Molecular detection of rifampin and isoniazid resistance to guide chronic TB patient management in Burkina Faso

<p>Abstract</p> <p>Background</p> <p>Drug-resistant tuberculosis (DR-TB) is considered a real threat to the achievement of TB control. Testing of mycobacterial culture and testing of drug susceptibility (DST) capacity are limited in resource-poor countries, therefore inadequate treatment may occur, favouring resistance development. We evaluated the molecular assay GenoType^®MTBDR<it>plus </it>(Hain Lifescience, Germany) in order to detect DR-TB directly in clinical specimens as a means of providing a more accurate management of chronic TB patients in Burkina Faso, a country with a high TB-HIV co-infection prevalence.</p> <p>Methods</p> <p>Samples were collected in Burkina Faso where culture and DST are not currently available, and where chronic cases are therefore classified and treated based on clinical evaluation and sputum-smear microscopy results. One hundred and eight chronic TB patients (sputum smear-positive, after completing a re-treatment regimen for pulmonary TB under directly observed therapy) were enrolled in the study from December 2006 to October 2008. Two early morning sputum samples were collected from each patient, immediately frozen, and shipped to Italy in dry ice. Samples were decontaminated, processed for smear microscopy and DNA extraction. Culture was attempted on MGIT960 (Becton Dickinson, Cockeysville, USA) and decontaminated specimens were analyzed for the presence of mutations conferring resistance to rifampin and isoniazid by the molecular assay GenoType^®MTBDR<it>plus</it>.</p> <p>Results</p> <p>We obtained a valid molecular test result in 60/61 smear-positive and 47/47 smear-negative patients.</p> <p>Among 108 chronic TB cases we identified patients who (i) harboured rifampin- and isoniazid-susceptible strains (n 24), (ii) were negative for MTB complex DNA (n 24), and (iii) had non-tuberculous mycobacteria infections (n 13). The most represented mutation conferring rifampin-resistance was the D516V substitution in the hotspot region of the <it>rpoB </it>gene (43.8% of cases). Other mutations recognized were the H526D (15.6%), the H526Y (15.6%), and the S531L (9.4%).</p> <p>All isoniazid-resistant cases (n 36) identified by the molecular assay were carrying a S315T substitution in the <it>katG </it>gene. In 41.7% of cases, a mutation affecting the promoter region of the <it>inhA </it>gene was also detected.</p> <p>Conclusion</p> <p>The GenoType^®MTBDR<it>plus </it>assay performed directly on sputum specimens improves the management of chronic TB cases allowing more appropriate anti-TB regimens.</p

Monitoring the quality of laboraties and the prevalence of resistance to antituberculosis drugs: Italy, 1998-2000

In 1998 a network of 20 regional tuberculosis (TB) laboratories (the Italian Multicentre Study on Resistance to Antituberculosis drugs (SMIRA) network) was established in Italy to implement proficiency testing and to monitor the prevalence of drug resistance nationwide. The network managed 30% of all TB cases reported in Italy each year. The aim of the present report is to describe: 1) the accuracy of drug-susceptibility testing in the network; 2) the prevalence of drug resistance for the period 1998-2000. Data were collected from the network laboratories. Sensitivity to streptomycin and ethambutol increased from the first survey (1998-1999) to the second survey (2000) from 87.7 to 91.9%. Specificity, predictive values for resistance and susceptibility, efficiency and reproducibility were consistent in both surveys. In previously untreated cases, the prevalence of multidrug-resistance was the same in both surveys (1.2%), while a slight decrease from the first to the second survey was observed for monoresistance to rifampicin (from 0.8 to 0.4%) and isoniazid (from 2.9 to 2%,). The significant association found between isoniazid resistance and immigration is a useful indicator for both clinicians managing individual tuberculosis cases and public health services planning control strategies

Mycobacteriun szulgai

depositario sequenza genica del batterio Mycobacterium szulga

Mycetoma of the maxillary sinus: endodontic and microbiological correlations.

Objective. The purpose was to show the capacity of zinc oxide and eugenol to affect the growth of Aspergillus fumigatus. Study design. An in vitro microbiological analysis was conducted on samples from infected maxillary sinuses and on 3 different endodontic sealers. Results. Testsshowed that zinc oxide in solution favors the growth of Aspergillus fumigatus, while eugenol inhibits this growth, even when mixed with zinc oxide powder. This inhibiting effect decreases over time. A reduced effectiveness was demonstrated over a 75-day period. Conclusions. The hypothesis is that the diminishing concentration of eugenol over time in endodontic sealers allows the zinc oxide to support growth of Aspergillus fumigatus. This is reinforced by clinical experience, where mycetoma has developed years after endodontic therapy with excess sealer in the maxillary sinus