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Diagnosis & Pathogen Identification - Coggle Diagram
Diagnosis & Pathogen Identification
Standard Microbiological Practices
Minimal guidelines and precautions based on biosafety level
Decontamination: Autoclave
Saturated steam under pressure - enters through top, forced out through bottom vent
Signs/ Symptoms of Disease
Clinical Profile
May induce characteristic symptoms
Measles: Red rash, fever, sore through, grey spots in mouth
Evaluation Methods
Microscopy
Rapid/ immunoassay tests
Molecular testing
Biochemical testing
Culture
(Direct Identification)
Serology
Immunofluorescence
(Indirect Identification)
Growth/ Biochemical Characteristics
Culture based identification used for bacterial/ fungal pathogens (protists rarely)
Viruses cultured in tissue culture
Isolation of Pure Culture
Population of cells from single cell
Developed by Robert Koch
Different plate techniques
Media Types
Colony Morphology
Differences in growth rates from edge to centre based on nutrients
Affected by media/ incubation
Culture Media Types
Must contain nutrients
Auxotrophs have specific growth factors
Defined Media
Chemically defines, concentration is known
Complex Media
Concentration unknown
Physical Nature of Media
Liquid/ solidified media used for culturing
Functional Media Types
Enriched
- general purpose media with special nutrients
Selective
- Favour or inhibit growth
Differential
- Distinguish between species
Case Study 1:
Mycobacterium tuberculosis
Discovered by Koch
Weak Gram positive rod
Cell wall has high mycolic acid conc.
TB = ancient human disease
95% infections are latent, survive in granulomas and become dormant. May be reactivated
Detection
Ziehl Neelsen stain (differentiate acid-fast bacteria)
Stained with carbolfuschin (acid fast retain stain)
X-ray
Mantoux test
Treatment/ Prevention
Isoniazid - interferes with mycolic synthesis
Pyrazinamide - action unknown (activated in liver)
Rifampicin - inhibits transcription
Prophylaxis for 1 year with Isoniazid for those in contact
Epidemiology
Top 10 leading cause of death
Leading cause from single infectious agent
2 billion latently infected
Case Study 2:
HIV
Enveloped virus ssRNA
Transmission multiple way
Aids
- Affects CD4+ lymphocytes, cell count decreases
Symptoms/ Diagnosis
Flu-like symptoms 2-6 weeks post infections
No symptoms for years
Post immune system damage:
Weight loss
Fatigue
Recurrent Infections
Treatment/ Prevention
HAART - highly active antiretroviral therapy
RT inhibitors
No vaccine
Safe sex, no needles
Case Study 3:
Escherichia coli
Discovered 1885, Theodor Eschrich
Gram negative, facultative
Human/ animal commensal
Gastroenteritis
EPEC
: destroy microvilli of small intestines
ETEC
: bind receptors of SI cells
EHIC
: makes verotoxin (acts on intestinal epithelium)
EIEC
: Attach to mucosa of
large
intestine
EAEC
- clump on small intestine cells
DAEC
- produce alpha hemolysin and cytotoxin necrotising factor 1
Symptoms
Vomiting
Mild fever
Stomach cramps
Watery diarrhoea
Detection
Stool samples
Microbiological testing
Treatment/ Prevention
Rehydration
Antibiotics
Cook food/ treat water
Hygiene