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Gastrointestinal infections are often mild and self-limiting, and the patient does not seek medical help. Even where medical assistance is obtained, most infections can be managed in the community. However, gastrointestinal infections can kill. They are a particular problem in:
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They are therefore a serious threat to the hospital patient, and nosocomial outbreaks can cause high morbidity.
The gastrointestinal tract has a very high level of exposure to pathogens, and consequently a very wide range of microorganisms can cause diarrhoea and vomiting. Management consists primarily of supportive treatment, in particular, rehydration therapy. However, it is important to determine the causative organism, for two reasons. First, in some cases specific treatment is available, and second, in some cases inappropriate antibiotic therapy may worsen the prognosis.
Some of the causative organisms are zoonotic and contact with animals or their by-products, either directly or indirectly, may play an important role in infection.
A wide range of pathogens can cause diarrhoea and vomiting:
The causative organisms of diarrhoea and vomiting are principally identified by culture or microscopy of stool samples, but serology and blood culture may be useful, especially if septicaemia is involved or suspected.
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Diagnostic test |
Organism identified |
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Standard media: Escherichia coli, Salmonella, Shigella
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Light microscopy |
Entamoeba histolytica in stool plus wet film test for cysts and live organisms, Cryptosporidium parvum, Giardia lamblia |
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Electron microscopy |
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Serology |
Entamoeba histolytica, Escherichia coli O157:H7, enteroviruses, rotaviruses, Salmonella typhi, Salmonella paratyphi, Q fever |
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Other immunological tests |
Bacillus cereus test for toxin (but this test is done in very few laboratories), Staphylococcus aureus enterotoxin may be identified in stool samples during outbreaks of infection Yersinia agglutination Clostridium difficile toxin detection in stool |
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Salmonella typhi, Salmonella paratyphi in blood < 10 days after infection and in urine and bone marrow > 10 days after infection. PCR and cell culture are used for viral gastroenteritis |
Gastrointestinal disorders mainly kill by dehydration. Diarrhoea and vomiting, the two most common symptoms of gastrointestinal infection, can lead to extremely rapid fluid loss and hypovolaemic shock within only a few hours. The very young, the elderly and the debilitated can succumb even more rapidly.
Despite the fact that many infections damage the intestinal mucosa, oral rehydration is usually possible.
Intravenous rehydration is used if oral rehydration fails or cannot be used, eg. if the patient is in shock.
0.9% sodium chloride solution is useful for IV rehydration.
There is controversy about the use of agents such as loperamide. Occasionally codeine phosphate can be used to reduce symptoms, to avoid exhaustion. Antimotility agents are contraindicated in Escherichia coli O157 infection.
The use of antibiotics for gastrointestinal infections is not clear-cut. Many antibiotics have gastrointestinal side-effects and may paradoxically prolong symptoms. Equally, unnecessary antibiotic treatment may predispose the patient to Clostridium difficile nosocomial infection. Antibiotic use in diarrhoea and vomiting may also increase the risk of inducing resistant strains of the infectious agent.
Appropriate antibiotic therapy should be initiated for severe infections, typically involving:
Appropriate antibiotics are determined from stool and blood culture. Antibiotics
may also be useful to reduce the risk of transmission, eg. in Shigella.
It has been suggested that the use of antibiotics leading to cell lysis for infections caused by verocytotoxin-producing organisms may increase the risk of developing haemolytic uraemic syndrome (HUS), although this is controversial.
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Summary of useful antibiotics for diarrhoea and vomiting |
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For severe disease, erythromycin or ciprofloxacin orally |
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Ciprofloxacin when severe |
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Ciprofloxacin |
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Usually supportive |
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Antibiotics should be used with caution |
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When infection is severe, ciprofloxacin |
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Ciprofloxacin or tetracycline |
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Metronidazole or vancomycin |
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Tinidazole: alternatively metronidazole |
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Metronidazole, followed by diloxanide furoate |
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Paromomycin in severe disease |
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Ciprofloxacin or chloramphenicol |
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Supportive treatment only |
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In the hospital setting, gastroenteritis can be acquired:
Particular points to note on the ward:
Key steps to reduce infection:
bypass many defence mechanisms and special care is needed..Fresh water and foods, particularly foods associated with water, such as fish.
The incidence increased from 1981 to 1997 (from 96 notifications in England and Wales to 518 respectively), but fell to 1999 (284 notifications). Aeromonas hydrophila is the most common isolate.
Usually supportive.
The pathogen is spread by the faecal—oral route and from infected food.
The pathogen of amoebiasis is Entamoeba histolytica. In 1999, the last year for which figures are complete, there were 304 notifications. The incubation period may be years, with gradual onset of symptoms. Complications include:
with high fever, right upper quadrant pain, tenderness and sweats (may require
aspiration).Usually metronidazole for 5 days, followed by diloxanide furoate for a further 10 days to destroy any cysts.
