Long-term antibiotic therapy in tropical sprue

Tropical sprue in 2014: the new face of an old disease

Tropical sprue (TS), once known to be a common cause of malabsorption syndrome (MAS) in India and other tropical countries, is believed to be uncommon currently in spite of contrary evidence. Several recent studies from India showed TS to be the commonest cause of sporadic MAS in Indian adults. TS is diagnosed in patients presenting with suggestive clinical presentation, which cannot be explained by another cause of MAS and investigations revealing malabsorption of two unrelated substances, abnormal small-intestinal mucosal histology, which responds to treatment with antibiotics such as tetracycline and folic acid. There is substantial overlap between TS and postinfectious irritable bowel syndrome. There have been several advances in epidemiology, pathogenesis, and diagnosis of TS, hitherto an enigmatic condition.

Tropical sprue

Tropical sprue (TS) is a clinical entity of unknown etiology characterized by an acquired chronic diarrheal illness and malabsorption that affects indigenous inhabitants and expatriates, either long-term residents or short-term visitors, in the tropical countries. The exact pathogenetic sequence of TS remains incompletely characterized. Bacterial overgrowth, disturbed gut motility, and hormonal and histopathologic abnormalities contribute to the development of TS in a susceptible host. Treatment with tetracycline and folate is effective in some patients, although relapses after treatment are common. Research in the areas of microbial factors, pathogenesis, immunogenetics, and hormonal and immune regulation, using modern diagnostic techniques, may be able to settle some of the unanswered issues and open new venues for diagnosis, prevention, and treatment of tropical sprue.

Tropical Sprue

Tropical sprue is a disease that causes progressive villus atrophy in the small intestine, similar to nontropical (celiac) sprue. The loss of intestinal villi profoundly affects intestinal absorptive function, and patients with tropical or nontropical sprue present with malabsorption. Whereas the etiology of celiac sprue has been elucidated in considerable detail, the etiology of tropical sprue remains obscure. The favored hypothesis is that the disease is either initiated or sustained by a still-undefined infection. Patients with tropical sprue typically present with macrocytic anemia due to malabsorption of folate and/or vitamin B(12). Treatment of tropical sprue with folic acid replacement was introduced more than 50 years ago and has become standard medical treatment. Vitamin B(12) replacement is usually added if there is evidence of B(12) deficiency or malabsorption. Treatment of tropical sprue with folate and B(12) cures the macrocytic anemia and the accompanying glossitis, and often results in increased appetite and weight gain. However, even prolonged treatment with these vitamins fails to restore villus atrophy, and malabsorption usually persists. The benefit of antibiotic treatment of tropical sprue was first documented during World War II, when sulfonamides were used to treat epidemics of tropical sprue in British and Italian troops in India. Antibiotic treatment has since become the standard treatment, and tetracycline has replaced sulfonamides. The recommended length of treatment with tetracycline is 6 months and it is given in combination with folate. The treatment has been shown to normalize mucosal structure in the small intestine and resolve malabsorption in most patients with tropical sprue. However, there is a substantial relapse rate in treated patients who return to, or remain in, endemic areas in the tropics.

Tropical sprue is associated with contamination of small bowel with aerobic bacteria and reversible prolongation of orocecal transit time

BACKGROUND

In tropical sprue (TS), response to antibiotics may suggest a role for bacterial contamination of the small bowel, which is known in diseases with prolonged orocecal transit time (OCTT).

METHODS

We studied 13 patients with TS (diagnosed by standard criteria) for frequency, nature and degree of bacterial contamination of the small bowel by quantitative culture of jejunal aspirate, glucose hydrogen breath test (GHBT), and OCTT by lactulose hydrogen breath test before and after treatment. Twelve patients with constipation-predominant irritable bowel syndrome (IBS) and 12 healthy subjects served as controls.

RESULTS

Ten of 13 patients with TS had bacterial contamination compared with 3/12 with IBS (all aerobic, P < 0.05). Median colony count in TS (36 000 CFU/mL, 400 to > 100 000) was higher than IBS (700 CFU/mL, 100-1000, P < 0.05). Gram-negative aerobic bacilli were commonly isolated in TS but not in IBS. Median OCTT was longer in TS (180 m, 40 - 240) than IBS (110 m, 70 - 150, P = 0.008) and healthy subjects (65 m, 40 - 110, P = 0.0007, Wilcoxon rank sum test). Orocecal transit time in TS correlated with fecal fat (Spearman's rank correlation coefficient 0.69, P < 0.05). Orocecal transit time and fecal fat, repeated in 8/13 patients, decreased with treatment for TS (195 m, 130-240 vs 125 m, 90-200, P = 0.02; 8 g/24 h, 6.8-19.6 vs 7 g/24 h, 4.2-9, P = 0.04, respectively).

CONCLUSION

Aerobic bacterial contamination of the small bowel is common in patients with TS. Prolonged OCTT in TS correlated with fecal fat and normalized in a subset of patients after treatment.

A perspective on tropical sprue

A diagnosis of tropical sprue, an infrequent affliction of inhabitants and travelers in tropical regions, should be considered in patients with a compatible history, malabsorption, and chronic diarrhea. It can occur in either endemic or epidemic form and can be preceded by acute gastroenteritis. The cause of tropical sprue is still unknown, although most data support an infectious etiology. Therapeutic experience is greatest with folic acid and tetracycline. Most patients can be expected to recover with proper nutritional support, although relapses and slow responses occur.

Tropical sprue and subclinical enteropathy: a vision for the nineties

Aside from infectious intestinal diseases with known etiology, there is a group of gastrointestinal disorders mainly affecting the small intestine of individuals predominantly living in and less often visiting or returning from the Third World, usually the tropics, and ranging from asymptomatic structural and/or functional abnormalities of the gastrointestinal mucosa (subclinical enteropathy, SE) to a fully symptomatic condition highlighted by malabsorption of nutrients with associated nutritional deficiencies responsive to folate and broad spectrum antibiotic treatment (tropical sprue, TS). Mounting evidence supports an infectious cause in many instances. The exact nature of the infection, whether initiated and/or perpetuated by enterotoxigenic coliform bacteria, virus(es) or a combination of these, is not clear. Further studies, including those using molecular techniques, are needed in order to clarify various aspects of these widely prevalent disorders.

Enterotoxigenicity of colonising coliform bacteria in tropical sprue and blind-loop syndrome

The enterotoxigenicity of strains of Klebsiella pneumoniae, Enterobacter cloacae, and Escherichia coli, which represented the predominant coliform species isolated from the jejunum of 12 patients with tropical sprue and 5 with the blind-loop syndrome, was quantitatively assessed in terms of the ability of toxin preparations to induce water secretion as assayed by in-vivo perfusion in the rat jejunum. All 12 patients with sprue harboured 1 or more highly toxigenic strains--14 of the 16 strains isolated from this group produced heat-labile and/or heat-stable toxins which were as potent as toxins derived from strains isolated from persons with acute diarrhoea and documented as toxigenic. None of the 9 strains isolated from patients with the blind-loop syndrome produced potent toxins. This difference between the coliform bacteria in sprue and the blind-loop syndrome probably accounts, at least partly, for the different intestinal response in these two disorders to contamination by these organisms.

Treatment of overt and subclinical malabsorption in Haiti

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