Respiratory System Module 2021-2022 Dr. Mohammad Odibate ...
Transcript of Respiratory System Module 2021-2022 Dr. Mohammad Odibate ...
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Laboratory Diagnosis of Group A Streptococcus
Steps of Laboratory Diagnosis of Group A
\: i,~~ Streptococcus ~ \~~ p
ro , li"J ---±;l> Specimen co 11 ecti on
J,«y,a >•• 2. Direct Antigen detection
3. Group A streptococci screening culture
4. Identification of GAS ,, & ro ~~ A s \-r~ p ~0 c 0 c, u.~ ''
5. Reporti ng results.
Laboratory Diagnosis of Group A Streptococcus
1- Specimen:
Throat swab of tonsillar area and/or posterior
pharynx (Avoid the tongue and uv~ la)
Swc1b
Throat is swabbed
in the area o f
the tonsi ls
Laboratory Diagnosis of Group A Streptococcus
~ . 2. Direct Antigen detection: 1. The pati ent's throat is first swabbed to collect a sampl e of mucu s. 2. The sample is applied to a strip of nitrocellulose film and, if GAS ant ige ns
are present, these will migrate along the film to form a vi sibl e line of antigen bound to labeled antibodies
3. Because a common probl em is the low se nsitivity. All negat ive res u lt s should be followed by culture.
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Laboratory Diagnosis of Group A Streptococcus L ~ - \il<: ¥V\ c) J ~ ,·c_
3. Group A streptococci screening culture Incubate cultures under atmospheric conditions (35°C for 18-24h) Examine the presence of hemolytic colonies on blood agar Re incubate negative cultures for an additional 18-24h ~ --==--------
~-hemolys is (Group A streptococci)
a -he mo lys is +-------iii~----.,._;.
cl e."r \ :: •
Z c' tt e q ro\.\" J ·. -hemolysis
Laboratory Diagnosis of Group A Streptococcus
4. 1ldentification of GAS:
Catalasetest - ve_
~acitracin susceptibilty (\(\ '--' b \·.)\-t'c_ - Pr inciple:
• Fo r identification of group A
• dist ingujsh between 5. pyogenes from other beta hemolytic streptococ€i
~ e,.,c; 1 h lJ e
• Strep. pyogenes is sensitive to Bacitracin giving zone of inhibition aro und disk
Group A streptococci is susceptible to
Ba cit ra c i n disk ( I eft); The right shows
resistance
Laboratory Diagnosis of Group A Streptococcus
5. Reporting results:
The results on the microbiology request form may include
- 5. pyogenes group A isolated
beta hemoltyic streptococci, not group A streptococci
isolated
No 5. pyogenes or beta hemolytic steptococci
DIAGNOSIS OF DIPHTHERIA
Diagnosis r')(/''7 br<H\~ J , u-tJ
1. The initial diagnosis of diphtheria is entirely cli nical ~ _)\ ~ ._3
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2. Laboratory diagnosis C· c.1_,l;
A. Specimen: from the nose and throat and any other mucocuta neous
lesion. A portion of membrane should be removed and subm itted for
culture along with underlying exudate
B. Direct smear:
Gram stain: club shaped Gram positive bacilli with chinese lette r
arrangment
C. Culture media: cysteine-tellurite plate (Tisdale agar)
Results:
• C. diphtheriae : produce grayish -black coloni es, surround ed by a
brown/black halo.
