Bacteriology • Cultural & Biochemical Identification
Cultural and Biochemical Characteristics of Medically Important Bacteria
Laboratory culture appearances and biochemical reactions compiled from the supplied MBLOGSTU source material.
10 Bacterial Groups
Student Notes
Culture Media
Biochemical Tests
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1. Staphylococcus aureus
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Colonies on Mannitol Salt Agar (MSA)
Picture Credit: Ms. Samjhana Kapali
Colonies on Mueller Hinton Agar (MHA)
Colonies on Blood Agar (BA) Media
Picture Credit: Ms. Sanjita Khadka
Coagulase Test — [A] Negative; [B] Positive
A. Positive Control; B. Negative Control; C. Test: Positive.
Picture Credit: Ms. Samjhana Kapali
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2. Salmonella Typhi
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Colonies on MacConkey Agar (MA)
Colonies on Xylose-Lysine Deoxycholate Agar (XLD)
Picture Credit: Mr. Saroj Khadka
Colonies on Blood Agar (BA) Media
Picture Credit: Mr. Saroj Khadka
Biochemical Set of Salmonella Typhi.
A: Oxidative Test: Positive; B: Fermentative Test: Positive; C: Indole: Negative; D: Methyl Red: Positive; E: Voges Proskauer: Negative; F: Citrate Test: Negative; G: Triple Sugar Iron: Alkaline/Acid, Hydrogen Sulphide Positive, Gas Production Negative; H: Urea Hydrolysis: Negative.
A: Oxidative Test: Positive; B: Fermentative Test: Positive; C: Indole: Negative; D: Methyl Red: Positive; E: Voges Proskauer: Negative; F: Citrate Test: Negative; G: Triple Sugar Iron: Alkaline/Acid, Hydrogen Sulphide Positive, Gas Production Negative; H: Urea Hydrolysis: Negative.
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3. Vibrio cholerae
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Colonies on Thiosulfate-Citrate-Bile salts-Sucrose Agar (TCBS)
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4. Pseudomonas aeruginosa
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Green colonies on Mueller Hinton Agar (MHA)
Biochemical Set of Pseudomonas aeruginosa.
From Left to Right: 1: Indole Test: Negative; Motile. 2: Methyl Red: Negative; 3: Voges Proskauer: Negative; 4: Urea Hydrolysis: Negative; 5: Citrate Test: Positive; 6: Triple Sugar Iron: Alkaline/Alkaline, Hydrogen Sulphide Negative, Gas Production Negative; 7: Oxidative Test: Positive; however, due to pH of the media, the result here is diverted; 8: Fermentative: Negative.
Picture Credit: Ms. Shrijana Bhandari
From Left to Right: 1: Indole Test: Negative; Motile. 2: Methyl Red: Negative; 3: Voges Proskauer: Negative; 4: Urea Hydrolysis: Negative; 5: Citrate Test: Positive; 6: Triple Sugar Iron: Alkaline/Alkaline, Hydrogen Sulphide Negative, Gas Production Negative; 7: Oxidative Test: Positive; however, due to pH of the media, the result here is diverted; 8: Fermentative: Negative.
Picture Credit: Ms. Shrijana Bhandari
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5. Escherichia coli
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Cysteine Lactose Electrolyte Deficient Medium (CLED)
Biochemical Reaction from Left to Right of Anaerogenic E. coli.
[1] TSI: R/Y (A/A), H2S −ve, Gas −
[2] Citrate: Negative
[3] Urease: Negative (source notes this as actually variable +ve)
[4] SIM: Indole +ve, Motility +ve
Picture Credit: Mr. Saroj Khadka
[1] TSI: R/Y (A/A), H2S −ve, Gas −
[2] Citrate: Negative
[3] Urease: Negative (source notes this as actually variable +ve)
[4] SIM: Indole +ve, Motility +ve
Picture Credit: Mr. Saroj Khadka
Characteristic Green Metallic Sheen on Eosine Methylene Blue (EMB) Agar Media
Picture Credit: Mr. Saroj Khadka
Picture Credit: Mr. Saroj Khadka
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6. Salmonella Paratyphi A
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Colonies on Xylose-Lysine Deoxycholate Agar (XLD)
Biochemical Set of Salmonella Paratyphi A.
A: Oxidative Test: Positive; B: Fermentative Test: Positive; C: Indole: Negative; D: Methyl Red: Positive; E: Voges Proskauer: Negative; F: Citrate Test: Negative; G: Triple Sugar Iron: Alkaline/Acid, Hydrogen Sulphide Negative, Gas Production Positive; H: Urea Hydrolysis: Negative.
A: Oxidative Test: Positive; B: Fermentative Test: Positive; C: Indole: Negative; D: Methyl Red: Positive; E: Voges Proskauer: Negative; F: Citrate Test: Negative; G: Triple Sugar Iron: Alkaline/Acid, Hydrogen Sulphide Negative, Gas Production Positive; H: Urea Hydrolysis: Negative.
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7. Klebsiella pneumoniae
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Colonies on MacConkey Media
Picture Credit: Mr. Saroj Khadka
Colonies on CLED
Biochemical Set of Klebsiella pneumoniae.
A: Indole: Negative; B: Urea Hydrolysis: Positive; C: Citrate Test: Positive; D: Triple Sugar Iron: Acid/Acid, Hydrogen Sulphide Negative, Gas Production Positive.
Picture Credit: Mr. Saroj Khadka
A: Indole: Negative; B: Urea Hydrolysis: Positive; C: Citrate Test: Positive; D: Triple Sugar Iron: Acid/Acid, Hydrogen Sulphide Negative, Gas Production Positive.
Picture Credit: Mr. Saroj Khadka
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8. Enterobacter cloacae
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Biochemical Reaction from Left to Right
[1] TSI: Y/Y (A/A), H2S −ve, Gas +
[2] Citrate: Positive
[3] Urease: Negative (source notes this as actually variable +ve)
[4] SIM: Indole −ve, Motility +ve
Picture Credit: Mr. Saroj Khadka
[1] TSI: Y/Y (A/A), H2S −ve, Gas +
[2] Citrate: Positive
[3] Urease: Negative (source notes this as actually variable +ve)
[4] SIM: Indole −ve, Motility +ve
Picture Credit: Mr. Saroj Khadka
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9. Acinetobacter spp.
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Biochemical reaction — From Right to Left
[1] Indole: Negative, Non-motile
[2] TSI: Red/Red (i.e. lactose/sucrose non-fermenter), H2S negative, Gas negative
[3] Urease: Negative
[4] Citrate: Positive
Picture Credit: Mr. Saroj Khadka
[1] Indole: Negative, Non-motile
[2] TSI: Red/Red (i.e. lactose/sucrose non-fermenter), H2S negative, Gas negative
[3] Urease: Negative
[4] Citrate: Positive
Picture Credit: Mr. Saroj Khadka
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10. Proteus mirabilis
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Biochemical Reactions (from left to right)
[1] Citrate: Negative (source notes that most strains of P. mirabilis are citrate +ve, while some are citrate −ve.)
[2] TSI: Red/Yellow, i.e. lactose/sucrose non-fermenter, H2S production, Gas production
[3] Urease: Positive
[4] Indole: Negative, Motile
Picture Credit: Mr. Saroj Khadka
[1] Citrate: Negative (source notes that most strains of P. mirabilis are citrate +ve, while some are citrate −ve.)
[2] TSI: Red/Yellow, i.e. lactose/sucrose non-fermenter, H2S production, Gas production
[3] Urease: Positive
[4] Indole: Negative, Motile
Picture Credit: Mr. Saroj Khadka
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