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pdfCDC Model Performance Evaluation Program (MPEP) for Mycobacterium tuberculosis Drug
Susceptibility Testing
Attachment 13
Final Aggregate Report
Centers for Disease Control and Prevention
Model Performance Evaluation Program
Mycobacterium tuberculosis Complex
Drug Susceptibility Testing Program
Report of Results
February 2017
Mycobacterium tuberculosis Complex Drug Susceptibility
Testing Report for February 2017 Samples Survey
Purpose
The purpose of this report is to present results of the U.S. Centers for Disease Control and Prevention (CDC)
Model Performance Evaluation Program (MPEP) for Mycobacterium tuberculosis complex (MTBC) drug
susceptibility testing survey sent to participants in February 2017.
Report Content
The material in this report was developed and prepared by:
Cortney Stafford, MPH, MT (ASCP), Health Scientist, Laboratory Capacity Team, NCHHSTP, DTBE, LB
Acknowledged contributors: Beverly Metchock NCHHSTP, DTBE, LB; Stephanie Johnston NCHHSTP, DTBE,
LB; Lois Diem NCHHSTP, DTBE, LB; Mitchell Yakrus NCHHSTP, DTBE, LB; and Angela Starks NCHHSTP,
DTBE, LB
Contact Information
Comments and inquiries regarding this report should be directed to
TBMPEP@cdc.gov
404-639-4013
The findings and conclusions in this report are those of the author(s) and do not necessarily represent the views of the
Centers for Disease Control and Prevention.
Use of trade names and commercial sources is for identification only and does not imply endorsement by the U.S.
Department of Health and Human Services
2
CDC MPEP MTBC DST Report for February 2017
Table of Contents
Purpose.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
Report Content. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
Contact Information. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
Introduction: Overview of MPEP Final Report.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
Expected Susceptibility Testing Results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
Abbreviations and Acronyms. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
Technical Notes.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
Descriptive Information about Participant Laboratories. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
Primary Classification. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
Annual Number of MTBC Drug Susceptibility Tests Performed
.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
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MTBC DST Methods Used by Participants. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
Antituberculosis Drugs Tested by Participants. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
Detailed Information for Each Isolate
Isolate 2017A. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
Isolate 2017B. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
Isolate 2017C. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
Isolate 2017D. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
Isolate 2017E. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24
Equivalent Critical Concentrations. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27
References. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28
Appendix 1: Accessible Explanations of Figures. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30
CDC MPEP MTBC DST Report for February 2017
3
Introduction: Overview of MPEP Final Report
The Model Performance Evaluation Program (MPEP) is an educational self-assessment tool in which five isolates of
M. tuberculosis complex (MTBC) are sent to participating laboratories biannually for staff to monitor their ability to
determine drug resistance among the isolates. It is not a formal, graded proficiency testing program. This report includes
results for a subset of laboratories performing drug susceptibility tests (DST) for MTBC in the United States. MPEP is a
voluntary program, and this report reflects data received from participating laboratory personnel. This aggregate report
is prepared in a format that will allow laboratory personnel to compare their DST results with those obtained by other
participants using the same methods and drugs, for each isolate. We encourage circulation of this report to personnel who
are either involved with DST or reporting and interpreting results for MTBC isolates.
CDC is neither recommending nor endorsing testing practices reported by participants. For approved standards,
participants should refer to consensus documents published by the Clinical and Laboratory Standards Institute (CLSI),
“Susceptibility Testing of Mycobacteria, Nocardiae, and Other Aerobic Actinomycetes; Approved Standard,” M24-A2 [1].
Expected Susceptibility Testing Results
Anticipated growth-based and molecular results for the panel of MTBC isolates sent to participants in February 2017
are shown in the tables below. Although CDC recommends broth-based methods for routine first-line DST of MTBC
isolates, the results obtained by the reference agar proportion method (except for pyrazinamide, in which MGIT was
performed) are shown in Table 1. Molecular results obtained by using DNA sequencing are listed in Table 2 [2].
Table 1. Expected Growth-based Results for February 2017 Survey
Growth-based Results
First-Line Drugs
Second-Line Drugs
Isolate
RMP
INH
EMB
PZA
Resistant to:
2017A
S
S
S
S
OFL, CIP
2017B
S
R
S
S
STR
2017C
S
S
S
S
AMK, KAN, CAP
2017D
S
R
S
S
ETA
2017E
S
S
S
S
n/a
Note–S=susceptible, R=resistant
Table 2. Expected Molecular Results for February 2017 Survey
Mutations Detected in Loci Associated with Resistance
Isolate
rpoB
2017A
Phe514Phe
2017B
katG
fabG1
gyrA
Asp94Asn
Ser315Thr
2017C
A1401G
2017D
Arg528Arg
2017E
n/a
4
rrs
Leu203Leu
n/a
n/a
n/a
n/a
CDC MPEP MTBC DST Report for February 2017
Abbreviations and Acronyms
Abbreviations and Acronyms
AMK
AP
bp
CAP
CDC
CIP
CLSI
CYS
DNA
DST
EMB
ETA
HMO
INH
KAN
LEV
MDR
MGIT
MIC
MOX
MPEP
MTBC
PAS
PZA
OFL
R
RBT
RMP
RNA
S
Sensititre
STR
TB
VersaTREK
XDR
amikacin
agar proportion — performed on Middlebrook 7H10 or 7H11
base pair
capreomycin
U.S. Centers for Disease Control and Prevention
ciprofloxacin
Clinical and Laboratory Standards Institute
cycloserine
deoxyribonucleic acid
drug susceptibility testing
ethambutol
ethionamide
Health Maintenance Organization
isoniazid
kanamycin
levofloxacin
multidrug resistant
BACTEC MGIT 960 — Mycobacteria Growth Indicator Tube
minimum inhibitory concentration
moxifloxacin
Model Performance Evaluation Program
Mycobacterium tuberculosis complex
p-aminosalicylic acid
pyrazinamide
ofloxacin
resistant
rifabutin
rifampin
ribonucleic acid
susceptible
Thermo Scientific Sensititre Mycobacterium tuberculosis MIC plate
streptomycin
tuberculosis
Thermo Scientific VersaTREK Myco susceptibility
extensively drug resistant
CDC MPEP MTBC DST Report for February 2017
5
Technical Notes
The following information pertains to all of the tables and figures for the 2017 MTBC isolates A, B, C, D, and E in
this report.
●● The source of data in all tables and figures is the February 2017 MPEP MTBC DST survey.
●● The number of reported results (S represents susceptible and R represents resistant) for each drug are
indicated in each table.
