BACILLARY DYSENTERY / MedUrgent

BACILLARY DYSENTERY

SHIGELLOSIS

 It is caused by a group of Shigella organisms (gram -ve non motile rods). There are 4 groups of Shigella and about 40 types. Shigella dysentriae and S. flexeneri are commonly found in tropical countries, while S. sonnei is most frequently isolated in temperate climates. The 4 main groups are:

1- Shigella dysentriae (10 serotypes have been described including Shigella shiga)

2-Shigella flexeneri: (6 serotypes)

3- Shigella boydeii

4- Shigella sonnei

Man is the major reservoir and transmission from person to person occurs by oro-faecal route through infected hands when personal hygiene is poor, from contaminated food or drink or by vectors such as house flies. Infection is transmitted from infected cases who continue to shed bacilli for 2 - 6 weeks; convalescent patients and chronic carriers. Infants, young children and old people are more likely to be infected especially with the severe form of the disease.

PATHOGENESIS

On entering the gastrointestinal tract, it invades the upper gut where they multiply and subsequently invade the large bowel and lower epithelium unlike other enteric pathogens; a small number of organisms are needed to cause disease. Following invasion, Shigella organisms secrete entero- and eterotoxins which initiates diarrhea. The organism invades the epithelial

of the large bowel that leads to destruction and ulcer formation and blood in the stools. flat shallow ulcers or snail track ulcers are common to Shigella flexeneri. Neither bacteremia nor septicemia is a recognized complication in adults.

Perforation is unusual except in severe cases of Shigella shiga infection.

Enterotoxins produced by the organism are responsible for the diarrhea by influencing water and electrolyte movement across the entrocell membrane leading to dehydrationز

CLINICAL PICTURE

The incubation period varies; but is usually about 36 hours. Shigella cause a spectrum of clinical illness from asymptomatic infection to diarrhea without fever or severe illness manifested by blood and mucus in the stool associated with high fever, toxemia and convulsions in children. Fever which could be high may be associated with rigors. Seizure is common among children up to the age of 7 years which are related to fever, and not a neurotoxin as previously thought. (Neurotoxin is only produced in animals).

Abdominal pain, tenesmus, vomiting, and diarrhea are the main symptoms. The diarrhea is severe initially, but after a few days it presents with frequent motions and small amounts of stools (dysenteric motions) containing mucus, pus, sloughed mucosa and sometimes blood can be seen. In severe cases, motions can reach 20 to 60 /day with abdominal tenderness.

The onset is abrupt with chills, vomiting, rising temperature, tenesmus and toxemia. Abdominal distention and hiccups may occur. Muscular cramps and oliguria may develop due to dehydration. Toxemia is a feature, the pulse may become rapid, veins are collapsed, blood pressure is low and peripheral circulatory failure may occur. Other clinical findings include restless, anxiousness, flushed cheeks and the tongue may be coated. In adults the presentation is more or less similar to that of Children. Bacillary dysentery may relapse.

 

COMPLICATIONS

• Children under 5years may develop bacteremia with high mortality.

• Peritonitis. Treatment is conservative.

• Perforation: may rarely occur as the infection is generally confined to the mucosa

• Rectal prolapse have been reported in African children.

• Reiter's syndrome.

• Arthropathy (toxic arthritis) affecting larger joints (knees and ankles). It has sterile synovial effusion containing Shigella agglutinins and may occur in convalescence.

• Conjunctivitis, iritis or other ocular manifestations.

• Parotitis and Peripheral neuropathy may occur

• Intussusceptions of the small intestine may occur especially in children. 

• Extensive intestinal ulceration leads to loss of protein with hypoproteinema and malnutrition 

• Urinary tract infection, albuminuria and granular casts and Hemolytic Uremic Syndrome

• The patient may die of uremic coma.

• A cholera-like type has been described. It has an acute onset with collapse due to profuse watery diarrhea; which may later contain blood. This is usually fatal.

• Chronic peritonitis may occasionally develop with serum effusion into peritoneal cavity.

 

DIAGNOSIS

• Mild cases are difficult to differentiate from other cases of diarrhea such as invasive E. coli infection. Diagnosis is mainly based on the clinical picture and the macroscopic examination showing red colored jelly stools which are usually passed in small amounts. The stools are not offensive and give an alkaline reaction. Cellular exudates found in the stools may be of help.

• WBCs are increased at the beginning of the infection but could later be normal.

• Stool microscopy: Most of the stools are composed of cells (pus). The absence of pus excludes a diagnosis of bacillary dysentery.

• Typical cases show a preponderance of swollen polymorphonuclear leukocytes and RBCs in the stools. Macrophages show a sluggish movement

• Stool culture: a mucus containing part is taken immediately and inoculated in a medium of 30% glycerol saline.

• Blood cultures in young ill patients.

• Sigmoidoscopy which shows severe inflammation and mucosal ulcers is preferably avoided in the acute stage.

• Serology is of no diagnostic value.

Differential diagnosis of the acute attack:

 

1. Amoebic dysentery

2. Food poisoning particularly that due to staph organisms.

3. Dysenteric malaria: the patient is very ill with fever and rigors. Malaria parasite may be demonstrated in the blood.

4. Cholera: diarrhea and vomiting are painless. No blood in the stools

 

The differential diagnosis of the chronic attack:

 

1.Schistosomiasis; the patient is not ill and has no constitutional symptoms

2. Ulcerative colitis

3. Tuberculous colitis

4. Crohn's disease

 

TREATMENT IN ADULTS

 

• Supportive measures are extremely important in the dehydrated patient with electrolyte imbalance. Correction of dehydration and electrolyte disturbances is very important

• Food must be modified - small amounts with a low fiber diet.

• Symptomatic treatment to relief severe colic may be necessary by giving antispasmodics in adults.

• Anti-diarrheal drugs especially when the diarrhea is severe.

• Ciprofloxacin: drug of choice • Sulphonamides: sulphdiazine (soluble) or sulphaguanidine (insoluble), however, they are no longer used due to emergence of resistant organisms.

• Ampicillin – (is not the drug of choice):500 mg 6-hourly for 5 day

• Tetracycline in the same dose and for the same duration .

• Cotrimoxazole: 2 tablets twice daily for 5 days.

Treatment of Shigellosis in Children

In children, fever is expected to subside within one day after staring treatment and diarrhea to improve within 2-3 days. Anti-diarrheal and antibiotic drugs should not prescribe for children. In severely ill patients bacteremia the following drugs may be used.

·  Drugs of choice are: Trimethoprim (TMP)/Sulfamethoxazole (SMX): 10mg/kg/day + 50mg/kg/day oral or i.v. in 2 divided doses. Ampicillin 80 - 100mg/kg/day oral or i.v. in 4 divided doses

·        Nalidixic acid 55mg/kg/day oral in 4 divided doses

·        Ciprofloxacin (for ages 18 years or more) One gm/day oral in 2 divided doses

·        Norfloxacin (for ages 18 years or more) 800mg/kg/day oral in 2 divided doses.

·        In vitro (culture) the organisms are sensitive to most of these drugs but in vivo most are found to be non-effective.

·        The above drugs have two actions:

-      They reduce the number of motions

-      They reduce the bacterial load in the lumen of the intestine.

   N.B. anti-diarrheal drugs are used for severe adult cases, but not for children.