Low gastric acid as a risk factor for cholera transmission: application of a new non-invasive gastric acid field test.

Although gastric acid is thought to be an important host defense against certain enteric infections, field studies of the role of gastric acid in preventing enteric infections have been hampered by the lack of a suitable non-invasive test. Because low gastric acid output (GAO) is an established risk factor for cholera, we assessed after validation, whether a new non-invasive test which estimates GAO by measuring breath hydrogen excess after ingestion of magnesium and a stimulant of gastric acid secretion, could discriminate between persons at high and at low risk of developing cholera. Fifteen age-matched pairs, participants in the field trial of two oral cholera vaccines in rural Bangladesh, were tested. In each pair the "case" was a person who had recovered from severe cholera at least 6 months before testing and the "control" was a person who resided in the home of a cholera patient but remained uninfected. The stimulated breath hydrogen was higher in controls (median hydrogen excess = 369 mumol/80 min) than in cases (median hydrogen excess = 150 mumol/80 min) (p less than 0.05) and was higher in controls in 12 out of 15 pairs. The results, which are consistent with past invasive assessments of the association between hypochlorhydria and cholera, suggest that this non-invasive test may be useful in evaluating GAO in epidemiological field studies.

Family latrines and paediatric shigellosis in rural Bangladesh: benefit or risk?

BACKGROUND: The potential benefits of installing excreta disposal facilities on the burden of paediatric diarrhoea in less-developed settings remain controversial. We conducted a longitudinal study to evaluate whether family latrines are associated with interruption of the transmission of shigellosis to younger children in rural Bangladesh. METHODS: We prospectively studied 1529 children under 5 years of age exposed to index cases of Shigella dysentery. In all 219 children with culture-proven shigellosis detected during 1 month of follow-up were compared with 1310 control children who did not develop shigellosis or Shigella-negative dysentery. RESULTS: Overall, the presence of a family latrine appeared to be associated with a higher, not a lower, risk of paediatric shigellosis (adjusted odds ratio (ORa) = 1.37, 95% confidence interval (CI): 0.99-1.89). While use of a pit or sanitary latrine revealed no evidence of a protective association (ORa = 0.96, 95% CI: 0.43-2.15), use of a hanging latrine in which faeces were discharged directly onto the ground or into a body of water was associated with a notable increase of risk (ORa = 1.42, 95% CI: 1.02-1.98, P < 0.05). CONCLUSIONS: While cautioning that installation of sanitary latrines may not be sufficient to reduce the burden of paediatric shigellosis in less-developed settings, these data suggest that eliminating unsanitary latrines constitutes a potentially important intervention in its own right in these settings.

The effect of L-glutamine on salt and water absorption: a jejunal perfusion study in cholera in humans.

OBJECTIVES: To assess the efficacy of an L-glutamine solution on jejunal salt and water absorption in cholera patients. DESIGN: A randomized double-blind jejunal perfusion study. SETTING: International Centre for Diarrhoeal Disease Research, Bangladesh. PATIENTS: Nineteen adults with acute cholera. INTERVENTIONS: Perfusion of balanced salt solutions alternated with defined glucose salt solution and glutamine glucose salt or alanine glucose salt solutions. MAIN OUTCOME MEASURES: Net jejunal water and sodium secretion. RESULTS: Perfusion of glutamine in the presence of glucose significantly reduced net water secretion (JnetH2O = -2.6 +/- 1.3 ml/h/cm) and also reduced net sodium secretion (JnetNa = -213 +/- 153 mumol/h/cm). Similar results were observed during the perfusion of solutions that contained alanine in addition to glucose (JnetH2O = -4.2 +/- 1.1 ml/h/cm and JnetNa = -444 U +/- 142 mumol/h/cm, respectively) or glucose alone (JnetH2O = -4.3 +/- 1.7 ml/h/cm and JnetNa = -452 +/- 212 mumol/h/cm, respectively). In addition, a higher basal secretion was associated with a greater stimulation of water absorption (F = 17, P < 0.001). CONCLUSION: Glutamine in the presence of glucose significantly reduces net water secretion and also reduces sodium secretion; higher basal secretion is associated with greater water absorption. As glutamine is able to stimulate water absorption to the same degree as glucose and alanine, and because it has the theoretical advantage of providing fuel for the mucosa, the inclusion of glutamine as the sole substrate in oral rehydration solution warrants further study.