●● First-line and second-line drugs have been separated into individual tables for each isolate. Streptomycin is
classified as a second-line drug for this report.
●● Separate tables for molecular testing are included.
●● Laboratories that use more than one DST method are encouraged to test isolates with each of those methods
at either CLSI-recommended or equivalent critical concentrations. Some laboratories have provided results
for multiple DST methods. Consequently, the number of results for some drugs may be greater than 80 (the
number of participating laboratories). This report contains all results reported by participating laboratories.
●● Critical concentrations of antituberculosis drugs used for each DST method are listed at the end of this
report.
●● The Trek Sensititre system allows determination of a minimum inhibitory concentration (MIC) for each
drug in the panel. Laboratories using this method must establish breakpoints to provide a categorical
interpretation of S or R.
●● For 30 laboratories reporting second-line drug results (with the exception of streptomycin), nine (30%)
tested all three second-line injectable drugs and at least one fluoroquinolone needed to confidently define
XDR TB. The second-line injectable drugs are amikacin, kanamycin, and capreomycin. Fluoroquinolones
include ofloxacin, ciprofloxacin, levofloxacin, and moxifloxacin.
6
CDC MPEP MTBC DST Report for February 2017
Descriptive Information about Participant Laboratories
Primary Classification
This report contains DST results submitted to CDC by survey participants at 80 laboratories in 36 states.
The participants were asked to indicate the primary classification of their laboratory (Figure 1). MPEP participants
self-classified as:
●● 53 (66%): Health department laboratory (e.g., local, county, state)
●● 15 (19%): Hospital laboratory
●● 8 (10%): Independent / Reference laboratory (non-hospital based)
●● 3 (4%): Federal government laboratory
Other1.(quality
control manufacturer)
Primary Classification
of Participating Laboratories, February 2017
●● 1 (1%): Figure
Figure 1. Primary Classification of Participating Laboratories, February 2017
Accessible information for all figures is located in Appendix 1, page 30.
Health department laboratory
4%
Hospital laboratory
1%
Independent/Reference laboratory
Federal government laboratory
Other
10%
19%
66%
66%
CDC MPEP MTBC DST Report for February 2017
7
Annual
Number
MTBC
Drug
Performed
n of the Annual
Volume
of MTBCofIsolates
Tested
forSusceptibility
Drug SusceptibilityTests
by Participants
in Previous Calendar Year (n=80)
The number of MTBC isolates tested for drug susceptibility by the 80 participants in 2016 (excluding isolates used
for quality control) is shown in Figure 2. In 2016, the counts ranged from 0 to 1,119 tests. Participants at 29 (36%)
laboratories reported testing 50 or fewer DST isolates per year. Laboratories with low MTBC DST volumes are
encouraged to consider referral of testing because of concerns about maintaining proficiency [3].
Figure 2. Distribution of the Annual Volume of MTBC Isolates Tested for Drug Susceptibility
by Participants in Previous Calendar Year (n=80)
Accessible information for all figures is located in Appendix 1, page 30.
Number of Laboratori es Respondi ng
35
30
25
23
20
15
10
6
5
0
8
29
7
6
2
51-100
3
3
1
101-150 151-200 201-250 251-300 301-500 501-1000
Number of Isolates Tested
CDC MPEP MTBC DST Report for February 2017
MTBC DST Methods Used by Participants
The DST methods that were used by participating laboratories for this panel of MTBC isolates are displayed in
Figure 3. Furthermore, 45 (56%) laboratories reported results for only one method, 30 laboratories reported two
methods, and five laboratories noted three susceptibility methods.
Figure 3. MTBC Drug Susceptibility Test Method Used by Participants (n=120)
Number of
Laboratories Responding
Accessible information for all figures is located in Appendix 1, page 30.
80
70
60
50
40
30
20
10
0
76
25
13
MGIT
Agar
Proportion
4
2
Sensititre
VersaTREK
Molecular
Methods
Drug Susceptibility Test Method
Figure 4. Molecular Method Reported (n=13)
Molecular methods reported by thirteen participants are shown in Figure 4. The method used most frequently by
laboratories was targeted DNA sequencing (46%), including pyrosequencing and Sanger sequencing. Four laboratories
reported results for the Cepheid Xpert MTB / RIF assay, two reported use of the line probe assays Genotype MTBDRplus
and MTBDRsl by Hain Lifescience, and one reported results from whole genome sequencing.
Figure 4. Molecular Method Reported (n=13)
Accessible information for all figures is located in Appendix 1, page 30.
Whole Genome
Sequencing, 1
Hain Line
Probe, 2
Targeted DNA
Sequencing, 6
Cepheid Xpert, 4
CDC MPEP MTBC DST Report for February 2017
9
Figure 5. Antituberculosis Drugs Tested by Participants
Antituberculosis Drugs Tested by Participants
The number of participating laboratories that reported testing each antituberculosis drug in the February 2017 survey
is shown in Figure 5. CLSI recommends testing a full panel of first-line drugs (rifampin [RMP], isoniazid [INH],
ethambutol [EMB], and pyrazinamide [PZA])[1], because it represents a combination of tests that provides the
clinician with comprehensive information related to the four-drug antituberculosis therapy currently recommended
for most patients. All participants reported results for two of the first-line drugs (RMP and INH), 79 (99%) of the
participants reported results for EMB, and 73 (91%) also reported results for PZA. The number of laboratories testing
second-line drugs has decreased slightly since the August 2016 survey.
Figure 5. Antituberculosis Drugs Tested by Participants
Accessible information for all figures is located in Appendix 1, page 30.
Rifampin
Isoniazid
Ethambutol
Pyrazinamide
80
80
79
73
Antituberculosis Drugs Tested
Streptomycin
53
Ofloxacin
Moxifloxacin
Ciprofloxacin
Levofloxacin
19
8
8
5
Kanamycin
Capreomycin
Amikacin
19
20
17
Ethionamide
p-Aminosalicyclic Acid
Rifabutin
Cycloserine
25
18
14
11
0
10
10
20
30
40
50
60
70
Number of Participating Laboratories Reporting
80
90
CDC MPEP MTBC DST Report for February 2017
Isolate 2017A
Expected Result: Resistant to OFL at 2.0 µg / ml by agar proportion
Ofloxacin
Fluoroquinolones (FQ) are one of the most commonly prescribed classes of antibiotic in the United States due to their
activity against various types of bacteria. They are an important class of drugs used to treat TB resistant to first-line
drugs but also have the potential to become an important part of new TB regimens [4]. In the United States, resistance
to FQ is relatively uncommon in strains of MTBC susceptible to first-line drugs, however prolonged treatment with
a FQ (>10 days) before a diagnosis of TB is associated with a higher risk for FQ resistance and diagnostic delays [4,
5]. The primary mechanism of action of FQ is the inhibition of DNA synthesis [6] by inhibiting DNA gyrase. The
enzyme DNA gyrase generates the activity for cleaving and resealing double-stranded DNA. This action is necessary
for DNA replication, transcription, and recombination.
