Gastrointestinal Infections

GASTROINTESTINAL INFECTIONS

The gut is vulnerable to infection by viruses, bacteria, parasites and occasionally fungi. Virus infections are the most prevalent but are not susceptible to chemotherapeutic intervention. Bacterial infections are more readily recognized and raise questions concerning the role of antibiotic management. Parasitic infections of the gut are beyond the scope of this article.

Bacteria cause disease of the gut as a result of either mucosal invasion or toxin production or a combination of the two mechanisms, as summarized in Table 14.4. Treatment is largely directed at replacing and maintaining an adequate intake of fluid and electrolytes. Antibiotics are generally not recommended for infective gastroenteritis, but deserve consideration where they have been demonstrated to abbreviate the acute disease or to prevent complications including prolonged gastrointestinal excretion of the pathogen where this poses a public health hazard.

It should be emphasized that most gut infections are self-limiting. However, attacks can be severe and may result in hospitalization. Antibiotics are used to treat severe Campylobacter and Shigella infections; erythromycin and ciprofloxacin, respectively, are the preferred agents. Such treatment abbreviates the disease and eliminates gut excretion in Shigella infection. However, in severe Campylobacter infection the data are currently equivocal, although the clinical impression favours the use of erythromycin for severe infections. The role of antibiotics for Campylobacter and Shigella infections should be contrasted with gastrointestinal salmonellosis, for which antibiotics are contraindicated as they do not abbreviate symptoms, are associated with more prolonged gut excretion and introduce the risk of adverse drug reactions. However, in severe salmonellosis, especially at extremes of age, systemic toxaemia and bloodstream infection can occur and under these circumstances treatment with either ciprofloxacin or trimethoprim is appropriate.

Typhoid and paratyphoid fevers (known as enteric fevers), although acquired by ingestion of salmonellae, Sal. enterica serovar Typhi and Sal. enterica serovar Paratyphi, respectively, are largely systemic infections and antibiotic therapy is mandatory; ciprofloxacin is now the drug of choice although trimethoprim or chloramphenicol are satisfactory alternatives. Prolonged gut excretion of Sal. enterica serovar Typhi is a well-known complication of typhoid fever and is a major public health hazard in developing countries. Treatment with ciprofloxacin or high-dose ampicillin can eliminate the gall bladder excretion which is the major site of persistent infection in carriers. However, the presence of gallstones reduces the chance of cure.

Cholera is a serious infection causing epidemics throughout Asia. Although a toxin-mediated disease, largely controlled with replacement of fluid and electrolyte losses, tetracycline has proved effective in eliminating the causative vibrio from the bowel, thereby abbreviating the course of the illness and reducing the total fluid and electrolyte losses.

Traveller’s diarrhoea may be caused by one of many gastrointestinal pathogens (Table 14.4). However, enterotoxigenic Escherichia coli is the most common pathogen. While it is generally short-lived, traveller’s diarrhoea can seriously mar a brief period abroad, be it for holiday or business purposes. Although not universally accepted, the use of short-course trimethoprim or quinolone such as ciprofloxacin can abbreviate an attack in patients with severe disease.