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Drug-Resistant Tuberculosis
Your name Institution/organizationMeetingDate
International Standard 11
ISTC TB Training Modules 2009
Drug-Resistant Tuberculosis
Objectives: At the end of this presentation,participants will be able to: Define the areas with the highest global burden of
MDR. Understand the microbiological basis for the
development of drug resistance. Recognize the clinical errors and programmatic
factors that can lead to the development of drug resistance.
Recognize the risk factors for MDR/XDR and the signs of treatment failure that should trigger an evaluation for drug resistance and treatment adjustment.
Drug-Resistant Tuberculosis
Overview: Definitions Global burden and individual
impact Pathogenesis and
clinical/programmatic contributors to development
Early identification and risk factors
Recommendations for diagnosis
International Standard 11
ISTC TB Training Modules 2009
Drug-Resistant Tuberculosis
MDR-TB is a manmade problem…It is costly, deadly, debilitating and is a major threat to our current control strategies.
ISTC TB Training Modules 2009
Standard 11: Drug-Resistant TB(1 of 3)
An assessment of the likelihood of drug resistance, • based on history of prior treatment, • exposure to a possible source case
having drug-resistant organisms, • and the community prevalence of drug
resistance,
should be obtained for all patients.
ISTC TB Training Modules 2009
Standard 11: Drug-Resistant TB
Drug susceptibility testing should be performed at the start of therapy for all previously treated patients
Patients who remain sputum smear-positive at completion of 3 months of treatment and patients who have failed, defaulted from, or relapsed following one of more courses of treatment should always be assessed for drug resistance
(2 of 3)
ISTC TB Training Modules 2009
Standard 11: Drug-Resistant TB
For patients in whom drug resistance is considered to be likely, culture and testing for susceptibility/resistance to at least isoniazid and rifampicin should be performed promptly
Patient counseling and education should begin immediately to minimize the potential for transmission
Infection control measures appropriate to the setting should be applied
(3 of 3)
ISTC TB Training Modules 2009
Drug-Resistant TB: Definitions
Mono-resistant: Resistance to a single drug Poly-resistant: Resistance to more than one
drug, but not the combination of isoniazid and rifampicin
Multidrug-resistant (MDR): Resistance to at least isoniazid and rifampicin
Extensively drug-resistant (XDR): MDR plus resistance to fluoroquinolones and at least 1 of the 3 injectable drugs (amikacin, kanamycin, capreomycin)
ISTC TB Training Modules 2009
Drug-Resistant TB: Definitions
Primary drug-resistance: “New Cases”Drug resistance in a patient who has never been treated for tuberculosis or received less than one month of therapy
Secondary (acquired) drug-resistance:“Previously Treated Cases”
Drug resistance in a patient who has received at least one month of anti-TB therapy
ISTC TB Training Modules 2009
WHO Anti-tuberculosis drug resistance in the world, Fourth global report, 2008
Estimated global incidence and proportionof MDR among TB cases, 2006
Estimated Global MDR Cases
2006 TB cases MDR cases %
New Cases* 9,123,922 285,718 3.8
Previously treated cases* 1,052,145 203,230 19.3
Total cases** 10,192,986 489,139 4.8
*175 countries reporting; **185 countries reporting*175 countries reporting; **185 countries reporting
WHO Anti-tuberculosis drug resistance in the world, Fourth global report, 2008
Estimated Global MDR Cases
Estimated global prevalence of MDR (based on 2-3 year duration as an active case): 1,000,000 –1,500,000 cases
Estimated 42% of global MDR cases have had prior treatment
China and India carry 50% of the global MDR burden, with the Russian Federation carrying a further 7%
ISTC TB Training Modules 2009
Distribution of MDR: No Prior Treatment
Zignol M, et al. JID 2006; 194: 479-85
Distribution of MDR rates among new cases (previously untreated)
ISTC TB Training Modules 2009
Zignol M, et al. JID 2006; 194: 479-85
Distribution of MDR: Prior Treatment
Distribution of MDR rates among previously treated cases
