Microbial cultivation Flashcards
koch’s Postulates theory
Pathogen must be in all cases, Grown in pure culture, cells grown must cause disease in healthy, Pathogen then reisolated
Microbial diversity
Diff species utilize+ tolerate diff nutrients
Medical Micro does
Isolation, Identification + control of human pathogens
Cultures
Self amplifies - Grow until colony visible
Sub lethal injury
consequence of exposure to chemical/ physical Process that clamages but doesn’t kill Microorganism
May need resuscitation
conditions for culture
gaseous requirements
optimum temp
nutrients needed for growth
competitors discouraged
Bacteriology does
Isolates pathogens via culture (24-48 hrs) , phenotypic testing
Mycology (Fungi) uses
Culture then m microscopy to identify species
Selective agents
suppress growth of contaminants e.g antibiotics, crystal violet, bile salts
Differential agents
Allows growth of 2 or more organisms = diff colours E. g PH indicators, coloured substates
Faecal sample cons
High background flora (competitors)
wound sample cons
contaminated with Skin flora use blood or McConkey agar
Culture Pros + cons
cheap, effective but slow
Bacteria + fungi methods
Culture, microscopy, PCR
viruses methods
Serology (Abs) , PCR
Parasite methods
Microscopy, FISH, PCR
Microscopic methods Pros
Quick results needed e.g meningitis
Urine analysis
Microscopy or Flow Cytometry
Blood Cultures for
Septicemia
Parasitology method
Microscopic detection of structures
Virology method
Serology to detect Abs, Molecular tests e.g PCR
Igm = current infection
I GG = previous infection/ vaccination
Positive culture
Further ID to confirm e.g Gram stain or MALDI
Presumptive ID
Selective+ differential agars then further tests
Molecular ID method example
16 S r RNA gene sequencing
what ID techniques do?
give genus + species
Typing methods
further discrimination based on phenotype/ genotype that differ between Single Species
clone
Bacterial strains indistinguishable by genotype
clonal complex
Natural diversity between mother + daughter cells
Why type bacterial species (x4)
identify cases v outbreaks, chain of transmission, strain evolution, new pathogens
phenotypic typing methods example
phage typing, serotyping, biotyping (enzymes)
phage typing
infected cells lyse=plaques
Serotyping
Abs raised to o Ag : Agglutination= Positive
Genotyping
DNA polymorphisms using PCR+ electrophoresis
Ribotyping
1) Isolate DNA+ fragment with enzymes
2) Gel electrophoresis +transfer to membrane
3) Membrane with labelled probes hybridized to target r RNA
4) visualization: phonographic/ X-ray film
5) Banding pattern compared to database
