Tuberculosis.Diagnostics, Treatment.

General MedicineEnglish Learning Programme

Phthisiology, Lecture #2

Diagnostics

• history (epidemiological, social, alcohol, elicit drugs, comorbidities)

• physical examination• imaging (plane X-ray, CT...)• tuberculine skin test (TST)• bacteriology

Primary (Ghon) focus, primary complex

Miliary TB

Postprimary TB

Postprimary TB with cavitations

Clacified pleural involvement

Tuberculin skin testing (TST)

• 2 TU v 0,1 ml (Mantoux II) intradermally!• read after 72 hours (induration in mm)• Interpretation issues:• previous vaccination• population examined

• European population:• <5 mm = negative• <10 mm = postvaccination positivity• >14 mm = postinfectious positivity

• North American hispanic and afroamericans• >5 mm = positive

• HIV+ person• any reaction (even erythema) = positive

Tuberculin skin testing cont.

False positivity False negativity

Systemic conditions:• malnutrition• imunoincompetency• malignancy• renal failure• liver failure• IBD• ageing

Local conditions:• Skin ageing• Severe skin diseases

(erythrodermia...)

• Atopic skin• Boost• Non-TB

mycobacteriosis

Positive anergy

Negative anergy

Microbiological testing• smear

– low sensitivity ≈ 34-62% (10000 bacilli / 1 ml)

– fast– false positivity

• culture – the gold standard– higher sensitity (100 bacilli / 1 ml)– drug susceptibility testing– time consuming

Radiometric culture (BD BACTEC™ 460 TB)

• palmitic acid labelled by 14C

• CO2 production• radiometric detection• 4-12 days

BD BACTEC™ MGIT™ 960

• Fluorometric detection of O2 consumption

• Naturel fluorescency of Ruthenium salt is inhibited by O2

• Capable to detect 1 to 10 bacteria from treated samples

• 7-14 days

Differentiation of MTB complex vs. Non-tuberculous mycobacteria (NTM)

• Immunochromatographicassay (ICA)

• Detection of MPT64 antigen (specific forMTB)

• 15 minutes• 100 ul of a positive liquid

culture

Newer microbiological methodesIGRA (Interferon Gamma Release Assay)

• presence of activated T-cells• all specimens containing T-

cells• incubation with M. TB antigens

(ESAT-6, CFP 10, TB 7.7)• IFN-γ detection• 1 day!• detection of the infection (not

of the disease!)

Mycobacterial species identification I.• DNA probes

–species-specific DNA probes that hybridize with rRNAreleased from bacteria

–probes labeled with acridinium ester, measured with a luminometer

–2-3.5 h–very easy to perform, no special instrumentation is

needed–not available for all pathogenic mycobacterial species–M. tuberculosis complex probe cannot differentiate

between the members of this complex (M. tuberculosis, M. bovis, M. bovis BCG, M. africanum, and M. microti)– Enhanced M. TB Direct Test (E-MTD)– sensitivity similar to culture

Mycobacterial species identification II.•pcr-based sequencing

–PCR amplification of mycobacterial DNA with genus-specific primers and sequencing of the amplicons

–the organism is identified by comparison of the nucleotide sequence with reference sequences

–the target most commonly used is the gene coding for the 16S rRNA

–members of the M. tuberculosis complex cannot be distinguished, M. kansasii has a sequence identical to that of a nonpathogenic species

–photometry–6.5 h–less sensitive than culture–Amplicor Mycobacterium tuberculosis Test

Combined methodes for identification of MTB and drug resistance

• GeneXpert MTB/RIF• FluoroType MTBDR (resistance to H, R)

Mycobacterial species identification III.•DNA microarrays (biochip)

–hybridization of fluorescently labeled PCR amplicons generated from bacterial colonies to a DNA array containing nucleotide probes

–probes based on 82 unique 16S rRNA sequences (discrimination of 54 mycobacterial species)

–covalent bond of the probes on solid surface

–4 h

Specimens used for microbiological testing

• sputum• induced sputum• throat swab• gastric secretions• bronchoalveolar

lavage• pleural fluid

• urine• blood• cerebrospinal fluid• smears from the fistulas• stool • sanitary pad• prostatic secretions• ascitic or pericardial fluid• synovial fluid• biopsies

HIV testing

• WHO: HIV testing for patients withsuspected TB.

