi) in Georgia between January 1, 2001 and December 31, 2004.

RESULTS

Among 1422 patients with suspected pulmonary TB, 996 (70.0%) were culture positive; 931/996 (93.5%) had drug susceptibility testing performed. Overall, 64.0% of patients (48.3% of new and 85.3% of retreatment cases) had positive cultures for Mycobacterium tuberculosis resistant to >or=1 first-line antituberculosis drugs. The overall prevalence of MDR-TB was 28.1% (10.5% of newly diagnosed patients and 53.1% of retreatment cases). In multivariate analysis, risk factors for MDR-TB included: being a retreatment case (prevalence ratio (PR)=5.28, 95% CI 3.95-7.07), history of injection drug use (PR=1.59, 95% CI 1.21-2.09), and female gender (PR=1.36, 95% CI 1.12-1.65).

CONCLUSIONS

MDR-TB has emerged as a serious public health problem in Georgia and will greatly impact TB control strategies.

Risk factors and algorithms to identify hepatitis C, hepatitis B, and HIV among Georgian tuberculosis patients

OBJECTIVES

To determine prevalence, risk factors, and simple identification algorithms for HIV, hepatitis B, and hepatitis C co-infection; factors that may predispose for anti-tuberculosis therapy-induced hepatotoxicity.

METHODS

We recruited 300 individuals at in-patient tuberculosis hospitals in three cities in Georgia, administered a behavioral questionnaire, and tested for antibody to HIV, hepatitis C (HCV), hepatitis B core antigen (anti-HBc), and the hepatitis B surface antigen (HBsAg).

RESULTS

Of the individuals tested, 0.7% were HIV positive, 4.3% were HBsAg positive, 8.7% were anti-HBc positive, and 12.0% were HCV positive. In multivariable analysis, a history of blood transfusion, injection drug use, and prison were significant independent risk factors for HCV, while a history of blood transfusion, injection drug use, younger age at sexual debut, and a high number of sex partners were significant risk factors for HBV. Three-questionnaire item algorithms predicted HCV serostatus 74.1% of the time and HBV serostatus 85.2% of the time.

CONCLUSIONS

Treatment of tuberculosis patients in resource-limited countries with concurrent epidemics of HCV, HBV, and HIV may be associated with significant hepatotoxicity. Serologic screening of tuberculosis patients for HBV, HCV, and HIV or using behavioral algorithms to identify patients in need of intensive monitoring during anti-tuberculosis therapy may reduce this risk.

Worldwide emergence of extensively drug-resistant tuberculosis

Mycobacterium tuberculosis strains are becoming resistant to not only the most powerful first-line drugs but also many second-line drugs.

Mycobacterium tuberculosis strains that are resistant to an increasing number of second-line drugs used to treat multidrug-resistant tuberculosis (MDR-TB) are becoming a threat to public health worldwide. We surveyed the Network of Supranational Reference Laboratories for M. tuberculosis isolates that were resistant to second-line anti-TB drugs during 2000–2004. We defined extensively drug-resistant TB (XDR-TB) as MDR-TB with further resistance to ≥3 of the 6 classes of second-line drugs. Of 23 eligible laboratories, 14 (61%) contributed data on 17,690 isolates, which reflected drug susceptibility results from 48 countries. Of 3,520 (19.9%) MDR-TB isolates, 347 (9.9%) met criteria for XDR-TB. Further investigation of population-based trends and expanded efforts to prevent drug resistance and effectively treat patients with MDR-TB are crucial for protection of public health and control of TB.

Risk of Acquired Drug Resistance during Short-Course Directly Observed Treatment of Tuberculosis in an Area with High Levels of Drug Resistance

BACKGROUND

Data on the performance of standardized short-course directly observed treatment (DOTS) of tuberculosis (TB) in areas with high levels of drug resistance and on the potential impact of DOTS on amplification of resistance are limited. Therefore, we analyzed treatment results from a cross-sectional sample of patients with TB enrolled in a DOTS program in an area with high levels of drug resistance in Uzbekistan and Turkmenistan in Central Asia.

METHODS

Sputum samples for testing for susceptibility to 5 first-line drugs and for molecular typing were obtained from patients starting treatment in 8 districts. Patients with sputum smear results positive for TB at the end of the intensive phase of treatment and/or at 2 months into the continuation phase were tested again. RESULTS. Among 382 patients with diagnoses of TB, 62 did not respond well to treatment and were found to be infected with an identical Mycobacterium tuberculosis strain when tested again; 19 of these patients had strains that developed new or additional drug resistance. Amplification occurred in only 1.2% of patients with initially susceptible or monoresistant TB strains, but it occurred in 17% of those with polyresistant strains (but not multidrug-resistant strains, defined as strains with resistance to at least isoniazid and rifampicin) and in 7% of those with multidrug-resistant strains at diagnosis. Overall, 3.5% of the patients not initially infected with multidrug-resistant TB strains developed such strains during treatment. Amplification of resistance, however, was found only in polyresistant Beijing genotype strains.

CONCLUSIONS

High levels of amplification of drug resistance demonstrated under well-established DOTS program conditions reinforce the need for implementation of DOTS-Plus for multidrug-resistant TB in areas with high levels of drug resistance. The strong association of Beijing genotype and amplification in situations of preexisting resistance is striking and may underlie the strong association between this genotype and drug resistance.

Usefulness of the BACTEC MGIT 960 system for isolation of mycobacterium tuberculosis from sputa subjected to long-term storage

The recovery of Mycobacterium tuberculosis from sputa positive or negative for acid-fast bacilli that were stored for 17 +/- 7 days and inoculated in the BACTEC MGIT 960 system (MGIT) was higher than that from sputa inoculated in Lowenstein-Jensen medium. MGIT is useful for isolation of M. tuberculosis from sputa subjected to long-term storage.