Table of Contents
- 1 Is Shigella dysenteriae citrate positive or negative?
- 2 Does Shigella dysenteriae ferment glucose?
- 3 Is Shigella flexneri Onpg positive?
- 4 Is Shigella flexneri indole positive or negative?
- 5 Is Shigella Sonnei oxidase positive or negative?
- 6 Is Shigella flexneri motile?
- 7 Is Enterobacter indole positive or negative?
- 8 Is Shigella oxidase positive or negative?
- 9 Why is the mucosa of Shigella dysenteriae magenta?
- 10 How are the biochemical properties of Shigella determined?
Is Shigella dysenteriae citrate positive or negative?
Escherichia coli and Shigella dysenteriae are citrate negative.
Does Shigella dysenteriae ferment glucose?
Nonetheless, Shigella species are Gram-negative, facultatively anaerobic, nonsporulating, nonmotile rods in the family Enterobacteriaceae. They do not decarboxylate lysine or ferment lactose within 2 days. They utilize glucose and other carbohydrates, producing acid but not gas.
Is Shigella dysenteriae indole positive?
The above three properties are generally negative in Shigella strains. In the case of Shigella, the indole reaction is consistently negative only in specific serotypes within each traditional species of Shigella, including 7 of the 10 S. dysenteriae serotypes, 9 of the 15 S. boydii serotypes, 1 of the 6 S.
Is Shigella flexneri Onpg positive?
The 5% lactose fermentation test in parallel is suggested when the O.N.P.G. test is used for isolating routine pathogens, because organisms such as Shigella sonnei, Shigella dysenteriae 1, and Pasteurella pseudotuberculosis are O.N.P.G. positive.
Is Shigella flexneri indole positive or negative?
Biochemical Test and Identification of Shigella flexneri
| Basic Characteristics | Properties (Shigella flexneri) |
|---|---|
| H2S | Negative (-ve) |
| Indole | Variable |
| Motility | Non-Motile |
| MR (Methyl Red) | Positive (+ve) |
Is Shigella positive for urease test?
Shigella species are urease negative. Urease positive samples are non-shigella species. Shigella species that are oxidase and urease negative should follow the Carbohydrate fermentation test (Manitol). A negative Carbohydrate fermentation test (Manitol) indicates Shigella dysenteriae.
Is Shigella Sonnei oxidase positive or negative?
Oxidase Test (optional) (TP 26 – Oxidase Test) Shigella species are oxidase negative. All Shigella species ferment mannitol except Shigella dysenteriae and some serotypes of Shigella flexneri.
Is Shigella flexneri motile?
Since the discovery of Shigella as the aetiologic agent of acute dysentery almost 100 years ago, this organism has been described as a non-motile and nonflagellated organism that invades the human colonic mucosa.
Is Shigella Sonnei catalase positive or negative?
Biochemical Test and Identification of Shigella flexneri
| Basic Characteristics | Properties (Shigella flexneri) |
|---|---|
| Catalase | Positive (+ve) |
| Citrate | Negative (-ve) |
| Gas | Positive (+ve) |
| Gelatin Hydrolysis | Negative (-ve) |
Is Enterobacter indole positive or negative?
E. coli is indole-positive; Enterobacter aerogenes is indole- negative. Glucose is the major substrate oxidized by enteric bacteria for energy production.
Is Shigella oxidase positive or negative?
Specimens should have the Oxidase test (TP 26) and Urease test (TP 36). Shigella species are oxidase negative. Oxidase positive samples are non-shigella species. Shigella species are urease negative.
How are Shigella dysenteriae type 1 strains identified?
S. sonnei and upto 15% Shigella dysenteriae type 1 strains and minority of S. boydii strains are ONPG positive. Acid produced from a number of carbohydrates. Serological identification is dependent upon the O antigens. Shigella are non-motile organisms that have no H antigens.
Why is the mucosa of Shigella dysenteriae magenta?
The mucosa often appears magenta-colored because of the intense erythema. S. dysenteriae infection is diagnosed with stool culture, which is positive in only 50% of cases. Shigella dysenteriae, Shigella flexneri, Shigella boydii and Shigella sonnei20 are responsible for acute diarrhea.
How are the biochemical properties of Shigella determined?
On Triple Sugar Iron (TSI) agar test, they cause an alkaline slant and an acid butt, with no gas and no hydrogen sulphide. Confirmation of the organism as Shigella and determination of its group is done by slide agglutination test. Biochemical properties of Shigellae Catalase +ve (Shigella dysenteriae type 1 is always catalase -ve)
How are Shigella species tolerant to low pH?
Shigella species are tolerant to low pH and are able to transit the harsh environment of the stomach. Pathogenic mechanism of shigellosis is complex which involves: Shigellas are taken up by M cells and transported beneath the epithelium. Macrophage takes up shigellas, die and release the bacteria.