Bacteriology Flashcards
What colour do gram positive bacteria stain?
Purple
What colour do gram negative bacteria stain?
Pink
Name the two clinically important aerobic cocci geni
1) Staphylococcus
2) Streptococcus
Name the two clinically important Staphlococci
1) S. aureus
2) S. epidermidis
What are streptococci sub-divided into?
1) Beta-haemolytic
2) Alpha-haemolytic
3) Non-haemolytic
What medium does haemolysis occur on?
Blood agar
What is the appearance of beta-haemolysis?
Transparent when held up to the light
What is the appearance of alpha-haemolysis?
Translucent and green
What further test would you do to identify alpha-haemolytic Streptococcus pneumoniae?
Optochin test
Is S. pneumoniae sensitive or resistant to the optochin test?
Sensitive
What test would you do to distinguish between Staphlococci?
Coagulase test (or DNAse)
Which Staphlococcus is coagulase positive?
S. aureus
Which Staphlococci are coagulase negative?
Multiple including S. epidermidis
What happens if you carry out a coagulase test with S. aureus?
The solution solidifies (positive)
What happens if you carry out a coagulase test with S. epidermidis?
It remains liquid (negative)
How can you distinguish between gram negative bacilli?
Lactose fermentation test
Is Shigella lactose fermenting or non-lactose fermenting?
Non-lactose fermenting
Is E.coli lactose fermenting or non-lactose fermenting?
Lactose fermenting
Is salmonella lactose fermenting or non-lactose fermenting?
Non lactose fermenting
How do you distinguish between non-lactose fermenting gram negative bacilli?
Oxidase test
Which gram negative bacilli have a positive oxidase test?
Pseudomonas
What bacteria are resistant to the optochin test?
Viridans Strep
What is the appearance of S. aureus on agar?
Golden colonies
What is the appearance of S. epidermidis on agar?
White colonies