Resistance to FQ has mainly been attributed to point mutations in a 21-bp region of the MTBC gyrA gene, often
called the quinolone resistance determining region (QRDR). These mutations, commonly occurring at codons 90, 91,
and 94, prevent the drugs from effectively binding DNA gyrase [2, 6, 7]. Mutations in the gyrB gene have been noted
with varying rates of resistance, but high-level resistance is less common without a concurrent gyrA mutation [6].
Heteroresistance is the result of varying levels of resistance within a population of MTBC due to the presence of
sub-populations with differing nucleotides at a loci associated with drug resistance, resulting in both drug-resistant
and drug-susceptible organisms [8, 9]. This phenomenon is not limited to FQ but is commonly noted with this class of
drugs.
As newer FQ are assessed for use as antituberculosis drugs, it is important to determine cross-resistance between these
and older FQ that are tested in growth-based DST methods. Studies suggest that there may not be full cross-resistance
between ofloxacin (OFL), ciprofloxacin (CIP), levofloxacin (LVX), and moxifloxacin (MOX) at the defined critical
concentrations and that low- and high-level resistance, as seen with INH, may be applicable to FQ as well, particularly
MOX [10, 11].
DNA sequencing of gyrA revealed a G>A point mutation in codon 94 resulting in wild-type aspartate being replaced
with asparagine (Asp94Asn). Sequencing of gyrB was wild-type (i.e., no mutations were detected).
Among three methods, 14 results for OFL were reported for Isolate 2017A. This isolate was reported as resistant to
OFL by method, as follows:
●● 89% (8 / 9) of the results when using AP
●● 100% (3 / 3) of the results when using MGIT
●● 100% (2 / 2) of the results when using Sensititre
Participating laboratories also reported results for other FQ drugs (i.e., CIP, LVF, and MOX) for Isolate 2017A;
83% (15 / 18) of results noted resistance to these additional FQ. The isolate was reported resistant to three other
fluoroquinolones by method, as follows:
Ciprofloxacin
●● 71% (5 / 7) of the results when using AP
●● 100% (1 / 1) of the results when using MGIT
Moxifloxacin
●● 50% (1 / 2) of the results when using AP
●● 100% (3 / 3) of the results when using MGIT
●● 100% (2 / 2) of the results when using Sensititre
CDC MPEP MTBC DST Report for February 2017
11
Levofloxacin
●● 100% (3 / 3) of the results when using MGIT
This Asp94Asn mutation in the gyrA gene was detected by all (100%) laboratories that reported molecular testing for
FQ drugs.
Rifampin
Rifampin (RMP) is a bactericidal drug used as part of a standard first-line regimen for the treatment of TB. RMP’s
mechanism of action is to inhibit mycobacterial transcription by targeting DNA-dependent RNA polymerase [12].
The primary mechanism of resistance is a mutation within the 81-bp central region of the rpoB gene that encodes
the β-subunit of the bacterial DNA-dependent RNA polymerase [7]. Mutations in codons 531, 526, and 516 (E.
coli numbering system corresponding to 450, 445, and 435 in MTBC) are among the most frequent mutations in
RMP-resistant isolates and serve as predictors of RMP resistance [7, 12]. The activity of RMP on isolates with rpoB
mutations depends on both the mutation position and the type of amino acid change.
CDC has recommended that RMP resistance detected by the Xpert MTB / RIF assay be confirmed by DNA sequencing
of rpoB [13]. The Xpert MTB / RIF assay could generate results that falsely indicate resistance when compared to
growth-based methods because of the presence of silent / synonymous mutations [14]. Sequencing of rpoB will allow
for clarification of the result and understanding of possible discordance between rapid molecular and growth-based
testing results.
DNA sequence analysis of rpoB in Isolate 2017A revealed a C>T point mutation in codon 514 of the rpoB locus.
However, this mutation does not result in an amino acid change; phenylalanine remains phenylalanine (Phe514Phe).
This synonymous (i.e., silent) mutation in rpoB is not considered clinically significant and isolates with this mutation
reliably test as RMP-susceptible in growth-based systems. The Xpert MTB / RIF will generate a report of RMP
resistance detected for isolates with this mutation.
Among four methods, 97 results for RMP were reported for Isolate 2017A. This isolate was reported as susceptible to
RMP by method, as follows:
●● 100% (17 / 17) of the results when using AP
●● 100% (74 / 74) of the results when using MGIT
●● 100% (4 / 4) of the results when using Sensititre
●● 100% (2 / 2) of the results when using VersaTREK
Eleven (85%) of the molecular results reported for RMP noted that a mutation was detected; six of which noted
the silent mutation Phe514Phe. Three laboratories reported Mutation Not Detected, however this may be due to the
detection of a silent mutation not associated with resistance.
Complete first-line DST, second-line DST, and molecular results submitted by all participants for Isolate 2017A are
listed in Tables, 3, 4, and 5.
Four laboratories noted no growth for at least one antituberculosis drug tested for Isolate 2017A.
12
CDC MPEP MTBC DST Report for February 2017
Table 3. Isolate 2017A — Participant Results for First-Line DST
Results by Method for First-Line Drugs
AP
Drug
Rifampin
Isoniazid–Low
Isoniazid–High
Ethambutol
Pyrazinamide
MGIT
Sensititre
VersaTREK
S
R
Total
S
R
Total
S
R
Total
S
R
Total
17
0
17
74
0
74
4
0
4
2
0
2
17
0
17
72
1
73
4
0
4
2
0
2
17
0
17
25
1
26
4
0
4
2
0
2
18
0
18
72
0
72
4
0
4
2
0
2
59
12
71
1
0
1
Note — S=susceptible, R=resistant
Table 4. Isolate 2017A — Participant Results for Second-Line DST
Results by Method for Second-Line Drugs
AP
MGIT
Sensititre
Drug
S
R
Total
S
R
Total
S
R
Total
Streptomycin
18
0
18
38
0
38
3
0
3
Ofloxacin
1
8
9*
0
3
3
0
2
2
Ciprofloxacin
2
5
7
0
1
1
0
3
3
Levofloxacin
Moxifloxacin
1
1
2
0
3
3
0
2
2
Amikacin
9
0
9
3
0
3
3
0
3
Kanamycin
14
0
14
2
0
2
2
0
2
Capreomycin
13
1
14
4
0
4
1
0
1
Ethionamide
16
0
16
5
0
5
3
0
3
Rifabutin
7
0
7
4
0
4
3
0
3
Cycloserine
7
0
7
2
0
2
p-Aminosalicylic acid
12
0
12
3
0
3
Note — S=susceptible, R=resistant
*In addition, one laboratory reported borderline for OFL by AP.
