TY - JOUR T1 - Susceptibility of <em>mycobacterium avium complex</em> and <em>mycobacterium xenopi</em> to rifampin, rifapentine, clarithromycin and moxifloxacin, alone or in combination with ethambutol JF - European Respiratory Journal JO - Eur Respir J VL - 38 IS - Suppl 55 SP - p4416 AU - Claire Andrejak AU - Deepak Almeida AU - Eric Nuermberger AU - Jacques Grosset Y1 - 2011/09/01 UR - http://erj.ersjournals.com/content/38/Suppl_55/p4416.abstract N2 - Background: Pulmonary disease due to M. avium complex [MAC], and M. xenopi [Mx]) is a growing health problem in industrialized countries and the optimal antibiotic treatment is still debated. We conducted a in vitro study to evaluate the activity of the main antibiotics on MAC and Mx.Methods: For MAC strain 101 and Mx ATCC strain 700898, minimal inhibitory concentrations (MICs), of clarithromycin (CLA), moxifloxacin (MXF), rifampin (RIF), rifapentine (RPT), ethambutol (EMB) were determined on 7H11 media. Inoculum was 2.7 log10 CFU of Mx and 4.5 log10 CFU of MAC. Plates were read after 28 days of incubation at 37°C (MAC) or 42°C (Mx). MIC was defined as the lowest drug concentration that inhibits ≥99% of colonies compared to control. Combinations of EMB-RIF, EMB-RPT, MXF-CLA and EMB-MXF for Mx and MAC were tested using the checkerboard method.Results: For MAC, MIC was &gt;4 for CLA, 2 for MXF, &gt;16 for RIF, &gt;4 for RPT, 16 for EMB. For Mx, MIC was &gt;4 for CLA, 2 for MXF, &gt;16 for RIF, 4 for RPT, 16 for EMB. For both Mx and MAC, MIC was 1 for CLA when we used Mueller Hinton media (pH=7.3 for Mueller Hinton media vs pH=6.6 for 7H11). Synergy was observed for EMB-RIF, EMB-MXF, MXF-CLA against Mx, and for EMB-RPT against both Mx and MAC. An additive effect was found for CLA-MXF, EMB-RIF, EMB-MXF against MAC.Conclusion: The addition of EMB decreased the MIC of RPT against both MAC and Mx and decreased MIC of MXF and RIF against Mx. So, EMB could increase the in vivo activity of these antibiotics against these mycobacterial opportunistic pathogens. No antagonism between MXF and CLA was found. ER -