2. RESPIRATORY TRACT:
ANATOMICAL STRUCTURE
It is utmost important to be familiar with the
anatomic structure of the thoracic cavity, so that
specimens collected from various sites in the
lower respiratory tract are appropriately
processed by the laboratory.
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4. INITIATION………
Aspiration of colonizing flora into the alveoli
Inhalation of aerosols
Hematologic seeding of the lung from a distant
focus
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5. When paediatric patients with cystic fibrosis (CF)
have respiratory infections (exacerbations), the
trigger is most commonly related to an increased
growth of bacteria that are chronically present in
the airway.
However, in adult patients with COPD, the cause
of respiratory exacerbations is usually related to
the acquisition of new strains of bacteria, rather
than an increase in the number of bacteria
present when clinically stable.
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6. 1- Bronchitis.
A- Acute:
Usually caused by viruses.
In infants & preschool children is Bordetella pertussis.
B- Chronic:
It is defined by clinical symptoms in which excessive mucus production
leads to coughing up sputum on most days during at least 3 consecutive
months for more than 2 successive years.
2- Bronchiolitis.
It is the inflammation of smaller diameter bronchiolar epithelial surfaces.
It is an acute viral LRTI that primarily occurs during the first 2 years of
life.
Diseases of the Lower Respiratory Tract
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7. 2- Pneumonia
Community-Acquired Pneumonia:
patients are believed to have acquired infection outside the hospital
setting.
The etiology of acute pneumonias is strongly dependent on age. More
than 80% of pneumonias in infants & children are caused by viruses,
whereas 10%-20% of pneumonias in adults are viral.
Hospital-Acquired Pneumonia
It is the leading cause of death among patients with nosocomial infections
(as high as 50% mortality among patients in intensive care units).
Diseases of the Lower Respiratory Tract
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12. LABORATORY DIAGNOSIS
Specimen collection and Transport
A. Sputum
1. Expectorated
Food should not have been ingested for 1-2 hours before
expectoration.
Mouth should be rinsed with saline or water just before
expectoration.
The patient should be standing, if possible or sitting upright in bed.
He or she should take deep breath to full the lungs, and empty then in one
breath, coughing as hard and as deeply as possible.
Sputum brought up should be spit into screw capped container.
Visually inspect the specimen.
Tighten the cap of the container and send immediately to lab
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13. Sputum of less than
2ml should not be
processed unless
obviously purulent
Only 1 sputum per
24hr submitted
SPUTUM COLLECTION
Dr.T.V.RaoMD
13
14. TRANSPORTATION OF
SPUTUM
Transportation in <2 hr is
recommended with refrigeration if
delays anticipated.
Handle all samples using universal
precautions.
Perform Gram stain and plant
specimen as soon as possible
14
15. 2. Induced
Assisted by respiratory therapy technician.
Using postural drainage & thoracic percussion to
stimulate production of acceptable sputum.
Aerosol induced specimen:
Breathing of aerosolized droplets of a solution
containing 15% NaCl and 10% glycerin for
approximately 10 min. or until a strong cough
reflex is initiated.
No pre-screening required (Although these
specimen appear watery resembling saliva but
they contain material directly from alveolar
spaces ).
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16. SPECIMEN COLLECTION AND
TRANSPORT
3. Gastric aspirate:
For isolation of Acid-Fast bacilli.
Inability to produce sputum.
Nasogastric tube is inserted into the stomach and contests are
withdrawn.
The relative resistance of mycobacteria to acidity allows them to
remain viable for short period.
Acidity of content is neutralized.
B. Endotracheal or Tracheostomy suctions specimens.
Collected in Lukens trap.
Tracheostomy aspirates should be treated as sputum.
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18. SPECIMEN COLLECTION AND
TRANSPORT
C. Bronchoscopy
Fibreoptic devices
Bronchial washings
Bronchial aspirates
Broncoalveolar lavage BAL (100-300ml NS is infused).
Protected bronchial brushing samples.
Broncoalveolar lavage (BAL)
100-300ml NS is infused.
Estimated that: 1 million alveoli are sampled during this process.
Significant correlation : “Between”
Acute bacterial pneumonia and >103
-104
bacterial colonies
per mililitres of BAL fluid.