CDC MPEP MTBC DST Report for February 2017
13
Table 5. Isolate 2017A — Participant Results for Molecular Testing
Molecular Testing
Drug
Mutation Detected
Mutation Not Detected
Total
Rifampin
10
3
13
Isoniazid
0
9
9
Ethambutol
0
5
5
Pyrazinamide
0
4
4
Ofloxacin
5
0
5
Ciprofloxacin
5
0
5
Levofloxacin
4
0
4
Moxifloxacin
4
0
4
Amikacin
0
4
4
Kanamycin
0
5
5
Capreomycin
0
4
4
Ethionamide
0
2
2
Rifabutin
1
1
2
14
CDC MPEP MTBC DST Report for February 2017
Isolate 2017B
Expected Result: Resistant to INH at 0.2 µg / ml and 1.0 µg / ml, and STR at 2.0 µg / ml by agar proportion
Isoniazid
Isoniazid (INH) is the most widely used first-line antituberculosis drug and is a cornerstone of regimens used to treat
tuberculosis (TB) disease and latent infection. INH is a prodrug and is activated by the catalase-peroxidase enzyme
encoded by the katG gene [2, 12]. The target of activated INH is enoyl-acyl-carrier protein reductase (encoded by
the inhA gene); this binding inhibits cell wall mycolic acid biosynthesis. There are two mechanisms that account for
the majority of INH resistance [2, 7, 12]. The most common mechanism, mutations in katG, is generally associated
with high-level resistance to INH. Resistance to INH can also occur by mutations in the promoter region of the inhA
gene, which are generally associated with low-level resistance to INH and are less frequent than katG mutations.
Approximately 10 – 15% of isolates found to be INH resistant have no mutations detected in either of these loci.
Numerous loci have been investigated to identify additional genes correlated with INH resistance. The fabG1 (also
known as mabA) gene, like inhA, is involved in mycolic acid biosynthesis and at least one mutation in this region has
been associated with low-level INH resistance [15, 16]. In MTBC, ahpC codes for an alkyl hydroperoxide reductase
that is associated with resistance to reactive oxygen and reactive nitrogen intermediates; consequently it was initially
believed that mutations in the promoter region could be surrogate markers for INH resistance [12].
DNA sequence analysis of inhA, katG, fabG1, and ahpC of Isolate 2017B revealed a T>A point mutation at codon
315 in the katG locus resulting in wild-type serine being replaced by threonine (Ser315Thr); inhA, fabG1 and ahpC
were wild-type (i.e., no mutations were detected).
The recommended critical concentration and additional higher concentrations for testing INH using the AP method are
0.2 µg / ml and 1.0 µg / ml, respectively. The equivalent concentrations for MGIT and VersaTREK are 0.1 µg / ml and
0.4 µg / ml [1].
For Isolate 2017B, 101 INH results were reported. This isolate was reported resistant to INH by method, as follows:
●● 100% (22 / 22) of the results when using AP
●● 100% (73 / 73) of the results when using MGIT
●● 100% (4 / 4) of the results when using Sensititre
●● 100% (2 / 2) of the results when using VersaTREK
Sixty-seven (98%) results were reported as resistant at the higher concentrations of INH. Only 40 laboratories
performing MGIT DST reported a result for the higher concentration of INH, although some may have tested the
higher concentration by a second DST method.
For the nine molecular results reported for INH, all (100%) reported Mutation Detected.
Streptomycin
Streptomycin (STR) belongs to the aminoglycoside class of drugs and its primary mechanism of action is to inhibit
protein synthesis by preventing the initiation of translation by binding to the 16s rRNA[7, 12]. In MTBC, the genetic
basis of the majority of resistance to STR is usually due to mutations in rrs or rpsL[6, 7]. CLSI recommended testing
STR as a second-line drug based on American Thoracic Society’s categorization of STR as a second-line drug for
treatment due to increased resistance in many parts of the world [1, 17].
Among three methods, 63 results for STR were reported for Isolate 2017B. This isolate was reported as resistant to
STR by method, as follows:
●● 100% (22 / 22) of the results when using AP
●● 100% (38 / 38) of the results when using MGIT
●● 100% (3 / 3) of the results when using Sensititre
CDC MPEP MTBC DST Report for February 2017
15
Ethionamide
Ethionamide (ETA) is a structural analog of INH. ETA, like INH, targets inhA, an enzyme involved in mycolic acid
biosynthesis [18]. Resistance to INH and ETA can occur by mutations in the promoter region of the inhA gene which
are generally associated with low‑level resistance to INH. Mutations in ethA also confer resistance to ETA, without
concomitant resistance to INH [18].
Sequencing analysis of ethA was not performed and, as noted above, sequencing of the inhA gene revealed wild-type
(i.e., no mutations were detected) for the expected result of Isolate 2017B.
Issues with reproducibility of DST results for ETA have been reported [19] and remain a potential concern.
Isolate 2017B was expected to be susceptible to ETA; however, of those testing ETA, resistance was reported by
method, as follows:
●● 100% (19 / 19) of the results when using AP
●● 100% (4 / 4) of the results when using MGIT
●● 0% (0 / 2) of the results when using Sensititre
For the two molecular results reported for ETA, one (50%) reported Mutation Detected.
Complete first-line DST, second-line DST, and molecular results submitted by all participants for Isolate 2017B are
listed in Tables 6, 7, and 8.
One laboratory noted no growth for at least one antituberculosis drug tested for Isolate 2017B.
