Bacillary Dysentery Overview

Study Notes

Bacillary dysentery is an inflammatory colitis caused by the Shigella group of organisms.
Shigella organisms are gram-negative, non-spore-forming bacilli.
The primary site of infection is the large intestine.
Four serological subgroups exist: Sh. dysenteriae (with 10 subtypes, type 1 being the most severe), Sh. flexneri (6 serotypes), Sh. boydii (15 serotypes), and Sh. sonnei (1 type).

Approximately 140 million cases of shigellosis and almost 600,000 deaths occur annually.
Poor sanitation and overcrowding contribute to transmission and outbreaks.
Epidemic rates range from 2-6%.
Transmission is fecal-oral, and humans are the primary hosts.

The disease depends on various cytotoxins produced by the bacteria.
Neurotoxin can cause convulsions and peripheral neuropathy.
Enterotoxin leads to secretory diarrhea.
Cytotoxin damages epithelial cells, leading to ulcers, microabscesses, exudative inflammation, and fibrosis, potentially resulting in chronic dysentery or colitis.
Bacteremia (bacteria in the bloodstream) is relatively uncommon (8%).

The clinical presentation varies depending on the infecting Shigella type and severity.
Incubation period typically ranges from 1 to 5 days.
Onset is usually abrupt with fever (up to 40-41°C).
Initial diarrhea is watery, transitioning to dysentery (passage of stool containing blood, mucus, and pus) within a few days.
Patients experience frequent bowel movements (10-30 per day), abdominal cramps, and tenesmus (straining during bowel movements).
Severe cases can progress to dehydration, shock, and acute kidney injury (ARF).

Potential complications include perforation, peritonitis, severe dehydration, shock, acute kidney injury (ARF), sepsis, convulsions, portal pyemia (liver abscess), and stricture of the large intestine.
In children, complications might include prolapse of rectal mucosa or hemorrhoids.

HUS can develop in certain cases, typically with Shigella dysenteriae type 1.
It is characterized by severe hemolysis (red blood cell destruction) and acute kidney injury.
The condition is often seen during the first week of the infection.
Complications frequently include significant drops in red blood cell count potentially causing heart failure, reduced urine output (oliguria) that progresses to complete kidney failure, anemia, low platelet counts, low sodium concentrations and severe electrolyte imbalances.
Mortality rates vary but can be substantial (5-10% die from acute kidney injury; 50% who survive progress to chronic kidney disease).

Diagnosis relies on stool microscopy (presence of blood, pus, and other characteristics) and culture.
Stool macroscopy usually shows mucous, pus, and blood.
Stool culture is crucial for confirmation

The initial presentation of acute bacillary dysentery can overlap with other conditions, including amoebic dysentery, food poisoning, Campylobacter infections, and other bacterial/viral diarrheal illnesses.

Persistent symptoms may be associated with other intestinal diseases/conditions such as Schistosomiasis, inflammatory bowel disease, or even colon cancer.

Treatment focuses on fluid and electrolyte replacement, particularly in severe cases where dehydration is pronounced.
Antibiotics like nalidixic acid or newer generation quinolones are often utilized, taking into consideration antibiotic resistance issues.
Supportive care, including control of dehydration, is crucial.
Anti-diarrhea agents may be used to reduce the frequency of stools; but their role is somewhat controversial, since they may prolong the infection.