donovan neo Flashcards
Assign each feature to Legionella spp., Chlamydia spp. and Mycoplasma spp.
Altered liposaccharides (LPS) in outer membrane
No peptidoglycan layer
No cell wall
Altered liposaccharides (LPS) in outer membrane - Legionella spp.
No peptidoglycan layer - Chlamydia spp.
No cell wall - Mycoplasma spp.
Why do atypical and acid fast bacteria have poor gram staining?
They have very lipophilic and waxy cell wall which prevents the dye from gram stain to penetrate through.
(Mycolic acid on surface is very lipophilic. Dyes are charged and cannot bind to bacteria)
Why is mannitol salt agar selective?
Inhibits growth of many spp.
Why is mannitol salt agar differential?
Differentiates between mannitol-fermenters
Staphylococcus epidermis - White growth (should be red i think -ey)
Staphylococcus aureus - Yellow growth
Why is MacConkey’s agar selective?
Inhibits growth of Gram-positive (good to culture for gram-negative enteric bacteria [enterobacterales])
Why is MacConkey’s agar differential?
Differentiates between lactose-fermenters
(Lactose fermenters grow on pink side and Non-lactose fermenters grow on colourless/yellow side)
Chocolate agar promotes the growth of _________ spp. such as _____________?
fastidious spp. such as haemophilus influenzae
Why is blood agar differential?
Differentiates between hemolysin-producers
MOA that antimicrobials target (5)
Cell wall synthesis
Protein synthesis (translation)
RNA synthesis (transcription)
DNA Synthesis (replication)
Class II metabolism
What is the action of beta-lactams? How does it affect its use as an antimicrobial?
Inhibits peptidoglycan synthesis/cell wall synthesis.
Cannot use it if bacteria has no peptidoglycan
3 layer of cell wall for gram-negative bacteria
Outer membrane
Peptidoglycan cell wall
Cytoplasmic/Inner membrane
True or false: Antimicrobial therapy can only start once pathogen is identified through culture and tests.
Why?
False. Empiric therapy can be started based on signs and symptoms. Waiting for culture and identification of pathogen will take too long.
Reasons for failure (5)
- Failure to identify causative agent
- Drug in vitro activity =/= in vivo activity
- Drug causes unacceptable risks/adverse effects
- Impaired immunity affecting bug clearance
- Development of resistance
How to distinguish between Neisseria gonorrhea and Haemophilus influenzae?
Microscopy
How to differentiate between Enterococcus faecalis and Acinetobacter baumannii?
Gram staining
