Infectious colitis results in an inflammation of the colon due to various bacterial, viral, and parasitic infectious pathogens. The principal symptom is diarrhea together with other gastrointestinal and constitutional symptoms. The diagnosis is made based on clinical and microbiological findings, and treatment principles depend on the severity of the disease, including symptomatic therapy, rehydration, and pathogen-specific antimicrobial therapy.
The clinical presentation of patients with infectious colitis is uniformly characterized by the sudden onset of diarrhea, regardless of the cause . The incubation period between ingestion and development of infection is usually around several days, but it may be longer, up to a few week. Because of extensive tissue destruction and pus formation in the colon, diarrhea can contain mucus, pus, or blood (dysentery), which signalizes a more severe infection. In addition to diarrhea, GI symptoms such as abdominal pain and cramping, rectal pain, tenesmus, bloating, and nausea in some cases. Fever can be present as well, while constitutional symptoms, such as malaise, fatigue, weakness, and weight loss, appear depending on the severity of the infection. For infections that last for more than several days with persistent diarrhea, severe dehydration may occur, which can lead patients into hypotension and shock.
The diagnostic workup of patients in whom infectious colitis is suspected comprises laboratory tests and microbiological investigations. However, one of the most important aspects of workup is patient history, which may reveal important data that may provide significant information to the physician. Recent travel to Africa and Southeast Asia or eating contaminated food may suggest possible E. coli or Salmonella infection, while intake of water from suspicious sources may suggest amoebic colitis. Recent antibiotic use and hospitalization may suggest Clostridium difficile as the causative pathogen. Data regarding similar illness of friends or coworkers may suggest an outbreak, and these elements can be really useful if obtained properly.
Initial workup should involve a full blood count (CBC), to evaluate hemoglobin and erythrocyte levels for possible anemia, and leukocytes to see the immune response (in patients with severe immunodeficiency without leukocytosis, but leukopenia, CMV colitis is a possible diagnosis). Serum electrolytes, including Na+, K+, and Cl- should be measured to assess hydration, along with serum albumin, creatinine, and blood urea nitrogen (BUN). Inflammatory parameters, including sedimentation rate, CRP and fibrinogen should be tested as well.
In all patients, the key step in microbiological investigations is obtaining stool cultures, which is the method of choice for identifying the causative agent . Bacterial as well as parasitic pathogens can be detected in stool, while antigen testing may be performed in the case of Entamoeba histolytica and Clostridium difficile. In pseudomembranous colitis, Clostridium difficile toxins can be detected in stool by rapid testing, and the presumptive diagnosis can be confirmed within a day or two. CMV colitis is diagnosed using serological testing as well, while quantitative PCR techniques may be used to assess the severity of the infection. The presence of fecal leukocytes can also be investigated .
Other markers, such as calprotectin and lactoferrin, are proposed as markers of inflammatory processes in the bowels, but their sensitivity and specificity in infectious colitis is still controversial  .
Treatment of infectious colitis should be directed at the specific cause and provided along with supportive therapy.
Depending on the severity of illness, patients with infectious colitis may develop slight or severe dehydration, in which case rehydration therapy is necessary to prevent events such as electrolyte imbalance, hypotension, and hypovolemic shock. IV fluids and supplementation of deficient electrolytes should compensate fluid loss through diarrhea.
Since diarrhea is accompanied by accelerated gut motility, antimotility agents have been proposed in therapy, but more evidence is necessary to obtain clear data regarding the use of these agents . Moreover, they are contraindicated in the presence of bloody stools, or suspicion of hemolytic uremic syndrome (HUS), which is why their use is still reserved in clinical practice . However, in the setting of mild diarrhea, loperamide 4mg PO, with a 2mg rising dose after diarrhea, up to 16mg q24h can be used.
Targeted antimicrobial therapy is the key to resolving the infection, but until the causative agent is confirmed, empiric therapy should be initiated in patients with severe diarrhea (>6 unformed stools q24h, high fever, tenesmus, blood, or confirmation of fecal leukocytes). Fluoroquinolones, including ciprofloxacin 500mg PO q12h or levofloxacin 500mg PO q24h for 3-5 days may be given as first-line empiric therapy. Alternatives include double-strength trimethoprim-sulfamethoxazole PO q12h for 3-5 days. In patients who were recently hospitalized, or report prior antibiotic consumption, either metronidazole 500mg PO q8h for 10-14 days or vancomycin 125mg should be included because of possible Clostridium difficile infection.
Once the microbiological testing confirms the pathogen, directed therapy can be initiated. Therapy of microorganisms responsible for infectious colitis include :
Despite the fact that guidelines for treatment of infectious colitis have been made, it is imperative to obtain antimicrobial susceptibility testing in the case of bacterial colitis, because local resistance rates may significantly vary from country to country.
