What type of media is blood agar?
Differential (based on hemolysis patterns)
What does MacConkey agar test for?
Lactose fermentation in Gram-negative bacteria
Which hemolysis type causes green discoloration?
Alpha-hemolysis (partial RBC breakdown)
Which bacteria are lactose fermenters?
Escherichia coli and Klebsiella pneumoniae
Purpose of enrichment media?
To support growth of fastidious organisms
Which media is both selective and differential?
MacConkey agar
What causes the color change in Mannitol Salt Agar (MSA)?
Fermentation of mannitol producing acid (phenol red turns yellow)
Which bacteria produces yellow colonies on MSA?
Staphylococcus aureus
Which Streptococcus species causes complete hemolysis?
Streptococcus pyogenes (beta-hemolysis)
Which media is used for antibiotic susceptibility testing?
Mueller-Hinton agar
What is chocolate agar used for?
To grow fastidious bacteria like Haemophilus influenzae
Role of selective media?
Inhibits growth of some organisms while allowing others to grow
What color colonies indicate lactose fermentation on MacConkey agar?
Pink to red colonies
Beta-hemolysis
Complete clearing around colonies (complete RBC lysis)
Gamma-hemolysis
No hemolysis (no color change)
What makes MacConkey selective?
Bile salts and crystal violet (inhibit Gram-positive bacteria)
What makes MSA selective?
High salt concentration (7.5% NaCl)
What indicator dye is in MSA?
Phenol red