Mineral Nutrition of Aspergillus niger for citric acid production.

The mineral requirements of a strain of Aspergillus niger for the production of citric acid in a synthetic medium were studied. It was observed that K2HPO4 and MgSO4. 7 H2O were required at concentrations of 0.1% and 0.02% respectively. The optimum level of each of the trace elements Fe, Mn and Zn was 1.0 mug/ml. NaC1 and CaC12 at lower concentrations had no effect on citric acid production. Trace elements, Cu, Co and Mo, had an adverse effect on the production of citric acid while Ni and V were without effect.

Induction of nutritional mutants of Micrococcus glutamicus and their amino acid accumulation.

Micrococcus glutamicus ATCC 13032, a glutamic acid-producing organism, was treated with 0.2M ethylmethane sulfonate, the auxotrophs isolated showing varied patterns of extracellular amino acids. Eighty auxotrophic strains were obtained, out of which 31 excreted 1.0-4.0 mg threonine per ml and all the auxotrophs required biotin for growth and production of the amino acid. Eleven auxotrophs produced 1.5 to 3.0 mg alanine per ml and these auxotrophs required amino acids for their growth. Other auxotrophs lost their excretion capacity in subsequent fermentation trials. Further mutation of the biotin-requiring auxotroph Micrococcus glutamicus EM with gamma rays resulted in the isolation of 89 auxotrophic strains, out of which 28 excreted threonine (up to 5.0 mg per ml) higher than the parent auxotroph. Exposure to X-rays yielded 97 auxotrophs, out of these 35 producing 1.0-3.0 mg methionine per ml and requiring biotin for growth and production of the amino acid. Other auxotrophs produced alanine (0.5 to 2.0 mg per ml) and threonine (2.0 to 3.3 mg per ml). Irradiation with gamma rays favoured the development of threonine producing auxotrophs while X-rays favoured methionine-producing auxotrophs.

Development of a mutant strain of Aspergillus niger and optimization of some physical factors for improved calcium gluconate production.

In the course of mutation studies of Aspergillus niger strain AB with ethylene imine (1:4000), a mutant A. niger AB 501, produced greater amount of calcium gluconate in the culture broth (88.0 g/lit) as against the parent strain (36.0 g/lit) by the surface culture method of fermentation. This mutant was then exposed to UV-rays and a mutant, A.niger AB 1801, was found to produce high calcium gluconate in the culture broth (120 g/lit). The optimum cultural conditions for the production of calcium gluconate by A.niger AB 1801 were pH, 6.5; period of incubation, 9 days; volume of medium in 1 litre flask, 150 ml; temperature, 30 degrees C, volume of inoculum, 7.5 ml of cell suspension containing 2.6 x 10(7) spores and age of inoculum, 6 days old spores of A. niger AB 1801. The maximum yield of calcium gluconate to the above conditions was 168 g/lit. The cultural conditions that support maximum cultural growth did not, however, give optimal yield of calcium gluconate because after having yielded the maximum of calcium gluconate the growth of organism continued to increase further.

Optimisation of different physical parameters for bioleaching of phosphate by Aspergillus niger from Indian rock phosphate.

