Practical Flashcards
single colonies are not always derived from a single cell, true or false ?
true, thats why we use CFU
MaConkey agar
contains bile salts, support growth of coliforms and enteric pathogens and colour change based on lactose metabolism
selective vs differential media
selective - enhance the growth of organisms and suppress others
differential - allow for a difference appearance so we can differentiate the species
fastidious vs non-fastidious
fastidious - specific nutritional requirements
non-fastidious - not specific nutritional requirements
colioforms
group of Gram-negative, rod-shaped, facultatively anaerobic bacteria that ferment lactose
indicate enteric pathogens in water
include klebsiella, enterobacter, citrobacter, E. coli
counting bacteria
counting chamber - similar to haemocytometer, counts cells in a known volume
flow cytometer - cells pass a light source - includes dead cells
what factors can affect the type and number of microbes in the microbiota ?
genetics, mode of birth, diet, antibiotic use, age, environment, infection, immune system, hygiene, lifestyle, medication
Bacillus cereus and Bacillus anthracis spores can pose significant threats to human health, but in very different ways
B. cereus - foodborne, survive cooking and pasteurization
B. anthracis - germination leads to toxin production, long dormancy period
blood agar
Base: Tryptic soy agar or nutrient agar
Additive: ~5% sheep blood (sometimes horse or human blood)
It’s mainly used to detect hemolytic activity — the ability of bacteria to break down red blood cells
blood agar nutrients
C N P S K Mg Ca Fe B-vitamins
TVC
total viable count, the quantification of viable microorganisms capable of growing on a nonselective solid media incubated aerobically at mesophilic temperatures
can be used to detect contamination
sterilisation
inactivation of all viable microorganisms
pasteurisation
heat treatment to reduce total number
disinfection
reduce number of organisms present
antisepsis
used on living tissue to reduce the growth of microorganisms.
asepsis
prevent introduction of microorganisms to the site.
2 types of heat sterilisation
moist and dry
types of sterilisation
heat, radiation, chemical
Nutrient agar
general purpose medium that allows the growth of a wide range of organisms
mannitol salt agar
differential and selective and indicator medium to isolate S. aureus particularly pathogenic strains.
mannitol –> acid = colour change to yellow (if not remains pink)
contains high salt concentration which means only staphylococcus can grow
CFC agar
isolation of Pseudomonas, green colonies whilst others are colourless
ChromID agar
contains chromogenic substrates like esculin which is digested by C. difficile
improving lettuce micrbiota
irradiation, ultrasound, chlorine washing
B. subtilis spores are resistant to …
heat, desiccation, pressure, radiation, chemicals
lateral flow assay
The technique is based on capillary action to detect toxins and antigens
agglutination assay
An agglutination assay is a laboratory technique used to detect the presence of specific antigens or antibodies in a sample, based on their ability to cause agglutination, or clumping, of particles (such as red blood cells or latex beads)
C-reactive protein (CRP) in serum
shows inflammation, use anti-CRP antibodies conjugated to beads
leads to positive agglutination result
Anti-streptolysin O (ASO) antibody in serum
produced by immune system when streptococcus is present
streptolysin O is the toxin produced by the strain
latex beads are surrounded by streptolysin O for anti-ASO to bind
What other parameters could we vary that
would influence how effective UV radiation
is in inhibiting bacterial growth?
wavelength of UV, exposure time, distance, species, cell density, growth phase, moisture, intensity
