Shigellosis

Shigellosis or bacillary dysentery (bacterial dysentery) is an acute, highly infectious diarrheal disease with a typical mucus and blood in the stool, often accompanied by fever and abdominal cramps.

Etiology and pathogenesis
Shigellas are gram-negative stationary sticks. The genus Shigella is divided into:


 * Shigella dysenteriae – group A shigellosis (Shiga-Kruse dysentery),
 * Shigella flexneri – group B shigellosis,
 * Shigella boydii – group C shigellosis,
 * Shigella sonnei – group D shigellosis.

They are sensitive to disinfectants but survive in acidic environments for several hours. Bacteria multiply rapidly in the small intestine, but only in the large intestine is the intestinal epithelium damaged, into which shigellas penetrate and multiply in them. Subsequently, they also attack neighboring enterocytes, which then die of necrosis. Macroscopically, we see an inflammatory to necrotically altered mucosa, especially the distal sections of the colon. Shigella is characterized by the production of toxins, which make it easier to get intracellularly and induce apoptosis. In addition, Shigella dysenteriae serotype I produces shiga toxin with the properties of cytotoxin, neurotoxin, and enterotoxin and cause more severe diseases. Shiga toxin is very similar to verotoxin of enterohemorrhagic E. coli.

Epidemiology
The source of infection is contaminated food, sick or convalescent person. It is an exclusively human disease, it is a typical disease of "dirty hands", occurring epidemically in groups where it is difficult to maintain hygiene (children's camps, social institutions, psychiatric hospitals, etc.). The alimentary transmission occurs through infected food, especially milk and water. The infectious dose is only 10-100 bacteria. Shigellosis is the most infectious bacterial intestinal infection. The global incidence is estimated at 200 million cases per year. Due to hygienic measures, the disease is uncommon in the Czech Republic – about 400 cases per year, of which 20% of diseases are imported. Children are most often affected during the summer months.

Clinical symptoms

 * Sudden fever (febrile convulsions and symptoms of meningeal irritation in children), chills,
 * cramping abdominal pain, located more to the left,
 * diarrhea – first large watery stools, with a decrease in temperature it turns into numerous small stools with blood and mucus,
 * painful tenesmus,
 * vomiting rarely.

The course depends on the age, nutrition of the patient and his general condition. A complication may be hemolytic uraemic syndrome in strains producing shiga toxin or intestinal abscess.

Diagnosis
We use stool culture to confirm the diagnosis. In case of ambiguity, we realize a serotyping.

Therapy

 * rehydration,
 * antibiotics – therapeutic and epidemiological effect,
 * co-trimoxazole,
 * fluoroquinolones,
 * rifaximin,
 * azithromycin,
 * probiotics,
 * drugs decreasing the frequency of diarrhea are not suitable (risk of toxic megacolon).

Differential diagnosis
We also consider differential diagnosis of EIEC, EHEC, amoebiasis, campylobacter infection, yersiniosis, and non-typhoid salmonellosis.

Related Articles

 * Enterotoxicosis

External References

 * Mim's Microbiology: