Is Shigella flexneri indole positive?
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. flexneri serotypes, and S.
Which Shigella species is indole positive?
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 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.
How do you identify a Shigella?
The type species is Shigella dysenteriae. Isolates from primary culture are identified by colonial appearance, biochemical tests and serology (agglutination with specific antisera).
Is Shigella flexneri Gram positive or negative?
Shigellae are Gram-negative, nonmotile, facultatively anaerobic, non-spore-forming rods. Shigella are differentiated from the closely related Escherichia coli on the basis of pathogenicity, physiology (failure to ferment lactose or decarboxylate lysine) and serology.
Is Shigella flexneri catalase positive or negative?
Shigella species are facultative anaerobes, are non-motile, oxidase negative, urease negative, do not decarboxylate lysine, and all except S. dysenteriae type 1 are catalase positive1. The species may be differentiated by biochemical tests and serology of their lipopolysaccharides2.
What is the positive result for indole test?
A positive result is shown by the presence of a red or red-violet color in the surface alcohol layer of the broth. A negative result appears yellow. A variable result can also occur, showing an orange color as a result.
How can you tell Shigella species?
Shigella species are so closely related to Escherichia coli that routine matrix-assisted laser desorption/ionization–time of flight mass spectrometry (MALDI-TOF MS) cannot reliably differentiate them. Biochemical and serological methods are typically used to distinguish these species; however, “inactive” isolates of E.
What is the color of Shigella flexneri?
Reciprocal agglutinin absorption studies with the virulent translucent red-gold and gold-green colony forms of Shigella flexneri 2a and their antisera showed that these two colony forms were identical.
Why is Shigella flexneri gram-negative?
Shigella flexneri is a species of Gram-negative bacteria in the genus Shigella that can cause diarrhea in humans. Several different serogroups of Shigella are described; S. flexneri belongs to group B….
| Shigella flexneri | |
|---|---|
| Genus: | Shigella |
| Species: | S. flexneri |
| Binomial name | |
| Shigella flexneri Castellani & Chalmers 1919 |
Is Shigella urease negative?
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 Yersinia indole positive?
Yersinia enterocolitica, indole-negative and indole-positive biotypes. Isolation, identification and sensitivity to chemotherapeutics.
What are the characteristics of Shigella flexneri?
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)
What is the Indole reaction in Shigella?
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. dysenteriaeserotypes, 9 of the 15 S. boydiiserotypes, 1 of the 6 S. flexneriserotypes, and S. sonnei(9). S. flexneri1 to 4 are variable with regard to this trait.
How do you identify Shigella dysenteriae?
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)
Why are shigellaserotypes considered indole negative?
Analysis of the tnaoperon of strains representing each of the 25 Shigellaserotypes that are consistently indole negative revealed at least nine IS-related events that damaged the tnaoperon, leading to a block in conversion of tryptophan to indole.