Examination of throat and mouth specimens.pptx

Presentation of Examination of throat and mouth specimens for Laboratories Faculty of Sana'a Yemen University
For Identification of pathogens

1. الثاني مختبرات ال ثاني Diagnostic Bactriology الثانية 23-5-2021م د.دينا هاشم   Examination of throat and mouth specimens 1

2. Possible pathogens Gram positive Streptococcus pyogenes Corynebacterium diphtheriae Corynebacterium ulcerans Gram negative Vincent’s organisms 2

3. COLLECTION AND TRANSPORT OF THROAT AND MOUTH SWABS In a hospital with a microbiology laboratory 1 In a good light and using the handle of a spoon to depress the tongue, examine the inside of the mouth. Look for inflammation, and the presence of any membrane, exudate, or pus . – With diphtheria, a greyish-yellow membrane (later becoming greyish green-black and smelly) can often be seen extending forwards over the soft palate and backwards onto the pharyngeal wall . – With a streptococcal sore throat, the tonsils are inflamed and often covered in yellow spots . – With Vincent’s angina, there is ulceration of the mouth, throat, or lips. 3

4. COLLECTION AND TRANSPORT OF THROAT AND MOUTH SWABS 2 Swab the affected area using a sterile cotton wool swab. Taking care not to contaminate the swab with saliva, return it to its sterile container. Important : For 8 hours before swabbing, the patient must not be treated with antibiotics or antiseptic mouthwashes (gargles ). Caution : It can be dangerous to swab the throat of a child with acute haemophilus epiglottitis because this may cause a spasm that can obstruct the child’s airway. Blood for culture should be collected instead. 3 Within two hours of collection, deliver the swab with a completed request form to the laboratory. 4

5. In a health center for dispatch to a microbiology laboratory 1 Using a sterile swab (supplied in a tube of silica gel by the microbiology laboratory), collect a specimen from the infected area as described under the hospital collection of throat swabs. 2 Taking care not to contaminate the swab, return it to its tube. Seal with adhesive tape and label the tube. 5

6. Culture the specimen Blood agar – Inoculate the swab on a plate of blood agar Use the loop to make also a few stabs in the agar (well area). Colonies of S. pyogenes growing below the surface will show more distinct zones of haemolysis because of the anaerobic conditions provided . – When a swab is received in silica gel (e.g. from a health centre ), moisten it first with sterile nutrient broth and then inoculate the plate . – Add a 0.05 unit bacitracin disc to the plate. This will help in the identification of S. pyogenes . Some workers also add a co- trimoxazole disc (as used for susceptibility testing) which prevents the growth of other bacteria, making it easier to see betahaemolytic S. pyogenes colonies . – Incubate the plate preferably anaerobically or, when this is not possible, in a carbon dioxide enriched atmosphere overnight at 35–37 C. Candle jar incubation will detect 6

7. Culture the specimen Culture : Blood agar: S . pyogenes produces betahaemolytic colonies , i.e. the colonies are surrounded by a zone of complete haemolysis with decolorization of the haemoglobin . Colonies are usually small (0.5–1 mm), colourless , dry, shiny or mucoid . Haemolysis is more marked under anaerobic conditions as seen in colonies growing below the agar surface (following stabs made in the culture medium. 7

8. Laboratory Examination First Day Culture on Blood agar and incubate anaerobic or in C02 condition (add Bacitracin Disc) When diphtheria suspected culture on Tellurite Blood Agar Second Day Gram stain: G+ve pleomorphic Rod when diphtheria suspect Examine and report culture: look for Beta Hemolysis and sensivity to Bacitracin. 8

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