ISTC TB Training Modules 2009
Individual Impact of MDR
Average direct medical costs per case in the US: $27,752 [Burgos, et al. CID 2005; 40: 968-75]
Long treatment duration (18-24 mos.), often difficult and toxic
Long periods of isolation may be necessary
Depression is common Disease may be incurable (chronic) Higher rate of death
ISTC TB Training Modules 2009
Impact of Resistance on Outcome
Resistance pattern New Cases (%) Retreatment (%)
Pan-susceptible 4 10
Any Resistance 5 21
MDR 30 45
INH (not MDR) 6 23
RIF (not MDR) 13 29
Other 4 15
% of cases with failure or death, standard 4-drug regimen
Espinal MA, et al. JAMA. 2000;283(19):2537-45
ISTC TB Training Modules 2009
Adapted from Paul Nunn, StopTB/WHO 2009
Global TB estimates: XDR and MDR 2007
Estimated Global XDR
2007 Estimated number of cases
Estimated number of
deaths
All forms of TB 9.2 million(139 per 100,000)
1.77 million(27 per 100,000)
MDR 511,000 ~150,000
XDR ~50,000 ~30,000
ISTC TB Training Modules 2009WHO 2009
Distribution of XDR
Countries that had reported at least one XDR-TB caseby end of April 2009
ISTC TB Training Modules 2009
Pathogenesis ofDrug Resistance
ISTC TB Training Modules 2009
INH = 1 in 106
RIF = 1 in 108
EMB = 1 in 106
Strep = 1 in 106
INH + RIF = 1 in 1014
Frequency of Resistance Mutations
ISTC TB Training Modules 2009
Development of Drug Resistance
1 2
3
Multiple Drugs vs. Monotherapy
I = INH resistant, R = RIF resistant, P = PZA resistant, E = EMB resistant
INH
IR
EP
RIFPZAEMB
INH II
I I
I
I
ISTC TB Training Modules 2009
Development of Drug Resistance
I = INH resistant, R = RIF resistant, P = PZA resistant
Further acquired resistance after single drug added
II
I I
I
I
IR IRIR
IRIR
IR
IR
IR
IRIR IR
IRIR
IRP
III
I
II
I
II
I II
IIP
IRI
INHRIFINH
ISTC TB Training Modules 2009
Mixed population (susceptible and resistant)
INH-resistant bacilli
0 2 4 6 8 10 12 14 16 18 20 22 24
Emergence of INH-resistant strain because of ineffective treatment (INH monotherapy)
Effective multi-drug therapy
Development of Drug Resistance
Weeks
ISTC TB Training Modules 2009
Months of Rx 0 5 7 9
INH
RIF
EMB
Smear + + + +
Culture + + + +
Susceptibility
INH R* R R R
RIF S* R R R
EMB S* S S R* Results not known to clinician
Resistance: Unintended Monotherapy
ISTC TB Training Modules 2009
Resistance: Unintended Acquired
Months of Rx 0 2 4 8
INH/RIF/EMB/PZA
Capreo/Moxi
Smear + + + -
Culture + + + -
Susceptibility
INH R* R R R
RIF S* R R R
EMB R* R R R
* Results not known to clinician
ISTC TB Training Modules 2009
Factors that Lead to Drug Resistance
Causes of inadequate treatment: Patient-related factors Healthcare provider-related factors Healthcare system-related factors
ISTC TB Training Modules 2009
Factors that Lead to Drug Resistance
Patient-related factors: Non-adherence, default Malabsorption of drugs Adverse drug reactions Lack of information, transportation, money Social barriers to treatment adherence Substance dependency disorders
ISTC TB Training Modules 2009
Factors that Lead to Drug Resistance
Healthcare provider-related factors: Inadequate initial treatment regimen: Wrong
combination or doses, guideline noncompliance Treatment “in the dark” for retreatment cases:
no drug susceptibility testing available, or results delayed
Clinical errors: Adding a single drug to a failing regimen
Lack of proper monitoring Lack of proper provider awareness
ISTC TB Training Modules 2009
Factors that Lead to Drug Resistance
Healthcare program-related factors: Inconsistent access to care Unavailability of drugs (stock-outs or delivery
disruptions) Poor drug quality, poor storage conditions Poorly organized or under-funded TB-control
programs Inappropriate or no guidelines Lack of appropriate or timely laboratory testing
ISTC TB Training Modules 2009
Common Causes Interventions
Nonadherence, default
Patient-centered DOT, education, support, incentives
Management errors, lack of expertise
Consultation with experts, vigilant patient monitoring for treatment failure, provider training
Inadequate regimen in presence of drug resistance
Improved access to drugs and susceptibility testing
Strategies to Prevent Drug Resistance
ISTC TB Training Modules 2009
Diagnosis of MDR-TB