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19. BRONCHOALVEOLAR LAVAGE
(BAL)
SPECIMEN ACCEPTABILITY
Microscopic examination of Gram-
stained smear
Acceptable
<1% of cells present are squamous
epithelial cells
Unacceptable
>1% of cells present are squamous
epithelial cells
Thorpe JE et. al. 1987. Bronchoalveolar lavage for diagnosing acute bacterial
pneumonia. J. Infect. Dis. 155:855-861
19
20. SPECIMEN COLLECTION AND
TRANSPORT
Mini-BAL:
Bedside, Non-bronchoscopic.
Using metras catheter.
20ml or less saline is infused.
Protected bronchial brushing:
Can collect 0.001 to 0.01 ml of material.
Material can be suspended in 1 ml of broth dilution with vigorous
vortexing.
Inoculate into culture media using 0.001 ml calibrated inoculating
loop.
Correlation to infection:
≥ 1000 CFU/ml of broth diluent.
≥10^6
CFU/ml of original specimen.
Have been considered to correlate with infection.
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21. SPECIMEN COLLECTION AND
TRANSPORT
D. Transtracheal Aspirates(TTA):
Reduces the likelihood of contamination by upper respiratory
tract flora.
Inserting small plastic catheter into the trachea via a needle
previously inserted through the skin and cricothyroid membrane.
E. Other invasive procedure:
Thoracentesis (In pleural empyema).
Open lung biopsy.
F. Blood culture:
Only 20% of patients requiring hospitalization due to pnuemonia
are Blood culture positive.
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22. CRITERIA FOR
REJECTING SAMPLES
22
Mismatch of information on the label and the
request
Inappropriate transport temperature
Excessive delay in transportation
Inappropriate transport medium
specimen received in a fixative
dry specimen
sample with questionable relevance
Insufficient quantity
Leakage
23. SPECIMEN PROCESSING
The purulent material which contains most of the relevant
pathogens, is usually embeded in clear mucoid secretion.
If homogenised:
Every drop & loopful of it will contains some of pathogen.
Suitable for quantitative examinations.
Dithiothreitol or Buffered Pancreatin
Mix and incubate equal volumes of the sputum and a solution of
dithiothreitol or buffered pancreatin.
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24. SPECIMEN PROCESSING
I. Dithiothreitol
Mix rapidly on a vortex mixer for 15 seconds and stand for 15
minutes at ambient temperature.
Or mix gently and continuously on a machine that tilts to & fro
placed for 30 minutes in an incubator at 37ºC.
I. Pancreatin
Incubate for 30 min. at 37ºC with continuous or occasional
shaking.
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25. MICROSCOPY
▓ Gram’s stain ▓10 % KOH ▓Calcofluor white stain ▓PASstain.
Fig: Gram’s stain of sputum
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(LPF)
26. MICROSCOPY
Screening by Gram’s stain
Acceptable criteria:
<10 epithelial cells /LPF.
>25 WBCs/LPF ( Except in leucopenic patients).
Reasonable rejection criteria:
>10 epithelial cells /LPF.
Rejection criteria for ETA:
>10 epithelial cells /LPF.
Or no organism seen under oil immersion.
In Legionella pneumophila
Should not be subjected to screening by gram’s stain since sputum may
be scant and watery, with few or no host cells. 26
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28. CALCULATION OF COMPOSITE Q-
SCORE
Use a specimen with a Composite Q score of +1, +2 or +3 for the additional
tests. Tests are performed on a specimen with a Composite Q score of <+1
only if specifically ordered by the physician.
28
32. INOCULATION:
Inoculated onto MA and BA at 37ºC.
CA at 37ºC in increased carbondioxide condition.
5ug optochin (Ethyl hydrocupriene dihydrocloride to screen
for S. pneumoniae.
5-20 Unit (10U) Bacitracin for H. influenzae.
Only specimens obtained by percutaneous aspiration
(including transtracheal aspiration) and by protected
bronchial brush are suitable for anaerobic culture.
Buffered charcoal-yeast extract (BCYE) agar for Legionella
spp.
PC 0r OFPBL agars for B. cepacia.
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33. PROCESSING SPECIMENS FOR
CULTURE
Process specimens in biological safety cabinet, as
aerosol can result in laboratory-squired respiratory
infections.
Process all specimens as rapidly as possible, especially
specimen from emergency department, and inpatients.
