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Memórias do Instituto Oswaldo Cruz
Fundação Oswaldo Cruz, Fiocruz
ISSN: 1678-8060
EISSN: 1678-8060
Vol. 99, No. 1, 2004, pp. 107-110
Bioline Code: oc04019
Full paper language: English
Document type: Research Article
Document available free of charge

Memórias do Instituto Oswaldo Cruz, Vol. 99, No. 1, 2004, pp. 107-110

 en Antimicrobial Susceptibility Determined by the E Test, Löwenstein-Jensen Proportion, and DNA Sequencing Methods among Mycobacterium tuberculosis check for this species in other resources Isolates Discrepancies, Preliminary Results
Maria Inês Moura Freixo; Paulo CS Caldas; Abbadi Said; Fátima Martins; Rossana Coimbra Brito; Leila de Souza Fonseca & Maria Helena Féres Saad

Abstract

Mycobacterium tuberculosis check for this species in other resources strains resistant to streptomycin (SM), isoniazid (INH), and/or rifampin (RIF) as determined by the conventional Löwenstein-Jensen proportion method (LJPM) were compared with the E test, a minimum inhibitory concentration susceptibility method. Discrepant isolates were further evaluated by BACTEC and by DNA sequence analyses for mutations in genes most often associated with resistance to these drugs (rpsL, katG, inhA, and rpoB). Preliminary discordant E test results were seen in 75% of isolates resistant to SM and in 11% to INH. Discordance improved for these two drugs (63%) for SM and none for INH when isolates were re-tested but worsened for RIF (30%). Despite good agreement between phenotypic results and sequencing analyses, wild type profiles were detected on resistant strains mainly for SM and INH. It should be aware that susceptible isolates according to molecular methods might contain other mechanisms of resistance. Although reproducibility of the LJPM susceptibility method has been established, variable E test results for some M. tuberculosis isolates poses questions regarding its reproducibility particularly the impact of E test performance which may vary among laboratories despite adherence to recommended protocols. Further studies must be done to enlarge the evaluated samples and looked possible mutations outside of the hot spot sequenced gene among discrepant strains.

Keywords
Mycobacterium tuberculosis check for this species in other resources - susceptibility test - DNA sequencing - E test

 
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