ISTC TB Training Modules 2009
Diagnosis of MDR
Appropriate diagnosis and timely treatmentintervention for MDR-TB is facilitated by:
Recognition of risk factors for MDR-TB Early recognition of treatment failure Drug-susceptibility testing (if available)
ISTC TB Training Modules 2009
Recognition of risk factors: History of prior therapy (most powerful
predictor)
• Failure of a retreatment regimen
• Failure of the initial treatment regimen
• Relapse after apparently successful treatment
• Return after default without recent treatment failure
Clinical Suspicion for MDR
ISTC TB Training Modules 2009
Recognition of risk factors: Close contact to known or suspected
MDR-TB case (“incurable” TB or TB requiring multiple treatment courses)
Residence in an MDR-endemic area Exposure in institutions that have drug-
resistance outbreaks or high prevelance HIV infection (in some settings)
Clinical Suspicion for MDR
ISTC TB Training Modules 2009
Early recognition of treatment failure:
Cough should improve within the first two weeks of effective treatment
Signs of failure: lack of sputum conversion, persistent or recurrent cough, continued fever, night sweats and failure to gain weight
Clinical Suspicion for MDR
ISTC TB Training Modules 2009
Laboratory Diagnosis of MDR
Drug-susceptibility testing, if available,should be ordered when: Risk factors for MDR are present There is evidence of treatment failure
Results can both: Confirm diagnosis of drug resistance Guide treatment choices
ISTC TB Training Modules 2009
Drug-Susceptibility Results: Problems
Identification of MDR may take 4 – 8 weeks, andsecond-line drug testing 6 – 12 weeks for results:
• 2 – 4 weeks for initial culture to become positive
• Additional 2 – 4 weeks to get 1st-line DST
• Additional 2 – 4 weeks to get 2nd-line DST
In view of this inherent delay, don’t wait to treat with an augmented regimen if MDR suspicion is high and resistance pattern can be predicted.
ISTC TB Training Modules 2009
Rapid Drug-Susceptibility Tests
Line-probe assays• Identifies M.tb and
genetic mutations associated with INH and RIF resistance
• Can be used directly on sputum specimens, results within 1-2 days
Endorsed for use on either direct smear positive sputum or culture specimens
*GenoType MTDBRplus strips (Hain Lifescience)
ISTC TB Training Modules 2009
Drug-Susceptibility Results: Problems
Drug-susceptibility testing requires training and experience
Quality assurance is difficult Testing is unreliable for some drugs,
especially ethambutol and pyrazinamide Results will sometimes differ in different
laboratories
ISTC TB Training Modules 2009
Predicting Patterns of Resistance
Examine prior treatment regimen:
Consider all drugs used previously as potentially ineffective
Example: A symptomatic patient with 2 prior treatment courses using red capsules, white pills and shotsPredict: Resistance to INH, RIF, and streptomycin
ISTC TB Training Modules 2009
Predicting Risk for MDR
If there has been contact to a known MDR case, use pattern of drug resistance in index case
Use epidemiologic information determined from surveys to identify patterns and rates of resistance
Presence of RIF resistance predicts MDR
ISTC TB Training Modules 2009
Predicting Risk for XDR
Two strongest risk factors for XDR are: Failure of a TB treatment which contains
second-line drugs including an injectable agent and a fluoroquinolone
Close contact with an individual with documented XDR or for whom treatment with second-line drugs is failing or has failed
ISTC TB Training Modules 2009
Summary: Early suspicion, diagnosis and appropriate
treatment is critical in preventing further progression and transmission of drug-resistant disease
Prior treatment is the most significant predictor for drug resistance, but learn to recognize all risk factors
Drug-Resistant Tuberculosis
ISTC TB Training Modules 2009
Summary (cont.): Recognize when your patient is failing
standard treatment
Obtain first- line drug susceptibility testing whenever possible for patients with suspected MDR
Drug-Resistant Tuberculosis
ISTC TB Training Modules 2009
Summary: ISTC Standard Covered*
Standard 11: Assessment for drug resistance should be obtained based on