Table 6. Isolate 2017B — Participant Results for First-Line DST
Results by Method for First-Line Drugs
AP
MGIT
Sensititre
VersaTREK
Drug
S
R
Total
S
R
Total
S
R
Total
S
R
Total
Rifampin
22
0
22
74
0
74
4
0
4
2
0
2
Isoniazid–Low
0
22
22
0
73
73
0
4
4
0
2
2
Isoniazid–High
0
22
22
1
39
40
0
4
4
0
2
2
Ethambutol
23
1
24
73
0
73
4
0
4
2
0
2
69
3
72
1
0
1
Pyrazinamide
Note — S=susceptible, R=resistant
16
CDC MPEP MTBC DST Report for February 2017
Table 7. Isolate 2017B — Participant Results for Second-Line DST
Results by Method for Second-Line Drugs
AP
MGIT
Sensititre
Drug
S
R
Total
S
R
Total
S
R
Total
Streptomycin
0
22
22
0
38
38
0
3
3
Ofloxacin
14
0
14
4
0
4
2
0
2
Ciprofloxacin
7
0
7
1
0
1
Levofloxacin
1
0
1
3
0
3
1
0
1
Moxifloxacin
3
0
3
3
0
3
2
0
2
Amikacin
11
0
11
3
0
3
3
0
3
Kanamycin
16
0
16
2
0
2
2
0
2
Capreomycin
14
1
15
4
0
4
Ethionamide
0
19
19
0
4
4
2
0
2*
Rifabutin
7
0
7
3
0
3
2
0
2*
Cycloserine
8
1
9
1
0
1*
p-Aminosalicylic acid
15
0
15
2
0
2*
Note — S=susceptible, R=resistant
*In addition, one laboratory reported borderline for CAP, ETA, RBT, CYC, and PAS by Sensititre.
Table 8. Isolate 2017B — Participant Results for Molecular Testing
Molecular Testing
Drug
Rifampin
Isoniazid
Ethambutol
Pyrazinamide
Ofloxacin
Ciprofloxacin
Levofloxacin
Moxifloxacin
Amikacin
Kanamycin
Capreomycin
Ethionamide
Rifabutin
Mutation Detected
Mutation Not Detected
Total
0
13
13
9
0
9
0
5
5
0
4
0
5
4
5
0
5
5
0
4
4
0
4
4
0
4
4
0
5
5
0
4
4
1
1
2
2
0
2
CDC MPEP MTBC DST Report for February 2017
17
Isolate 2017C
Expected Result: Resistant to AMK at 4.0 µg / ml, CAP at 10.0 µg / ml, and KAN at 5.0 µg / ml by
agar proportion
Second-line Injectables
The second-line injectable drugs include a cyclic-peptide antibiotic, capreomycin (CAP), and two aminoglycoside
antibiotics, kanamycin (KAN) and amikacin (AMK). All three drugs inhibit protein synthesis and the primary
mechanisms of resistance occur due to mutations in the following genes: rrs for AMK; rrs and eis for KAN; and rrs
and tlyA for CAP [6]. Since these drugs share a molecular target and bind at similar locations, cross-resistance has
frequently been observed for mutations in the rrs that codes for 16S rRNA [2, 20]. The most common rrs mutation for
cross-resistance to all three drugs is the A1401G point mutation [20].
Isolate 2017C was resistant to all of the second-line injectable drugs (AMK, KAN, and CAP) by the AP method and
DNA sequence analysis of rrs revealed the A1401G mutation.
For Isolate 2017C, 54 results were reported for AMK, KAN, and CAP. The isolate was reported resistant to the three
second-line injectables by method, as follows:
Amikacin
●● 100% (11 / 11) of the results when using AP
●● 100% (3 / 3) of the results when using MGIT
●● 100% (2 / 2) of the results when using Sensititre
Capreomycin
●● 100% (15 / 15) of the results when using AP
●● 100% (4 / 4) of the results when using MGIT
Kanamycin
●● 100% (15 / 15) of the results when using AP
●● 100% (2 / 2) of the results when using MGIT
●● 100% (2 / 2) of the results when using Sensititre
This A1401G mutation in the rrs gene was detected by all (100%) laboratories that reported molecular testing for
AMK, KAN, and CAP.
Complete first-line DST, second-line DST, and molecular results submitted by all participant for Isolate
2017C are listed in Tables 9, 10, and 11.
One laboratory noted no growth for at least one antituberculosis drug tested for Isolate 2017C.
18
CDC MPEP MTBC DST Report for February 2017
Table 9. Isolate 2017C — Participant Results for First-Line DST
Results by Method for First-Line Drugs
Drug
Rifampin
Isoniazid–Low
Isoniazid–High
Ethambutol
Pyrazinamide
S
AP
R
MGIT
R
Total
Sensititre
S
R
Total
VersaTREK
S
R
Total
Total
S
20
0
20
74
0
74
4
0
4
2
0
2
20
0
20
72
1
73
4
0
4
2
0
2
20
0
20
26
1
27
4
0
4
2
0
2
19
2
21
73
0
73
4
0
4
2
0
2
69
2
71*
1
0
1
Note — S=susceptible, R=resistant
*In addition, one laboratory reported borderline for PZA by MGIT.
Table 10. Isolate 2017C — Participant Results for Second-Line DST
Results by Method for Second-Line Drugs
AP
Drug
Streptomycin
Ofloxacin
Ciprofloxacin
Levofloxacin
Moxifloxacin
Amikacin
Kanamycin
Capreomycin
Ethionamide
Rifabutin
Cycloserine
p-Aminosalicylic acid
MGIT
Sensititre
S
R
Total
S
R
Total
S
R
Total
20
0
20
39
0
39
3
0
3
13
0
13
3
0
3
1
0
1*
6
0
6
1
0
1
1
0
1
3
0
3
1
0
1
3
0
3
3
0
3
1
0
1*
0
11
11
0
3
3
0
2
2
0
15
15
0
2
2
0
2
2
0
15
15
0
4
4
18
0
18
4
0
4
2
0
2*
7
0
7
3
0
3
2
0
2*
9
0
9
14
0
14
2
0
2*
Note — S=susceptible, R=resistant
*In addition, one laboratory reported borderline for OFL, MOX, ETA, RBT, CYC, and PAS by Sensititre.
CDC MPEP MTBC DST Report for February 2017
19
Table 11. Isolate 2017C — Participant Results for Molecular Testing
Molecular Testing
Drug
Mutation Detected
Mutation Not Detected
Total
Rifampin
0
13
13
Isoniazid
0
9
9
Ethambutol
0
5
5
Pyrazinamide
0
4
4
Ofloxacin
0
5
5
Ciprofloxacin
0
5
5
Levofloxacin
0
4
4
Moxifloxacin
0
4
4
Amikacin
4
0
4
Kanamycin
5
0
5
Capreomycin
4
0
4
Ethionamide
0
2
2
Rifabutin
0
2
2
20
CDC MPEP MTBC DST Report for February 2017
Isolate 2017D
Expected Result: Resistant to INH at 0.2 µg / ml and ETA at 5.0 µg / ml by agar proportion
Isoniazid
As previously noted, resistance to INH most commonly occurs due to mutations in the katG gene or the promoter
region of the inhA gene, however, mutations in fabG1 and ahpC can also cause resistance. Within fabG1, the
silent / synonymous mutation (i.e., nucleotide change but no corresponding change in amino acid) Leu203Leu
has been found to confer INH resistance through the formation of an alternative promoter, thereby increasing the
transcriptional levels of inhA [16]. Although silent mutations were previously believed to not play a role in drug
resistance, the Leu203Leu mutation demonstrates that silent mutations could be associated with resistance depending
on the specific gene and the location of the mutation.
