Gram - negative

Group 20 2025

Morphology

scattered, short enteric rods

Staining

Gram -

Types

• E.coli

• Salmonella

• Shingella

• Proteus

• Klebsiella

• Pseudomonas

Pathogenic factor

• Endotoxins

• rare: Exotoxins

Cultivation (General)

Deoxychocolate agar:

• pink - lactose fermenting (E.coli/klebsiella)

• colorless - non-lactose fermenting (Salmonella, Shingella)

• Salmonella: Black centre (H2S production)

• Shingella: colorless with no H2S production

Levine agar:

• lactose fermenting: ink blue colonies (E.coli/klebsiella)

• lactose non-fermenting: colorless (Salmonella/Shingella)

Cultivation E.coli

EMB agar:

• black colonies with green metal sheen

DCA agar:

• pink (due to lactose fermentation)

Klingler:

• Yellow everywhere

Cultivation Salmonella

EMB agar /DCA agar

• black spots on agar

Mac Conkey agar

• negative -ve

Selenite broth:

• Salmonella: red

• Sterile: transparent

Kligler Agar:

• Red

• Black ring

• Yellow

Cultivation Proteus

Kligler Agar:

• completely black

Cultivation Shingella/Klebsiella

Kligler Agar:

• Red

• Yellow

Specimen

• feces

• urine

• blood

• sputum

• wound swab

Symptoms

E.coli:

• Diarrhea

• abdominal cramps

• fever

Salmonella:

• Diarrhea

• fever

• abdominal cramps

• vomiting

Klebsiella:

• Pneumonia

Pseudomonas:

• wound infections

Antibiotics

• Amoxicillin

• Fluorchinolones

Vaccine

only Salmonella (Typhoid)