Small intestinal mucosal immunity and morphometry in luminal overgrowth of indigenous gut flora

OBJECTIVE

The aim of this study was to investigate the separate effects of indigenous oropharyngeal- and colonic-type flora on small intestinal mucosal immunity and morphometry in small intestinal bacterial overgrowth (SIBO).

METHODS

A duodenal aspirate and random biopsies of underlying mucosa were obtained from 52 adult subjects (age range, 18-90 yr; median, 60 yr) without disorders that may otherwise disturb small intestinal histology or mucosal immunity. Villus height, crypt depth, villus/crypt ratios, counts of intraepithelial lymphocytes (IELs) and lamina propria total mononuclear cells, IgA, IgM, and IgG plasma cells, mast cells, and B and T lymphocytes were determined in relation to the presence or absence of SIBO and the nature of the overgrowth flora in all subjects. CD4+ve and CD8+ve T-cell counts were determined in 24 subjects.

RESULTS

SIBO was present in 26 of 52 (50%) subjects. Overgrowth flora included colonic-type bacteria in 20 subjects and oropharyngeal-type flora alone in 6 subjects. Lamina propria IgA plasma cell counts were significantly increased in subjects with SIBO, irrespective of whether the overgrowth flora comprised oropharyngeal-type flora alone or included colonic-type bacteria. Neither villus height, crypt depth, villus/crypt ratios, nor total or other mononuclear cell counts in lamina propria differed significantly between subjects with and without SIBO, irrespective of the nature of the overgrowth flora. IEL counts were significantly higher than in culture-negative subjects only when the overgrowth flora included colonic-type bacteria. Even then, IEL counts were within a range currently considered normal. A significant, inverse correlation between advancing age and IEL counts became apparent after adjusting for the effect of SIBO of colonic-type flora.

CONCLUSIONS

SIBO of oropharyngeal- and colonic-type flora are associated with differing disturbances of local duodenal mucosa. Nonetheless, these would not be readily apparent during routine histological assessment. Old age independently influences duodenal IEL counts.

Evaluation of the rice breath hydrogen test for small intestinal bacterial overgrowth

OBJECTIVES

The aims of this study were 1) to document the sensitivity, specificity, and predictive values of the rice breath hydrogen test for small intestinal bacterial overgrowth; 2) to determine the possible influence of concurrent gastric bacterial overgrowth and gastroduodenal pH on the efficacy of this test; and 3) to investigate whether reliability is limited by an inability of small intestinal luminal flora to ferment rice or its product of hydrolysis, maltose.

METHODS

Twenty adult subjects were investigated with microbiological culture of proximal small intestinal aspirate and a 3-g/kg rice breath hydrogen test. Gastroduodenal pH, the presence or absence of gastric bacterial overgrowth, and the in vitro capability of small intestinal luminal flora to ferment rice and maltose, its product of hydrolysis, were determined.

RESULTS

Sensitivity of the rice breath hydrogen test for small intestinal bacterial overgrowth was 33% and remained low even when subjects with small intestinal overgrowth with oropharyngeal-type (38%) and colonic-type flora (20%) and those with concurrent small intestinal and gastric bacterial overgrowth (40%) were considered separately. Sensitivity remained suboptimal despite favorable gastroduodenal luminal pH and documented ability of bacterial isolates to ferment rice and maltose in vitro. Specificity of the rice breath hydrogen test for small intestinal bacterial overgrowth was 91%. Positive predictive value, negative predictive value, and predictive accuracy were 75%, 63%, and 65%, respectively.

CONCLUSIONS

Clinical value of the rice breath hydrogen test for detecting small intestinal bacterial overgrowth is limited. The rice breath hydrogen test is not a suitable alternative to small intestinal intubation and culture of secretions for the detection of small intestinal bacterial overgrowth.

Serum immunoglobulin and soluble IL-2 receptor levels in small intestinal overgrowth with indigenous gut flora

Murine studies have demonstrated that the presence of indigenous gut flora is crucial for the induction of systemic immune hyporesponsiveness to antigens initially encountered within the gastrointestinal lumen. This study investigated whether increased titers of such flora, as occur in human small intestinal bacterial overgrowth, may be associated with increased suppression of systemic immune responsiveness and the possible relation between systemic and mucosal immunity in this setting. Serum total immunoglobulin (Ig), immunoglobulin subclass, and soluble interleukin-2 receptor levels and lamina propria IgA plasma cell counts were determined in 50 consecutive subjects with (N = 30) and without (N = 20) small intestinal bacterial overgrowth. Luminal IgA levels were measured in 35 of these subjects. Serum concentrations of IgG3, but not of other immunoglobulin isotypes or soluble interleukin-2 receptors, were significantly reduced in subjects with bacterial overgrowth (P < 0.0005). Small intestinal lamina propria IgA plasma cell counts (P < 0.0005) and luminal IgA concentrations (P = 0.001) were significantly increased in this group. Serum IgG3 levels were significantly inversely correlated with luminal IgA levels (P < 0.01) and fell below the lower limit of normal (0.41 g/liter) in 17/30 (56.7%) subjects with bacterial overgrowth compared to 1/20 (5.0%) subjects without (P < 0.0005). These findings document an association between small intestinal bacterial overgrowth with indigenous gut flora and reduced serum IgG3 reactivity in humans, possibly via an interaction with mucosa-related immunoregulatory mechanisms. The possibility of underlying small intestinal bacterial overgrowth should be considered in patients with serum IgG3 deficiency, especially those with compatible symptoms and/or known predisposition.

Interleukin-6 and small intestinal luminal immunoglobulins

Our aim was to determine the relationships between interleukin-6 and immunoglobulin levels within small intestinal luminal secretions. Twenty adult subjects with small intestinal bacterial overgrowth (N = 13), irritable bowel syndrome (N = 4), and nonulcer dyspepsia (N = 3) underwent endoscopic aspiration of secretions from the small intestinal mucosal surface for assessment of IL-6, IgA1, IgA2, IgM, IgG1, IgG2, IgG3, and IgG4 concentrations. Serum immunoglobulin concentrations and small intestinal histology were also determined. IgA2 and IgG3 were the predominant IgA and IgG subclasses in luminal secretions in 19/20 (95%) and 20/20 (100%) subjects, respectively. IgA1 and IgG1 predominated in serum in all subjects. No subject had villous atrophy. Luminal IL-6 concentrations correlated significantly with luminal IgA2, IgM, and IgG3 concentrations but not with IgA1 or any other IgG subclass levels. Conversely, luminal IL-6 or immunoglobulin concentrations did not correlate significantly with levels of any immunoglobulin isotype in serum. These observations suggest that important relationships exist between local IL-6 and IgA2, IgM, and IgG3 responses in human small intestinal luminal secretions. Local investigation is mandatory when assessing intestinal immune activity.