DNA sequence analysis of inhA, katG, fabG1, and ahpC for Isolate 2017D revealed a G>A point mutation at
codon 203 resulting in the synonymous / silent mutation Leu203Leu; inhA, katG, and ahpC were wild-type (i.e., no
mutations were detected).
For Isolate 2017D, 98 INH results were reported. This isolate was reported resistant to low-level INH by method, as
follows:
●● 90% (18 / 20) of the results when using AP
●● 17% (12 / 72) of the results when using MGIT
●● 25% (1 / 4) of the results when using Sensititre
●● 100% (2 / 2) of the results when using VersaTREK
For the nine molecular results reported for INH, two (22%) laboratories reported Mutation Detected noting it was a
silent mutation.
Ethionamide
Resistance to INH and ETA can occur by mutations in the fabG1–inhA regulatory region, which are generally
associated with low-level resistance to INH. Mutations in ethA also confer resistance to ETA, without concomitant
resistance to INH [18].
Sequencing analysis of ethA was not performed and as previously noted, sequencing of the inhA gene revealed wildtype (i.e., no mutations were detected). The synonymous / silent mutation Leu203Leu was detected in the fabG1 locus
for Isolate 2017D.
For Isolate 2017D, 25 ETA results were reported. This isolate was reported resistant to ETA by method, as follows:
●● 95% (18 / 19) of the results when using AP
●● 100% (4 / 4) of the results when using MGIT
●● 0% (0 / 2) of the results when using Sensititre
Rifampin
DNA sequence analysis of rpoB in Isolate 2017D revealed a C>T point mutation in codon 528 of the rpoB locus.
However, this mutation does not result in an amino acid change; arginine remains arginine (Arg528Arg). Unlike
the fabG1 silent mutation in this isolate that was associated with INH resistance, the Arg528Arg synonymous (i.e.,
silent) mutation in rpoB is not considered clinically significant and isolates with this mutation reliably test as RMPsusceptible in growth-based systems.
The Xpert MTB / RIF could generate a report of RMP resistance detected for isolates with this mutation. Sequencing
of rpoB will allow for clarifying the result and understanding discordance between the Xpert result and results from
growth-based testing.
CDC MPEP MTBC DST Report for February 2017
21
Among four methods, 101 results for RMP were reported for Isolate 2017D. This isolate was reported as susceptible
to RMP by method, as follows:
●● 100% (21 / 21) of the results when using AP
●● 100% (74 / 74) of the results when using MGIT
●● 100% (4 / 4) of the results when using Sensititre
●● 100% (2 / 2) of the results when using VersaTREK
Of the thirteen molecular results reported for RMP, four (31%) reported Mutation Detected; however, five laboratories
noted that a silent mutation was detected as a comment.
Complete first-line DST, second-line DST, and molecular results submitted by all participants for Isolate 2017D are
listed in Tables 12, 13, and 14.
One laboratory noted no growth for at least one antituberculosis drug tested for Isolate 2017D.
Table 12. Isolate 2017D — Participant Results for First-Line DST
Results by Method for First-Line Drugs
AP
MGIT
Sensititre
VersaTREK
Drug
S
R
Total
S
R
Total
S
R
Total
S
R
Total
Rifampin
21
0
21
74
0
74
4
0
4
2
0
2
Isoniazid–Low
2
18
20
60
12
72
3
1
4
0
2
2
Isoniazid–High
21
0
21
28
1
29
4
0
4
2
0
2
Ethambutol
21
0
21*
73
0
73
4
0
4
2
0
2
66
6
72
1
0
1
Pyrazinamide
Note — S=susceptible, R=resistant
* In addition, one laboratory reported borderline for EMB by AP.
22
CDC MPEP MTBC DST Report for February 2017
Table 13. Isolate 2017D — Participant Results for Second-Line DST
Results by Method for Second-Line Drugs
Drug
Streptomycin
Ofloxacin
Ciprofloxacin
Levofloxacin
Moxifloxacin
Amikacin
Kanamycin
Capreomycin
Ethionamide
Rifabutin
Cycloserine
p-Aminosalicylic acid
S
AP
R
S
MGIT
R
Total
21
0
14
Sensititre
R
Total
Total
S
21
39
0
39
3
0
3
0
14
3
0
3
1
1
2
7
0
7
1
0
1
1
0
1
3
0
3
1
0
1
3
0
3
3
0
3
1
1
2
11
1
12
3
0
3
3
0
3
16
0
16
2
0
2
1
0
1*
15
1
16
4
0
4
1
0
1
1
18
19
0
4
4
2
0
2*
8
0
8
3
0
3
3
0
3
9
0
9
1
0
1
15
0
15
2
0
2
Note — S=susceptible, R=resistant
* In addition, one laboratory reported borderline for KAN and ETA by Sensititre.
Table 14. Isolate 2017D — Participant Results for Molecular Testing
Molecular Testing
Drug
Rifampin
Isoniazid
Ethambutol
Pyrazinamide
Ofloxacin
Ciprofloxacin
Levofloxacin
Moxifloxacin
Amikacin
Kanamycin
Capreomycin
Ethionamide
Rifabutin
Mutation Detected
Mutation Not Detected
Total
4
9
13
2
7
9
0
5
5
0
4
4
0
5
5
0
5
5
0
4
4
0
4
4
0
4
4
0
5
5
0
5
5
2
0
2
1
1
2
CDC MPEP MTBC DST Report for February 2017
23
Isolate 2017E
Expected Result: Susceptible to all first- and second-line drugs by agar proportion
Isolate 2017E is susceptible to all first- and second-line drugs.
Most (99%) results were reported susceptible for this isolate across all methods.
Complete first-line DST, second-line DST, and molecular results submitted by all participants for Isolate 2017E are
listed in Tables 15, 16, and 17.
Two laboratories noted no growth for at least one antituberculosis drug tested for Isolate 2017E.
