Acquired drug resistance during inadequate therapy in a young child with tuberculosis.

Drug resistance in children with tuberculosis is usually primary (transmitted); however, resistance acquisition during treatment is possible. We describe a child with tuberculosis who acquired drug resistance while receiving directly observed but inadequate first-line therapy and the programmatic and clinical factors that may have contributed to resistance acquisition.

Discordant drug susceptibility for mycobacterium tuberculosis within families.

Children with presumed tuberculosis who are in contact with a multidrug-resistant source case should be treated according to the drug susceptibility of the source case's isolate. However, it is important to obtain a microbiologic diagnosis as it is possible for the child to have a different susceptibility profile to the source case. We present 2 such cases.

Impact of drug resistance on clinical outcome in children with tuberculous meningitis.

BACKGROUND: Tuberculous meningitis (TBM) is associated with delayed diagnosis and poor outcome in children. This study investigated the impact of drug resistance on clinical outcome in children with TBM. METHODS: All children (0-13 years) were included if admitted to Tygerberg Children's Hospital, Cape Town, South Africa, from January 2003 to April 2009 with a diagnosis of either confirmed TBM, or probable TBM with mycobacterial isolation from a site other than cerebrospinal fluid. Mycobacterial samples underwent drug susceptibility testing to rifampin and isoniazid. Children were treated with isoniazid, rifampin, pyrazinamide and ethionamide according to local guidelines. RESULTS: One hundred twenty-three children were included; 13% (16 of 123) had any form of drug resistance, and 4% (5 of 123) had multidrug-resistant tuberculosis. Time from start of symptoms to appropriate treatment was longer in children with any drug resistance (median: 31 days versus 9 days; P=0.001). In multivariable analysis, young age (P=0.013) and multidrug-resistant tuberculosis (adjusted odds ratio: 12.4 [95% confidence interval: 1.17-132.3]; P=0.037) remained risk factors for unfavorable outcome, and multidrug-resistant tuberculosis remained a risk for death (adjusted odds ratio: 63.9 [95% confidence interval: 4.84-843.2]; P=0.002). We did not detect any difference in outcome between those with isolates resistant to only isoniazid and those with fully susceptible strains (adjusted odds ratio: 0.22 [confidence interval: 0.03-1.87]; P=0.17). CONCLUSION: Multidrug-resistant TBM in children has poor clinical outcome and is associated with death. We did not find any difference in the outcomes between children with isoniazid monoresistant TBM and those with drug-susceptible TBM. One explanation could be the local treatment regimen. Further investigation of this regimen is indicated.

Analysis of isoniazid, streptomycin and ethambutol resistance in Mycobacterium tuberculosis isolates from Morocco.

BACKGROUND: Drug-resistant tuberculosis is a major problem worldwide. Based on the knowledge of specific mutations occurring in Mycobacterium tuberculosis genome, drug resistance can be detected earlier. The aim of this study was to determine the prevalence of the most common mutations associated with resistance to Isoniazid (INH), Streptomycin (SM) and Ethambutol (EMB) in Mycobacterium tuberculosis isolates from Morocco in order to select target mutations to develop tests for rapid detection of drug-resistant Mycobacterium tuberculosis Moroccan isolates. METHODOLOGY: A total of 199 M. tuberculosis isolates collected from the National Tuberculosis Reference Laboratory in Morocco were subject to katG, inhA, rrs, rpsL and emb mutation analysis by PCR probe-based assay. The genotypic results were then compared to drug susceptibility testing results for the corresponding drugs. RESULTS: Among 66 phenotypically INH resistant isolates, 80.3% (53/66) were found to be genotypically INH resistant from which 77.3% (51/66) and 3% (2/66) had respective mutations in katG315 and inhp-15 codons. Of the 58 phenotypically SM resistant isolates, genotypic SM resistance was confirmed in 17.2% (10/58) cases. Nucleotide mutations at codons 43 and 88 of rpsL gene and at codon 512 of rrs gene were found respectively in 12.1% (7/58); 1.7% (1/58) and 3.4% (2/58) of the phenotypically SM resistant Mycobacterium tuberculosis isolates. Finally, mutations at codon 306 of embB gene were identified in 42.3% (11/26) of Mycobacterium tuberculosis isolates phenotypically EMB resistant. CONCLUSION: This study showed that a large proportion of Mycobacterium tuberculosis resistant isolates from Morocco carry a large number of mutations in different codons (especially katG315, embB306 and rpsL43) of the corresponding genes associated with drug resistance. Thus, molecular analysis based on the identification of such mutations is useful but not fully sufficient to predict all drug resistance cases. Based on these results, rapid drug resistance genotyping can be used as an adjunct to the traditional culture based methods in reference laboratories.

Drug susceptibility testing using molecular techniques can enhance tuberculosis diagnosis.

BACKGROUND: Sputum samples were collected from tuberculosis patients in a high tuberculosis incidence area in the Western Cape, South Africa. The aim of this study was to evaluate the performance and time to diagnosis of a genotypic drug susceptibility testing method. METHODOLOGY: During June 2000 and November 2003, a total of 1,540 samples were sent for drug susceptibility testing (DST) to the national health laboratory services, and of those, a phenotypic DST result was obtained for 1,373 samples whereas a genotypic DST result was obtained for 1,301 of 1,540 samples. Performance-based calculations were done on 1,244 samples for which both a phenotypic and genotypic DST result was available. RESULTS: The reproducibility of the genotypic and phenotypic DST methods was 97% and 95%, respectively. The sensitivity and specificity of the genotypic DST method was 68% and 99% for Isoniazid and 87% and 99% for Rifampicin, respectively. Smear gradation was found to influence the performance of the genotypic DST method. The genotypic DST method gave accurate DST results for 75% of the samples within 20 days (range, 15-25), whereas the phenotypic DST results were only available for 75% of the samples after 38 days (range, 26-115) (p<0.001). CONCLUSION: This study showed that the genotypic DST could improve tuberculosis control by rapid diagnosis of drug resistant tuberculosis. This finding may have important implications for the control of drug resistant tuberculosis as it may reduce the chance for further transmission events.