Luminal antigliadin antibodies in small intestinal bacterial overgrowth

OBJECTIVE

Elevated antigliadin antibody levels in small intestinal luminal secretions of subjects with normal or only mildly abnormal small intestinal histology are considered indicative of "latent" or "potential" celiac disease. The purpose of this study was to determine whether small intestinal bacterial overgrowth (SIBO) might provide an alternative explanation for positive luminal antigliadin antibodies in such subjects.

METHODS

Twenty-six adult subjects without predisposition to disturbed mucosal immunity were investigated with culture of small intestinal luminal secretions. Luminal total IgA and IgA-antigliadin antibody concentrations were measured by radial immunodiffusion and indirect enzyme immunoassay, respectively. Local mucosal counts of IgA-plasma cells were determined by immunohistochemistry. Small intestinal histology and intraepithelial lymphocyte counts were assessed by light microscopy. Corresponding serum antigliadin antibody concentrations were determined.

RESULTS

SIBO was present in 17/26 (65.4%) subjects. No subject with SIBO had villous atrophy. Luminal total IgA concentrations (p < 0.0005), mucosal IgA-plasma cell counts (p < 0.01), and intraepithelial lymphocyte counts (p < 0.01) were significantly increased in subjects with SIBO. Luminal IgA-antigliadin antibodies were detected in 6/17 (35.3%) subjects with SIBO and 0/9 (0%) subjects without SIBO. Luminal IgA-antigliadin antibody concentrations correlated significantly with luminal total IgA levels (p < 0.01) but not with serum values (p < 0.1). Serum IgG-antigliadin antibody concentrations were elevated in 2/6 (33.3%) subjects with SIBO and positive luminal antigliadin antibodies.

CONCLUSIONS

SIBO may be an alternative explanation to "latent" or "potential" celiac disease for positive luminal antigliadin antibodies in subjects with either normal or only mildly abnormal small intestinal histology, even when serum antigliadin antibody concentrations are elevated. Positive luminal antigliadin antibodies in SIBO probably occur as epiphenomena in the context of a graded mucosal immune response to local bacterial antigens.

Luminal bacteria and small-intestinal permeability

BACKGROUND

The influence of luminal bacteria on small-intestinal permeability has not been fully assessed. This study addressed this issue.

METHODS

Thirty-four subjects (mean age 64 years; range 22-95 years) were investigated for possible small-intestinal bacterial overgrowth (SIBO) with culture of a small-intestinal aspirate. A lactulose/mannitol small-intestinal permeability test was performed, small-intestinal histology assessed and serum vitamin B12 concentrations measured in all subjects. Permeability was also assessed in a control group of 34 asymptomatic volunteers.

RESULTS

Urinary lactulose/mannitol ratios were significantly increased in subjects with SIBO with colonic-type flora (P < 0.0005), even in the absence of villous atrophy. Urinary lactulose/mannitol ratios were increased in this group due to significantly increased urinary lactulose concentrations (P < 0.0005) rather than reduced urinary mannitol levels, after correcting for inter-subject variations in renal function. Counts of intraepithelial lymphocytes of CD8 phenotype were significantly increased in this group (P = 0.003). Although a significant correlation was found between intraepithelial lymphocyte counts and small-intestinal permeability overall (P < 0.002), these counts were not significantly different in subjects with SIBO with colonic-type flora whose permeability values were < or = > 0.028, the upper limit of normal in asymptomatic controls. Serum vitamin B12 concentrations did not differ significantly between groups (P > 0.5). Ageing did not independently influence small-intestinal permeability (P > 0.5).

CONCLUSIONS

Small-intestinal permeability is increased in subjects with SIBO with colonic-type bacteria. This effect is independent of ageing and not mediated by vitamin B12 deficiency. Although counts of intraepithelial lymphocytes of CD8 phenotype are increased in this disorder, it is also unlikely that these cells play an important causative role in this process. Routine light microscopic assessment underestimates the prevalence of small-intestinal functional disturbance in this disorder.

Local and systemic complement activity in small intestinal bacterial overgrowth

It is unknown whether bacteriolysis due to luminal complement activation contributes to local defense mechanisms against small intestinal bacterial overgrowth, particularly with gram-negative bacteria. This study addressed this issue. Thirty adult subjects were investigated with culture of luminal secretions adherent to proximal small intestinal mucosa. Luminal and plasma concentrations of C3 and C3d and C3d/C3 ratios were determined. Activated terminal complement complex was sought in surface epithelium to which aspirated secretions had been adherent. Small intestinal bacterial overgrowth with gram-negative bacteria was present in 12/30 (40.0%) subjects. C3, C3d, and C3d/C3 profile indicated that increased local but not systemic C3 activation occurs in this group. Conversely, no activation of terminal complement complex was evident in this circumstance. Thus, complement-mediated bacteriolysis is unlike to contribute to local defense mechanisms against small intestinal bacterial overgrowth, even when overgrowth flora includes gram-negative bacteria. Factors preventing full local activation of the complement cascade in this circumstance require investigation.

Small intestinal bacterial overgrowth in the symptomatic elderly

OBJECTIVE

1) To determine the prevalence of small intestinal overgrowth with colonic-type bacteria in symptomatic elderly subjects, particularly those without important "clues" such as clinically apparent predisposition or vitamin B12 deficiency, and 2) to investigate defense mechanisms such as gastric acidity, small intestinal motility, and luminal IgA in this setting.

METHODS

Fifty-two symptomatic subjects without vitamin B12 deficiency or clinically apparent predisposition to bacterial overgrowth or disturbed mucosal immunity, including 22 subjects > or = 75 yr old, underwent culture of small intestinal luminal secretions. Indicator paper was used to measure fasting gastric pH. The presence of bacteria of confirmed nonsalivary origin in small intestinal secretions served as an index of small intestinal dysmotility. Small intestinal luminal IgA concentrations were measured by radial immunodiffusion.

RESULTS

Small intestinal overgrowth with colonic-type flora was not present in any subject investigated for dyspepsia, irrespective of age. In subjects with chronic diarrhea, anorexia, or nausea, overgrowth with colonic-type flora (Enterobacteriaceae) was present in 0/12 (0%), 1/10 (10.0%), and 9/14 (64.3%) subjects aged < 50 yr, 50-74 yr, and > or = 75 yr, respectively. Enterobacteriaceae were not concurrently recovered from saliva of any subject > or = 75 yr old with small intestinal overgrowth with these bacteria. Fasting hypochlorhydria was present in only 1/9 (11.1%) such subjects. Luminal IgA concentrations were significantly greater in subjects > or = 75 yr old with bacterial overgrowth than in culture-negative subjects (p < or = 0.003).