Table 15. Isolate 2017E — Participant Results for First-Line DST
Results by Method for First-Line Drugs
Drug
S
AP
R
Rifampin
20
0
20
72
0
72
4
0
4
2
0
2
Isoniazid–Low
20
0
20
71
0
71
4
0
4
2
0
2
Isoniazid–High
20
0
20
26
0
26
4
0
4
2
0
2
Ethambutol
20
1
21
71
0
71
4
0
4
2
0
2
70
1
71
1
0
1
Pyrazinamide
Total
S
MGIT
R
Total
Sensititre
S
R
Total
VersaTREK
S
R
Total
Note — S=susceptible, R=resistant
24
CDC MPEP MTBC DST Report for February 2017
Table 16. Isolate 2017E — Participant Results for Second-Line DST
Results by Method for Second-Line Drugs
Drug
S
AP
R
Streptomycin
20
0
20
37
0
37
3
0
3
Ofloxacin
13
0
13
3
0
3
2
0
2
Ciprofloxacin
6
0
6
1
0
1
Levofloxacin
1
0
1
3
0
3
1
0
1
Moxifloxacin
3
0
3
3
0
3
1
0
1†
Amikacin
10
1
11
3
0
3
3
0
3
Kanamycin
15
0
15
2
0
2
2
0
2
Capreomycin
14
1
15
4
0
4
1
0
1
Ethionamide
16
1
17*
4
0
4
3
0
3
Rifabutin
7
0
7
3
0
3
3
0
3
Cycloserine
8
1
9
2
0
2
p-Aminosalicylic acid
14
0
14
2
0
2
Total
S
MGIT
R
Total
S
Sensititre
R
Total
Note — S=susceptible, R=resistant
*In addition, one laboratory reported borderline for ETA by AP.
†In addition, one laboratory reported borderline for MOX by Sensititre.
CDC MPEP MTBC DST Report for February 2017
25
Table 17. Isolate 2017E — Participant Results for Molecular Testing
Molecular Testing
Drug
Mutation Detected
Mutation Not Detected
Total
Rifampin
3*
11
14
Isoniazid
0
9
9
Ethambutol
0
5
5
Pyrazinamide
0
4
4
Ofloxacin
0
5
5
Ciprofloxacin
0
5
5
Levofloxacin
0
4
4
Moxifloxacin
0
4
4
Amikacin
0
4
4
Kanamycin
0
5
5
Capreomycin
0
4
4
Ethionamide
0
2
2
Rifabutin
0
2
2
*Three laboratories noted detection of Pro535Ser mutation.
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CDC MPEP MTBC DST Report for February 2017
Equivalent Critical Concentrations (Concentrations listed as µg / ml)
Agar Proportion
Drugs
7H10 agar
7H11 agar
Isoniazid
0.2 and 1.0*
0.2 and 1.0*
Rifampin
1.0
1.0
5.0 and 10.0*
7.5
Not recommended
Not recommended
2.0 and 10.0
2.0 and 10.0
Amikacin
4.0
-†
Capreomycin
10.0
10.0
Kanamycin
5.0
6.0
Levofloxacin
1.0
-†
Moxifloxacin
0.5
0.5
Ofloxacin
2.0
2.0
Ethionamide
5.0
10.0
Rifabutin
0.5
0.5
p-Aminosalicylic acid
2.0
8.0
First-Line Drugs
Ethambutol
Pyrazinamide
Second-Line Drugs
Streptomycin
NOTE — Critical concentrations as indicated in CLSI M24-A2 document [1]
* The higher concentration of INH and EMB should be tested as second-line drugs after resistance at the critical concentration is detected.
† Breakpoints for establishing susceptibility have not be determined.
Broth Based Media
Drugs
MGIT
VersaTREK
Isoniazid
0.1 (and 0.4*)
0.1 (and 0.4*)
Rifampin
1.0
1.0
Ethambutol
5.0
5.0 (and 8.0*)
100.0
300.0
First-Line Drugs
Pyrazinamide
Second-Line Drugs
Streptomycin
1.0 (and 4.0*)
NOTE — Critical concentrations as indicated in applicable manufacturer package inserts
*The higher concentration of INH, EMB, and STR should be tested after resistance at the critical concentration is detected.
CDC MPEP MTBC DST Report for February 2017
27
References
1. CLSI, Susceptibility Testing of Mycobacteria, Nocardiae, and Other Aerobic Actinomycetes; Approved Standard Second Edition in CLSI Document M24 A-2. 2011, Clinical and Laboratory Standards Institute: Wayne, PA.
2. Campbell, P.J., et al., Molecular detection of mutations associated with first- and second-line drug resistance
compared with conventional drug susceptibility testing of Mycobacterium tuberculosis. Antimicrob Agents
Chemother, 2011. 55(5): p. 2032-41.
3. APHL, TB Drug Susceptibility Testing Expert Panel Meeting Summary Report. 2007, Association of Public
Health Laboratories: Washington, D.C.
4. Devasia, R.A., et al., Fluoroquinolone resistance in Mycobacterium tuberculosis: the effect of duration and
timing of fluoroquinolone exposure. Am J Respir Crit Care Med, 2009. 180(4): p. 365-70.
5. Chen, T.C., et al., Fluoroquinolones are associated with delayed treatment and resistance in tuberculosis: a
systematic review and meta-analysis. Int J Infect Dis, 2011. 15(3): p. e211-6.
6. Zhang, Y. and W.W. Yew, Mechanisms of drug resistance in Mycobacterium tuberculosis: update 2015. Int J
Tuberc Lung Dis, 2015. 19(11): p. 1276-89.
7. Zhang, Y. and W.W. Yew, Mechanisms of drug resistance in Mycobacterium tuberculosis. Int J Tuberc Lung Dis,
2009. 13(11): p. 1320-30.
8. Eilertson, B., et al., High proportion of heteroresistance in gyrA and gyrB in fluoroquinolone-resistant
Mycobacterium tuberculosis clinical isolates. Antimicrob Agents Chemother, 2014. 58(6): p. 3270-5.
9. Rinder, H., K.T. Mieskes, and T. Loscher, Heteroresistance in Mycobacterium tuberculosis. Int J Tuberc Lung
Dis, 2001. 5(4): p. 339-45.
10. Willby, M., et al., Correlation between GyrA substitutions and ofloxacin, levofloxacin, and moxifloxacin crossresistance in Mycobacterium tuberculosis. Antimicrob Agents Chemother, 2015. 59(9): p. 5427-34.
