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ANTIMICROBIAL SUSCEPTIBILITY DETERMINED BY THE E TEST, LÖWENSTEIN-JENSEN PROPORTION, AND DNA SEQUENCING METHODS AMONG MYCOBACTERIUM TUBERCULOSIS ISOLATES DISCREPANCIES, PRELIMINARY RESULTS
E test
Testes de Sensibilidade Microbiana
Análise de Sequência de DNA
Author
Affilliation
Universidade Federal do Rio de Janeiro. Instituto de Microbiologia Paulo de Góes. Rio de Janeiro, RJ, Brasil.
Ministério da Saúde. Centro de Referência Prof. Hélio Fraga. Rio de Janeiro, RJ, Brasil.
Suez Canal University.School of Medicine. Ismailia, Egypt.
Ministério da Saúde. Centro de Referência Prof. Hélio Fraga. Rio de Janeiro, RJ, Brasil.
Universidade do Estado do Rio de Janeiro. Hospital Pedro Ernesto. Rio de Janeiro, RJ, Brasil.
Universidade Federal do Rio de Janeiro. Instituto de Microbiologia Paulo de Góes. Rio de Janeiro, RJ, Brasil.
Fundação Oswaldo Cruz. Instituto Oswaldo Cruz. Departamento de Medicina Tropical. Laboratório de Hanseníase. Rio de Janeiro, RJ, Brasil.
Ministério da Saúde. Centro de Referência Prof. Hélio Fraga. Rio de Janeiro, RJ, Brasil.
Suez Canal University.School of Medicine. Ismailia, Egypt.
Ministério da Saúde. Centro de Referência Prof. Hélio Fraga. Rio de Janeiro, RJ, Brasil.
Universidade do Estado do Rio de Janeiro. Hospital Pedro Ernesto. Rio de Janeiro, RJ, Brasil.
Universidade Federal do Rio de Janeiro. Instituto de Microbiologia Paulo de Góes. Rio de Janeiro, RJ, Brasil.
Fundação Oswaldo Cruz. Instituto Oswaldo Cruz. Departamento de Medicina Tropical. Laboratório de Hanseníase. Rio de Janeiro, RJ, Brasil.
Abstract
Mycobacterium tuberculosis 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 in Portuguese
Mycobacterium tuberculosisE test
Testes de Sensibilidade Microbiana
Análise de Sequência de DNA
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