Shigella is a genus of highly contagious bacteria responsible for shigellosis, characterized by severe diarrhea predominantly affecting children in unsanitary conditions, with millions of cases and significant mortality worldwide. The infection primarily spreads through contaminated food and water or direct person-to-person contact, leading to severe inflammation of the colon and toxic symptoms such as hemolytic-uremic syndrome. Prevention focuses on hygiene practices, while treatment often emphasizes fluid replacement, with antibiotics reserved for severe cases.

1. Shigella
GROUP 3

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3. INTRODUCTION
-Shigella is a genus of bacteria that causes shigellosis, an intestinal
infection.
-The bacteria are Gram-negative, facultatively anaerobic, non-
spore-forming, non-motile, rod-shaped, and genetically closely
related to Escherichia.
-Shigella is highly contagious and spreads through direct person-
to-person contact, contaminated food, or water
The genus Shigella exclusively infects human intestine.
-Shigella dysenteriae is the causative agent of bacillary dysentery
or shigellosis in humans.
It is a diarrheal illness which is characterized by
frequent passage of blood stained mucopurulent stools.
-The four important species of the genus Shigella are:
- Shigella dysenteriae
- Shigella flexneri
- Shigella sonnei
- Shigella boydii.

4. EPIDEMIOLOGY
-Shigella is a leading cause of bacterial diarrhea worldwide, with annually 80–165
million annual cases (estimated) and 74,000 to 600,000 deaths .
-It is one of the top four pathogens that cause moderate-to-severe diarrhea in African
and South Asian children.
-Shigella infection is more common in children under age 5, especially those who live
in crowded or unsanitary conditions.
-Shigella infection is caused predominantly by S. sonnei in high-income countries,
whereas S. flexneri is prevalent in low- and middle-income countries. Infections
caused by S. boydii and S. dysenteriae are less common globally
-Shigella genus is named after Kiyoshi Shiga a Japanese bactiologist who first
discovered it in 1897.
According to the world health organization, it has been estimated that
about 120 million cases of severe dysentery, due to shigellosis are
reported worldwide annually (Lampel 2005 & khan 2008), .
• The WHO further reported that about 1.1 million people die from this
infection globally, every year of which 60% are children ( Khan 2008),
in Zambia dysentery has been classified as a notifiable disease, as it is
extremely dangerous and has the capacity to affect a large number of people
in the short period of time, just like cholera.

5. TRANSMISSION
-shigella infection is typically by ingestion of
contaminated food, water, or feces
-Shigella is very contagious and can spread
through direct person-to-person contact, such as
in child care settings or group activities.
-Shigella can survive in the environment for
several days
-Shigella bacteria are relatively resistant to gastric
acid, which means they can survive the acidic
environment of the stomach and reach the colon,
where they cause damage to the mucosa.
- in Water & ice 1-6 months
-1-6 weeks on dried stools
-Acidic stools - few hours

6. PATHOGENESIS
-Shigella is bacteria that invades the epithelial lining of the
colon, causing severe inflammation and cell death.
-Shigella is the most virulent pathogen that it only needs 10-
100 organisms to produces disease.
-S. Dysenteriae is resistant to acid in the stomach. Small
intestinal infections do not occur unless the patient has
disturbance immobility of intestine.
-In the colon, the bacteria penetrate the intestinal mucous
epithelium and are taken up by M or microfold epithelial
cells
-Proliferate inside the cytoplasm of these epithelial cells and
penetrate into the lamina propria.
-Shigella produces toxins that contribute to diarrhea and
dysentery, such as Shiga toxin or verotoxin which prevents
protein synthesis and can cause hemolytic-uremic syndrome,
a potentially fatal complication that affects the kidneys and
blood vessel
-The A1 fragment of the shiga toxin blocks binding of the
aminoacyl-tRNA to the 28S rRNA of the 60S subunit.
-Prevention of proteins synthesis results in cell death,
necrosis and ulceration of the intestinal mucosa.

7. CLINICAL SYMPTOMS
The main sign of shigella infection is diarrhea.
-Frequent passage of loose, scanty faeces containing blood and
mucus.
-Abdominal cramps and tenesmus (straining to defecate).
-Fever and vomiting.Symptoms usually begin a day or two after
contact but may take up to a week to develop.
Symptoms generally last for about five to seven days, but may last
longer in some cases of people with malnourished immune system

8. DIAGNOSIS
-Shigella infection is diagnosed by testing a stool
sample for the presence of shigella bacteria or
their toxins.
Laboratory tests can also identify the specific
species and serotype of shigella and their
antibiotic resistance patterns.
-The best test could be a culture that isolates the
bacteria or a rapid diagnostic test that detects the
genetic material of the bacteria

9. TREATMENT
-In most cases of shigella infection are mild and resolve on
their own without treatment.
-fluids and electrolytes replacement is important to
prevent dehydration from diarrhea.
-Antibiotics may be prescribed for severe case
such as Immunocompromised people (Ciprofloxacin or
norfloxa) can be give to reduce the simptoms.
-Many strains are sensitive to Nalidixic acid and
Norfloxacin.
-Nutrition
involves eating foods that are easy to digest and rich in
potassium, such as bananas, lentils, pineapples, pawpaw,
and coconut milk.

10. PREVENTIVE MEASURES
-practice good hygiene and sanitation
-washing hands thoroughly with soap
and water before eating or preparing
food.
-Washing fter using the toilet or
changing diapers,and after contact
with animals or sick people.
-Disinfecting surfaces and utensils
that may have been contaminated
with stool.

11. CONCLUSION
-The incidence bacillary dysentery is still high comparatively in the
region as we stand at 25.1% per 10,000 population(as observed by
ZPHI in 2016.
-This calls for concerted effort to put in preventative measures and
effective curative. Baring mind with the increased reports of
antimicrobial resistant being reported world wide.
-The short term measure has to be continued health education on
the risk factors, how to prevent them as well as provision of clean
water in high case areas.

12. REFERENCES
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. Citation Style For This Aticle : katemba BM Kayeyi,P Sakubita P.Ngoma A Ganetti
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Zambia Buil(2019);3(7);pp5-9.
• Khan,N.A., 2008. Microbial pathogens and Human Diseases.CRC press .
• Lampel ,K.A.,2005. Shigella Species .Foodborne Pathogens: Microbiology &
Molecular biology, pp,341-356.