11. Kam, K.M., et al., Stepwise decrease in moxifloxacin susceptibility amongst clinical isolates of multidrugresistant Mycobacterium tuberculosis: correlation with ofloxacin susceptibility. Microb Drug Resist, 2006. 12(1):
p. 7-11.
12. Almeida Da Silva, P.E. and J.C. Palomino, Molecular basis and mechanisms of drug resistance in
Mycobacterium tuberculosis: classical and new drugs. J Antimicrob Chemother, 2011. 66(7): p. 1417-30.
13. Availability of an assay for detecting Mycobacterium tuberculosis, including rifampin-resistant strains, and
considerations for its use — United States, 2013. MMWR Morb Mortal Wkly Rep, 2013. 62(41): p. 821-7.
14. Van Deun, A., et al., Rifampin drug resistance tests for tuberculosis: challenging the gold standard. J Clin
Microbiol, 2013. 51(8): p. 2633-40.
15. Ramaswamy, S.V., et al., Single nucleotide polymorphisms in genes associated with isoniazid resistance in
Mycobacterium tuberculosis. Antimicrob Agents Chemother, 2003. 47(4): p. 1241-50.
16. Ando, H., et al., A silent mutation in mabA confers isoniazid resistance on Mycobacterium tuberculosis. Mol
Microbiol, 2014. 91(3): p. 538-47.
17. Centers for Disease Control and Prevention, Treatment of Tuberculosis, American Thoracic Society, CDC, and
Infectious Diseases Society of America. 2003, MMWR. p. 4,11,19-20.
18. Morlock, G.P., et al., ethA, inhA, and katG loci of ethionamide-resistant clinical Mycobacterium tuberculosis
isolates. Antimicrob Agents Chemother, 2003. 47(12): p. 3799-805.
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CDC MPEP MTBC DST Report for February 2017
19. Varma-Basil, M. and R. Prasad, Dilemmas with ethionamide susceptibility testing of Mycobacterium tuberculosis:
A microbiologist & physician’s nightmare. Indian J Med Res, 2015. 142(5): p. 512-4.
20. Maus, C.E., B.B. Plikaytis, and T.M. Shinnick, Molecular analysis of cross-resistance to capreomycin,
kanamycin, amikacin, and viomycin in Mycobacterium tuberculosis. Antimicrob Agents Chemother, 2005. 49(8):
p. 3192-7.
CDC MPEP MTBC DST Report for February 2017
29
Appendix 1: Accessible Explanations of Figures
Figure 1. Primary Classification of Participating Laboratories, February 2017. The primary classification of the
80 laboratories participating in the February 2017 MPEP survey is shown in this pie chart. The largest slice, at 66%,
represents 53 laboratories that have self-classified as a health department laboratory. The next major slice signifies
15 hospital laboratories. The remaining three slices of the pie chart represent 8 independent laboratories, 3 federal
government laboratories, and 1 laboratory that identified as a quality control manufacturer.
Figure 2. Distribution of the Annual Volume of MTBC Isolates Tested for Drug Susceptibility by Participants
in Previous Calendar Year. The annual volume of MTBC isolates tested for drug susceptibility by participating
laboratories (N=80) in 2015 is displayed in this vertical bar graph. The vertical y –axis is the number of laboratories
responding and ranges from 0 to 35 using increments of 5. Along the horizontal x-axis are nine vertical bars
representing the number of isolates tested per year. From left to right, 29 laboratories tested less than or equal to 50
isolates per year; 23 laboratories tested between 51 to 100 isolates per year; 6 laboratories tested between 101 to 150
isolates per year; 6 laboratories tested between 151 to 200 isolates per year; 2 laboratories tested between 201 to 250
isolates per year; 3 laboratories tested between 251 to 300 isolates per year; 3 laboratories tested between 301 to 500
isolates per year; 7 laboratories tested between 501 to 1000 isolates per year, and 1 laboratory tested between greater
than or equal to 1001 isolates per year.
Figure 3. MTBC Drug Susceptibility Test Method Used by Participants. The drug susceptibility testing methods
used by MPEP participants (N=120) is displayed in this vertical bar graph. The vertical y-axis is the number of
laboratories reporting and ranges from 0 to 80, by increments of 10, and the horizontal x- axis lists the susceptibility
testing methods. Each bar represents the number of reporting laboratories performing a particular drug susceptibility
test method. From left to right: 76 used MGIT, 25 used agar proportion, 4 used Sensititre, 2 used VersaTREK, and 13
used a molecular method.
Figure 4. Molecular Method Reported. The molecular methods used by MPEP participants (N=13) are displayed
in this pie chart. The largest slice represents the 6 laboratories that perform targeted DNA sequencing. The next three
slices represent 4 laboratories that use the Cepheid Xpert TB/RIF assay, 2 laboratories that reported results for the
Hain line probe assays, and the 1 laboratory that reported results by whole genome sequencing.
Figure 5. Antituberculosis Drugs Tested by Participants. The antituberculosis drugs tested by MPEP participants
is displayed in a horizontal bar graph. The vertical y -axis contains a list of each drug tested and the horizontal x-axis
contains the number of laboratories and ranges from 0 to 90, by increments of 10. There are 16 horizontal bars with
each bar representing the number of laboratories reporting a result for a particular drug for susceptibility testing. 80
laboratories tested rifampin; 80 laboratories tested isoniazid; 79 laboratories tested ethambutol; laboratories tested
pyrazinamide; 53 laboratories tested streptomycin; 19 laboratories tested ofloxacin; 8 laboratories tested moxifloxacin;
8 laboratories tested ciprofloxacin; 5 laboratories tested levofloxacin; 19 laboratories tested kanamycin; 20
laboratories tested capreomycin; 17 laboratories tested amikacin; 25 laboratories tested ethionamide; 18 laboratories
tested PAS; 14 laboratories tested rifabutin; and 11 laboratories tested cycloserine.
30
CDC MPEP MTBC DST Report for February 2017
Notes:
CDC MPEP MTBC DST Report for February 2017
31
For more information please contact
Centers for Disease Control and Prevention
1600 Clifton Road NE, Atlanta, GA 33029-4027
Telephone: 1-800-CDC-INFO (232-4636)
MPEP Telephone: 404-639-4013
MPEP Email: TBMPEP@cdc.gov
MPEP Web: www.cdc.gov / tb / topic / laboratory / mpep / default.htm
Publication date: September 2017
| File Type | application/pdf |
| Author | Yakrus, Mitchell (CDC/OID/NCHHSTP) |
| File Modified | 2018-06-27 |
| File Created | 2018-02-02 |