Correction: In Vitro Activity of Rifampicin and Verapamil Combination in Multidrug-Resistant Mycobacterium tuberculosis.

The aim of the present study was to evaluate the effect of the combination of rifampicin (RIF) and verapamil (VP) against the Mycobacterium tuberculosis H37Rv reference strain and six multidrug-resistant (MDR) M. tuberculosis clinical isolates by determining Time-Kill Curves and the ability to efflux drug by fluorometry. The RIF+VP combination showed synergism in one MDR clinical isolate. For the other five MDR clinical isolates, the drug combination showed no interaction. The MDR clinical isolate had lower ethidium bromide (EtBr) accumulation when exposed to the RIF+VP combination, compared with RIF and VP exposure alone. The other MDR clinical isolates showed no significant difference in EtBr accumulation. These results suggest greater efflux action in one of the MDR clinical isolates compared with the M. tuberculosis H37Rv reference strain. The other five MDR isolates may have additional mechanisms of drug resistance to RIF. The use of the RIF+VP combination made one MDR bacillus more susceptible to RIF probably by inhibiting efflux pumps, and this combination therapy, in some cases, may contribute to a reduction of resistance to RIF in M. tuberculosis

Molecular characterization, drug susceptibility profile, minimum inhibitory concentration, and drug interaction in the <i>M. tuberculosis</i> H₃₇Rv reference strain and multidrug-resistant clinical isolates.

<p>R, resistant; NP, not performed; INH, isoniazid; RIF, rifampicin; EMB, ethambutol; PZA, pirazinamid; FICI, fractional inhibitory concentration index; REDCA; Resazurin Drugs Combination Microtiter Assay. VP, verapamil; EtBr, ethidium bromide. Numbers in bold represent synergism.</p><p>Molecular characterization, drug susceptibility profile, minimum inhibitory concentration, and drug interaction in the <i>M. tuberculosis</i> H₃₇Rv reference strain and multidrug-resistant clinical isolates.</p

Time-kill curve of the <i>Mycobacterium tuberculosis</i> H₃₇Rv reference strain and multidrug-resistant clinical isolates 71A, 18, 19, 109, 3614, and 64A exposed to rifampicin (RIF), verapamil (VP), and RIF+VP combination for 7 days at 35–37°C.

<p>Time-kill curve of the <i>Mycobacterium tuberculosis</i> H₃₇Rv reference strain and multidrug-resistant clinical isolates 71A, 18, 19, 109, 3614, and 64A exposed to rifampicin (RIF), verapamil (VP), and RIF+VP combination for 7 days at 35–37°C.</p