TABLE 4.

Fraction of drug resistance acquired through person-to-person transmission versus de novo evolution of resistance within individual patients for each drug^a

Drug	No. of acquisitions	Estimated % de novo	Estimated % transmission
First-line drugs
Isoniazid	7	10	90
Rifampin	9	13	87
Ethambutol	15	22	78
Pyrazinamide	9	47	53
Second-line drugs
Amikacin	10	26	74
Ethionamide	9	39	61
Ofloxacin	27	54	46
Other drugs
Streptomycin	10	13	87

^aParsimony was used to estimate the number of times genotypic resistance was gained in isolates with AST results. This number was divided by the total number of phenotypically resistant isolates to estimate the fraction of resistance to each drug acquired through de novo evolution, while the remaining fraction was assigned to acquisition from person-to-person transmission.