Biochemical Testing Reference Chart

MAC (MacConkey Agar):
- Medium: MacConkey agar
- Indicator: Neutral red
- Selective agents: Bile salts and crystal violet inhibit Gram-positive bacteria
- Positive ( $+$ , pink / LF): Lactose fermenter ( $\text{Lactose} \rightarrow \text{acid}$ )
- Negative ( $-$ ): Tan or no growth
PEA (Phenylethyl Alcohol Agar):
- Medium: Phenylethyl alcohol agar
- Indicator: None
- Selective agent: Alcohol inhibits Gram-negative bacteria
- Positive ( $+$ , growth): $\text{Gram}\oplus$
- Negative ( $-$ ): No growth ( $\text{Gram}\ominus$ )
EMB (Eosin Methylene Blue Agar):
- Medium: Eosin methylene blue agar
- Indicator & selective agents: Eosin and methylene blue (inhibit Gram-positive bacteria)
- Positive ( $+$ , pink or green): Fermenter ( $\text{Lactose/sucrose} \rightarrow \text{acid}$ )
- Negative ( $-$ ): Purple, colorless, or no growth
MSA (Mannitol Salt Agar):
- Medium: Mannitol salt agar
- Indicator: Phenol red
- Selective agent: High salt inhibits non-Staphylococcus species
- Positive ( $+$ , growth with yellow color): Mannitol fermentation ( $\text{mannitol} \rightarrow \text{acid}$ )
- Negative ( $-$ ): Pink growth or no growth

BAP (Sheep's Blood Agar):
- Medium: Sheep's Blood agar
- Indicator: Blood cells
- Beta Hemolysis: Positive shows a clear halo around colonies; negative shows no halo or no change
- Alpha Hemolysis: Positive shows green/yellow around colonies; negative shows no change
- Gamma Hemolysis: No change for both positive and negative
FTM (Fluid Thioglycollate Broth):
- Medium: Fluid thioglycollate broth
- Indicator: Resazurin
- Aerobe: Growth exclusively in top
- Anaerobe: Growth exclusively in bottom
- Facultative anaerobe: Growth in both top and bottom

Medium & Indicator: Phenol red lactose, sucrose, or dextrose broth; phenol red indicator
Fermentation:
- Positive ( $+$ , yellow): $\text{carbohydrate} \rightarrow \text{acid}$
- Negative ( $-$ ): No change or red/pink
Gas Production:
- Positive ( $+$ , bubble