CONCLUSIONS

Small intestinal overgrowth with colonic-type bacterial should be considered in subjects > or = 75 yr old with chronic diarrhea, anorexia, or nausea, even in the absence of clues such as clinically apparent predisposition or vitamin B12 deficiency. Small intestinal dysmotility, rather than fasting hypochlorhydria or mucosal immunosenescence, probably is responsible for the prevalence of bacterial overgrowth in this group.

The expression of complement protein 4 and IgG3 in luminal secretions

BACKGROUND

Factors regulating proximal small-intestinal luminal concentrations of IgG3, the predominant IgG subclass at this site, are unclear. This study determined whether luminal IgG3 concentrations are related to those of complement protein 4 (C4), an acute-phase reactant predominantly derived from local mucosa.

METHODS

Proximal small-intestinal luminal and peripheral blood IgG subclass and C4 concentrations were measured by radial immunodiffusion in 30 adult subjects without predisposition to disturbed mucosal immunity. Mucosal C4 immunoreactivity and the presence or absence of small-intestinal bacterial overgrowth were determined in all subjects. Caecal luminal concentrations of IgG3 and C4 were measured in a separate cohort of eight asymptomatic subjects.

RESULTS

Proximal small-intestinal luminal C4 and IgG subclass concentrations were not significantly influenced by the presence of absence of small-intestinal bacterial overgrowth (P > 0.2). Nor did plasma C4 levels significantly influence C4 concentrations in small-intestinal luminal secretions (P > 0.2). Mucosal immunoreactivity for C4 was present in every subject. A significant correlation was found between C4 and IgG3 concentrations in proximal small-intestinal luminal secretions (P < 0.0005) and also in caecal secretions (P < 0.05) but not in peripheral blood (P > 0.1).

CONCLUSIONS

Common factors, not including the presence or absence of small-intestinal bacterial overgrowth, regulate luminal concentrations of C4 and IgG3. Local investigation is mandatory when assessing mucosal immune mechanisms.

Bacteriological method for detecting small intestinal hypomotility

OBJECTIVE

Small intestinal hypomotility is an important cause of small intestinal bacterial overgrowth, yet assessment of small intestinal motility in this setting is problematic. This study was performed to investigate the validity of a bacteriological method for detecting small intestinal hypomotility.

METHODS

Twenty-five subjects without previous gastric surgery were studied with (i) concurrent bacteriological analyses of fasting saliva and gastric and proximal small intestinal aspirates, (ii) measurement of gastric pH, and (iii) scintigraphic assessment of small intestinal transit rates of a liquid test meal. The reproducibility of bacteriological analyses of saliva and small intestinal secretions was determined in 12 subjects.

RESULTS

Serial bacteriological analyses of saliva and proximal small intestinal secretions yielded reproducible results over time periods of up to 1 month. Eleven subjects were deemed to harbor Enterobacteriaceae of nonsalivary origin in proximal small intestinal secretions. Orocaecal transit, but not gastric emptying, of a liquid test meal was significantly delayed in this group (p = 0.002 and p = 0.84, respectively), suggesting the presence of small intestinal hypomotility. Impaired gastric acidity unlikely confounded assessment of the origin of small intestinal Enterobacteriaceae in any instance.

CONCLUSIONS

The presence of Enterobacteriaceae of nonsalivary origin in proximal small intestinal secretions may be taken to reflect the presence of small intestinal hypomotility. The presence of impaired gastric acidity does not confound this approach. Because small intestinal intubation and culture of aspirate are required anyway to accurately diagnose small intestinal bacterial overgrowth, the simple addition of concurrent bacteriological analysis of saliva may allow small intestinal hypomotility to be detected at the same time as the presence or absence of small intestinal bacterial overgrowth itself is established, thus streamlining the investigation of subjects for this disorder and its possible causes.

Luminal immunity in small-intestinal bacterial overgrowth and old age

BACKGROUND

The independent influences of small-intestinal bacterial overgrowth and old age on mucosal immunoglobulin production and secretion have not been assessed. This is an important issue, since luminal IgA deficiency may exacerbate small-intestinal bacterial overgrowth, the prevalence of which is high in selected elderly populations.

METHODS

Proximal small-intestinal aspirates were obtained from 33 subjects for bacteriologic analysis and measurement of total IgA, IgM, total IgG. IgG subclass, and IgD concentrations. IgA subclasses were measured in 24 unselected subjects. Serum immunoglobulin and salivary IgA concentrations were measured in all subjects.

RESULTS

IgA2 and IgG3 were predominant IgA and IgG subclasses in proximal small-intestinal luminal secretions. Luminal concentrations of IgA2 and IgM, but not IgG3 or any other IgG subclass, were significantly increased in small-intestinal bacterial overgrowth, which was present in 19 of 33 (57.6%) subjects. Old age did not influence these levels. Luminal immunoglobulin concentrations did not correlate significantly with either serum or salivary values. IgD was not measureable in proximal small-intestinal secretions.

CONCLUSIONS

Increased luminal concentrations of the secretory immunoglobulins, IgA2 and IgM, occur in small-intestinal bacterial overgrowth. Local investigation is mandatory when assessing the mucosal immunopathology of this disorder. Luminal IgG3 is unlikely to be predominantly derived from serum. Old age does not independently influence luminal immunity.

Mucosal cytokine production in small-intestinal bacterial overgrowth

BACKGROUND

Mucosal production of interferon-gamma, interleukin-6, and tumour necrosis factor-alpha is increased in inflammatory bowel disease and parallels disease activity. Interferon-gamma production is also increased in coeliac disease. Conversely, local cytokine profiles have not been investigated in small-intestinal bacterial overgrowth. This study addressed this issue.

METHODS

Eighteen adult subjects were studies with culture of proximal small-intestinal luminal secretion and measurement of luminal interferon-gamma, interleukin-6, and tumour necrosis factor-alpha concentrations by enzyme-linked immunosorbent assay. Small-intestinal histology was assessed by light microscopy.

RESULTS

Interferon-gamma, interleukin-6, and tumour necrosis factor-alpha were measurable in proximal small-intestinal luminal secretions of all subjects, even in the absence of light microscopic evidence of enteropathy. Small-intestinal bacterial overgrowth was present in 12 of 18 (66.7%) subjects. Luminal concentrations of neither interferon-gamma nor tumour necrosis factor-alpha differed significantly in subjects with and without small-intestinal bacterial overgrowth (P + 0.06 and P = 1.0, respectively). Conversely, luminal interleukin-6 concentrations were significantly increased in subjects with this disorder (P = 0.02). Multivariate linear regression analysis suggested that colonic-type rather than salivary-type flora mediated this increased interleukin-6 response (P = 0.02 and P = 0.64, respectively). No correlation was found between luminal interleukin-6 and tumour necrosis factor-alpha concentrations, even after the confounding influence of colonic-type bacteria was excluded (P = 0.60).

