Simple Direct Drug Susceptibility Tests on Sputum Samples for Early Detection of Resistance in Tubercle Bacilli

摘要

Background: Direct sensitivity test either by sputum concentrate (DS) or swab method (DSM) set up along with theudprimary culture would avoid the delay of four or more weeks required for the indirect test. A comparison of these twoudmethods against the standard indirect sensitivity method under routine laboratory conditions is necessary to prove theirudmerit.udMethod: Smear positive sputum samples were aliquoted and sensitivity tests were set up by both the direct methods as alsoudan indirect test set up from the primary culture of the same sample.udResults: The agreement with the indirect test results for isoniazid (INH) ranged from 97-98% for the DS method and 93-ud97% for the DSM method. The corresponding figures were 96-98% by the DS and 94-99% by the DSM method forudrifampicin (R). The agreement was less satisfactory for ethambutol (Emb).udConclusion: This study showed that direct sensitivity tests such as DS and DSM methods can detect most of the culturesudresistant to INH and R (MDR) from the time growth appears on the primary culture , even as early as the second week ofudsetting up the tests.