Select the most purulent or most blood-tinged portion
of the specimen. Significant growth above the cutoff
should be reported; however if more than one pathogen
is isolated than it is suggestive of oropharyngeal
contamination and clinical correlation should be done
before reporting the samples.
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35. CONTAMINATION WITH
ORAL FLORA INTERFERES
RESULTS
Because of contaminating oral flora ,sputum
specimens, specimens obtained by bronchial
washing, and lavage tracheostomy, or
endotracheal tube aspirates are not inoculated
to enriched broth or incubated anaerobically.
Only specimens obtained by percutaneous
aspiration (including trans tracheal
aspiration )and by protected bronchial brush
are suitable for anaerobic culture: he latter
must be done quantitatively for proper
interpretation.
35
36. IDENTIFICATION OF
MICRORGANISM
Identification of microorganism is based on
the gram’s staining, colonial characters,
biochemical tests and specific anti-sera if
required.
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42. LABORATORY DIAGONOSIS
COLONY PROCEDURE /Rapid presumptive test
-This method works well on large or mucoid colonies
-Select a well-isolated single colony from a blood or chocolate
agar plate.
-Circle the colony on the bottom of the Petri dish to locate
- Place one drop of 2% sodium deoxycholate directly on the
colony.
-Incubate at 37°Cfor up to 30 minutes. Do not invert the plate.
The lid may be left slightly ajar to aid evaporation
- When the reagent has dried examine the area for lysis or
disintegration of the original colony
Positive result: Colony lysed or disintegrated
Negative result: No change
43. QUELLUNG REACTION (NEUFELD
QUELLUNG RXN)
Word origin: German quellung for "swelling"
quellung phenomenon
Increase in opacity and visibility of the capsule of
capsulated organisms exposed to specific agglutinating
anticapsular antibodies
Apparent swelling of the capsule upon binding of
homologous antibody due to change in refractive index
reagent - antipneumoccal rabbit sera (omniserum)is used
against 90 sero- types of S.pnuemoniae from State Serum
Institute, DK2300,Copenhagen, Denmark)
44. SEROTYPING
different serotypes causes different diseases
• Serotyping can be done by:
- Quellung reaction(described by Neufeld in 1902), classical method
Agglutination of the pneumococci with type specific antiserum
Capillary Precipitation of SSS with type specific antiserum
Coagglutination
dot blot assay
counterimmuno-electrophoresis (CIEP)
45. Properties Pneumococcus Viridans streptococci
Morphology Capsulated,lanceolate-
shaped diplococci
Non-capsulated,oval or
round cells in short chains
Colony on BA Raised/flat initially later
“draughtsman”
Dome-shaped
Broth culture Uniform turbidity granular with powdery
deposit
Bile solubility test + -
Optochin sensitivity Sensitive Resistant
Inulin fermentation + -
Quellung reaction + -
Mice/rabbbit pathogenicity Pathogenic Non -pathogenic
46. NUCLEIC ACID TECHNIQUE
Polymerase chain reaction
Samples : blood, serum, CSF and respiratory samples,
body fluids
Gene used as primers
The pneumolysin gene,
pneumococcal surface adhesin protein (PsaA) gene,
cell wall autolysin (LytA) protein gene
DNA/DNA hybridization
47. CASE STUDY…….
A 16-month-old boy was admitted with fever, lethargy and
trouble breathing. A diagnosis of pneumonia was made by
physical examination. The child had recently been to
Panama and at that time was treated with ceftriaxone for
cough and fever. His fever continued, despite treatment.
On admission, he was given erythromycin therapy.
Thacheal aspirate and blood cultures were obtained, but
the respiratory specimen contained numerous epithelial
cells and yielded normal respiratory flora on culture. A
pleural aspirate and blood cultures were positive with
Streptococcus pneumoniae, which was reisistant to
erythromycin and penicillin and intermediate in
susceptibility to ceftriaxone. The patient was given high
doses of ceftriaxone and vancomycin and responded to
therapy. 47
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48. QUESTIONS..???
What criteria are used in laboratories to reject sputum and
tracheal aspirates for culture?
If greater than 10 squamous epithelial cells per low-power field
are seen in a gram stain but the smear also has numerous white
blood cells (greater than 25/LPF), should the specimen be rejected
for culture?
In cases of pneumococcal pneumonia, what percentage of blood
and sputum cultures is positive for S. pneumoniae?