CONCLUSIONS

These findings suggest that increased mucosal production of interleukin-6 occurs in small-intestinal bacterial overgrowth, particularly when the overgrowth flora includes colonic-type bacteria. Conversely, luminal levels of neither interferon-gamma nor tumour necrosis factor-alpha are increased in the circumstance, distinguishing the local cytokine profile in this disorder from those that occur in coeliac disease and inflammatory bowel disease.

The lactulose breath hydrogen test and small intestinal bacterial overgrowth

OBJECTIVES

To i) document the sensitivity and specificity of a combined scintigraphic/lactulose breath hydrogen test for small intestinal bacterial overgrowth and ii) investigate the validity of currently accepted definitions of an abnormal lactulose breath hydrogen test based on "double peaks" in breath hydrogen concentrations.

METHODS

Twenty-eight subjects were investigated with culture of proximal small intestinal aspirate and a 10-g lactulose breath hydrogen test combined with scintigraphy. Gastroduodenal pH, the presence or absence of gastric bacterial overgrowth, and the in vitro capability of overgrowth flora to ferment lactulose were determined.

RESULTS

Sensitivity (16.7%) and specificity (70.0%) of the lactulose breath hydrogen test alone for small intestinal bacterial overgrowth were poor. Combination with scintigraphy resulted in 100% specificity, because double peaks in serial breath hydrogen concentrations may occur as a result of lactulose fermentation by cecal bacteria. Sensitivity increased to 38.9% with scintigraphy, because a single rise in breath hydrogen concentrations, commencing before the test meal reaches the cecum, may occur in this disorder. Sensitivity remained suboptimal irrespective of the definition of small intestinal bacterial overgrowth used, the nature of the overgrowth flora, favorable luminal pH, the presence of concurrent gastric bacterial overgrowth, or the in vitro ability of the overgrowth flora to ferment lactulose.

CONCLUSIONS

Definitions of an abnormal lactulose breath hydrogen test based on the occurrence of double peaks in breath hydrogen concentrations are inappropriate. Not even the addition of scintigraphy renders this test a clinically useful alternative to culture of aspirate for diagnosing small intestinal bacterial overgrowth.

Correlation of hydrogen and methane production to rice carbohydrate malabsorption in Burmese (Myanmar) children

Rice carbohydrate malabsorption is common in Burmese village children and adults and may contribute to diminished growth. Its diagnosis depends on a rice breath hydrogen test, which has limitations. Almost 20% of Burmese children under age 5 produce methane, compared with less than 7% of children in Africa and Hong Kong. If an increased carbohydrate load in the colon due to rice malabsorption provides increased substrate for methanogenic bacteria in the left colon, higher fasting breath methane concentrations might be a simpler method of diagnosing rice malabsorption. We tested breath hydrogen and methane over a 4-h period and did anthropometric measurements in 142 subjects, 79 children, and 63 adults. Seventy percent of children were rice-malabsorbers. Methane production occurred in 20% of children under 5 years of age and increased to 60% of adults. There is an association of rice malabsorption with reduced length. There was not correlation between rice malabsorption and breath methane, and the concentration of breath methane does not, therefore, indicate rice absorption status and cannot replace rice breath hydrogen tests.

Patterns of methane production in a Burmese (Myanmar) population

While up to 50% of Western populations produce methane, this is less than that of rural black Africans and there is no information on methane production in populations from Asian developing countries. Females consistently produce methane more commonly than males, and methane production in children under the age of five years, except in Nigeria, is unusual. Breath methane was sampled in 1426 subjects from Myanmar ranging in age from 1 month to 88 years, with a mean age of 26.2 years. Half (49.8%) of the Myanmar population produced methane, this figure comprising 53% of females and 46% of males sampled. Methane production increases with age and reaches adult levels after 10 years of age. A high prevalence of methane production was found in children under 3 years of age (15.8%). Methane production was absent in 13 solely breast-fed children and increased as other food was introduced into the diet. There was an association of methane production within families and with smoking. The prevalence of methane production increased in male and female smokers, with 75% of smokers producing methane. Methane production was not associated with occupation, education, income, water source, latrine type, previous diarrhoea, antibiotic usage or socio-economic status.

Factors influencing the 1-g 14C-D-xylose breath test for bacterial overgrowth

OBJECTIVES

To document the sensitivity of the 1-g 14C-D-xylose breath test for bacterial overgrowth and to investigate luminal and nonluminal factors that may influence breath 14CO2 levels and impact on the clinical utility of this test.

METHODS

Thirty-five adult subjects were investigated for bacterial overgrowth by culture of gastric and small intestinal aspirates and by a 1-g 14C-D-xylose breath test. Body weight, gastroduodenal pH and the in vitro capability of overgrowth flora to ferment D-xylose were assessed. Serial breath 14CO2 levels were also recorded before and after the resolution of malabsorption in a subject with celiac disease to determine the importance of postabsorptive metabolism of this substrate.

RESULTS

Gastric and small intestinal bacterial overgrowth were present in 19/35 (54.3%) and 21/35 (60.0%) subjects, respectively. The positivity rate of culture of aspirate exceeded that of the 1-g 14C-D-xylose breath test. Endogenous CO2 production independently influenced breath 14CO2 levels. After excluding this influence, sensitivity of the 1-g 14C-D-xylose breath test for gastric bacterial overgrowth or small intestinal bacterial overgrowth was poor, even when overgrowth with specific "marker organisms" was considered. Poor sensitivity could not be explained by unfavorable luminal pH. Overgrowth flora were proven capable of in vitro D-xylose fermentation in 81.8% of subjects. Systemic and/or colonic metabolism of 1-g 14C-D-xylose appear to be important factors influencing results of the 1-g 14C-D-xylose breath test, especially in partial gastrectomy subjects.

CONCLUSIONS

The 1-g 14C-D-xylose breath test is not a suitable alternative to culture of aspirate for the investigation of subjects for bacterial overgrowth.

Bacteriologic analysis of mucosal biopsy specimens for detecting small-intestinal bacterial overgrowth

BACKGROUND

Although culture of luminal secretions is regarded as the most accurate diagnostic test for small-intestinal bacterial overgrowth, obtaining an aspirate is often difficult owing to the sparseness of luminal secretions present at the time of aspiration. Obtaining a mucosal biopsy specimen for bacteriologic analysis would overcome this problem.

METHODS

Culture of small-intestinal and gastric aspirates and unwashed small-intestinal mucosal specimens was performed in 51 adult subjects investigated for small-intestinal overgrowth.

RESULTS

Highly significant (r = 0.85-0.90; p < 0.0005) correlations were found between viable bacterial counts in small-intestinal luminal secretions and biopsy specimens. Small-intestinal bacterial overgrowth was present in 60.8% of subjects. When specimens weighing 4.0-84.0 mg were suspended in diluent, total aerobic and/or anaerobic bacterial counts > or = 10(2) CFU/ml were found to have 90.3% sensitivity and 100% specificity for small-intestinal bacterial overgrowth.