A mutant strain of Aspergillus niger AB100 was incubated with samples of rock phosphate. Mutation resulted in a greater amount of solubilisation (30 to 35%) as against the parent strain (10 to 15%). The influence of leaching parameters such as ore concentration (pulp density), particle size, initial pH of the medium, temperature, volume of the medium in 250 ml flasks, inoculum concentration and age of inoculum was studied. When low quantity of rock phosphate is applied (0.1%) the solubilisation of phosphorus was optimal (40.5%). Optimum particle size was--200 to 240 mesh, initial pH of the medium 4.0, optimum volume of the fermentation medium 160 ml, time period of incubation was 8 days, inoculum volume was 7.5 ml, and age of inoculum 7 days. The maximum leaching of phosphorus by using these optimum physical parameters is 45 to 50%.

Effect of ammonium and nitrate ratio on glucose oxidase activity during gluconic acid fermentation by a mutant strain of Aspergillus niger.

Of the factors tested, the source and concentration of carbon and nitrogen in the medium exerted maximum effect on growth and acid production. Glucose (15%) and urea (0.14%) induced glucose oxidase synthesis and optimum yield of calcium gluconate. Potassium dihydrogen phosphate (0.2%) and magnesium sulphate (0.06%) stimulated glucose oxidase activity and calcium gluconate production. Borax at a concentration of 1.5 g/L induced maximum glucose oxidase and calcium gluconate production with increased glucose utilization.

Effect of chemical nutrients on aconitase activity during citric acid fermentation by a mutant strain of Aspergillus niger.

An ethyleneimine and UV irradiated mutant strain Aspergillus niger AB 1801 was explored for its aconitase activity, citric acid production and cell growth during citric acid fermentation. 10% sucrose and 0.25% urea served as the best carbon and nitrogen sources, respectively. Fe2+ stimulated aconitase activity and Co2+ (upto 5 micrograms/mL) and Ni2+ (10 micrograms/mL) strongly depressed enzyme activity. Boric acid (0.5 mg/L) had very good stimulatory response towards citric acid production. Aconitase activity has been found to vary inversely with the citric acid production upto a certain limit after which the activity was absent in the mycelial extract. Cell growth varied with the production parameter.

Perfusion studies in cholera: methods and procedures.

This paper reviews the characteristics of perfusion techniques in the study of intestinal functions by specifically examining the methods and procedures of perfusion in patients with diarrhoea due to infection with V. cholerae 01. Because of abundant jejunal secretion of water and electrolytes in cholera, perfusion studies require special approaches with regard to patient preparation, use of tubing material, selection of markers, and rate of perfusion. A discussion on specific problems involved in marker perfusion techniques in cholera and on the interpretation of the results is followed by practical recommendations.

Clostridium perfringens type C in bloody and watery diarrhea in Bangladesh.

A two-week age-matched case-control survey to detect Clostridium perfringens type C-associated illness was conducted among diarrheal patients hospitalized following the consumption of high protein meals on the occasion of an annual religious festival. From the stool of 33 patients screened, C. perfringens type C was isolated from one patient with bloody diarrhea and from two patients with watery diarrhea. In Bangladesh, C. perfringens type C has been isolated in both bloody and watery diarrhoeal illness and is not necessarily associated with necrotizing enteritis (pigbel).

Evidence that inactivated oral cholera vaccines both prevent and mitigate Vibrio cholerae O1 infections in a cholera-endemic area.

In a randomized, placebo-controlled field trial of B subunit-killed whole cell (BS-WC) and killed whole cell only (WC) inactivated oral cholera vaccines in rural Bangladesh, active surveillance of selected neighborhoods during the first year after vaccination identified 127 Vibrio cholerae O1 infections among 3285 three-dose recipients. For each vaccine, protective efficacy was greater against symptomatic (57%, P < .05 for BS-WC; 58%, P < .05 for WC) than against asymptomatic infections (46%, P < .05 for BS-WC; 32%, P = .09 for WC), and protection against each grade of infection was demonstrable for both the classical and El Tor biotypes. Although vaccine protection against symptomatic infections was evident in both young children and older persons, only persons vaccinated at age > 5 years were protected against asymptomatic infections. These results suggest that the inactivated oral vaccines acted both to protect against intestinal colonization by V. cholerae O1 and to interrupt the pathogenic sequence of established infections.