is shigella flexneri catalase positive or negative

Other characteristics of the species include that it is lactose and lysine negative and catalase positive, in addition, it does not sporulate or release gas when metabolizing carbohydrates. This bacterium belongs to serogroup D of the genus Shigella

and has only one serotype identified to date.

Full Answer

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) 45 more rows ...

What is the catalase test for Shigella dysenteriae?

The catalase test is useful in the rapid, presumptive identification of S. dysenteriae type 1, from appropriate culture media, because of its high predictive value, simplicity and speed. It would be particularly useful during dysentery outbreaks, when other Shigella would be uncommon.

Is Shigella positive or negative in all reactions?

Shigella species tend to be negative in all these reactions, whereas anaerogenic E. coli tend to be positive in at least one of the reactions ( Table 2) ( 2 ). Table 1. Biochemical reactions of serotypes of Shigella(a)

Is Shigella flexneri lactose free?

Shigella flexneri It is an immobile Gram negative Enterobacteriaceae bacillus that does not form spores, does not release gas as a result of carbohydrate fermentation and cannot metabolize (neither lactose nor lysine).

Which Shigella is catalase positive?

catalase-negative. All other Shigella isolates and all the EIEC and STEC tested were found catalase-positive.

Is Shigella flexneri positive or negative?

Shigella flexneri, a Gram-negative bacterium, causes diarrhea that is usually self-limiting.

Is Shigella flexneri oxidase 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 Sonnei catalase test?

Abstract. As epidemic dysentery caused by Shigella dysenteriae type 1 is associated with high mortality, early identification of outbreaks is important. Since S. dysenteriae type 1 differs from most of the Enterobacteriaceae in that it does not produce catalase, a test for catalase may provide a useful screening method ...

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.

Is Shigella flexneri a facultative anaerobe?

Shigella flexneri is a facultative anaerobe. It makes ATP via aerobic respiration in the presence of oxygen and via fermentation in the absence of oxygen. Although it is closely related to Escherichia coli, Shigella flexneri can be differentiated because it fails to ferment lactose or decarboxylate lysine (Jin et al.).

Is Salmonella catalase positive or negative?

Salmonella enterica, a Gram-negative, non-sporing, catalase-positive, oxidase-negative facultative anaerobic bacilli is a significant cause of morbidity and mortality in humans and animals, with multidrug-resistant S.

Is Shigella flexneri a lactose fermenter?

Shigella species are Gram-negative, nonmotile, rod-shaped, facultative anaerobes that almost universally are unable to produce hydrogen sulfide, do not ferment lactose or show late lactose fermentation, fail to utilize citrate as a sole carbon source, and do not generate gas from carbohydrate fermentation.

What method is used to identify Shigella?

Infection is diagnosed when a laboratory identifies Shigella in the stool (poop) of an ill person. The test could be a culture that isolates the bacteria or a rapid diagnostic test that detects genetic material of the bacteria.

What type of bacteria are catalase negative?

If no bubbles appear, the bacteria are catalase negative. Staphylococcus and Micrococcus spp. are catalase positive, whereas Streptococcus and Enterococcus spp. are catalase negative.

Does Shigella flexneri produce H2S?

Abstract. A mixture of Shigella sonnei and Eubacterium lentum produced H2S in triple sugar iron agar; however, neither produced any in pure culture.

Is Shigella Sonnei methyl red positive or negative?

Methyl-Red-positive. Lysine-Decarboxylase-negative. Arginine-Dihydrolyase-negative. Does not grow in KCN.

Is Shigella flexneri glucose positive?

The characteristics of Shigella are summarized as follows: Gram-negative rods; negative for H2S, urease, glucose (gas), motility, lysine decarboxylase, sucrose, adonitol, inositol, lactose (2 days), KCN, malonate, citrate, and salicin; positive for methyl red.

Is Shigella gram positive?

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 motility positive?

Shigella spp. are by definition non-motile and lysine decarboxylase negative.

What disease does Shigella flexneri cause?

Shigella bacteria cause an infection called shigellosis. Most people with Shigella infection have diarrhea (sometimes bloody), fever, and stomach cramps.

What is the Gram negative strain of Shigella?

Shigella flexneri. 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. S. flexneri infections can usually be treated with antibiotics, although some strains have become resistant.

How are E. coli and S. flexneri similar?

The genome of S. flexneri and Escherichia coli are nearly indistinguishable at the species level. S. flexneri has a circular chromosome with 4,599,354 base pairs. It is smaller than that of E. coli but the genes are similar. S. flexneri has about 4,084 known genes in the genome. The extensive similarity between E. coli and S. flexneri is proposed to be due to horizontal transfer. All of the genes needed for S. flexneri to invade the epithelial lining of the colon are found on a virulence plasmid called pINV. The genome of pINV is highly conserved between subspecies of S. flexneri. S. flexneri also has two other small multicopy plasmids, but some strains of S. flexneri have more plasmids that are suspected to confer antibiotic resistance. Some strains of S. flexneri have resistance to the antibiotics streptomycin, ampicillin, or trimethoprim. It has been found that chloramphenicol, nalidixic acid, and gentamicin are still effective antibiotics for some strains.

