Resistance of Mycobacterium tuberculosis to antibiotics in Lao PDR: first multicentric study conducted in 3 hospitals

BACKGROUND It is estimated that Lao People's Democratic Republic (Lao PDR) ranks fifth among the seven countries most affected by TB in the WHO Western Pacific Region. However, because of late implementation of mycobacterial culture, no study on resistance to anti-TB drugs had been performed yet. The objective of this study was to document drug resistance rate among patients hospitalized for pulmonary TB in threeprovinces of Lao PDR. METHODS A cross-sectional study was conducted in three sites, one central and two regional hospitals, from April to November 2010. For each TB suspected patient sputum smear microscopy and culture on Lowenstein-Jensen media were performed. GenoType® MTBDRplus assay was used to test the susceptibility to isoniazid (INH) and rifampicin (RMP), GenoType® MTBDRsl for second-line drugs and GenoType® Mycobacterium CMAS for non-tuberculous mycobacteria (NTM). RESULTS Out of 104 positive culture on Lowenstein-Jensen, 87 (83.6%) were M. tuberculosis and 17 (16.4%) were NTM. Of 73 new TB cases, 5 isolates (6.8%) were resistant to INH. Of 14 previously treated cases, 2 isolates (14.3%) were resistant to INH and one isolate was XDR. CONCLUSION Despite an overall rate of resistance still moderate, the frequency of mutations conferring INH monoresistance and identification of the first strain of XDR require strengthening surveillance of drug resistant tuberculosis in Lao PDR.