Flashcards in Bacteriology Deck (20):
What are the 4 most common diagnostic techniques?
Culture (sterile or nonsterile sites)
Molecular techniques e.g. PCR
Antimicrobial susceptibility testing
What are the different types of agar plate that can grow bacteria?
What is the chocoalte agar plate and what is the most common bacteria that grows on it?
What is the maccokey agar plate for?
Gram negative bacteria
Should be in done before giving antibiotics except for meningitis and meningococcal septicaemia
What is the neomycin agar plate for?
What is the difference in gram negative and gram positive bacteria?
Gram positive has large peitdoglycan wall. Gram negative has smaller, outer membrane and LPS.
What is the gram stain useful for?
Selecting antibiotics. Some antibiotics target the cell wall and so they won't be very good for gram negative bacteria e.g. vancomycin
What colour are gram positive bacteria and why?
Purple as they hold the gram stain
What colour are the gram negative bacteria and why?
Pink (counterstain) as they have an outer membrane which stops them taking up the stain
What is the staphylococci coagulase test for and what are the results?
Differentiate between the different Staphyloccoci bacteria. Coagulase positive = Staphyloccocus aureus. (MRSA)
Coagulase negactive - common skin microbes
How are the two groups of streptoccoci identified?
Grow them on blood agar.
Alpha haemolysis - incomplete haemolysis, green colour. Streptococcus pneumoniae.
Beta haemolysis - complete haemolysis, clear the agar. Group A - Streptocuccos pyogenes. Group B - Streptococcus agalaticae.
What pathogens can cause diarrhoea?
Bacteria - salmonella, shigella, campylobacter, E.coli, C diff, cholera
Parasites - amoeba, giarda, cyrptosporidium
What 3 pathogens are routinely checked for in stools in the UK?
Salmonella, camplyobacter and shigella
How is C diff identified?
Difficult to grow on plates. So mixture of toxin detection and PCR toxin gene
What special agar plate is used for salmonella and what are the results?
Xylose lysine deoxylate
Balck colonies formed - cannot ferment xylos
How long does campylobacter take to grow?
What special agar plate is used for cholera?
TCBS - thiosulphate citrate bile salts sucrose. Green colour
What is the minimum inhibitory concentration?
the lowest amount of antibiotics required to inhibit the growth of bacteria?
What does it mean when the MIC is above the breakpoint?
it should be reported as resistant