How does S. flexneri enter the colon?

This bacterium is acid tolerant and can survive conditions of pH 2. Thus, it is able to enter the mouth of its host and survive passage through the stomach to the colon. Once inside of the colon, S. flexneri can penetrate the epithelium in three ways: 1) The bacterium can alter the tight junctions between the epithelial cells, allowing it to cross into the sub-mucosa. 2) It can penetrate the highly endocytic M cells that are dispersed in the epithelial layer and cross into the sub-mucosa. 3) After reaching the sub-mucosa, the bacteria can be phagocytosed by macrophages and induce apoptosis, cell death. This releases cytokines that recruit polymorphonuclear cells (PMN) to the sub-mucosa. S. flexneri still in the lumen of the colon traverse the epithelial lining as the PMNs cross into the infected area. S. flexneri uses these three methods to reach the sub-mucosa to penetrate the epilithelial cells from the basolateral side. The bacterium has four known invasion plasmid antigens: IpaA, IpaB, IpaC, and IpaD. When S. flexneri makes contact with the basolateral side of an epithelial cell, IpaC and IpaB are fused together to make a pore in the epithelial cell membrane. It then uses a type-III secretion system (T3SS) to insert the other Ipa proteins into the cytoplasm of the epithelial cell. S. flexneri can pass to neighboring epithelial cells by using its own outer membrane protein, IcsA, to activate the host's actin assembly machinery. The IcsA protein is first localized to one pole of the bacterium where it will then bind with the host's protein, Neural Wiskott-Aldrich Syndrome Protein (N-WASP). This IcsA/N-WASP complex then activates the Actin-related protein (Arp) 2/3 Complex. Arp 2/3 Complex is the protein responsible for rapidly initiating actin polymerization and propelling the bacteria forward. When S. flexneri reaches the adjoining membrane, it creates a protrusion into the neighboring cell's cytoplasm. The bacteria becomes surrounded by two layers of cellular membrane. It then uses another IpaBC complex to make a pore and enter the next cell. VacJ is a protein that is also needed by S. flexneri to exit the protrusion. Its exact function is still being studied but it is known that intercellular spread is greatly impaired without it. Bacterial replication within the epithelial cell is detrimental to the cell but it is proposed that epithelial cell death is largely due to the host’s own inflammatory response.

What secretion system does Flexneri use?

It then uses a type-III secretion system (T3SS) to insert the other Ipa proteins into the cytoplasm of the epithelial cell. S. flexneri can pass to neighboring epithelial cells by using its own outer membrane protein, IcsA, to activate the host's actin assembly machinery.

How many base pairs does S. flexneri have?

The genome of S. flexneri and Escherichia coli are nearly indistinguishable at the species level. S. flexneri has a circular chromosome with 4,599,354 base pairs. It is smaller than that of E. coli but the genes are similar. S. flexneri has about 4,084 known genes in the genome.

What is the morphology of S. flexneri?

Morphology. S. flexneri is a rod shaped, nonflagellar bacterium that relies on actin-based motility. It produces the protein actin in a swift and continuous fashion to propel itself forward within and between the host’s cells. This bacterium is gram-negative, non-spore forming Shigella from serogroup B.

What group is Flexneri?

S. flexneri belongs to group B (i.e. agglutinate with B antisera) which further subclassified by six type-specific and four group-specific antisera. Until now atleast 23 different subserotypes have been identified and reported

Why is Shigella flexneri so deadly?

Its high incidence in these countries is due to inadequate water treatment, malnutrition and also the cost of medicines .

How big is Shigella Flexneri?

Shigella flexneri it is a short bacillus, 0.7–1.5 µm long, as well as 0.3–0.8 µm in diameter.

What temperature should Shigella flexneri be incubated at?

The temperature at which the broth must be maintained to achieve maximum growth of bacteria is 35 ° C, however, to favor the development of Shigella flexneri Some authors suggest that the ideal incubation temperature is 42 ° C.

What is the name of the bacteria that causes bloody diarrhea?

Bacteria of the genus Shigella they are all responsible for basilar dysentery, also known as shigellosis. This disease is an acute infection of the epithelium and it can cause bloody diarrhea, high fevers, rectal bleeding, as well as nausea, vomiting, headaches and even death.

What broths inhibit Gram positive bacteria?