Mainly food-borne, and is particularly associated with rice.
Bacillus cereus causes toxin-induced diarrhoea. The infection has a short incubation period of 1–5 hours, with vomiting followed a few hours later by diarrhoea.
Usually supportive.
Campylobacter is found in raw and undercooked meat and poultry, and can also be spread by domestic pets and by person-to-person contact.
Notifications of Campylobacter species increased significantly from 1986 to 1999.
Laboratory reports of Campylobacter in faecal isolates in England and Wales
Source: PHLS 2002
Incubation period is 2–5 days.
Treatment is primarily supportive, although for severe disease antibiotic treatment may be required. Bacteraemia may rarely occur.
Campylobacter jejuni grows best at 42°C; it thus grows poorly in blood culture and this may explain why it is not often detected as a cause of bacteraemia. More than one blood culture may be needed for detection.
Campylobacter jejuni is susceptible to a wide range of antimicrobial agents. Ciprofloxacin has activity against a broad-spectrum of bacteria causing diarrhoeal diseases, including Campylobacter, and is thus a suitable empirical choice for diarrhoea and vomiting, but if the infection is known to be caused by Campylobacter spp., erythromycin is a better choice for treatment. Early treatment is most effective.
Food-borne, particularly associated with meat, meat products and gravy.
The disease is caused by an exotoxin: incubation after ingestion of cooked meats is 12–18 h.
Supportive.
Transmitted from farm and domesticated animals, and via faeces. Contamination of drinking water has resulted in a number of outbreaks.
Although infection may occur at any age, it is most common in infants and young children. The disease is usually self-limiting, although diarrhoea may persist for some weeks. More recently these organisms have come to prominence as the cause of severe intractable diarrhoea in AIDS patients (infection is seen in 10–50% of those with AIDS).
The incubation period is 2–5 days. Very low numbers of oocysts are required for infection. The organism is chlorine-resistant and small enough to pass most water filters. AIDS patients excrete oocysts in large amounts, and may become a source of nosocomial infection if enteric precautions are inadequate. Person-to-person spread is also common in outbreaks.
Systemic infection does not occur, although localised spread to the biliary or respiratory tract has been seen. The infection can be very serious in the immunocompromised, even leading to death. Symptoms include watery diarrhoea, with abdominal pain, low-grade fever and vomiting. Weight loss also occurs.
Very few agents are effective against cryptosporidosis. Paromomycin has been used in the treatment of intractable symptoms and is available on a named patient basis in the UK. It is not absorbed from the gastrointestinal tract in significant amounts, and therefore is only useful for infections confined to the gut. In immunocompromised patients, it does not eradicate the parasite, but reduces parasite load.
Enterotoxigenic Escherichia coli (ETEC) is mainly water-borne.
It is one of the causes of travellers’ diarrhoea, which is watery and copious and results from an enterotoxin acting on the secretory mechanisms in the gut. The disease can last for up to two weeks.
Antibiotic treatment has been shown to reduce the duration of the illness. However, as the illness itself is often mild and self-limiting, this practice increases the risk of resistance developing and exposes the patient to potential side-effects, such as phototoxicity from quinolones. The advantages of treatment should be balanced against the risk of resistance developing and the severity of the disease. The agent used is usually:
Prophylaxis is not recommended.
Food.
Enteroinvasive Escherichia coli produce bloody diarrhoea and are spread by poor hygiene. The organism invades enterocytes, leading to inflammatory diarrhoea: spread to the bloodstream can occur. These pathogens lead to sporadic outbreaks in babies and young children.
Usually supportive.
Verotoxin-producing Escherichia coli (VTEC) are found in the intestines of cattle, and thus the commonest sources of infection are consumption of contaminated foodstuffs and direct or indirect contact with animals (usually bovines) or their by-products. Undercooked beef (in particular, mince) or milk have been implicated, but other products have also become contaminated (apple juice, water, cheese etc.). There is a significant risk of person-to-person spread within households and institutions.
The best-known strain of VTEC is Escherichia coli O157:H7. The number of isolations has increased since the early 1990s to 1084 in 1999. The incidence of Escherichia coli O157 infection is higher in Scotland (where data are collected separately) than in the rest of the UK. The infectious dose is low, and the duration of incubation is generally 2–4 days, but can be as long as 14 days.
Escherichia coli O157 infection is often mild, but it can lead to severe complications including:
Treatment is mainly supportive, but about one-third of patients require hospital admission.
.Water, salads.
Numbers of Giardia infections have declined slightly recently. The disease has a long incubation period of 5–25 days. Transmission is from person-to-person and there is little food-borne transmission, although water is a possible source of infection.
Antibiotics are useful in the treatment of Giardia, in addition to supportive treatment. Metronidazole penetrates tissues well and is bactericidal. A single dose of tinidazole is as effective as longer courses in terms of reducing parasite load, and has a higher clinical cure rate.
single dose.Transmission is mainly food-borne, and frequently from poultry products, including eggs.