CONCLUSION

Culture of an unwashed small-intestinal mucosal biopsy specimen is a useful alternative to culture of a small-intestinal aspirate for detecting subjects with small-intestinal bacterial overgrowth, especially when luminal secretions are scanty at the time of aspiration.

An appraisal of a 'string test' for the detection of small bowel bacterial overgrowth

The efficacy of a string test for the detection of small bowel bacterial overgrowth (SBBO) was determined by comparison with a sterile endoscopic method for sampling small bowel secretions in 15 subjects investigated for SBBO. Clinical value was found to be limited by poor sensitivity, specificity and positive predictive value. The string test is not an adequate substitute for oro-duodenal intubation for the detection of SBBO.

Fasting breath hydrogen concentrations in gastric and small-intestinal bacterial overgrowth

BACKGROUND

Although elevated fasting breath hydrogen concentrations have been reported in small-intestinal bacterial overgrowth, this diagnosis has been presumptive or based on definitions that vary from study to study. The influence of gastric bacterial overgrowth and gastroduodenal pH has not been documented. Conflicting evidence exists as to the reproducibility of breath hydrogen measurements.

METHODS

Forty-two subjects underwent culture of gastric and duodenal aspirates. The pH was measured by indicator paper. Paired fasting breath hydrogen concentrations were measured by gas chromatography within 7 days of endoscopy.

RESULTS

Paired fasting breath hydrogen concentrations differed in terms of normality or abnormality in 21% of subjects. Paired concentrations correlated significantly in overgrowth but not in culture-negative subjects. Sensitivity for bacterial overgrowth was 4-29%, and specificity 71-100%. No correlation with gastroduodenal pH was found.

CONCLUSIONS

The clinical relevance of a single fasting breath hydrogen concentration is limited. The efficacy of paired measurements for gastric or small-intestinal bacterial overgrowth is poor.

Absorption of carbohydrate from rice in Ascaris lumbricoides infected Burmese village children

With the objective of determining the relationship between ascariasis and carbohydrate absorption from rice, breath hydrogen tests (BHT's) were performed in two study populations of Burmese village children. Using a rice test meal, breath hydrogen peaks greater than 10 ppm above baseline within 4 hours (indicating rice malabsorption) were seen in 24 out of 55 (44 per cent) Ascaris lumbricoides infected children and 3 out of 18 (17 per cent) non-infected children (age 18-59 months). In another ascaris endemic village 139 children (age 36-108 months) underwent a rice meal BHT. Seventy children had been regularly dewormed for 2 years (single dose levamisole 50 mg every 3 months) whilst 69 children had been dewormed once in 2 years, 6 weeks before breath testing. Regularly dewormed children showed a lower prevalence of rice malabsorption (33 per cent) compared to the control group (54 per cent) (P < 0.05). These findings suggest that malabsorption of carbohydrate from rice can occur during Ascaris lumbricoides infection in children.

Epidemiology of small bowel bacterial overgrowth and rice carbohydrate malabsorption in Burmese (Myanmar) village children

Breath hydrogen tests were performed after a rice meal (3 g of cooked rice/kg of body weight, equivalent to 1 g of carbohydrate/kg of body weight) on 256 village children (age range 1-59 months) who were known hydrogen (H2) producers. Anthropometric measurements were made every three months and growth rates were calculated. A breath H2 excretion pattern that suggested small bowel bacterial overgrowth (SBBO), which was recognized as a transient maximum level of 10 ppm or more at 20-, 40-, or 60-min breath samples following the rice meal, was present in 53 (20.7%) children, and was more frequent in children 36-47 and 48-59 months old. This breath H2 excretion pattern was detected in 48 (33.3%) of 144 children who were rice malabsorbers (greater than 10 ppm H2 above baseline values in one of the breath samples taken between 90 and 240 min), and in only five (4.5%) of 112 rice absorbers. Children who had SBBO had a high relative risk (10.7) of being rice malabsorbers. Rice malabsorbers have a high relative risk (59.7) of having faltered growth, accompanied by a large etiologic fraction (94%). This same risk (6.68) and an etiologic fraction of 62% exist in children with untreated SBBO. These findings emphasize the need for interventions aimed at reducing the prevalence of SBBO or similar conditions as detected by the breath H2 excretion pattern to prevent rice malabsorption and growth faltering.

In vitro hydrogen production by enteric bacteria cultured from children with small bowel bacterial overgrowth

Lactulose breath hydrogen test and Enterotest string test were carried out simultaneously on 19 children 3-5 years old. Bacteria isolated from the jejunal fluid in upper small intestines of these children were incubated with lactulose at neutral pH. Anaerobes were present in all but one child, and in 15 children they were present in numbers greater than 5 log10 organisms per ml. Most of these bacteria did not produce hydrogen in vitro. Hydrogen production (greater than 100 ppm) was observed with the following bacteria: Bacteroides (5%), clostridia (8%), anaerobic corynebacteria (5%), Escherichia coli (67%), Lactobacillus (8%), Staphylococcus (8%), and Streptococcus (9%). The following bacteria did not produce hydrogen in vitro: Actinobacter, Actinomyces, anaerobic cocci, Bifidobacterium, Fusobacterium, micrococci, Neisseria, Sarcina, and Veillonella. This study suggests that in the diagnosis of small bowel bacterial overgrowth using lactulose breath hydrogen test, it is important to consider that patients with a flat breath hydrogen response to a carbohydrate challenge during the first 60 min may be infected with enteric bacteria which are not capable of producing H2.

Comparison of an in vitro faecal hydrogen test with the lactulose breath test: assessment of in vivo hydrogen-producing capability in Burmese village children

In the assessment of carbohydrate malabsorption, it is important to determine if patients with a flat breath hydrogen (H2) response to an absorbable carbohydrate challenge are capable of producing H2. We compared the reliability of a rapid faecal incubation system with the lactulose breath test to assess in vivo H2 production in 64 children. Overall, 70% of subjects were in vivo H2-producers, with breath H2 peaks greater than 10 parts per million within 3 h of ingesting 10 g of the non-absorbable disaccharide lactulose. Faecal specimens from the 64 children had a mean (SE) pH of 5.0 (0.077). Faecal homogenates were incubated with lactulose at both the initially measured faecal pH and at neutral pH. In predicting a normal in vivo H2-producing ability (sensitivity), the faecal H2 test was correct in only 22% (faecal pH) to 44% (pH7) of cases. In predicting an abnormal lactulose breath test result (specificity), faecal homogenate analysis was correct in 53% of cases, at both faecal and neutral pH. These findings indicate that the faecal hydrogen test is unsuitable as a screening test for in vivo H2 production.

