SP1 Flashcards
What are the 6 rapid based approaches to detecting pathogens?
→Molecular detection
→Gene targeting
→Genome targeting
→Biomarkers of virulence
→Rapid sequencing
→Future Directions
How many of the mycobacterium genus are obligate human pathogens?
→M .tu bercuolssi
→M .elprae
→M. uclerans
What is an example of commensal non pathogen?
→Bacterodies thetaoi taomciron
What are the three types of pathogen?
→Commensal Non pathogen
→Zoonotic Non pathogen
→Commensal Opportunist
Define pathogen
→microbe CAPABLE of causing a specific degree of host damage
What are non sterile sites in the body?
→faeces
→mouth
→skin
What types of samples have low pathogen load and what do they require?
→ CSF,
→Ascites,
→24 hr Urine
→requires concentration (centrifugation, filtering)
What are the two types of preparation phase?
→culture: Enrichment, Purification, Amplification
→direct: concentration and sample treatment
What is a benefit of light microscopy for detection?
→no need for DNA
→just need to know what organism looks like
What type of pathogens can be detected by EM?
→viruses
Give examples of virus detected by EM?
→Rotavirus
→Hepatitis B
→ Tonsillitis
→Rabies
What colour does gram negative bacteria stain and why?
→red
→thinner peptidoglycan wall
What colour does gram positive bacteria stain and why?
→purple
→thicker peptidoglycan wall
Give examples of gram positive bacteria
→staphylococci
→streptococci
→Cornynebacterium diphtheriae
→Bacillus anthracis
Give examples of gram negative bacteria
→Escherichia coli
→Salmonella
→Shigella
→Helicobacter
Give examples of spore forming bacteria
→Bacillus (aerobic)
→Clostridium (anaerobic)
What are advantages of microscopy for detection?
→Easy to perform
→Rapid screening
→Some parasites have SPECIFIC morphology
→Specific Immunoflourescence staining possible
What are the disadvantages of microscopy for detection?
→Not Sensitive
→screening sputum smears requires at least 10,000 orgs per ml to be visualised
→General stains are not specific
→Labour intensive (expensive)
→Requires specialist interpretive expertise (more expensive)
What are the 3 different types of media for culturing?
→Non Selective Media
→Semi Selective Media
→Selective growth temperatures
Example of non selective media
→blood agar
Examples of semi selective media
→MacConkey Agar, →DCA,
→CLED- Cysteine Lactose Electrolyte Deficient
Examples of selective growth temperatures
→Campylobacter species
What is deoxycholate agar?
→Selective for Shigella and Salmonella on a faecal sample
→produce colours depending on organism
What are facultative anaerobes?
→organism that is capable of producing energy through aerobic respiration and then switching back to anaerobic respiration depending on the amounts of oxygen
What is characteristic of the ileum?
→No oxygen in centre
How can gas gangrene be cultured?
→Tryptose sulphite cycloserine (TSC) agar
→Black sulphite producing colonies some with lecithinase
→grown in anaerobic conditions
What are the selective conditions of campylocbacter?
→42°C
→10% CO2
What are hemolysins?
→lipids and proteins that cause lysis of red blood cells by disrupting the cell membrane
What can be used to detect streptococcus pneumoniae A?
→Optochin, antibiotic
→interferes with the ATPase and production of (ATP) in microorganisms
What criteria is used to identify bacteria?
→Colony morphology,
→Colour, Haemolysis →Colony Count
→Colony Identification →Systematic identification
→Colony Resistance to antibiotics
What are two metabolic testing for bacteria?
→catalase: E.coli = +ve
Clostridium perfringens –ve
→indole test:E.coli = +ve
Clostridium perfringens –ve
What type of tests is used to identify enterobacteriacae?
→Metabolic function
→sugar utilisation
→Salmonella, Shigella, E.coli
What is phage typing?
→uses bacteriophages for detecting and identifying single strains of bacteria
What is antibiotic sensitivity testing?
→test that determines the susceptibility of bacteria to an antibiotic
→also how resistant a bacteria is to an antibiotic
What is minimum inhibitory concentration?
→the lowest concentration of an antimicrobial that will inhibit the visible growth of a microorganism
What is the course of testing for food poisoning?
→Direct microscopy for cysts/eggs of amoebae or parasites
→MacConkey agar & Deoxycholate agar plates aerobically at 37 degrees
→Identify bacteria by biochemical profiling (API 20E strip)
→Spread on Campy CVA selective media plate- Positive growth (silver grey colonies)
→Gram negative curved rods
What does viral culture require?
→permissive cell lines
→Kidney epithelial
What are the two ways of viral identification visually?
→Culture & microscopy
→Direct Antigen Detection eg ELISA
How long does viral culture take?
→3-10 days
How log does repaid ELISA fluA take?
→15 mins
What is hemagglutinin?
→responsible for binding of the virus to cell surface receptors
How many types of haemagglutinin?
→4 types
How many types of neuraaminidase?
→enzymes that cleave sialic acid to allow virus to leave cell
What are the advantages of culturing?
→Cheap simple, reliable reagents →Sensitive
→Validated specificity
→Direct in vivo measurement of effectiveness of therapy
→Easily archived
What are the disadvantages of culturing?
→Some pathogens cannot be grown
→ Some pathogens cannot be well differentiated by biochemistry alone
→ Some pathogens grow too slowly to aid rapid diagnosis
→Labour intensive (expensive)
→Requires specialist interpretive expertise (more expensive)
Example of pathogen that can’t be cultured
→mycobacterium
