Search

Aerobic (5-day-old cultures) and nonreplicating (dormant) Mycobacterium tuberculosis (5-, 12-, and 19-day-old cultures) bacteria were treated with rifampin (R), moxifloxacin (MX), metronidazole (MZ), amikacin (AK), or capreomycin (CP) for 7, 14, and 21 days. R-MX-MZ-AK and R-MX-MZ-CP killed both aerobic and dormant bacilli in 21 days, as shown by lack of regrowth in solid and liquid media. R-MX-MZ-AK and R-MX-MZ-CP also caused a strong decrease of nonreplicating bacilli in 7 days in a cell-based dormancy model.

Setting: Quality assurance for the World Health Organization (WHO)/International Union Against Tuberculosis and Lung Disease (The Union) global tuberculosis (TB) drug resistance surveillance programme., Objective: To monitor the quality of drug susceptibility testing (DST) in different countries., Methods: In 2002-2003 and 2005-2006, 20 Mycobacterium tuberculosis strains were sent by the WHO/Union Supranational Reference Laboratory of Rome to TB reference laboratories in Albania, Bahrain, Kosovo, Mozambique, Oman, Qatar and Turkey for external quality control (EQC)., Results: In 2002-2003, the specificity, sensitivity, efficiency, reproducibility and predictive values for resistance/susceptibility were >or=90% for streptomycin (SM), isoniazid (INH) and ethambutol (EMB). In 2005-2006, all statistical values were >or=96% for SM, INH, rifampicin and EMB., Conclusion: EQC improved the quality of M. tuberculosis DST in the participating countries.

Long-term nonreplicating (dormant) Mycobacterium tuberculosis populations (26-day-old cells) were sterilized by metronidazole plus rifampin, but not by metronidazole or rifampin alone, after 7 and 11 days of exposure to the drugs. Lower or no drug activity was observed against 19- or 12-day-old dormant or 5-day-old actively replicating populations.

Moxifloxacin (MOX), an 8-methoxyquinolone compound, is now widely used for the treatment of bacterial infections and also accepted as 2nd-line drug for the treatment of multidrug-resistant (MDR) tuberculosis. To tentatively correlate the clinical outcome with in vitro results, we sought to set up susceptibility test conditions for Mycobacterium tuberculosis against MOX by using the reference agar proportion method, the BACTEC 460 radiometric system, and the recently validated nonradiometric BACTEC MGIT 960 system. Our aim was to determine the critical MOX test concentration to be used with the abovementioned methods for routine susceptibility testing. MICs were determined for 20 pan-susceptible strains, 10 MDR strains, and 10 fluoroquinolone-resistant strains with defined gyrA mutations. MOX MICs resulted in a bimodal pattern with values for gyrA mutants considerably higher than those for pan-susceptible and MDR strains. Our data showed that a concentration of 0.5 microg/mL allowed a clear-cut separation between susceptible and resistant strains when tested by all the studied methods. Confirmatory test with a subset of pan-susceptible and MDR isolates appeared to validate the selected critical concentration. The MOX-resistant strains were almost isolated from patients with prior fluoroquinolone exposure.

Setting: After the collapse of the Soviet Union, countries in the region faced a dramatic increase in tuberculosis cases and the emergence of drug resistance., Objective: To discuss the relevance of the DOTS strategy in settings with a high prevalence of drug resistance., Design: Retrospective analysis of one-year treatment outcomes of short-course chemotherapy (SCC) and results of drug susceptibility testing (DST) surveys of six programmes located in the former Soviet Union: Kemerovo prison, Russia; Abkhasia, Georgia; Nagorno-Karabagh, Azerbaijan; Karakalpakstan, Uzbekistan; Dashoguz Velayat, Turkmenistan; and South Kazakhstan Oblast, Kazakhstan. Results are reported for new and previously treated smear-positive patients., Results: Treatment outcomes of 3090 patients and DST results of 1383 patients were collected. Treatment success rates ranged between 87% and 61%, in Nagorno-Karabagh and Kemerovo, respectively, and failure rates between 7% and 23%. Any drug resistance ranged between 66% and 31% in the same programmes. MDR rates ranged between 28% in Karakalpakstan and Kemerovo prison and 4% in Nagorno-Karabagh., Conclusion: These results show the limits of SCC in settings with a high prevalence of drug resistance. They demonstrate that adapting treatment according to resistance patterns, access to reliable culture, DST and good quality second-line drugs are necessary.