A pattern of breath hydrogen excretion suggesting small bowel bacterial overgrowth in Burmese village children

Breath hydrogen tests (BHTs) were performed on 340 Burmese village children aged 1-59 months. Normalization (correction of breath H2 values to a constant mean O2 level) eliminated the variations in H2 levels due to sleep, storage temperature, or duration of storage. After a 10 g lactulose test meal, 145 (42.6%) children produced less than 10 ppm H2 above basal values (non-H2 producers). Of 195 H2 producers, a pattern of breath hydrogen excretion suggesting small bowel bacterial overgrowth (SBBO)--recognized as a transient peak at the 20, 40, or 60 min breath samples following the lactulose test meal and distinguishable from the later colonic peak--was observed in 53 (27.2%), being significantly more frequent in male children, and exhibiting an age-prevalence pattern similar to that of acute childhood diarrhea in these villages. Diarrhea did not alter the state of H2 production (non-H2 producers remain non-H2 producers, and H2 producers remain H2 producers) although the magnitude of peak breath H2 changed.

Effect of short-term intermittent antibiotic treatment on growth of Burmese (Myanmar) village children

To test the hypothesis that subclinical enteric infection (such as bacterial overgrowth), rice malabsorption, and growth faltering are causally linked, a field trial of low-dose, short-term, intermittent antibiotic treatment was carried out in 142 hydrogen-producing (by lactulose breath hydrogen test) Burmese village children aged 6-59 months. The children were randomly allocated treatment with metronidazole (20 mg/kg or 5 mg/kg daily), amoxycillin (25 mg/kg daily), or placebo given 1 week per month for 6 months. A cooked rice meal breath hydrogen test was done to classify the children as rice absorbers (RA) or rice malabsorbers (RM) before treatment and monthly on the day before each cycle of treatment. There were no differences between the treatment groups, so they were considered together. Factorial analysis showed that antibiotic treatment did not significantly affect the proportion of RM children. The only significant difference between antibiotic-treated and placebo-treated children's growth was in the subgroup of RM children aged 36-47 months; the antibiotic-treated children had significantly greater linear growth. In other age groups antibiotic treatment had no effect on growth.

Malabsorption of carbohydrate from rice and child growth: a longitudinal study with the breath-hydrogen test in Burmese village children

Breath-hydrogen tests were performed after a rice meal (3 g cooked rice/kg body wt, equivalent to 1 g carbohydrate/kg body wt) at monthly intervals for 6 mo on 75 village children aged 1-59 mo who were known hydrogen producers. The overall rate for rice-carbohydrate malabsorption was 46.7% (range 37.3-56.0%). Anthropometric measurements were made every 3 mo and growth rates were calculated. Forty-six percent to 59% of children were less than or equal to -3 SD of the National Center for Health Statistics (NCHS) median weight-for-age and length-for-age and less than -2 SD of the NCHS median weight-for-length. Rice malabsorbers (ie, those with hydrogen peaks greater than or equal to 10 ppm above baseline concentrations) in the age groups 36-47 mo and 48-59 mo had statistically significant diminished growth expressed as percent gain in length per annum per child (p less than 0.02). Thus, rice malabsorbers had a deficit in linear growth of 2.7 cm/y (range 2.5-2.9 cm/y) for children aged 36-47 mo old and 1.9 cm/y (range 1.7-2.1 cm/y) for children aged 48-59 mo.

Absorption of carbohydrate from rice in Burmese village children and adults

Breath-hydrogen tests (BHTs) were performed on 310 Burmese village children aged 1-59 mo. After a 10-g lactulose test meal, 94 (30.3%) children produced less than 10 ppm H2 above basal values (nonhydrogen producers). Of 216 hydrogen producers, 210 were tested after a cooked rice meal (3 g cooked rice/kg body wt, equivalent to 1 g carbohydrate/kg body wt) with the BHT. Hydrogen peaks greater than or equal to 10 ppm above baseline concentrations were produced by 133 (66.5%) children who were defined as rice malabsorbers. Forty-three percent to 62% of children were less than or equal to -3 SD of the National Center of Health Statistics (NCHS) median weight-for-age and length-for-age and less than -2 SD of the NCHS median weight-for-length. There were no differences between rice absorbers (peak hydrogen less than 10 ppm above baseline) and rice malabsorbers in the allometric indices (the Ehrenberg index and the Dugdale index) of weight-for-length. Rice-carbohydrate malabsorption was also detected by BHTs in 26.7% of 86 school children (aged 5-15 y), 38.5% of 39 young adults (aged 15-39 y), and 50% of 34 older adults (aged 40-70 y).

Role of maintenance sucralfate in prevention of duodenal ulcer recurrence

Fifty-nine patients who had duodenal ulcers that were healed following sucralfate administration in a dose of 1 g four times a day were randomly entered into a double-blind, placebo-controlled, 12-month maintenance study to determine whether sucralfate 1 g twice daily prevents recurrence of duodenal ulceration. Patients were assessed endoscopically at four, eight, and 12 months after healing or earlier if clinical relapse occurred. Of the original 59 patients, 53 showed healing with six weeks of therapy, and the remaining six patients required 10 weeks of treatment. Nine patients were subsequently lost to follow-up because of non-compliance, leaving 50 patients for the analysis, 24 who received sucralfate and 26 who received placebo. There were 10 ulcer recurrences in the sucralfate group and the ulcers in 14 (58 percent) patients remaining healed at the end of 12 months. In contrast, there were 21 recurrences in the placebo group with the ulcers in five patients (19 percent) remaining healed at 12 months. Patients who received placebo experienced recurrence more quickly than those who received sucralfate and there was no difference between the two groups in terms of symptomatic and asymptomatic recurrence. There was no alteration in serum aluminium and phosphate levels throughout the study. Smoking seemed to have no adverse effect on recurrence once initial healing had been achieved. Sucralfate is, therefore, an effective and safe maintenance treatment for duodenal ulcer disease.

The effect of protein deficiency on systemic release of rat mucosal mast cell protease II during Nippostrongylus brasiliensis infection and following systemic anaphylaxis

Serum rat mucosal mast cell protease II (RMCPII) was measured in protein-deficient rats to assess mucosal mast cell (MMC) activation during primary infection with the nematode, Nippostrongylus brasiliensis, and during systemic anaphylaxis produced by Nippostrongylus antigen in immune animals. In the first study, serum RMCPII increased 4-fold by day 15 after infection. By day 20, serum RMCPII continued to rise in protein-deficient animals, but decreased in nutritionally normal animals. This was associated with impaired worm rejection in protein-deficient rats. During systemic anaphylaxis, serum RMCPII was elevated in three groups of protein-deficient rats on 6%, 8% and 10% low protein diets and in nutritionally normal rats. All protein-deficient rats exhibited 3 to 7-fold less mucosal permeability of the small intestine to Evan's blue dye injected intravenously compared to nutritionally normal animals following anaphylactic stimulation. These results demonstrated that MMC are activated during infection in protein deficiency, and suggest that reduced MMC function does not explain delay in worm expulsion. Impaired mucosal anaphylaxis in protein deficiency could not be attributed to a failure of MMC response.

