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

PP-101
COMPARISON OF RAPID COLORIMETRIC METHOD,
PROPORTION METHOD AND BACTEC460 TB SYSTEM FOR TESTING
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SUSCEPTIBILITY OF M.tuberculosis TO RIFAMPINE AND ISONIASIDE
o
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Begum KAYAR, Ülkü ORAL ZEYTINLI, Ayse , KARACALI, Ayben SOYAL, Togrul Nagiyev, Fatih KÖKSAL
Cukurova University, Medical Faculity
Introduction
Multidrug-resistant (MDR) M. tuberculosis (MTB) strains founded resistant to at least isoniaside [INH] and rifampin [RIF],
the two most important first-line drugs pose a serious threat to the control of tuberculosis (TB) and the spread of these
strains has become a major public health problem. In this study, the performance of antimycobacterial susceptibility testing
for the first line drugs (RIF and INH) with colorimetric nitrate reductase-based antibiotic susceptibility (CONRAS)
and conventional proportion method depend on solid agar culture (LJ) were compared to BACTEC 460 TB system as
the gold standard.
Methods
Of the total of 187 MTB strains, when 24 isolates were found as resistant to RIF and INH by Bactec 460 TB other 163
strains were susceptible for these antibiotics. All of strains were isolated in sputum from patient with pulmonary disease
and identified as MTB by NAP test in Bactec 460 system. The CONRAS test was performed with 0.1 mg/mL of
INH and 1 mg/mL of RIF on LJ as modification of standart methods described by H.Syre et al . Antibiotic susceptibility
testing with proportion method was performed on LJ medium according to the standard protocol laid down by WHO.
Results: The sensitivity, specificity and overall agreement of the CONRAS test were 95.83% (23/24), 99.38%(162/163) and
97.60% for RIF and 83.33% (20/24), 99.38% (162/163) and 91.35% for INH, respectively. Results for proportion tests were
found as; 91.66% (22/24), 93.25% (152/163) and 92.45% for RIF and 75% (18/24), 97.54% (159/163) and 86.27% for
INH, respectively by Bactec 460TB system as the gold standart.
Interpretation & conclusion
CONRAS test showed good agreement with Bactec 460 (the overall agreement of this test was 94.47%) for each of the
antimicrobial tested. CONRAS test is simple, easy to perform, less expensive, reliable and may be used as a preliminary
screen for susceptibility testing of MTB in particularly for resource-poor countries.
European Society of Mycobacteriology | 30 th Annual Congress | July 2009 | Porto - Portugal
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