Foodborne Infection by Shigella - Shigellosis Food Poisoning

Describe the Shigella infection

The ideal and the colonic epithelium is harmed by acute gastrointestinal tract infections caused by Shigella species, which also result in bacillary dysentery. Developing and undeveloped nations with low sanitation, hygiene, and medical facilities are where shigella infections are most frequently recorded.

  • Shigellosis has a significant death rate, particularly in malnourished children under the age of five.
  • Due to the significant loss of fluids and blood during diarrhea, which might cause mortality, the Shigella infection sufferer experiences decreased nutrition.
  • S. dysenteriae (serogroup A), S. flexneri (serogroup B), S. boydii (serogroup C), and S. sonnei are the four serogroups that Shigella species are divided into (serogroup D).
  • Among them, S. dysenteriae Type 1 is in charge of deadly epidemic outbreaks, whilst other serotypes are in charge of little and uncommon illnesses.

Biological characteristics of Shigella

  • Gram-negative
  • Facultative anaerobes
  • Non-sporulating
  • Non-motile
  • Non-encapsulated
  • Prokaryotic rods
  • Optimum temperature – 7 to 46°C
  • Can resist 5% NaCl and pH 
  • Can survive harsh physical and chemical conditions
  • Sensitive to pasteurization temperature

Shigella infection sources and routes of transmission

  • The human host’s digestive system serves as the primary reservoir for Shigella species.
  • Rarely does Shigella infection occur in animals.
  • The fecal-oral pathway or person-to-person contact is the route of transmission.
  • The main sources include drinking contaminated water and eating tainted food.
  • Fruits and vegetables are contaminated by the contaminated irrigation water used by farmers.
  • Due to a lack of sanitary facilities and adequate hygiene practices, children and newborns are more susceptible to shigellosis, particularly in impoverished and developing nations.

Infection with Shigella Epidemiology

  • The Japanese microbiologist Kiyoshi Shiga came up with the name Shigella dysenteriae while looking into a severe dysentery epidemic that struck Japan in 1896.
  • Shigellosis can be brought on by just 10 to 100 bacterial cells, as opposed to the 1000–100,000 required by other diseases.
  • The World Health Organization (WHO) estimates that there are 165 cases of shigellosis worldwide each year, with 55,000 child deaths under the age of five.
  • A sporadic outbreak of S. dysenteriae and S. flexneri, which were isolated from an infected person’s stool sample, occurred in Kolkata.
  • Epidemics and endemic diseases have primarily affected South Asia and East Africa in recent decades.

Shigella-related illnesses and signs and symptoms

  • The onset of symptoms is typically 1 to 3 days after ingesting bacterial cells, while it can be anywhere between 12 hours and 7 days depending on the dose.
  • Fever, appetite loss, abdominal pain, bloody or watery diarrhea, colon inflammation, weariness, malaise, and fever are typical symptoms.
  • Dehydration may happen as a result of the outflow of too much watery fluid, but it rarely does and shouldn’t be a major issue.
  • Malnutrition and anorexia, which are the leading causes of death in children under the age of five, require aggressive management.
  • Some patients may experience neurological issues such as headaches, drowsiness, and abnormal body movement.
  • The illness goes away on its own in 5 to 7 days, but an infected individual may continue to pass bacteria in their feces while asymptomatic and provide a risk of infection spreading.

Shigella infection toxicity mechanism

  • When the organism enters the body through the mouth and travels to the large intestine, the infection begins.
  • Due to the increased mobility of epithelial cells and rapid liquid flux, Shigella can withstand the stomach pH and does not cling to the small intestine.
  • Once inside the intestinal epithelial layer, pathogens are bound by M cells in vacuoles.
  • After escaping, the infection moves on to the macrophages, where it is phagocytized and causes apoptosis.
  • Shigella reproduces quickly in the large intestine and spreads to neighboring cells as it travels through the epithelial layer, inflicting inflammation and tissue damage.
  • Due to the secretion of the proinflammatory cytokine IL-12, which causes necrosis in the host body, S. flexneri is known to kill mitochondria.
  • The pathogens are encased by a plasma membrane and begin intracellular reproduction and cell-to-cell bacterial dissemination during inter and intracellular (cell-to-cell) migration.
  • According to reports, the immune system of the host is what triggers the inflammation and ulceration of the mucosal layer; the pathogen’s intracellular proliferation is not a factor.
  • Shiga toxin is a powerful toxin that produces bloody diarrhea and is known to be produced by S. dysenteriae.
  • The host cells die as a result of the toxin’s termination of the protein production pathway after entering the host cell via endocytosis.
  • The gram-negative bacteria’s lipopolysaccharide (LPS) layer also functions as an endotoxin that only becomes active when the cell is destroyed and harms the epithelial tissues.

Shigella laboratory diagnostic

Methods for bacterial cultivation

  • Dysentery patients should have a stool sample collected and examined right away because the organism only survives outside the host body for a brief period of time.
  • To isolate the bacteria, the sample to be examined should be taken during the very beginning of the infection.
  • Xylose-Lysine Deoxycholate Agar, MacConkey Agar, and Salmonella-Shigella Agar are the specific media used to culture Shigella.

Bioassays

  • To measure the impact of the pathogens, various animals including guinea pigs, rats, rabbits, and monkeys are given oral medications.
  • Some had obvious eye inflammation that progressed to massive intestinal tissue damage.
  • Animal use is nevertheless restricted because of moral concerns.

Immune system tests

  • There are kits for enzyme immunoassay (EIA), also known as a dot blot assay, which is used to detect infections.
  • EIA kits typically cost little money to use and have a 94% efficiency rate.
  • Dipstick immunoassays, the Wellcolex Color Shigella test, and the latex agglutination test are further immunoassays (WCT-Shigella).

Using molecular methods

  • The most reliable method to quickly find the Shigella gene is matrix-assisted laser desorption/ionization-time of flight mass spectrometry (MALDI-TOF MS).
  • Conventional PCR improved the diagnosis by 50% by identifying the different Shigella species.
  • Target genes like ipaH, virA, iral, LPS, and plasmid DNA can be found by them.

Taking care of shigellosis

  • Shigella can become resistant to antibiotics, which might make it difficult to treat a patient with shigellosis symptoms.
  • In a clinical trial, ciprofloxacin, ampicillin, sulfamethoxazole, and nalidixic acid were used to demonstrate their efficiency against Shigella.
  • Azithromycin and fluoroquinolones are the antibiotics of choice for shigellosis at the moment.
  • Treatment should begin early in the course of the sickness and is dependent on how severe the infection is.
  • For an infected person to replenish the electrolyte loss, oral rehydration and intravenous fluid therapy are frequently used as treatments.

Shigellosis Prevention and Control

  • Shigellosis can be prevented most successfully by using proper sanitation, decent personal hygiene, and proper feces disposal.
  • Given that shigellosis is spread by the fecal-oral channel, it is advisable to prevent someone from preparing food if they are displaying signs of a digestive issue.
  • Utilizing chlorinated water to wash produce before eating.
  • Food goods should be refrigerated properly to prevent bacterial growth.
  • Shigellosis typically occurs in undeveloped and underdeveloped nations, so it is important to educate people about proper hygiene and sanitation, to avoid consuming feces-contaminated food and water, and to consume nutrient-rich meals while ill in order to reduce the number of cases.