The organism was reported as resistant to penicillin and
intermediate in susceptibility to third-generation cephalosporins .
How does the laboratory perform testing for this organism?
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49. SPECIAL CONSIDERATION TO
PULMONARY TUBERCULOSIS
Recovery of mycobacteria from clinical samples is more
time consuming procedure than for normal pathogenic
bacteria, requiring as it does the following steps:
1. Homogenization
2. Centrifugation
3. Neutralization
4. Inoculation
5. Incubation for at least 6wks
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50. CULTURAL
CHARACTERISTICS
(M. TUBERCULOSIS)
M. tuberculosis is an obligate aerobe while M.
bovis is microaerophilic on primary isolation
(aerobic on subculture)
Grows slowly (G.T. 15-20 hours)
Optimum temperature 370
C
pH 6.4-7.0
Does not grow <250
C and >400
C
Increased carbondioxide (5-10%) enhances
growth
Grows more luxuriantly in culture (eugonic)
than M. bovis (dysgonic)
51. Addition of 0.5% glycerol improves the growth of
M. tuberculosis but has no effect on or even
impair the growth of M. bovis.
Sodium pyruvate helps the growth of both types
Human tubercle bacilli do not grow in presence of p-
nitrobenzoic acid (500 mg/l), unlike other slow growing
nonchromogens.
Highly susceptible even to traces of toxic substance
like fatty acid in culture media which can be
neutralized by serum albumin or charcoal.
52. CULTURE MEDIA
Solid media:
Egg containing – Lowenstein-Jensen media
Petragnani media
Dorset egg media
Ogawa media
Blood containing – Tarshis media
Serum containing – Loeffler’s serum slope
Potato containing – Pawlowsky’s media
Liquid media:
Dubo’s media
Middlebrook’s media 7H9
Proskauer and Beck’s media
Sula’s and Sauton’s media
Kirchner media
53. To prevent overgrowth by contaminants,
Cocktail of antibiotics
Polymyxin B
Amphotericin B
Nalidixic acid
Trimethoprim
Azlocillin
PANTA
Polymyxin B
Amphotericin B
Carbenicillin
Trimethoprim
PACT
54. COLONY CHARACTERS
Solid media:
M. tuberculosis:
Colonies appear after 2-3 weeks.
Colonies first appear as small, dry,
friable, rough and granular, creamy
white (Rough, tough, buff)
Typical colonies have a flat irregular
margin and look like a cauliflower in the
center.
M. bovis:
Colonies appear after 3-6 weeks
Colonies are smooth, translucent and
pyramidal
55. QUANTIFICATION SCALE FOR
MYCOBACTERIAL GROWTH ON AGAR
PLATES (ATS, 2000)
No. of colonies seen Quantity reported
No colonies seen
<50 colonies
50-100 colonies
100-200 colonies
200-500 colonies (almost confluence)
>500 colonies (confluence)
Negative
Report actual number seen
1 +
2 +
3 +
4+
56. Liquid media:
Bacilli grow either on surface as pellicle or as floccules
throughout the medium due to hydrophobic nature of their
cell wall lipid.
Generally, virulent strains often grow as twisted rope like
colonies called serpentine cords??????
Diffuse bacterial growth is obtained by adding a detergent
Tween 80.
57. Lowenstein-Jensen media
Fresh whole eggs
Defined salts
Glycerol
Potato flour
Asparagine
Malachite green
59. Ogawa media
Potassium dihydrogen phosphate
Sodium glutamate
Glycerine
2% malachite green
Distilled water
Whole egg homogenate
60. Niacin test- Niacin test is positive with human
type and negative with bovine type of bacilli.
Aryl sulphatase test- Aryl sulphatase test is
positive with atypical mycobacteria.
Neutral red test- Neutral red test is positive with
virulent strains of tubercle bacilli while avirulent
strains are negative.
Catalase-peroxidase test-
Atypical mycobacterial strains - strongly catalase
positive
Tubercle bacilli - only weakly positive for catalase
Tubercle bacilli - peroxidase positive
Atypical mycobacteria – peroxidase negative
Catalase and peroxidase activity are lost when tubercle
bacilli become INH resistant.
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61. Amidase test- Amidase test differentiates
mycobacteria by its ability to split amides. A
useful pattern is provided by testing five
amides, acetamide, benzamide, carbamide,
nicotinamide and pyrazinamide.
