SHIGELLOSIS ---- By Dr Sandeep Tak
DEFINITION
- An acute infectious inflammatory colitis by Shigella grp also c/a bacillary dysentery
ETIOLOGIC AGENT
- Gm -ive, nonmotile bacilli, family Enterobacteriaceae
- 4 Shigella species (S. dysenteriae, S. flexneri, S. boydii, and S. sonnei)
- Characterized by its ability to invade intestinal epithelial cells and to cause infection and illness in humans, small inoculum is enough (a few hundred to few thousand organisms)
EPIDEMIOLOGY
- Poor sanitation help in spread / Pathogen only of humans and a few other primates
- Transmission fecal-oral route, generally via direct contact but sometimes through contaminated vectors such as food, water, flies, and fomites. high rate of secondary household transmission (20-40%)
PATHOGENESIS
- Orally ingested → low pH in stomach tolerated → invasion of colonic epithelial cells and cell-to-cell spread of infection → rapid multiplication → cell damage → mucosal ulceration → bloody diarrhea
- Once a single Shigella organism has invaded a single host cell, the entire process of bacterial escape from the phagocytic vesicle into the host cell's cytoplasm, multiplication, and cell-to-cell spread can take place without exposure of the bacterium to the extracellular milieu and to the host's defenses.
- S. dysenteriae type1-produce Shiga toxin → inhibiting protein synthesis
- Immunity develops and is serotype-specific
CLINICAL MANIFESTATIONS
- 25% asymptomatic, 25% develop transient fever, 25% have fever & self-limited watery diarrhea, and the remaining 25% had fever and bloody diarrhea/dysentery
- Dysentery is characterized by frequent passage (usually 10 to 30 times per day) of small-volume stools consisting of blood, mucus, and pus
- abdominal cramps and tenesmus, rectal prolapse, especially in young children.
- Severe dysentery is most likely in infection due to S. dysenteriae type 1, occurs less commonly with S. flexneri, and is least likely in S. sonnei infection.
- Severe shigellosis: toxic dilatation and colonic perforation, may be fatal.
- Endoscopy: hemorrhagic, with mucous discharge and focal ulcerations. The majority of lesions are in the distal colon and progressively diminish in the more proximal segments of large bowel.
Extraintestinal complications
- HUS may occur with S. dysenteriae type 1 infection. HUS usually develops toward the end of the first week of shigellosis, when dysentery is already resolving. Oliguria / anuria with renal failure and to severe anemia with congestive heart failure. 5 to 10% of patients with HUS die of the acute illness. Leukemoid reactions,thrombocytopenia is common.
- Less common: seizures, and reactive arthritis
D/DIAGNOSIS
- Shigellosis is the principal bacterial cause of bloody diarrhea
- The differential diagnosis includes inflammatory colitis due to other microbial agents: EHEC, EIEC, Campylobacter jejuni, Salmonella enteritidis, Yersinia enterocolitica, Clostridium difficile, and the protozoan Entamoeba histolytica. Ulcerative colitis and Crohn's colitis are among the "noninfectious" conditions.
TREATMENT
- The mild to moderate dehydration : oral rehydration
- Ampicillin (50 to 100 mg/kg per day in children or 2 g/d in adults, in divided doses) or
- Cotrimoxazole(8/40 mg/kg per day or DS tab twice a day in adults, given for 5 days)
- Ciproflox 500 BD x 3 days
- Ceftriaxone 1gm single dose
