Diagnostic Bacteriology Flashcards
What are the five types of infection?
Bacteria
Fungi
Viruses
Protozo
Helminth Worms
What colour does gram positive bacteria stain?
Purple
What is the cell wall of a gram positive bacteria?
Thick peptidoglycan cell wall
What colour does gram negative bacteria stain?
Pink
What is the cell wall of gram negative bacteria like?
two outer membranes with a thin peptidoglycan cell wall between it
What part of the bacterial cell wall “holds” the stain?
The peptidoglycan
In what order are the gram stain substances applied?
Crystal Violet
Iodine
Alcohol
Safranin
Explain fully how gram positive bacteria stains purple?
After the crystal violet stain has been applied, it is held by the peptidoglycan layers. Then iodine is added, and alcohol. Iodine forms a crystal violet- iodine complex to prevent easy removal of dye, meaning in gram positive since there are a lot of layers, the purple crystal violet cannot be washed out. The alcohol is used to remove the dye.
How do gram negative bacteria stain pink?
After the alcohol has washed all the crystal violet out, safranin is added which stains any remaining bacteria pink
What does the shape coccus describe?
Sphere
What does the term bacillus describe?
The rounded oval shape
What shape can coccus bacteria sometimes form?
Groups / clusters like grapes
Describe the shape of diplococci
Spherical in pairs
What does staphylcocci look like
Purple, spherical in grape like clusters
What does streptococci look like?
Purple, spherical in long chains
What does the hemolytic test do?
tests capacity of bacteria to produce haemolysins which are enzymes that damage RBCs