Salmonellosis is a common disease, which increased in incidence until the mid-1990s.
Salmonella reports in England and Wales
Source: PHLS 2002
Salmonella has a short incubation period of 12 to 72 hours. Person-to-person spread can occur. The symptoms are diarrhoea and vomiting, abdominal pain and fever, with possible complications of septicaemia and local infections. Salmonella enteritidis accounted for about 57% of all Salmonella infections in 2000 (Salmonella enteritidis phage type 4 accounted for 57% of these). The proportion of Salmonella enteritidis infections rose throughout the 1980s and 1990s, but has started to fall over the last few years, since 1997. This may result from improvements in food hygiene and vaccination of poultry flocks.
Antibiotic treatment in uncomplicated disease may prolong symptoms.
Multi-drug resistant Salmonella typhimurium DT 104 has emerged as a major cause of salmonellosis in the UK; for this reason also, antibiotics are best avoided in uncomplicated disease.
Bacteraemia is seen in less than <5% of cases but should be suspected if systemic signs occur in the weeks after an episode of diarrhoea: there may be a metastatic focus of infection. Achlorhydria, immunosuppression and inflammatory bowel disease increase the risk of systemic disease.
In the case of bacteraemia or if the patient is immunocompromised, treatment is advisable:
Spread is faecal–oral and there is no animal reservoir.
Salmonella typhi and Salmonella paratyphi cause enteric fever. The organisms penetrate the gut mucosa via Peyer’s patches and multiply within intestinal lymph nodes. They are eventually passed into the blood via the lymphatic system, and thus lead to multisystem disease via invasion of first the reticuloendothelial system and later, through further bacteraemia, invasion of other organs.
(Adapted from: Wain, J., Diep, T. S., Ho, A. V., Walsh, A. M., Hoa, N. T. T., Parry, C. M., et al. (1998). Quantitation of bacteria in blood of typhoid fever patients and relationship between counts and clinical features, transmissibility, and antibiotic resistance. Journal of Clinical Microbiology 36, 1683–7)
Presentation is with malaise, headache, fever, cough, constipation or diarrhoea. CNS signs can occur in serious disease. There is usually a history of recent foreign travel and suspicion should be higher in patients from endemic areas. The incubation period is up to 21 days.
Blood culture is useful for diagnosis in the first 10 days of illness; faeces, urine and bone marrow can also be cultured in the second 10 days of illness. Diagnosis and differentiation of the two species depend on culture. An agglutinin test can be used, but results may be affected by previous vaccination: acute vs. convalescent phase titres are the most useful serological test. Mortality is high if untreated.
Antibiotic treatment is useful, but although many agents are effective in vitro, the range of agents useful in vivo is much more limited. Effective agents are:
Treatment should last for 14 days.
Faeces.
Shigella infections have fallen dramatically from a peak in 1992: most of the peak was due to Shigella sonnei, and even though the incidence of this pathogen has declined relative to other Shigella species, it still provided 68% of all isolates in 1998. However, Shigella sonnei infection is generally milder than infections due to other species of Shigella, which are usually acquired outside the UK. Spread is mainly faecal–oral, with only occasional spread from food and water. The disease is highly contagious. The incubation period is 1–7 days.
Shigella dysenteriae infection is generally acquired overseas and can lead to severe disease with toxic megacolon and haemolytic uraemic syndrome.
Antibiotic treatment is only required in high-risk patients (those with severe
disease, the already ill, the immunosuppressed or the elderly) or in those with
dysentery.
Furthermore, only ciprofloxacin and trimethoprim are advised because of the
increasing problem of resistance. Treatment shortens the clinical illness.
Treatment is with:
Contaminated food.
Diarrhoea and vomiting caused by Staphylococcus aureus has an incubation period of 1–6 hours. The disease is mediated by an exotoxin and the infection is usually self-limiting. Infection is normally from the hands or nasal passages of carriers who have handled food, particularly foods stored at room temperature and then eaten cold.
Usually supportive.
Contaminated food and water.
Yersinia incidence peaked at the start of the 1990s, but has since fallen. Most cases result from Yersinia enterocolitica.
Yersinia is spread from animals via contaminated food and water, especially
pork. Refrigeration does not stop multiplication. Diagnosis is by culture or
serology.
Some strains of Yersinia infection can also lead to reactive arthritis via an inflammatory process, possibly mediated by the presence of antigens on the surface of phagocytes. Early treatment of Yersinia enterocolitica infection, within three days of development of arthritis, can prevent the further development of and cure arthritis. Patients with HLA-B27 histocompatability complexes are at high risk of developing reactive arthritis, and should be treated for a primary infection. Yersinia are facultative intracellular organisms; therefore, antibiotics able to penetrate into cells are required.
Treatment is usually reserved for severe disease. Suitable antibiotics include:
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