Invasive (dysentery-like) Diarrhea - Gastrointestinal Infections

Bacillary Dysentery (Shigellosis)

Four species of Shigella are most often associated with disease: S. dysenteriae type I, S. flexneri, S. bovdii, and S. sonnei.
Poor sanitation, poor personal hygiene, inadequate water supply, malnutrition, and increased population density are associated with increased risk of Shigella gastroenteritis epidemics, even in developed countries. The majority of cases are thought to result from fecal-oral transmission.
Shigella spp. cause dysentery upon penetrating the epithelial cells lining the colon. Microabscesses may eventually coalesce, forming larger abscesses. Some Shigella species produce a cytotoxin, or shigatoxin, the pathogenic role of which is unclear although it is thought to damage endothelial cells of the lamina propria, resulting in microangiopathic changes that can progress to hemolytic uremic syndrome. Watery diarrhea commonly precedes the dysentery and may be a result of these toxins.
Initial signs and symptoms include abdominal pain, cramping, and fever followed by frequent watery stools. Watery stools start within 48 hours of infection and are followed by bloody diarrhea and other signs of dysentery within a few days.
If untreated, bacillary dysentery usually lasts about 1 week (range 1 to 30 days).
Shigellosis is usually a self-limiting disease. Most patients recover in 4 to 7 days. Treatment of bacillary dysentery generally includes correction of fluid and electrolyte disturbances and, occasionally, antimicrobials.
Antimicrobials are indicated in the infirm, those who are immunocompromised, children in day care centers, the elderly, malnourished children, and health care workers. Antimicrobials may shorten the period of fecal shedding and attenuate the clinical illness.
The agent of choice is trimethoprim/sulfamethoxazole for infections acquired in the United States. For infections acquired outside the United States, the agents of choice are ciprofloxacin, norfloxacin, and azithromycin. Fluoroquinolones are generally contraindicated in children and adolescents.
Fluid and electrolyte losses can generally be replaced with oral therapy, as dysentery is generally not associated with significant fluid loss. Intravenous replacement is necessary only for children or the elderly.
Antimotility agents such as diphenoxylate are not recommended because they can worsen dysentery.

Salmonellosis

Human disease caused by Salmonella generally falls into four categories: acute gastroenteritis (enterocolitis), bacteremia, extraintestinal localized infection, and enteric fever (typhoid and paratyphoid fever), and a chronic carrier state. S. typhimurium is the most common cause of salmonellosis.
Salmonella enterocolitis occurs secondary to mucosal invasion of microorganisms, but it may involve enterotoxin production or local inflammatory exudates as possible mechanisms of pathology. Organisms may invade beyond the mucosa and enter the mesenteric lymphatics, which then carry bacteria to the general circulation via the thoracic duct. Bacteria not cleared by the reticuloendothelial system may cause metastatic infection in various organs.
With enterocolitis, patients often complain of nausea and vomiting within 72 hours of ingestion followed by crampy abdominal pain, fever, and diarrhea, although the actual presentation is quite variable.
Stool cultures inevitably yield the causative organism, if obtained early. However, recovery of organisms continues to decrease with time so that by 3 to 4 weeks, only 5% to 15% of adult patients are passing Salmonella.
Some patients may continue to shed Salmonella for a year or longer. These «chronic carrier» states are rare for serotypes other than S. typhi.
Salmonella can produce bacteremia without classic enterocolitis or enteric fever. The clinical syndrome is characterized by persistent bacteremia and prolonged intermittent fever with chills. Stool cultures are frequently nega- tive.
Extraluminal infection and/or abscess formation can occur at any site after any of the other syndromes or may be the primary presentation. Metastatic infections have been reported to involve bone, cysts, heart, kidney, liver, lungs, pericardium, spleen, and tumors.
Enteric fever caused by S. typhi is called typhoid fever. If caused by any other serotype, it is referred to as paratyphoid fever. The onset of symptoms is gradual. Nonspecific symptoms of fever, dull headache, malaise, anorexia, and myalgias are most common. Initially, fever tends to be remittent but gradually progresses over the first week to temperatures that are often sustained over 104В°F. Other frequently encountered symptoms include chills, nausea, vomiting, cough, weakness, and sore throat.
About 80% of patients have positive blood cultures. Bacteremia persists in about one-third of patients for several weeks if not treated. Diagnostic tests other than culture are unreliable.