Nitrate reduction test-
M. tuberculosis +
M. bovis -
62. LABORATORY DIAGNOSIS
Sample is collected according to the site of infection
Primary tuberculosis- 3 early morning sputum
samples, laryngeal swab, bronchial washings,
stomach washings in children
Transport medium for preserving M. tuberculosis in sputum specimens –
Cetylpyridinium chloride – Sodium chloride (CPC-NaCl) transport medium.
63. Conventional techniques
Sputum microscopy
Acid fast stains:
Ziehl Neelsen stain
Kinyoun’s modification of ZN stain
Auramine-Rhodamine stain
Sputum culture
Mantoux skin test
64. Direct methods
Smear
Culture
Phage based assays
Phenotypic methods- lipid analysis
Molecular methods- Probes, PCR
Indirect methods
Serology- ELISA, Latex agglutination
ELISPOT Assays
Demonstration of biological products
ADA estimation
Tuberculostearic acid test
Bromide partition test
65. SPUTUM SMEAR EXAMINATION
Most widely applicable, most reliable ( WHO )
Minimum 3 samples (spot- early morning-spot)
Sensitivity- 50-70%
66. DISADVANTAGES OF SMEAR
EXAMINATION
Lower limit of detection - 104
bacilli/ml
Sample
Cannot determine viability
Cannot identify species
False positive/ False negative result
67. INTERNATIONAL UNION AGAINST
TUBERCULOSIS (IUAT)
If definite pink bacilli are not seen – AFB not found
If 1 or 2 bacilli in the entire field – Doubtful, repeat for another
sample
If 1-9 AFB/100 fields – AFB found (exact number)
10-100 AFB/ 100 fields – AFB found (+)
1-10 AFB/ field – AFB found (++)
> 10 AFB/ field – AFB found (+++)
68. DIGESTION, CONCENTRATION
AND CULTURAL METHODS
Homogenization – To release the mycobacteria
from the body fluid or tissue in which they are
contained
Decontamination – To kill the contaminants or
else they will overgrow the medium
69. 1. Petroff’s method
Equal vol. of Sputum and 4% NaOH
370
C – 30 mins with occasional shaking
Centrifugation 3000g – 20-30mins
Discard the supernatant
Neutralize the deposit with 8% HCl in presence of
phenol red indicator
Centrifugation
Deposit
Inoculated on to the culture media
Smear preparation
Animal inoculation
Molecular methods
70. 2. Modified Petroff’s method
Sputum + Double vol. of 4% NaOH
R.T. – 15mins with occasional shaking
Centrifugation 3000g – 15mins
Discard the supernatant
15 ml saline or water + sediment
Centrifugation 3000g – 15mins
Deposit – inoculated on to the culture media
72. ANIMAL INOCULATION
Intramuscular inoculation of 0.5 ml bacterial suspension into the
thigh of 12 week old guinea pig
The tuberculin test becomes positive after 3-4 weeks and there
will be progressive loss of weight of the animal
The animal is autopsied after 6wks or 12 wks.
Results:
Caseous lesion at the site of inoculation
Enlarged inguinal LN
Tubercules in the lungs
Splenomegaly
The identity of the bacteria is confirmed by demonstration of
AFB from the lesions to exclude the Y. pseudotuberculosis,
Brucella as their lesions macroscopically simulate tubercles.
ROOT INDEX OF VIRULENCE
73. CDC CLASSIFICATION OF
TUBERCULIN REACTION
An induration (palpable raised hardened area of skin)
of more than 5–15 mm (depending upon the person's
risk factors) to 10 Mantoux units is considered a
positive result, indicating TB infection.
5 mm or more is positive in
HIV-positive person,
Patients with organ transplants and other immunosuppressed
patients
10 mm or more is positive in
Recent arrivals (less than 5 years) from high-prevalent countries
Residents and employees of high-risk congregate settings (e.g.,
prisons, nursing homes, hospitals, homeless shelters, etc.)
