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

IDENTIFICATION OF NONTUBERCULOUS MYCOBACTERIA
IN CLINICAL SAMPLES USING MOLECULAR METHODS: A THREE-YEAR STUDY
PP-55
Isabel Couto 1,2* , Diana Machado 1 , Miguel Viveiros 1,3 , Liliana Rodrigues 1,4 and Leonard Amaral 1,3,4
1 - Unit of Mycobacteriology, Instituto de Higiene e Medicina Tropical, Universidade Nova de Lisboa (IHMT/UNL), Lisbon, Portugal
2 - Centro de Recursos Microbiológicos (CREM), Faculdade de Ciências e Tecnologia, UNL, Caparica, Portugal
3 - COST ACTION BM0701 (ATENS)
4 - UPMM, IHMT/UNL, Lisbon, Portugal
Although Mycobacterium tuberculosis, the etiologic agent of human tuberculosis is the main cause of mycobacteriosis in
Man, other species of mycobacteria may also cause infection in humans. The increasing importance of nontuberculous
mycobacteria (NTM) is now consensually recognized and demands for faster methods for their identification and selection
of appropriate therapy. In this work we report our experience on the identification of NTM received from 12
hospitals of the Lisbon Health Region (Portugal) over a three-year period using the GenoType Mycobacterium (CM/AS)
assays (HAIN Lifescience). From 1 January 2005 to 31 December 2007, our laboratory received a total of 1192 acid-fast
bacilli (AFB) positive isolates from 1174 patients presenting with presumptive active mycobacteriosis. All isolates were
processed for Ziehl-Neelsen staining and inoculated into MGIT tubes of the BACTEC MGIT 960 system. M. tuberculosis
isolated from culture were identified by the Accuprobe system (Gen-Probe). Full-grown AFB cultures, negative for M.
tuberculosis, were identified by GenoType Mycobacterium (CM/AS) kits. Out of the 1192 specimen received, 1181 were
identified as members of the Mycobacterium genus. From these, 1032 cultures (87.4%) were positive for M. tuberculosis
complex. The remaining 149 cultures were NTM, corresponding to 12.6% of the total number of cultures from which
mycobacteria were isolated. During the study period, NTM prevalence increased steadily, starting with 8.7% in 2005 and
rising to 15.2% in 2007. The joint use of the CM and AS kits identified 96.6% of all NTM isolates tested. Among the 18
NTM species identified, M. avium complex was the most frequent, although it accounted for only 34% of all NTM. In
countries with high incidence of tuberculosis and, particularly, multidrug resistant tuberculosis (MDRTB) such as Portugal,
therapeutic failure with isoniazid and rifampicin is anticipated to be due to an MDRTB strain. Since many NTM species
are resistant to these drugs, the identification of the mycobacteria causing therapeutic failure (MDRTB versus NTM) is of
major importance. The introduction of molecular methods for the identification of NTM in our laboratory has resulted
in an increased awareness of the importance of being able to rapidly identify NTM as potential pathogens and the key
role played by the laboratory in assisting the selection of therapeutic modality.
European Society of Mycobacteriology | 30 th Annual Congress | July 2009 | Porto - Portugal
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