a history of:• Prior treatment• Exposure to a possible drug-resistant source• High community prevalence
Drug-susceptibility testing should be performed at the start of therapy for all patients previously treated, or smear+ at three months of treatment, or if failed/defaulted/relapsed
If drug-resistance likely, do culture and DST for at least isoniazid and rifampicin
Patient counseling/education should begin immediately to minimize potential for transmission
Infection control measures should be applied*[Abbreviated version]
ISTC TB Training Modules 2009
Alternate Slides
ISTC TB Training Modules 2009
Resources WHO: Guidelines for the programmatic
management of drug-resistant tuberculosis, Emergency update 2008 www.who.int/tb
Drug-Resistant Tuberculosis, A Survival Guide for Clinicians 2nd edition, 2008 www.nationaltbcenter.ucsf.edu
The PIH guide to the Medical Management of Multidrug-Resistant Tuberculosis, International Edition. Partners in Health 2003. www.pih.org
ISTC TB Training Modules 2009
Resource Availability
The following tests are available at _________: Smear microscopy
• Direct smear / light microscopy
• Fluorescence microscopy
• Concentration/chemical processing
Culture• Solid media
• Liquid media
Drug susceptibility testing Other
ISTC TB Training Modules 2009
Resource Contact Information
Laboratory testing: Microscopy/culture/DST
[Name, addresses, e-mail, etc.]
Specimen transport:
[Name, addresses, e-mail, etc.]
ISTC TB Training Modules 2009
Purpose of ISTC
ISTC TB Training Modules 2009
ISTC: Key Points
21 Standards (revised/renumbered in 2009) Differ from existing guidelines: standards
present what should be done, whereas, guidelines describe how the action is to be accomplished
Evidence-based, living document Developed in tandem with Patients’ Charter
for Tuberculosis Care Handbook for using the International
Standards for Tuberculosis Care
ISTC TB Training Modules 2009
Audience: all health care practitioners, public and private
Scope: diagnosis, treatment, and public health responsibilities; intended to complement local and national guidelines
Rationale: sound tuberculosis control requires the effective engagement of all providers in providing high quality care and in collaborating with TB control programs
ISTC: Key Points
ISTC TB Training Modules 2009
Questions
ISTC TB Training Modules 2009
Drug-resistant Tuberculosis
1. A 68 year-old man presents with cough and weight loss for 2 months. He recalls treatment for TB eight years ago, but believes it only lasted a few months. A chest film reveals a cavitary infiltrate in the right apex of the lung. Factors that predict or are associated with a risk for the development of drug-resistance would include all of the following except:
A. Prior inadequate TB treatment
B. Development of chronic diarrhea with possible malabsorption of drugs
C. New diagnosis of diabetes
D. Persistent cough and weight loss after two months of standard therapy
ISTC TB Training Modules 2009
Drug-resistant Tuberculosis
2. Extensively-drug resistant (XDR) TB is defined as TB that is resistant to:
A. At least six anti-tuberculosis drugs
B. At least isoniazid and rifampicin
C. Isoniazid, rifampicin, ethambutol, pyrazinamide, streptomycin, and a fluoroquinolone
D. Isoniazid, rifampicin, a fluoroquinolone, and at least one of these three injectable agents (amikacin, kanamycin, capreomycin)
ISTC TB Training Modules 2009
Drug-resistant Tuberculosis
3. Which of the following statements regarding the microbiologic pathogenesis of drug-resistant tuberculosis is most correct?A. Patients with cavitary tuberculosis have a low bacillary load and
therefore are unlikely to harbor any naturally occurring drug-resistant organisms
B. Mono-therapy with a single anti-tuberculosis drug can lead to selective proliferation of naturally occurring drug-resistant organisms
C. Acquired resistance to anti-tuberculosis drugs only occurs for isoniazid and rifampicin
D. In a patient on a standard initial four-drug treatment regimen with evidence for clinical failure in whom there is a high suspicion for drug resistance, the addition of a fluoroquinolone alone will reduce the risk for further development of drug resistance