The effect of methionine and protein deficiency in delaying expulsion of Nippostrongylus brasiliensis in the rat

Three protein-deficient diets containing 5%, 6%, or 7% casein, with and without 0.3% methionine supplementation, were fed to Wistar rats from weaning for 6 wk. Animals were infected subcutaneously with 1500 larvae of Nippostrongylus brasiliensis and killed after 14 days when nutritionally normal animals have expelled more than 97% of the worm burden. There was a delay in worm expulsion that was related to both the protein content (p = 0.0006) and to methionine content (p less than 0.0001). Methionine supplementation significantly reduced the worm burden in animals fed the 7% protein diet from a geometric mean of 32.4 to 5.2 (p = 0.0408) and in rats fed the 6% protein diet from a mean of 162 to 8.1 (p = 0.0002) but had no effect in rats on the 5% casein diet. Thus, addition of methionine overcame the adverse effect of protein deficiency in these less severely affected groups.

Blood loss during Nippostrongylus brasiliensis infection in the rat

Faecal blood loss was measured during Nippostrongylus brasiliensis infection in the DA rat using 51Cr-labelled red blood cells (r.b.c.s). In an initial study, faecal blood loss was measured on day 7 of primary infection with 3000 larvae administered subcutaneously (s.c.), and found to be 0.03 ml/24 h in uninfected animals and 0.14 ml/24 h in infected animals. In a further experiment, blood loss was measured on the day before infection and for 13 days after primary s.c. infection with 5000 larvae. Faecal blood loss was 0.05 ml/24 h or less until day 3, began to rise from day 5, reached a peak of 0.51 ml/24 h on day 8, and fell until day 13. This was closely associated with the rise and fall of the pooled faecal egg count. Direct worm count confirmed a high worm burden on day 7 and expulsion by day 14. The effect of the worm burden on the haemoglobin concentration (Hb) was measured in a further experiment and showed a fall in Hb with a mean worm burden of 726 compared to that of 47 or 284 worms. The study concluded that there is minimal background blood loss in uninfected rats but that infection with N. brasiliensis is a cause of intestinal blood loss and this is associated with a fall in Hb concentration that is dependent on the worm burden.

Reversible nutritional myopathy with myotonia in the protein-deficient rat given methionine

Rats fed a protein-deficient synthetic diet developed hind limb weakness caused by a myopathy with myotonic features on electromyography. Deficiency of vitamin E and selenium, known causes of nutritional myopathy, were excluded. Methionine supplementation of the diet reversed the clinical signs of weakness within 12 h.

Serum pancreatic isoamylase estimation by the inhibitor method as a diagnostic test for chronic pancreatitis

The diagnosis of chronic pancreatitis is often difficult to establish and may involve invasive diagnostic procedures. Serum pancreatic isoamylase has been estimated by the inhibitor method in controls and in 38 patients with known chronic pancreatitis in order to evaluate its use as a diagnostic test. The mean pancreatic isoamylase in those with chronic pancreatitis (68 +/- 77 IU/l) was significantly lower (p less than 0.005) than in controls (113 +/- 60 IU/l). The diagnostic sensitivity of pancreatic isoamylase was 50% (compared to total amylase 9%) and had a specificity of 95%. Stimulation tests with cholecystokinin and secretin failed to increase the sensitivity of the test. A low value of pancreatic isoamylase strongly supports a diagnosis of chronic pancreatitis and may obviate the need for further investigation.

Studies on intestinal calcium absorption in patients with idiopathic hypercalciuria

Using an in vitro method, the uptake of radio-labelled Ca2+ by jejunal biopsy specimens from control subjects, patients with idiopathic hypercalciuria and patients with renal stones without hypercalciuria, were compared. Radio-labelled Ca2+ uptake was investigated over the concentration range 0.1-5.0 mmol/l. For all subjects there was a linear relationship between Ca2+ uptake and medium concentration suggesting that Ca2+ uptake was a passive process. There was no significant difference in Ca2+ uptake between control subjects and patients with renal stones without hypercalciuria. Patients with idiopathic hypercalciuria, both absorptive and renal subtypes, showed increased Ca2+ uptake at all incubation medium concentrations. Assays of various biochemical parameters including alkaline phosphatase, Ca2+-activated ATPase, cyclic AMP and Ca2+-binding protein, in jejunal biopsy specimens showed no significant differences between control subjects and patients with idiopathic hypercalciuria. The results suggest that the intestinal abnormality in idiopathic hypercalciuria is due to enhanced permeability of the brush border membrane to Ca2+, possibly mediated by alterations in membrane lipids.

A prospective study of persistent diarrhoea

A prospective study was undertaken in 100 patients with diarrhoea to identify the causes and to better define the prevalence of the irritable bowel syndrome (IBS) and to determine if there was a diagnostic symptom complex evident in patients with IBS. A diagnosis of IBS was made in 28 patients and in this group the prevalence of lactase deficiency was found to be 40%. Pain in association with urgency was usual and urgency occurring in the absence of pain was more likely to be found in association with an organic colonic lesion. The two most important symptoms which distinguish IBS from other causes were blood in the motions and weight loss. Giardia lamblia were found in nine patients and 15 patients responded to an empirical course of either metronidazole or tinidazole, without a positive diagnosis of giardiasis being made. Fourteen patients had inflammatory bowel disease and a variety of drugs were responsible for diarrhoea in 10% of patients. Sigmoidoscopy and small bowel biopsy were the most valuable diagnostic investigations.

The effect of iron and protein deficiency on plasma levels and parasite uptake of [14C] fenbendazole in rats infected with Nippostrongylus brasiliensis

The Nippostrongylus brasiliensis-rat model was used to determine whether iron and protein deficiency, which are commonly associated with parasitic infections, affected the pharmacokinetic behaviour of fenbendazole as measured by plasma concentrations and uptake by worms. Plasma 14C concentrations after [14C] fenbendazole administration were higher in iron and protein-deficient rats than in sufficient rats. However, the uptake of 14C by N. brasiliensis in iron and protein-deficient rats was significantly less than in worms from diet-sufficient rats. The reduced anthelmintic uptake by worms in protein and iron-deficient hosts may account, in part, for reduced anthelmintic efficacy under these circumstances. These findings are relevant to understanding variations in response to chemotherapy in populations of parasitised hosts containing malnourished individuals.

