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January - March 2017: 
Volume 30, Issue 1

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Pneumon 2017, 30(1):24-31
Drug susceptibility testing of first-line anti-tuberculosis drugs: clinical evaluation of the differences between laboratories
Authors Information

1: Pulmonary Department, Aristotle University of Thessaloniki, “G. Papanikolaou” Hospital, Thessaloniki, Greece
2: Greek National Reference Laboratory for Mycobacteria, General Hospital for Chest Diseases “SOTIRIA”, Athens, Greece
3: Laboratory for Tuberculosis of Northern Greece, “G. Papanikolaou” Hospital, Thessaloniki, Greece

Abstract
BACKGROUND: Tuberculosis (TB) remains a significant public health issue, partly due to drug resistance development. The rapid and reli-able diagnosis is essential for TB control. The purpose of the present study was to detect and present the differences of molecular and phenotypic drug susceptibility testing (DST) of Μ. tuberculosis strains, isolated from patients hospitalized in the Pulmonary Department of the Aristotle University of Thessaloniki, as they were recorded by the Greek National Reference Laboratory for Mycobacteria (NRLM) (General Hospital for Chest Diseases “SOTIRIA”, Athens, Greece) and the Laboratory for Tuberculosis (LT) of Northern Greece, G.H. “G. PAPANIKOLAOU”. METHODS: Twenty-one ΤΒ patients were in-cluded. Culture of the Mycobacterium strain was conducted using Lowenstein-Jensen medium and phenotypic antibiograms were obtained from NRLM and LT. Molecular testing was conducted by NRLM. Isoniazid and rifampicin were tested. RESULTS: Eleven isolates yielded discrepant DST results. For isoniazid, 6 cases were found to be molecularly and phenotypically susceptible by NRLM while resistant by LT. In 3 cases, resistance was attributed to a problematic reagent. For rifampicin, four molecularly susceptible strains demonstrated phenotypic susceptibility at NRLM but resistance at LT. In one case, resistance was taken into account for treatment interventions. Furthermore, one strain demonstrated molecular and phenotypic resistance to rifampicin at NRLM, but susceptibility at LT. The strain was molecularly and phenotypically resistant to isoniazid and the patient was considered as a case of multidrug-resistant TB. CONCLISIONS: Discordance between DST requires full consideration of the clinical presentation and collaboration with the laboratory and TB experts.