Treatment

Most patients with enterocolitis require no therapeutic intervention. The most important part of therapy for Salmonella enterocolitis is fluid and electrolyte replacement. Antimotility drugs should be avoided since they increase the risk of mucosal invasion and complications.
Antibiotics have no effect on the duration of fever or diarrhea and their frequent use increases the likelihood of resistance and the duration of fecal shedding. Antibiotics should be used in neonates or infants younger than 6 months, patients with primary or secondary immunodeficiency, severely symptomatic patients with fever and bloody diarrhea, and patients after splenectomy.
Recommended antibiotics with adult doses include:
- Fluoroquinolones
- Trimethoprim/sulfamethoxazole
- Ampicillin
- Third-generation cephalosporins
For bacteremia, life-threatening treatment should include the combination of a third-generation cephalosporin (ceftriaxone 2 g intravenous daily) and ciprofloxacin 500 mg orally twice daily. The duration of antibiotic therapy is dictated by the site.
Fluoroquinolones such as ciprofloxacin (500 mg orally twice daily for 10 days in adults) are the drugs of choice for enteric fever, particularly in areas where multidrug resistance is common. A short course of 3 to 5 days is effective but a minimum of 10 days is recommended in severe cases.
The drug of choice for chronic carriers of Salmonella is norfloxacin, 400 mg orally twice daily for 28 days.
Vaccines are recommended for high-risk groups. Live oral attenuated vaccine Ty21a and parenteral polysaccharide vaccine have been shown to confer 42% to 77% efficacy for a duration of 3 to 5 years.

Campylobacteriosis

Campylobacter species are thought to be a major cause of diarrhea.
Transmission of infection occurs primarily by ingestion of contaminated food or water.
Incubation usually averages 2 to 4 days.
The most common symptoms include diarrhea of varying consistency and severity, abdominal pain, and fever. Nausea, vomiting, headache, myalgias, and malaise may also occur. Bowel movements may be numerous, bloody (dysentery-like), foul smelling, and melenic and range from loose to watery (dysentery-like).
The disease is self-limiting, and signs and symptoms usually resolve in about a week but may persist longer in 10% to 20% of patients.
As with other acute diarrheal illnesses, fluid and electrolyte support is a mainstay of therapy, mainly with oral rehydration therapy.
Antibiotics are not useful unless started within 4 days of the start of illness, as they do not shorten the duration or severity of diarrhea.
Antibiotics are warranted in patients who present with high fevers, severe bloody diarrhea, prolonged illness (greater than 1 week), pregnancy, and immunocompromised states, including HIV infection.
Erythromycin is considered the drug of choice for treatment. Clarithromycin or azithromycin are equally effective. Antimotility drugs are contraindicated.

Yersiniosis

Yersinia enterocolitica and Y. pseudotuberculosis are associated with intestinal infection. The organisms have been isolated from a variety of food sources, including raw goat and cow milk.
These bacteria cause a wide spectrum of clinical syndromes.
The majority of cases present with enterocolitis that is mild and self-limiting. Symptoms, generally lasting 1 to 3 weeks, include vomiting, abdominal pain, diarrhea, and fever.
A clinical syndrome seen in older children may resemble appendicitis.
Many patients develop a reactive arthritis 1 to 2 weeks after recovery from enteritis.
These diseases are generally self-limiting and are easily managed with oral rehydration solutions.
Antibiotics should be used in high-risk patients who develop bacteremia (i.e. infants younger than 3 months and patients with cirrhosis or iron overload) or in patients with bone and joint infections.
Y. enterocolitica is generally susceptible to fluoroquinolones, alone or in combination with third-generation cephalosporins or aminoglycosides. Alternative agents include chloramphenicol, tetracycline, and trimethoprim/sulfamethoxazole.