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Performance of the Abbott RealTime MTB RIF/INH resistance assay when used to test Mycobacterium tuberculosis specimens from Bangladesh
Infection and Drug Resistance
Performance of the Abbott RealTime MTB RIF/INH resistance assay when used to test Mycobacterium tuberculosis specimens from Bangladesh
0 Abbott Molecular , Abbott Laboratories, Des Plaines, IL , USA
PowerdbyTCPDF(ww.tcpdf.org) Introduction: The Abbott RealTime MTB RIF/INH Resistance Assay (RT MTB RIF/INH) is an assay for the detection of rifampicin (RIF)- and/or isoniazid (INH)-resistant Mycobacterium tuberculosis (MTB). The assay can be used to test sputum, bronchial alveolar lavage, and N-Acetyl-L-Cysteine (NALC)/NaOH pellets prepared from these samples. The assay can be used in direct testing mode, or in reflex mode following a MTB positive result produced by its companion assay, Abbott RT MTB. Methods: In this study, the direct testing mode was used to test paired sputum and NALC/ NaOH pellets prepared from sputum collected from Bangladesh TB patients. One hundred and thirty two paired samples were tested. Results: The RT MTB RIF/INH inhibition rate was 0%. One hundred and twenty-two paired samples had results above the assay limit of detection and were analyzed by comparing with results from phenotypic drug sensitivity testing, GeneXpert MTB/RIF (Xpert), and MTBDR plus (Hain). RT MTB RIF/INH results were in good agreement with those of GeneXpert and Hain. Conclusion: The ability of this assay to detect RIF and INH resistance may contribute to the global control of multidrug resistant tuberculosis.
Introduction
Mycobacterium tuberculosis (MTB) remains a significant disease with 10.4 million
new cases of tuberculosis (TB) reported in 2015.1 Anti-TB therapy is effective in at
least 85% of cases when the causative strain of MTB is sensitive to the four drugs
(rifampicin [RIF], isoniazid [INH], ethambutol, and pyrazinamide) that constitute
frontline therapy.1 Treatment with front-line therapy is less effective when MTB is resistant
to one or more of these drugs.1 It is therefore important to detect MTB resistance to
one or more of these front-line drugs so that therapy can be modified appropriately.1
Detection of drug-resistant MTB is often performed using the accurate but slow (up to
12 weeks) culture-based (phenotypic) drug sensitivity testing (DST).1 In response to
the relative length of time to generate a phenotypic DST result, more rapid nucleic acid
amplification tests (NAAT) have been developed.2 The Cepheid GeneXpert MTB/RIF
(Xpert) assay detects mutations associated with RIF resistance while Hain MTBDR
Plus (Hain) detects mutations associated with RIF and INH resistance.3–6
Abbott RealTime MTB RIF/INH Resistance (RT MTB RIF/INH) detects mutations
associated with resistance to RIF and INH.7 RT MTB RIF/INH is a companion assay
to Abbott RealTime MTB (RT MTB).8,9 It can be used in direct testing mode to test
Infection and Drug Resistance 2018:11 695–699 695
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respiratory specimens (sputum, bronchial alveolar lavage,
or N-Acetyl-L-Cysteine (NALC)/NaOH sediments prepared
from sputum or bronchial alveolar lavage) or used in reflex
mode following a positive RT MTB result.7 The performance
of RT MTB RIF/INH has been studied in in Germany, Hong
Kong, and South Africa in reflex mode, following an RT
MTB positive result.10–12
The intent of this study was to review the performance
of RT MTB RIF/INH when used in direct testing mode with
MTB culture-positive samples from Bangladesh for which
phenotypic DST, Xpert, and Hain results had been
generated. The inclusion of DST, as well as Xpert and MTBDR
plus results for this patient population provides a measure of
performance for RT MTB RIF/INH against phenotypic DST
and Xpert and Hain assays.
Methods
Samples
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/sw lna under the supervision of the National TB Reference Lab
/
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ttp rso
h e Institutional Review Board and Intercenter Agreement. All
p
from roF subjects enrolled in this study provided written informed
ded consent. The three sputum specimens were collected from
loan each patient over a maximum period of 5 days, with at least
dow 5 hours between collections. Collection was performed at the
cen National Reference Laboratory in Dhaka, Bangladesh.
Speciitssa mens were collected following Institutional Review B (...truncated)