D. Urease and oxidase negative, Catalase positive
UIAUNOSIS O F DIPHTHERIA
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DIAGNOSIS OF DIPHTHERIA
F. Toxin demonstration. As the pathogenesis is due to diphtheria toxin, isol ation of bacill i dose not complete the diagnosis. Toxin demonstration should be done following isolation, which can be of two types, in vivo and in vitro
□ In vitro test: Elek's test ~ od--c:...- , ..,, J , ~ ..> ~ ~
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DIAGNOSIS OF DIPHTHERIA L_ __ ~~:..:..:.~-=----=--=------------
Elek 's test: rapid diagnosis (16-24 hrs) Sterile filter paper with C. diphtheriae antitoxin
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Known toxigenic C. diphtheriae ...---.;i
(positive contro l)
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lfc c~ I~~.~ 1"-- Result: positive toxigenic C. diphtheriae Nutrient agar with selective agent for Corynebacterium - v~ J , ~ + v,
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DIAGNOSIS OF DIPHTHERIA btl)JJ,::11 c? -
Elek 's test: rapid diagnosis (16-24 hrs)
DIAGNOSIS OF DIPHTHERIA t ~<~ ~ ), 1~~r
Elek 's t est: rapid d iagnosis (16-24 hrs)
Results:
Positive test: formation of four radiating lines resulting from the precipitation reaction between exotoxin and diphtheria antitoxin.
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Laboratory Diagn osis Lower Respiratory Infecti on
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Re» f'•,.,,r~putum culture 1' \ ~ C'c. ~.·v"' Th I · · . I e sputum cu ture 1s an important part of the diagnostic evalu at ion of potent1 a
lower respiratory tract infections . However, expectorated sputum specimens are
variably contaminated by colonizing oropha ryngeal flora , ma king resu Its hard to
interpret. Proper collection of the specimen is crucial to the re covery of the
etiological agent.
Specimen criteria: • If possible, specimen should be collected before antimicrobial treat m ent.
• First morning specimen is best.
• Spec imen must be collected in a sterile container.
• If multiple cultures are ordered they should be collected at least 24 hours
a pa rt.
Laboratory Diagnosis Lower Respiratory Infection
~ ~ xpectorated sputum ;.::,. l; • Specimen collection should be supervised by a trained
()e.,q> _h req H-, professional. 0 \.:_\ ~
~\ ~_J_) • Request the patient to remove any dentures and to
rinse the mouth or gargle with plain water before
specimen collection.
• Tell the patient to provide a specimen fro m a deep
cough, avoiding, as much as possible, mixing the
specimen with saliva or nasal secretions.
• Make sure the patient understands the difference
between saliva (from mouth) and sputum (from chest).
Laboratory Diagnosis Lower Respiratory Infection
Specimen Quality
Poor quality sputum Better quality
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Laboratory Diagnosis of H. lnfluenzae 1. Specimen collection and transport
D Depending on the site of infection, various specimn s m ay be collected such as CSF, blood, respiratory tract sputum, throat swabs, midd le ear, and sinuses
□ As H. influenze is highly sensitive to low tempertures, the specimen should neve r be refragutrated
□ Sample should be trasported and proscessed immdediatly w it hout any delay.
2. Direct detection: □ Gram staining : preparation from different sampls may show gram -negat ive
coccobacilli z;, \S \ )\ --0
c,,rs,, h ra--J 0 Capsule detection (Quellung reaction)
Antigen detection: The t yp e b ca psular anti gen can be detcted in CSF, urine , or other bdy fuids by
latex agg lutin ation using particl es co at ed with anti bodi es to type b antige n o r Direct im mun oflurcscnce tes t .
Laboratory Diagnosis of H. lnflu~r,_zpe . .. - - - ~- ,, .. . , .. . . ._.., - . . . .. "" .. ,.... ..,
Capsule detection (Quellung reaction}
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Anti capsular )...,_ y "W Under
_j Ab microscope
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Laboratory Diagnosis of H. lnfluenzae
Culture: L~ ~ L'\ $ ~ i J I ,., \,\ )
A.
B.
Culture conditions: aerobic with 5-10 % CO2.
Culture media used are as follows:
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Blood aga r wi th 5. auru es strea k line : Co lo nies of H. influenzae grow adjacent to). RB <..
aurues strea k line (ph enomenon is known as sat elli ti srn)
Choclet agar
H. !nfluenzae grow around 5. aureus utilizing
X & V factors released from hemolyzed RBCs H. lnflu enzae grown on Choclet agar
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Laboratory Diagnosis of H. lnfluenzae ~ ,
Growth requirements