Topic 13 Diagnosis of Infection Flashcards
(13 cards)
Detection and Identification of Microbial Pathogens
- identify _
- monitor _ _
- initiate _ _ _
- understand _
- for certification in _ _ (_ and _)
- identify diseases
- monitor treatment effectiveness
- initiate appropriate control measure
- understand epidemiology
- for certification in international trade (export and import)
Laboratory investigation of bacterial disease
1. _ - accompanied by full clinical history of sick or dead animal and of othe members of the groyp with signs of illness; fluids, faeces, swabs from affected tissues or structures, tissues, other material
2. Collected carefully to minimize _
3. Transported in _ _; some require transport media; should not be frozen
-> identification of _ _ - microscopic id, cultural and biochemical characterization of pathogens, id by immunological or molecular methods
- Specimens
- Collected carefully to minimize contamination
- Transported in suitable containers
-> identification of pathogenic bacteria
Proper selection, collection and transport of clinical samples
1. Proper _ of the specimen - with relevant history of disease, clinical signs, and treatment
- specimen must be approp type to diagnose infectious diseases suspected by clinician: from a site of pathogen is most likely to be found, acute stage is best, before antimicrobial therapy has begun
2. Proper _ of the specimen - eliminates or minimizes contamination of the specimen
- specimen shoul be placed or collected into sterile container, sufficient quantity
3. Proper _ of the specimen - must be viable, transport must preserve agent morphology
- selection
- collection
- transport
Identification/Demonstration of Pathogenic Bacteria
_ _ _ _ _ may be accomplished by:
- Examination of stained smears made from a portion of the clinical sample
- Culture techniques
- Molecular/Immunologic methods
- Or a combination of these methods
Presence of an infectious agent
Examination of Stained Smear
- _ Stain - CLAS 1 1 10 1 (Gram + purple, Gram - red)
- _ _ Stain - CHAM (Acid fast + pink, Acid fast - blue)
- Gram Stain
- Acid Fast Stain
_ _ _ Characteristics
- Sample is inoculated for culture and identification either in pre enrichment or selective for broth culture.
- Incubated at suitable temperature for suitable time an proper environment
- Streaked on either selective, differential or both type of agar media for suitable time in proper environment
- Individual colonies are picked and grown as pure culture
- Tentative ID made based on colony shape and staining
- Definitive ID required biochemical, serological and various tests
Cultural and Biochemical Characteristics
Routine isolation - Aerobic bacteria
BAP, MAC
Plate inoculation technique for obtaining isolated colonies on agar
24-48 hour incubation at 37 deg C
Streak plate method
Examples of media used in diagnostic bacteriology
NBMBX TSEEPC
Eosin methylene blue agar with Proteus sp, EC, and Salmonella sp
MacConkey agar with PA, Kleibsella sp, and Salmonella sp
Nutrient agar, Blood agar, MacConkey agar, Brilliant green agar, XLD agar, TSI agar, Selenite broth agar, EMB agar, Edwards medium, Purple base agar, Chocolate agar
_ _
- performed to identify the bacteria on the basis of their biochemical activities towards different biochemical compounds
- carbohydrate fermentation test, urease test, TSI agar test
Biochemical Test
_ _
- Based on nucleic acid detection
- _ _ _ (PCR) is the most widely used method of nucleic acid amplification
- Amplify a specific region of DNA millions - fold within a few hours. PCR can be used to identify the microorganism in a sample, from culture or in
fixed tissue.
- PCR requires only small amounts of sample material for the detection of infection
- Advantage over culture-based diagnostic:
- Speed, ready detection of fastidious, unculturable and/or dangerous pathogens, ease of strain typing
Molecular Techniques
- polymerase chain reaction
Immunological Techniques
_ _
- Used to detect and measure antibody in a sample
- Helps diagnosis of infections and determine if someone has been exposed to a specific pathogen
- Advantage: generally less expensive and easier to perform than the isolation, only requires clotted blood samples
- ELISA, Agglutination tests etc.
Serological assays
_ _ _ (NGS)
- can sequence the DNA of bacteria (millions of DNA simultaneously)
- Nucleic acid extraction -> library preparation -> sequencing and analysis
Next Generation Sequencing
MALDI-TOF
_ _ _ _ _ _ _ _; Mass Spectrometry
- Technique that uses a laser to measure the mass of molecules in a sample; can identify bacterial isolates using their mass
Matrix-Assisted Laser Desorption/Ionization Time-of-Flight
