Day 2: Interpretation Flashcards
What is a positive DN’ase test
Zone of clearance around colonies
What is a negative DN’ase test
No zone of clearance around the colonies
What organisms produce a positive DN’ase result
S. aureus
M. Catarrhalis
What organisms produce a negative DN’ase result
S. epidermidis, S. saprophyticus
N. species e.g. N. meningitidis,
What is a positive mannitol salt agar test
Yellow colonies on mannitol agar indicate mannitol fermenter and salt tolerant
What is a negative mannitol salt agar test
Red colonies on mannitol salt agar indicate non mannitol fermenter but salt tolerant
What species are positive on mannitol salt - yellow/pink and growth?
S. aureus
What species are negative on mannitol salt - red/pink but growth
S. epidermidis or S. saprophyticus
What does it mean if an organism doesn’t grow on mannitol agar
It is not salt tolerant i.e. its a staphylococcus
What does pink colonies on SAIDE agar indicate
Staphylococcus aureus
What is a negative Staphaurex plus result
No agglutination
What is a positive Staphaurex plus result
Agglutination
What species will give a positive Staphaurex plus result
Only S. aureus
What species of staphylococcus give a negative staphaurex plus result?
Coag negative staph e.g. S. epidermidis or S. saprophyticus
What is a positive result for optochin susceptibility?
Susceptibility -> zone of no growth around optochin disk
What is a negative result for optochin susceptibilty?
Resistance -> growth around optochin disk
What species will give a positive optochin result?
S. pneumonia (susceptible)
What species will give a negative optochin result?
S. viridans (resistant)
What is a positive Lancefield test?
Agglutination
What is a negative Lancefield test?
No agglutination
What does a Lancefield group A indicate?
Streptococcus pyogenes
What does a Lancefield group B indicate?
Streptococcus agalactiae
What does Lancefield group C indicate?
Streptococcus equi (most probable)
Streptococcus epidemicus
Streptococcus equisimilis
What does Lancefield group D indicate?
Streptococcus bovis
Or the more probable Enterococcus -> E. faecalis
What does Lancefield group F indicate?
Streptococcus anginosus
What does Lancefield group G indicate?
Streptococcus canis
Streptococcus dysgalactiae
What is a positive bacitracin test?
Susceptible to bacitracin
What is a negative bacitracin test?
Resistant to bacitracin
What species give a positive bacitracin test?
Streptococcus pyogenes (susceptible)
What species give a negative bacitracin test?
Enterococcus species
What is a positive result for MacConkey agar?
Pink colonies
What is a negative result for MacConkey agar?
Yellow colonies
What species will give a positive result on MacConkey?
Enterococci
What species will give a negative result on MacConkey?
Streptococci
What is a positive bile aesculin test?
Blackening of the medium
What is a negative bile aesculin result
No blackening of the medium
What species will give a positive result on bile aesculin agar?
Enterococci
What species will give a negative result on bile aesculin agar?
Streptococci
What TAXO sugars does N. Meningitidis utilise?
Glucose
Maltose
What TAXO sugars does N. Gonorrhoeae utilise?
Glucose
What TAXO sugars does N. flavescens utilise?
None
What TAXO sugars does N. lactamica utilise?
Glucose
Maltose
Lactose
What TAXO sugars does N. sicca utilise?
Glucose
Maltose
Sucrose
What Neisseria species ferments glucose only?
Gonorrhoeae
What Neisseria species ferments none of the TAXO sugars ?
N. flavescens
What Neisseria species ferments glucose and maltose?
N. meningitidis
What Neisseria species ferments glucose, maltose and lactose?
N. lactamica
What Neisseria species ferments glucose, maltose and sucrose?
N. sicca
What is a positive result for the TAXO sugar test?
Yellow colour -> colour change from red to yellow upon addition of the phenol red indicator
What is a negative result for the TAXO sugar test
Red colour -> no colour change upon addition of the phenol red indicator
What is a positive catarrhalis disc test?
Blue-green colour development
What is a negative catarrhalis disc test?
No colour development within 2 minutes
What species will give a positive catarrhalis disc test?
M. catarrhalise