Persons with clinical conditions that place them at high risk (e.g.,
diabetes, prolonged corticosteroid therapy, leukemia, end-stage renal
disease, chronic malabsorption syndromes, low body weight, etc)
15 mm or more is positive in
Persons with no known risk factors for TB
74. Recent advances
Serological diagnosis
IgM and IgG antibody to mycobacterial antigens (ELISA, LA)
IgG and IgA antibody against the mycobacterial antigen A60 in
patient with EPT
Radiometric BACTEC 460 TB method
MGIT 960 Mycobacterial detection system
Chemical detection of biological compounds
Adenosine deaminase
Tuberculostearic acid test
Bromide partition test
HPLC
Mycobacteriophage typing
Genotyping methods
75. BACTEC
Organisms multiply in the broth and metabolize
14
C – containing palmitic acid substrate producing
radioactively labelled 14
CO2 in the atmosphere
that collects above the broth in the bottle.
The BACTEC instrument withdraws the 14
CO2 –
containing atmosphere and measures the amount
of radioactivity present which is converted
proportionally to a quantitative growth index
(GI).
77. -It is based on a glass tube containing a modified
Middlebrook 7H9 broth enriched with OADC and
PANTA antibiotic mixture.
-A fluorescent compound is embedded at the bottom
of tube.
- The fluorescent compound does not fluoresce in the
presence of oxygen, but it fluoresces following
depletion of oxygen by actively respiring organisms
as a result of mycobacterial growth.
Mycobacterial growth indicator tube
(MGIT) system
78. CULTURE METHODS
Modern method Conventional
Detection 14 days 28 days
Susceptibility 3 wks 8 wks
Sensitivity 95% 84%
Contamination 4% 5%
79. LYSIS-CENTRIFUGATION BLOOD
CULTURE SYSTEM
- The recovery of mycobacterium from peripheral blood and bone
marrow samples may be improved by releasing the intracellular
mycobacterial cells into the blood culture broth, increasing the rate and
reducing the time of recovery.
- In the lysis- centrifugation blood culture method, blood is put into a
tube containing an anticoagulant and a lysing agent to effect rupture of
both erythrocytes and neutrophils.
- Following centrifugation of the tube, the sediment is inoculated into
the appropriate culture media.
- This method has increased both the yield and shortened the time of
recovery of mycobacteria from blood cultures.
80. LIPID ANALYSIS
Mycolic acid profiles
HPLC- Confirmation of isolate , directly
from clinical specimen
81. OTHER TESTS
Immunomagnetic separation of M. tuberculosis
(Murtagh et al 1995)
Magnetic polystrene microspheres coated with antibody to
mycobacteria are added to the specimen and mixed together
The beads and bound organisms are collected by using a
magnet and detected by microscopic examination with the use
of conventional method.
It improves mycobacterial detection level by 2-3 times more
than conventional method.
Used for CSF, Sputum.
82. Mycodot antibody test
Purified lipoarabinomannan is used as an antigen
and it detects antimycobacterial antibody levels
likely to be found in those with active diseases
Specificity 97-98%
Sensitivity 70-75%
87. NUCLEIC ACID PROBES
DNA probes
M. tuberculosis complex, M. avium
Not sensitive enough (104
organisms)
Ribosomal RNA based probes
Target r- RNA
M. tuberculosis , M. avium, M. gordonae
Chemiluminiscent system
88. PCR ASSAYS
Target
IS 6110 (10-20 times repeated in genome)
25% of Indian population lack IS 6110
PCR ( ROCHE AMPLICOR)
Target gene 16S-rRNA (584 bp)
Reproducible, sensitive, specific
Can detect 1-10 organisms
89. DRAWBACKS OF PCR ASSAY
Dead bacilli are detected.
False Positive due to contamination.
No prognostic value.
90. DEMONSTRATION OF BIOLOGICAL
PRODUCTS
Adenosine Deaminase Assay
Lymphocytic enzyme - Increase in TB
Surrogate marker for extrapulmonary
tuberculosis in Pleural, pericardial, CSF
Sensitivity & specificity > 90%
Limitations - False +
In COPD, the management protocol for these patients involves obtaining routine sputum cultures during healthy clinic visits, for the purpose of tracking bacterial pathogens. This information is used to guide antibiotic therapy should the patient develop signs or symptoms of a lower respiratory infection.
In COPD, surveillance cultures are of minimal value, and are rarely used, in guiding therapy during a COPD exacerbation. Currently, it is unclear whether the trigger for respiratory infections in children with tracheostomy tubes is more like that of CF, with an increase in colonizing bacteria, or more similar to COPD exacerbations, with acquisition of a new strain or strains of bacteria.