European Society of Mycobacteriology - Instituto Nacional de Saúde ...

PP-92
MTBDRPLUS ASSAY IS A USEFUL TOOL TO SCREEN FOR
MULTI-DRUG RESISTANT TUBERCULOSIS IN A NATIONAL SURVEY
De Haas, Petra 1 , Ramona Zenhorst 2 , Pike Mwamba 2 , Mweemba Muvwimi 3 ,
Winnie Mwanza 2 , Grace Mbulo 2 , Nathan Kapata 2 , Helen Ayles 1
1 - Zambart project, Lusaka, Zambia and LSHTM London
2 - Zambart project, Lusaka, Zambia
3 - National Reference laboratory, Lusaka, Zambia
Background
The World Health Organization requests that countries conduct tuberculosis drug resistance surveys (DRS) every five
years to monitor trends of drug resistance and to determine rates of multi-drug resistant tuberculosis (MDR-TB). Zambia
conducted its second nation-wide DRS in 2008. The objective of this study is to investigate whether the MTBDRplus
assay (HAIN), a new molecular assay performed directly on sputum, is a useful tool in conducting a DRS.
Method
Throughout Zambia approximately 900 sputum specimens were collected from consecutive smear-positive
TB patients and transported to the TB Reference Laboratory in Lusaka. Specimens were decontaminated
and concentrated smears were prepared. MGIT and LJ cultures were inoculated. Drug susceptibility testing
(DST) was performed on positive cultures. Remaining decontaminated sputum was heat-killed, sonicated
and stored at -80C. The MTBDRplus assay was performed using a 1:5 or 1:10 dilution of decontaminated sputum.
Results: Of the first 340 specimens tested using the MTBDRplus assay, 307 (90.3%) showed no evidence of resistance,
while thirty-three (9.7%) showed mutations consistent with resistance: 10 were MDR-TB, 20 were isoniazid (INH)
mono-resistant and 3 were rifampicin (RIF) mono-resistant. MGIT DST results were obtained from 271 (79.7%) of
340 specimens with an MTBDRplus result. We were unable to obtain MGIT DST results from the remaining 69 (20.3%)
specimens due to contamination or lack of growth. Thirteen (39.4%) of 33 specimens that showed mutations consistent
with resistance in the MTBDRplus assay failed to yield a DST result on MGIT. Six out of these 13 samples are according
to the MTBDRplus assay MDR, 5 are INH mono-resistant and 2 RIF mono-resistant . One sample that showed RIF monoresistance
using the MTBDRplus assay, showed both isoniazid and rifampicin resistance uses the MGIT DST.
Conclusion
In our study, the MTBDRplus assay performed directly on sputum was more rapid and cost-effective than culture to
screen for MDR-TB.
164 ESM 2009