Bronchoscopy

Pharmacological treatmentbasic principles and terms

• combination treatment• long-term treatment (short-course=6 months)• intensive/continuation phase• almost all administered once a day• first/second/third line drugs• MDR-TB = multi drug-resistant TB (resistance to

izoniazid and rifampicin) • XDR-TB = extensively drug-resistant TB (MDR-

TB + resistance to any fluoroquinolone and any of the second-line anti-TB injectable drugs: amikacin, kanamycin or capreomycin)

First line drugs

• H - izoniazid• R - rifampicin• Z - pyrazinamide• E - ethambutol• S - streptomycin• 2HRZE/4(HR)3

Second line drugs

• aminoglycosides (amikacin)• polypeptides (capreomycin, viomycin,

enviomycin)• fluoroquinolones (ciprofloxacin,

levofloxacin, moxifloxacin)• thioamides (ethionamide, prothionamide)• cycloserine• terizidone

Third line drugs

• rifabutin, rifapentin• macrolides• linezolid• thioacetazone• thioridazine• arginine• vitamin D• bedaquiline

Standard treatment regimens

New patients presumedor known to have drug-susceptible TB

Previously treated patients and multidrug resistance

S 2HRZE/4HR DST or2HRZES/1HRZE/5HREA 2HRZE/4(HR)3

HIV- 2(HRZE)3/4(HR)3

S - standard regimenA - alternative regimenHIV- - alternative for patients NOT living with HIV or living in an

HIV-prevalent settingDST- drug susceptibility testing

Drug susceptibility testing (DST)

• Standard DST (6-9 weeks)• Rapid DST - molecular-amplification

assays e.g. line probe test (2-7 days)

• If MDR prevalence > 3% then DST in all new cases

MDR-TB among new TB cases

Izoniazid• synthetic, bactericidal/bacteriostatic, intracelullar • inhibits synthesis of mycolic a.• clinically available since 1952• well resorbed from GIT, usually orally admin., i.v.

available• 4-6 mg/kg (up to 900 mg/day)• AE:

– GIT intollerance– hepatotoxicity– CNS effects (precipitation of seizures, mental

disorders, peripheral neuropathy)– anaemia– drug-induced SLE– allergy

Rifampicin• semisynthetic bactericidal antibiotic• inhibition of RNA-polymerase• clinically available since 1967• well resorbed from GIT, i.v. available• 8-12 mg/kg (up to 600 mg/day)• AE:

– GIT intollerance– hepatotoxicity– flu-like sy.– allergy (shock, purpura)– renal failure– adrenal dysfunction– orange-red colour of the body fluids

Pyrazinamide• bacteriostatic, cross haematoencephalic barrier• effective in acid environment• fast development of acquired resistance• inhibition of fatty acid syntetase• well resorbed from GIT• 20-30 mg/kg (up to 2000 mg/day)• AE:

– GIT intolerance– hepatotoxicity– hyperuricaemia– allergy, photosensitivity– anaemia

Ethambutol• bacteriostatic, synthetic• obstructs the formation of cell wall• well resorbed from GIT• 15-20 mg/kg (up to 1600 mg/day)• AE:

– optic neuritis– hyperurikaemia

Streptomycin

• bacteriostatic, in neutral- alcaline environment working aminoglycoside antibiotic

• protein synthesis inhibitor• clinically available since 1947 (first

antituberculotic)• not resorbed from GIT – exclusivelly i.m.• 1000 mg/day (500-750 mg/day in elderly)• AE:

– vestibulocochlear nerve toxicity (deafness, tinnitus, vertigo, ataxia)

– nephrotoxicity

Corticosteroids

• meningitis, pericarditis, pleurisy, extremely advanced TB - prednisolone 20-60 mg/day tapered off over 4-8 weeks.

• peritonitis, miliary disease, osteomyelitis, laryngeal TB, lymphadenitis and genitourinary disease?

Surgical treatment

• pneumothorax• plombage of pleural

cavity (porcelain balls)• thoracoplasty• phrenic nerve crushing• resection

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2010

not evaluated [%]defaulted [%]failed [%]died [%]completed [%]cured [%]

Global treatment outcomes(new smear-positive cases)

Global objectives of TB control

• To cure 85% of smear-positive cases• To diagnose > 70% of cases

Treatment using short-course chemotherapy

• standardized treatment• protection of rifampicin

– DOTS– fixed-dose combination– at least 3 other drug in smear +– prohibition of sale

Basic Principles of Treatment

• Provide safest, most effective therapy in shortest time

• Multiple drugs to which the organisms are susceptible

• Never add single drug to failing regimen• Ensure adherence to therapy

Directly Observed Therapy (DOT)

• watch patient swallow each dose of medication

• consider DOT for all patients• DOT should be used with all intermittent

regimens• DOT can lead to reductions in relapse

and acquired drug resistance• Use DOT with other measures to

promote adherence

Indications for hospitalization

• severe deterioration of the patient’s general state

• complications of TB (haemoptysis, pneumothorax)

• complications of treatment (severe liver impairment, purpura, allergic skin reaction)

• severe concomitant disease (diabetes, kidney failure, stomach ulcer)