Shigella Flexneri: Testing And Identification Methods 

Shigella flexneri are gram negative, citrate negative, non-sporing, non-motile, MR positive rod shaped bacteria. 

Shigella flexneri is the bacteria responsible for most cases of shigellosis. Shigellosis is bacterial dysentery that causes around 1.1 million deaths around the world every year. The majority of these deaths are children in the developing world. 

Shigella Flexneri: Testing And Identification Methods 

There are over 164 million causes of Shigellosis recorded every year. 

It can be so dangerous because Shigella flexneri has the ability to evade the host’s immune response and enter epithelial. 

Today, we are going to look at Shigella flexneri, why it is dangerous, and how to test for it. 

Shigella Family 

The Shigella family is split into four categories: 

They are responsible for a bacterial infection known as shigellosis or bacillary dysentery. This can be deadly if not treated early or caught by children. 

If you live in Europe or America then you are unlikely to encounter many of these strains of Shigella unless you travel. 

Shigella Flexneri Classifications: 

Domain: Bacteria

Phylum: Pseudomonadota

Class: Gammaproteobacteria

Order: Enterobacterales

Family: Enterobacteriaceae

Genus: Shigella

Species: S. flexneri

Shigellosis 

Shigellosis is a bacterial infection known as shigellosis or bacillary dysentery. In the Shigella family, most cases are caused by Shigella flexneri – reports vary between 2% and 30% of cases are caused by flexneri. 

There are over 164 million recorded cases of Shigellosis every year but it is likely that there are many more. Around 1.1 people are killed by Shigellosis every 12 months. 

Symptoms

Symptoms of Shigellosis include

  • Diaherra (often bloody) 
  • Stomach cramps 
  • Fever 
  • Dehydration 

Here are the four main symptoms of Shigellosis: 

Reactive arthritis – around 24% of people who get Shigellosis from Shigella flexneri develop reactive arthritis. This normally lasts for 3-5 months but has been known to lead to chronic arthritis. Early symptoms include joint pain, painful urination, and eye irritation. 

Hemolytic-uremic syndrome – this is the most dangerous symptom of Shigellosis. It is developed when the bacteria enter a person’s digestive system. This leads to red blood cells being destroyed and the kidneys stopping working. 

Seizures – Scientists are not yet sure why Shigellosis infections cause seizures in young children, but this symptom typically goes away without treatment. 

Bloodstream infections – up to 7.4% of people who contract Shigellosis develop bloodstream infections. This typically happens in people who experience this symptom already have weakened immune systems. 

Treatments 

Treatments 

If you have Shigellosis then you will be encouraged to stay hydrated, wash your hands, and get plenty of rest. 

If your symptoms are extreme or you do not improve after 7 days then you may be prescribed antibiotics to fight the infection and loperamide (Imodium) or diphenoxylate with atropine (Lomotil) to help with diarrhea. 

Testing 

Shigella Flexneri is non-motile. It is also non-sporing. 

Basic Characteristics

With positive (+ve) properties 

  • Catalase 
  • Gas
  • MR (Methyl Red) 
  • Nitrate Reduction

With variable properties

  • Indole 

With RODS properties

  • Shape 

With negative (-ve) properties

  • Citrate
  • Gelatin Hydrolysis 
  • Gram Staining
  • Growth in KCN 
  • H2S
  • Oxidase 
  • Pigment 
  • Urease 
  • VP (Voges Proskauer) 

Fermentations 

With positive (+ve) properties 

  • Mannitol
  • Mannose
  • Trehalose

With variable properties 

  • Arabinose 
  • Maltose 
  • Melibiose 
  • Sorbitol 
  • Tartrate 

With negative (-ve) properties 

  • Adonitol
  • Cellobiose
  • DNase
  • Dulcitol
  • Glycerol
  • Lactose
  • Malonate
  • Mucate
  • MyoInositol
  • Rhamnose
  • Salicin
  • Sucrose
  • Xylose

Enzymatic Reactions

With negative (-ve) properties

  • Acetate Utilization
  • Aesculine Hydrolysis
  • Arginine Dehydrolase
  • Lipase 
  • Lysine
  • ONPG (β-galactosidase)
  • Ornithine Decarboxylase
  • Phenylalanine Deaminase 

Shigella Flexneri Discovery 

Shigella Flexneri Discovery 

The Shigella family was first discovered by Japanese physician Kiyoshi Shiga, who was doing research into the cause of dysentery. This happened in 1897. 

The flexneri strand was found by an American physician, James Flexneri,  a few years later. 

In the 19th century, dysentery was killing the Japanese by the thousands. Towards the end of the century, there were several large epidemics and 20% of people getting the infection were killed by it. 

In 1897, Shiga studied 32 people with dysentery and used a method known as Koch’s Postulates to narrow down the bacterium causing the infection. Once discovered, Shiga set out to create a vaccine. 

Since Shiga’s work, three more Shigella strains have been found. It has also been discovered that Shigella is closely related to E-Coli. 

Shigella, Most Common Locations 

Across the world, four strains of Shigella exist. 

S. sonnei is most commonly found in industrialized countries. It can sometimes be found in infected water supplies but is most commonly found in sewage systems. 

Shigella flexneri can be found all over the developing world and is something to be aware of if you are traveling. It is one of the most potent Shigella strains. 

S. boydii and S. dysenteriae are the two rarest forms of Shigella. They are typically found in isolated locations and are most commonly found in Sub-Saharan Africa and South Asia. 

In developed countries, most cases of Shigellosis (up to 50% of cases) are found in people who have recently traveled to the developing world. 

How To Avoid Infection?

As with most bacterial infections, the most important thing you can do to prevent infection is to regularly wash and disinfect your hands. 

In some countries, you might want to filter your tap water before you drink it. You can check the local travel guidance for more information on this. 

If you think you have been infected by Shigellosis then it is best to visit a doctor as soon as possible. You may also want to be tested for related issues once you have returned home. 

Summary 

Shigella flexneri is a bacterial strain that was discovered in the early 20th century by James Flexneri. 

It is part of the Shigella family and is responsible for many cases of Shigellosis around the world. This infection kills up to 1.1 million people every year. Flexneri is found all over the developing world. 

It can cause bloodstream infections and reactive arthritis in patients. Anyone with a weakened immune system should see a doctor immediately if they are worried that they contracted any form of Shigellosis. 

Jennifer Dawkins

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