Delayed expulsion of the nematode Nippostrongylus brasiliensis from rats on a low protein diet: the role of a bone marrow derived component

Rats on a low protein diet, containing 10% casein as the only source of protein, have an impaired capacity to expel primary infections with the nematode Nippostrongylus brasiliensis and remain susceptible to reinfection. In the present study, the transfer of syngeneic bone marrow cells to rats on a low protein diet reconstituted the expulsion mechanism allowing parasite rejection to occur at the same rate as rats on a sufficient diet. Serum transfer, on the other hand, did not significantly alter the rate of worm expulsion. These results demonstrate that a bone marrow derived component plays an important role in the impaired immunity of rats fed a low protein diet.

In-vitro calcium uptake by jejunal biopsy specimens from patients with idiopathic hypercalciuria

In-vitro calcium influx was measured in jejunal biopsy specimens from 10 men with idiopathic hypercalciuria. Calcium uptake in these adults was a passive process which was not sensitive to inhibition by 2,4 dinitrophenol and sodium fluoride, and showed no evidence of carrier saturation. In 7 of 10 patients with idiopathic hypercalciuria calcium uptake was above the normal range, and the mean uptake for all patients was significantly higher than in 10 control subjects (p < 0.01). The kinetic features suggest that this increased influx was the result of increased brush border permeability to calcium ions.

The effect of iron deficiency, protein deficiency and dexamethasone on infection, re-infection and treatment of Giardia muris in the mouse

The association between nutrient deficiencies, steroid administration, anti-flagellate therapy and giardiasis was examined using the Giardia muris/mouse model. Administration of steroids to BALB/c mice resulted in persisting high levels of infection with G. muris, whereas untreated animals were able to eliminate this parasite. In addition, steroid treatment significantly reduced the efficacy of anti-flagellate therapy. Protein-deficient mice eliminated the parasite at the same rate as mice on an optimum diet and also developed strong acquired resistance to re-infection. A similar pattern was observed in iron-deficient mice, except that the number of parasites that became established during the first 2 weeks of infection was significantly reduced. Thus, there was no evidence of synergism between iron and protein deficiency and infection in this model.

Nippostrongylus brasiliensis infection in the rat: effect of iron and protein deficiency on the anthelmintic efficacy of mebendazole, pyrantel, piperazine, and levamisole

The benzimidazole anthelmintics mebendazole and fenbendazole have been shown to be much less effective against Nippostrongylus brasiliensis infections in the rat on a combined iron and protein deficient diet. In the present experiments it was shown that the anthelmintic efficacy of mebendazole was significantly impaired in the rat on either an iron deficient or a protein deficient diet. Furthermore, iron and protein deficiency reduced the efficacy of the anthelmintics pyrantel and piperazine but not levamisole. The finding that nutritional deficiencies reduce anthelmintic efficacy may well be relevant to worm eradication programmes in iron deficient and protein calorie malnourished populations.

The effect of iron and protein deficiency on the development of acquired resistance to reinfection with Nippostrongylus brasiliensis in rats

Iron and protein deficiency delays the immunological rejection of Nippostrongylus brasiliensis from the small intestine of rats undergoing a primary infection with the parasite. In the present study, iron and protein deficiency significantly reduced acquired resistance to reinfection with N. brasiliensis. Repletion of deficient animals with iron and protein restored their capacity to mount an effective immune response to a secondary infection with the parasite. These results suggest that chemotherapy of helminthiasis should be integrated with nutritional supplementation.

Suppression of rejection of Nippostrongylus brasiliensis in iron and protein deficient rats: effect of syngeneic lymphocyte transfer

Rejection of Nippostrongylus brasiliensis is impaired in iron and protein deficient rats and this suggests that iron and protein deficiency directly or indirectly suppresses the immune response. The site of the immunological defect in deficient rats was investigated using the technique of cellular transfer of resistance. The functional activity of immune mesenteric lymph node cells obtained from iron and protein deficient donors was not depressed as measured by their capacity to cause parasite rejection in nutritionally sufficient recipients. In contrast, immune lymph node cells obtained from either sufficient or deficient donors did not result in parasite rejection in iron and protein deficient recipients. These results indicate that there is no permanent defect of lymphocyte function in iron and protein deficient rats and suggest that either some other component of the rejection mechanism is defective, or that lymphocyte function is blocked in an iron and protein deficient environment.

Histopathology in giardiasis: a correlation with diarrhoea

There is controversy both in regard to the severity of small bowel mucosal damage attributable to giardiasis and to the causal relationship of these changes to the associated diarrhoea. In this series of 17 consecutive patients with giardiasis, small bowel histology and diarrhoea were independently assessed and compared. Disaccharidase assays were performed in 16 of these patients and a repeat biopsy obtained in seven cases. On histological examination the villous architecture varied from normal to sub-total villous atrophy. When these changes were compared with the severity of diarrhoea, a direct correlation was obtained, the more severe symptoms being associated with the more severe villous changes. Repeat biopsy after treatment demonstrated improvement in the histology which correlated with improvement in diarrhoea. Lactase activity was low in all patients with moderate or severe diarrhoea as well as in some patients with mild diarrhoea, two of whom had normal histology. This series demonstrates the occurrence of a spectrum of mucosal changes in giardiasis and supports the concept that these changes mediate the diarrhoea associated with this gut parasite.

The diagnosis and management of acute viral hepatitis

While there is a declining incidence of many infectious diseases, viral hepatitis persists as a major problem. In fact, there would appear to be an increasing incidence of hepatitis B paralleling the rising problem of drug addiction. The discovery of Australia antigen, now called hepatitis B surface antigen (HBsAG), represented a major breakthrough in our understanding of viral hepatitis. More recently, serological tests have become available for hepatitis A virus (HAV) which will further facilitate our understanding of acute and chronic hepatitis.

Nippostronglylus brasiliensis infection in the rat: effect of iron and protein deficiency and dexamethasone on the efficacy of benzimidazole anthelmintics

Malnutrition, anaemia, and gut parasites are commonly interrelated. Using the Nippostrongylus brasiliensis-rat model, the effect of iron and protein deficiency on the efficacy of benzimidazole anthelmintics was studied. It was demonstrated that the anthelmintics mebendazole and fenbendazole were significantly less effective in eradicating parasites when animals were deficient in iron and protein. This decreased efficacy of anthelmintics in iron and protein deficiency could not be overcome by intraperitoneal administration of the drug. Since nutritional deficiencies may act via impairment of the immune response, anthelmintic efficacy was determined in adequately nourished rats treated with the immunosuppressive drug dexamethasone. A similar decrease in efficacy of mebendazole was shown when these animals were treated with dexamethasone. Thus it is possible that lowered anthelmintic efficacy in iron and protein deficient animals is mediated by immune deficiency. These findings may be relevant to anthelmintic programmes in malnourished communities.