Gram negative broth and selenite cystine broth are recommended to inhibit the growth of Gram positive bacteria and promote the growth of Gram Negative bacteria that metabolize mannitol and tryptose, such as Salmonella spp., and Shigella spp. The incubation time in these broths is 16 hours.

Why is the symbiote non-mobile?

The species is non-mobile due to the absence of a flagellum, but it does present type 1 fimbriae, a characteristic that differentiates it from other congeneric species. In solid culture medium it grows only around the inoculation site.

Does Shigella Flexneri have a flagellum?

How Shigella flexneri it lacks a flagellum, it causes the polymerization of the actin filaments of the infected cell to favor their displacement in the cytosol of this. As long as the bacterial infection remains, some bacteria are flushed out of the body during bowel movements.

How to enrich Shigella sonnei?

Enrichment of Shigella sonnei. Aseptically weigh 25 g sample into 225 ml Shigella broth to which novobiocin (0.5 µg/ml) has been added. Hold suspension 10 min at room temperature and shake periodically. Pour supernatant into sterile 500 ml Erlenmeyer flask. Adjust pH, if necessary, to 7.0 ± 0.2 with sterile 1 N NaOH or 1 N HCl. Place flask in anaerobic jar, insert anaerobic gas generating pouch/sachet (use number recommended by the anaerobic jar manufacturer, according to the volume of the jar), insert an anaerobic indicator, and tighten the lid. Incubate jars at 44.0°C in a forced air incubator for 20 h. Agitate enrichment culture suspension and streak on a MacConkey agar plate. Incubate 20 h at 35°C.

What temperature to incubate Shigella?

Enrichment of other Shigella species. Proceed as above, but use novobiocin at 3.0 µg/ml and incubate anaerobically at 42.0°C in a forced air incubator.

How long to incubate Shigella?

Inoculate suspicious colonies into the following media: glucose broth, TSI agar slant, lysine decarboxylase broth , motility agar, and tryptone. Incubate at 35°C for 48 h, but examine at 20 h. Discard all cultures showing motility, H 2 S, gas formation, lysine decarboxylation, and fermentation of sucrose or lactose. With respect to indole formation, discard positive cultures from 44.0°C enrichment. All suspicious isolates from 42°C enrichment may be either positive or negative and consequently should be retained.

Is Shigella a single species?

Brenner ( 1) considers Shigella organisms and E. coli to be a single species, based on DNA homology. 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.

Do lysine and lactose decarboxylate?

They do not decarboxylate lysine or ferment lactose within 2 days. They utilize glucose and other carbohydrates, producing acid but not gas. However, because of their affinity to E. coli, frequent exceptions may be encountered, e.g., some biotypes produce gas from glucose and mannitol.

Is Shigellosis waterborne?

References. Shigellosis, although commonly regarded as waterborne, is also a foodborne disease restricted primarily to higher primates, including humans. It is usually spread among humans by food handlers with poor personal hygiene. Foods most often incriminated in the transmission have been potato salad, shellfish, raw vegetables, ...

Does novobiocin inhibit DNA gyrase?

The enzyme DNA gyrase induces negative supercoiling into closed circular DNA. It has been reported, however, that novobiocin inhibits DNA gyrase ( 3 ). Thus, the use of novobiocin in Shigella broth may cause this medium to be incompatible with DNA hybridization for detecting Shigella.

How many subgroups of Shigella are there?

There are 4 subgroups of Shigella. - S. dysenteriaea. - S. flexneri. - S. boydii. - S. sonnei. Natural habitats. Humans and other large primates are the only natural reservoirs of Shigella bacteria. Most transmission is by person-to-person spread, but infection is also caused by ingestion of contaminated food or water.

Is shigellosis endemic in child care?

Shigellosis is most common in situations in which hygiene is compromised (e.g., child care centers, and other institutional settings). In developing populations without running water and indoor plumbing, shigellosis can become endemic. Sexual transmission of Shigella among men who have sex with men also occurs. Clinical significance.

Does Shigella cause bloody diarrhea?

Shigella causes bloody diarrhea (dysentery) and non-bloody diarrhea. Shigellosis often begins with watery diarrhea accompanied by fever and abdominal cramps but may progress to classic dysentery with scant stool containing blood, mucus and pus.

Can Shigella cause dysentery?

Bloodstream infections can occur but are rare. All 4 subgroups of Shigella are capable of causing dysentery. S. dysenteriae serotype 1, is associated with the most severe form of dysentery.

Overview

Characterization

Shigella flexneri is a rod shaped, nonflagellar bacterium that relies on actin-based motility. It produces the protein actin in a swift and continuous fashion to propel itself forward within and between the host’s cells. This bacterium is gram-negative, non-spore forming Shigella from serogroup B. There are 6 serotypes within this serogroup.
Shigella flexneri belongs to group B (i.e. agglutinate with B antisera) which further subclassified …

Discovery

Infectious cycle

External links