The prognosis of infectious colitis depends on several factors. The disease may range from either asymptomatic colonization and a few episodes of watery diarrhea to profound fluid and blood loss from severe infections that may be life-threatening. Diarrheal diseases are still one of the leading causes of mortality in children worldwide, which is why the diagnosis of infectious colitis in both children and adults must be made promptly
It is important to distinguish pathogens that cause colitis from those that cause infection of the upper GI tract (gastroenteritis), such as Staphylococcus aureus, Bacillus cereus, and other bacterial species.
Apart from bacterial pathogens, other causes include:
Prevalence rates, mode of acquisition, as well as risk factors, vary depending on the causative agent. Key principles in the development of infectious colitis in terms of epidemiology are:
Prevalence rates of colitis are related to the underlying cause and significantly vary in various regions. Some data regarding the distribution and prevalence rates in the United States and worldwide include :
The pathogenesis of infectious colitis includes inflammatory changes in the colon, virulence factors of the causative agent, and tissue damage. Pathophysiology depends on the causative agent:
Prevention of infectious colitis comprises some general principles:
It is important to have these principles in mind, especially when traveling in developing and underdeveloped communities, since much higher rates of infection are observed in those areas.
Infectious colitis comprises a broad range of infections that result in inflammatory changes in the colon. Numerous pathogens may cause infection in the distal gastrointestinal tract, most commonly bacteria (Escherichia coli, Shigella, Salmonella, Campylobacter, Clostridium difficile, etc.) , but also viruses (Cytomegalovirus), parasitic (Entamoeba histolytica, Schistosoma mansoni), and fungi. In the majority of cases, pathogens are acquired through contaminated food and water, and person-to-person transmission is achieved through the feco-oral route. Cytomegalovirus (CMV) colitis and infection caused by fungi are seen in patients with severe immunosuppression, such as those with HIV infection and AIDS. Parasitic infection of the colon are more commonly observed in underdeveloped countries and are associated with poor hygiene and sanitation. Once the pathogens are inoculated into the gastrointestinal tract, they establish infection and cause a range of inflammatory changes in the colon, which impairs the permeability function of the colon, resulting in diarrhea. The prognosis varies significantly and depends on the cause, as well as the severity of the infection. Infectious colitis may range from mild watery diarrhea that can spontaneously resolve, to life-threatening infection that can progress to severe fluid loss and development of sepsis.
Depending on the features and virulence factors of the causative agent, different forms of colitis may be observed, and thus different symptoms may be encountered. In virtually all patients, however, diarrhea is the principal symptom and may be purulent and/or bloody (known as dysentery). Other symptoms include abdominal cramping, tenesmus, fever, and bloating. Constitutional symptoms, such as malaise, fatigue, and generalized weakness are almost always observed, while weight loss and anorexia are seen in severe cases.
The diagnosis of infectious colitis is aimed at identifying the causative agent, and microbiological investigation is the key. Clinical presentation may also be helpful in determining optimal therapy. Since the majority of cases are caused by bacterial species, stool cultures and the presence of fecal leukocytes should be performed. In patients with severe immunosuppression, serology or PCR for CMV, and investigation of fungal causes through serology testing should be performed from stool samples, while parasitic testing should be conducted in patients who report recent travel. Patient history, including recent food ingestion and travel, may provide vital clues that can help in determining the diagnosis.
Treatment principles of infectious colitis include symptomatic therapy, such as rehydration with either oral or IV fluids and electrolytes and pathogen-specific antimicrobial therapy. Because of growing issues of antimicrobial resistance, pathogen-specific therapy is necessary to treat infectious colitis successfully. Metronidazole, ciprofloxacin, doxycycline, azithromycin, and other drugs are used in the treatment of bacterial colitis, while ganciclovir is used for CMV colitis. Antiparasitic agents, such as praziquantel, paromomycin, or iodoquinol, are used in treating amoebic colitis.
Infectious colitis refers to inflammation and damage of the terminal segments of the gastrointestinal tract - the final parts of the small intestine and the colon, as a result of infection. Numerous bacterial, viral, parasitic, and fungal pathogens may be responsible for the development of infectious colitis. This infection is acquired by the feco-oral route, which means that it is either acquired from contaminated food that is not properly cooked or processed, but also from water contaminated with bacteria or parasitic cysts. Person-to-person transmission occurs due to poor hygiene. Infectious colitis is present throughout the world, and persons of all ages and ethnicity may be affected. The principal symptom of all patients is diarrhea, which may be mild and watery, or more frequent and contains pus and blood, in which case it is called dysentery. Other symptoms, such as abdominal pain, bloating, fever, malaise, weakness and fatigue are commonly encountered, and the diagnosis is obtained by examining the stool for the presence of microorganisms. Treatment is directed at the organism that is identified, but patients often need supportive therapy because of fluid loss through diarrhea, and they receive either oral or intravenous rehydration therapy. Antibiotics, such as ciprofloxacin, azithromycin, and many other, are given against bacteria, while other drugs are used in treating viral (such as ganciclovir) and parasitic (iodoquinol, metronidazole) infection. Prevention measures may significantly reduce the number of infected patients by improving daily hygiene measures, especially during travel, consuming meat which has been cooked properly and washing fruits and vegetables.