isolation and identification of pseudomonas and salmonella
TRANSCRIPT
Isolation and Identification of
Pseudomonas and Salmonella
Course: Medical Bacteriology
Lab. No 9
4th Grade – Fall Semester 2021-2022
Dr. Salah Tofik Balaky
Ph. D. Medical Microbiology
21/ 12/ 2021
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Pseudomonas (P. aeruginosa)
General characteristics
▪ G-ve rods, motile by polar flagella.
• Obligately aerobic, grow well at 42⁰C and Non-lactose
fermenting.
• Produce fruity odor (grape-like) on culture media.
• Oxidase test positive .
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Pseudomonas (P. aeruginosa)
Pigment production
They can produce pigments, such as:
• Pyocyanine (blue-green)
• Pyoverdin (fluorescent yellow- greenish pigment)
• Pyorubrin (red)
• Pyomelanin (brown)
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Laboratory diagnosis
▪ Specimen
▪ blood.
▪ Wound discharge
▪ sputum
▪ Urine
▪ CSF
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Microscopy
Gram stain
G-ve rod similar to members of enterobacteriaceae.
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On Nutrient Agar
• Colonies are smooth, large, translucent
• Greenish blue diffusible pigment
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On Blood Agar
• Grayish colonies
• Many are hemolytic
B-hemolytic colonies of P. aeruginosaColonies of Pseudomonas aeruginosa
cultivated aerobically on horse blood
agar at 37°C. colonies are gray in color.
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On MacConkey agar
Non-lactose fermenting (colourless colonies)
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On EMB
Colorless colonies due to non lactose fermenting
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Biochemical Test
• Oxidase test - positive
• Catalase test – positive
• Citrate test – positive
• Gelatin hydrolysis - positive
• Indole test – negative
• Urease test – negative
• H2S production – negative
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Salmonella
General characteristics
▪ They are rod-shaped bacteria, G-ve, motile by
peritrichous flagella.
▪ They are non-lactose fermenter, facultative anaerobes
and H2S producer
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Laboratory diagnosis
Specimen
1. For enteric fever
• Blood, Bone marrow, Stool, urine and Serum
2. For gastroenteritis
• Stool
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Gram stain
Gram-negative rod-shaped bacterium
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On MacConkey agar
The bacteria do not ferment lactose, the colonies growth
appear colorless and the agar surrounding the bacteria
remains relatively transparent.
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On EMB
Because Salmonella species do not ferment lactose or
produce acid, their colonies appear grey on EMB agar.
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On Salmonella Shigella Agar
The SS agar is used for the isolation of Salmonella spp. and
Shigella spp. The media inhibit G+ve bacteria, most coliform
bacteria, and inhibit swarming Proteus spp., while allowing
Salmonella spp. to grow.
Salmonella do not ferment lactose, but produce hydrogen sulfide
gas. The resulting bacterial colonies will appear colorless with
black centers.
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On Xylose lysine deoxycholate agar (XLD)
Salmonella metabolise thiosulfate to produce hydrogen sulfide,
which leads to the formation of colonies with black centers and
allows them to be differentiated from the similarly coloured
Shigella colonies.
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Biochemical test
Oxidase test Negative
Catalase test Positive
Indole Negative
Citrate Positive
H2S production Positive
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Next Lab
Acinetobacter and Vibrios
Any questions or comments