• Type III Hypersentivity exclusively in diffuse lepromatosis form of LL, usually in untreated patient.
• Treatment : – Neither glucocortiord nor thalidomide is effective.
UNIT
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BACTERIOLOGY
“Gram +ve Bacilli” Complications• MC complication of leprous neuropathy is plantar ulceration particularly at metatarsal heads. • Nerve abscess : – MC site is ulnar nerve.
– Treatment is rapid surgical decompression.
Diagnosis
• Biopsy of advancing edge of lesion in TT but in LL, biopsy of normal skin is also taken. • Hyperglobulinemia in LL.
• Lepromin test – Type IV delayed hypersentivity which is biphasic.
Early reaction of Fernandez – read in 24 - 48 hours (analogous to tuberculin reaction). Late reaction of Mitsuda – peak in 4 weeks. More meaningful.
It is of little diagnostic value but has more prognostic importance.
Treatment
Form of leprosy More Intensive regimen WHO recommended regime
i. Tuberculoid Dapsone 100 mg/d Dapsone 100 mg/d +
(paucibacillary) X 5 years Rifampin 600 mg/month for 6 months ii. Lepromatous Rifampin 600 mg/d Dapsone 100 mg/d +
(Multibacillary) or for 3 years + dapsone Clofazimine 50 mg/d and Rifampin
> 6 skin lesions 100 mg/d indefinitely 600 mg + clofazimine 300 mg monthly for 1year
• Single lesion paucibacillary leprosy - Single dose of ROM - rifampin, ofloxacin, minocycline. MYCOBACTERIA TUBERCULOSIS
Morphology
• Mammalian tubercle, isolated by Koch is stained by Ziehl - Neelsen method or by fluorescent dyes (auramine O, rhodamine).
• Resist decolourization by 20% H2SO4 and absolute alcohol for 10 minutes. Hence acid and alcohol fast. • Acid fastness is due to unsaponifiable wax (mycolic acid) or to a semipermeable membrane.
• It has thick cell wall; shows spheroplast and L forms.
Culture
• Generation time 14 – 15 hours.
• Colonies appear in about 2 weeks (may take upto 8 weeks).
• Grows luxuriantly in culture (Eugonic) and addition of 0.5% glycerol improves its growth but has no effect on M.bovis (causative agent of bovine tuberculosis) which is dysgonic (grows sparsely).
• Solid medium most widely employed for routine culture is Lowenstein - Jensen (LJ) medium without starch. • Liquid media are not generally used routinely, but used for senstivity testing, chemical analyses and preparation
of antigens and vaccines.
• Virulent strain form long serpentine rods in liquid media while avirulent strain grow in dispersed manner. Though cord factor itself is not a virulence factor but cord formation is coorelated with virulence. ... Jawets 24/e, p 322
SECTION
–
B
BIOCHEMICAL REACTION POSITIVE IN NEGATIVE IN
Niacin Test : N Human tubercle Bovine tubercle
Aryl Sulphatase : A Only with Atypical mycobacteria
Neutral red test : N Virulent strain of tubercle Avirulent strain
Peroxidase test : P Tubercle bacilli Atypical mycobacteria
Catalase test : C Most atypical mycobacteria Weakly positive in tubercle
Nitrate reduction text : N M.tuberculosis M. bovis
• Catalase and peroxidase activities are lost when tubercle bacilli become INH resistant.
• Ureas test is positive in M. tuberculosis, M. bovis and most of the atypical mycobacteria except MAIC complex.
M.tuberculosis M.bovis
Morphology Curved long rod Straighter, shorter, stouter
Stain Less uniform more uniform
O2 requirement Obligate aerobe Microaerophilic
Culture Dry, rough, raised, irregular Flat, smooth, moist, break up easily
Growth Eugonic Dysgonic
Virulence factors :
• Kat-G gene : encodes for oxidase, catalase enzyme.
• rpoV : main sigma factor initiating transcription of several genes.
• Erp gene : encodes for protein required for multiplication.
• Strains of Beijing / w genotype family.
Antigenic Property
• Group specificity is due to polysaccharide while type specificity is due to protein antigen. • Antibodies are not useful for diagnosis and immunity.
Pathogenicity
• It is due to escape killing by macrophages and inducion of type IV hypersensitivity.
• Following factors contribute in pathogenesis :
– Cord factor – Lipoarabinomannan – Complement system – M.TB heat shock protein.
• Risk of acquiring infection is determined mainly by exogenous factors while risk of developing disease depends largely on endogenous factors.
• Most potent risk factors - HIV coinfection.
Clinical features
• Divided into two categories : Pulmonary and extrapulmonary TB.
1. Pulmonary TB : Divided into two :
a. Primary Disease : usually localized in middle and lower zones.
Primary focus is usually peripheral in subpleural region and is accompained by draining lymphatics, inflamed regional lymph nodes which are collectively called Primary complex/Ghon’s facus.
Depending on the host immune response development of complex can follow healing by fibrosis/ calcification; cavitation or progressive primary TB in form of consolidation; obstructive emphysema or atelactasis; TB bronchitis; miliary TB; occult hematogenous dissemination to apex of lung (Simons Focus).
