Molecular and Growth-Based Drug Susceptibility Testing of Mycobacterium tuberculosis Complex for Ethambutol Resistance in the United States

Table 2

Cross-tabulation of CDC’s molecular detection with both PHL and CDC growth-based DST results for determination of EMB resistance.

Detection of embB mutation by CDC’s MDDR	Number of samples	Number of EMB-resistant MTBC samples (%)		value
		PHL growth-based DST	CDC agar proportion
Yes	39	23 (59.0)	33 (84.6)	0.002
No	131	7 (5.34)	10 (7.63)	0.317
Total	170	30 (17.6)	43 (25.3)	0.003

Including samples with Glu378Ala and Leu355Leu polymorphisms not associated with EMB resistance.
CDC: Centers for Disease Control and Prevention; PHL: public health laboratory; DST: drug susceptibility testing; EMB: ethambutol; MTBC: Mycobacterium tuberculosis complex; MDDR: molecular detection of drug resistance.