Molecular and Growth-Based Drug Susceptibility Testing of Mycobacterium tuberculosis Complex for Ethambutol Resistance in the United States
Table 3
Summary of 20 discordant results for detection of EMB resistance between PHL and CDC.
Number of samples
PHL growth-based DST result
PHL growth-based DST method
embB mutation detected by CDC’s MDDR
CDC’s agar proportion result
1
Susceptible
BACTEC 460 and agar proportion
Asn296Tyr
Resistant
1
Susceptible
MGIT 960
Met306Ile
Resistant
1
Susceptible
BACTEC 460 and agar proportion
Met306Ile
Resistant
3
Susceptible
MGIT 960
Met306Val
Resistant
1
Susceptible
BACTEC 460
Met306Val
Resistant
1
Resistant
MGIT 960
Glu378Ala
Susceptible
2
Susceptible
MGIT 960
Gly406Cys
Resistant
1
Susceptible
Not performed in-house
Gly406Ser
Resistant
3
Resistant
MGIT 960
None
Susceptible
5
Susceptible
MGIT 960
None
Resistant
1
Susceptible
Not performed in-house
None
Resistant
PHL: public health laboratory; DST: drug susceptibility testing; CDC: Centers for Disease Control and Prevention; MDDR: molecular detection of drug resistance.