UNIT
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I
BACTERIOLOGY
“Gram +ve Bacilli”b. Post primary disease (adult type or reactivation or secondary tuberculosis or chronic pulmonary TB). • Usually localized to apical and posterior segments of upper lobe due to high O2 concentration (Puhl’s
Lesion).
• MC hematologic finding - mild anemia and leucocytosis
• Infraclavicular lesion is called Assman’s Focus.
2. Extrapulmonary TB
• MC site lymph node (MC cervical and supraclavicular).
• Also involved-Pleura in the form of pleural effusion and empyema. – Genitourinary tract (culture negative pyuria in acidic urine). – Skeletal TB (MC site spine, hip, knee).
– TB meningitis (paresis of cranial nerves especially ocular, is frequent finding). – GI TB (MC site terminal ileum and caecum).
– Tuberculous pericarditis (MC cause of chronic constrictive pericarditis).
Diagnosis
Specimen – sputum is best collected in the morning before any meal (3 sample).
i. AFB microscopy : smear should be prepared from thick purulent part of sputum.
• Atleast 10000 AFB should be present per ml of sputum for demonstrating in direct smears. Positive report can be given only if >2 typical bacilli have seen.
• Fluorescent microscopy (stained with auramine phenol or auramine rhodamine fluorescent dye and examined
under UV illumination) screened smear rapidly in comparison of Ziehl–Neelsen method.
• Concentration method for microscopy can also used eg. Petroff’s method using NaOH solution is widely used.
ii. Culture :
• Very sensitive diagnostic technique detecting 10 to 100 bacilli per ml. • LJ is standard solid media.
• Negative report is given, if no growth occur after 8-12 weeks.
• Slow growing, nonpigmented niacin positive AFB is taken as M.tuberculosis.
• Liquid media with radiometric growth detection (eg. BACTEC 460) and nucleic acid probes, enables results to be given in 2-3 weeks.
iii. Nucleic acid technology :
• PCR and Ligase chain reaction are used as diagnostic technique. • RFLP and 15 fingerprinting used for epidemiological typing of strain.
iv. Immunodiagnosis :
• Demonstation of hypersensitivity to tuberculo protein (tuberculin test / Montoux intradermal test) is a standard procedure.
• 1 purified protein derivative (PPD) = 50000 tuberculin units per milligram. • WHO advocates PPD tuberculin known as - RT 23 with Tween 80.
• Routinely 1TU used.
• Clinically 5 TU used.
• Read after 72 hrs in which induration is measured in horizontal transverse diameter. • > 10 mm positive, < 5 mm negative.
SECTION
–
B
• Positive tuberculin test indicates exposure to bacilli (infection, immunization) with or without clinical disease. so persons who have never had contact with bacilli are tuberculin negative.
• Used as aid in diagnosing active infection in infants and young children; measure prevalence of infection; to select susceptibles ; as an indicator of successful vaccination.
• Tine Multiple puncture test and heaf test is used for screening and surveys.
Treatment
ATT is given : First line drug are :
Drugs Daily dose Dose in DOTS Thrice weekly dose
H Isoniazid 5 mg/kg 600 mg 10 mg/kg R Rifampin 10 mg/kg 450 mg 10 mg/kg Z Pyrazinamide 25 mg/kg 1500 mg 35 mg/kg E Ethambutol 15 mg/kg 1200 mg 30 mg/kg S Streptomycin 15 mg/kg 750 mg 15 mg/kg Prevention
• BCG vaccine : Live attenuated vaccine derived from attenuated bovine strain of tubercle bacilli.
– Normal saline is diluent
– Dose of 0.05 ml for age < 4 week and 0.1 ml for > 4 wk should be given intradermal (subcutaneous administration may lead to abscess).
• Neonate of infected mother : Give INH resistant BCG + INH prophylaxis for 6 wks. • Chemoprophylaxis (preventive treatment)
INH for 1 year or INH plus ethambutol for 9 months.
PERINATAL TB ... Nelson 17/e, 967, 971
– MC sign and symptoms of congenital TB are respiratory distress, fever, hepatic or splenic enlargement, poor feeding, lethargy, irritability, lymphadenopathy, abdominal distension, failure to thrive, ear drainage and skin lesions.
– Symptoms most commonly begin by 2nd or 3rd week of life.
– A positive acid fast stain of an early morning gastric aspirate from newborn usually indicate TB. – Most important clue for rapid diagnosis is maternal or family history of TB.
– Most effective way of preventing congenital TB is appropriate testing and treatment of mother and other family members.
High risk pregnant women
Before delivery At time of delivery
Tuberculin test done Neonate separated from mother
–ve +ve until chest X-ray done
No further Chest X-ray with oppropirate ↓ CXR abnormal
evaluation abdominal shielding Separation maintained until
+ve –ve mother examined thoroughly
ATT No separation of fetus including, sputum testing (isoniazid after delivery
Rifampicin CXR +ve CXR +ve
UNIT
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I
BACTERIOLOGY
“Gram +ve Bacilli” ↓ ↓• Mother : ATT given • Mother : ATT • Follow up care of infant • Infant : INH • All house mem- • House members
bers should be evaluated evaluated for TB • No separation of
mother & infant When sputum culture of mother become –ve for 3 months
↓↓↓↓↓
Montoux test of child done
+ ve – ve
Continued INH for total Discontinued INH duration of 9-12 month