The emergence and spread of multidrug-resistant (MDR) Mycobacterium tuberculosis (MT) represents a worldwide health care problem because of the difficulty in treating these infections. Development of drug resistance in MT arises mainly by mutation of chromosomal genes. To investigate the evolution of a MT population during a long-lasting infection, the phenotypic and genotypic changes in the drug resistance of 10 sequential MT isolates from a noncompliant chronically infected patient were investigated. During more than 12 years of active disease, a MDR population developed; molecular typing showed one single parental strain that infected the patient and persisted throughout the disease. Molecular analysis of the drug resistance-related genes revealed that discrete subpopulations evolved over time from the parental strain by acquiring and accumulating resistance-conferring mutations to isoniazid, rifampin, and streptomycin. Overall, these observations indicate that during a chronic infection, several subpopulations may coexist in the same patient with different drug susceptibility profiles.

Objective: To determine the prevalence of resistance to the main anti-tuberculosis drugs in newly and previously treated tuberculosis patients in Italy and to evaluate the contribution of foreign-born and human immunodeficiency virus (HIV) positive cases to drug resistance., Methods: Methods and definitions were derived from the WHO/IUATLD Global Project on Anti-tuberculosis Drug Resistance Surveillance. Univariate and multivariate analysis was used to study prevalence rates of drug resistance in risk groups., Results: In a national survey in Italy, 810 initial isolates of Mycobacterium tuberculosis (683 from new cases, 115 from retreatment cases and 12 from patients whose treatment history was unknown/dubious) were analysed. Low prevalence of drug and multidrug resistance was found in the new cases (isoniazid 2.9%; rifampicin 0.8%; multidrug resistance 1.2%; any drug resistance 12.3%). The prevalence of resistance to isoniazid and rifampicin was significantly higher in immigrants and HIV-positive subjects, respectively. A high prevalence of drug resistance was found in cases with previous treatment failure or default (isoniazid 5.2%; rifampicin 4.3%; multidrug resistance 36.5%; any drug resistance 61.7%)., Recommendations: Special efforts are necessary to monitor trends in drug resistance and to ensure favourable treatment outcomes among immigrants and HIV-positive tuberculosis cases.

The in vitro activity of 16 antimicrobial agents against 46 drug-resistant strains of Mycobacterium tuberculosis recently isolated from Italian patients was determined. As for first-line antituberculosis drugs, while isoniazid was ineffective against all the strains tested, resistance to streptomycin, rifampicin, pyrazinamide, and ethambutol was 80.4%, 71.7%, 39.1%, and 8.7%, respectively. Among second-line antituberculous drugs, resistance to ciprofloxacin, ofloxacin, and sparfloxacin and to amikacin and kanamycin was around 20%. About 10% of the strains were resistant to capreomycin and cycloserine and 4.3% were resistant to ethionamide; no strain was found to be resistant to thiacetazone, para-aminosalicylic acid, and viomycin. Although all strains displayed a rather continuous distribution of minimal inhibitory concentrations (MICs), a bimodal distribution was observed for rifampicin, amikacin, and kanamicin, with very high MIC values for resistant strains; relatively low MICs were found for fluoroquinolone-resistant strains. Among the small number of strains resistant to second-line agents, low resistant levels were observed. Restriction fragment length polymorphism analysis showed few strain clusters with resistance to first-line antituberculous drugs and aminoglycosides, fluoroquinolones, or both. Altogether, these results showed that second-line agents were still active against the isoniazid-resistant and multiply first-line resistant strains tested, with none or low resistance levels; these observations can be of importance for the treatment of multidrug-resistant tuberculosis in Italy.