New strategies in antimicrobial therapy

Yeast mediates lactic acidosis suppression after antibiotic cocktail treatment in short small bowel?

During acidotic periods in a girl with a short small bowel, very high D-lactic acid concentrations were measured in blood and urine; the patient's characteristic faecal flora contained mainly lactobacilli, and during antibiotic cocktail treatment also many yeasts. In this case report we sought to understand the beneficial effect of the antibiotic cocktail. Microbiological analysis was performed in faecal samples. Total lactic acid in serum and urine was studied using capillary gas chromatography-mass spectrometry, and D- and L-lactic acid in serum and urine by enzymatic assay. The results were coupled to patient's condition. Antibiotic cocktail therapy reduced the acidosis-associated symptoms, faecal lactobacilli and D-lactic acid production, but simultaneously the antibiotic therapy strongly increased the percentage of yeast in the faecal flora. Four to six weeks after each course of treatment the percentage of yeast decreased, whereas the percentage of intestinal lactobacilli increased; D-lactic acid also simultaneously increased in blood and urine. The patient felt well and showed a high percentage of intestinal yeast, but she often suffered from acidosis owing to a high percentage of lactobacilli. The yeast was identified as the pathogenic Candida glabrata. From the mentioned data together with data from the literature it was concluded that during several weeks the selected pathogenic yeast, C. glabrata, acted as a microbiological and metabolic buffer. Shortly after the course of antibiotic treatment this intestinal yeast strongly competed with the intestinal lactobacilli and thus prevented renewed rapid growth, massive D-lactic acid production from glucose and consequently also D-lactic acid-associated acidosis. The emergence of this yeast led us to consider probiotic lactobacilli or yeast for therapeutic use. The lack of knowledge regarding bile acid-deconjugating activity in both lactobacilli and probiotic yeast means that a final recommendation is not yet possible.

Preventive and curative effects of probiotics in atopic patients

Normally, the transport of allergens through the intestinal epithelia to the blood is limited. It is hypothesised that if these compounds arrive in the blood circulation, they must percolate through the epithelial cell layer. Thus, food allergy (and thus atopic eczema) implies an increased intercellular leakage of the gut wall. Such increased intercellular leakage is thought to be caused by a slightly changed cellular morphology due to a slight cytopathologic effect because of both a limited decay of the cytoskeleton and a slightly reduced turgor. These events may be due to a reduced production of intracellular metabolic energy in the epithelial cells due to an increased concentration of familiar, frequently occurring, potentially toxic bacterial metabolites, i.e., d-lactic acid and/or ethanol. In this hypothesis we suggest that adequate probiotics can (i) prevent the increased characteristic intestinal permeability of children with atopic eczema and food allergy, (ii) can thus prevent the uptake of allergens, and (iii) finally can prevent the expression of the atopic constitution. The use of adequate probiotic lactobacilli, i.e., homolactic and/or facultatively heterolactic l-lactic acid-producing lactobacilli, reduces the intestinal amounts of the bacterial, toxic metabolites, d-lactic acid and ethanol by fermentative production of merely the non-toxic l-lactic acid from glucose. Thus, it is thought that beneficial probiotic micro-organisms promote gut barrier function and both undo and prevent unfavourable intestinal micro-ecological alterations in allergic individuals.

Effect of antibiotics, prebiotics and probiotics in treatment for hepatic encephalopathy

In order to reduce ammonia production by urease-positive bacteria Solga recently hypothesised (S.F. Solga, Probiotics can treat hepatic encephalopathy, Medical Hypotheses 2003; 61: 307-13), that probiotics are new therapeutics for hepatic encephalopathy (HE), and that they may replace antibiotics and lactulose. This influenced our view of the effect of antibiotics, prebiotics, e.g., lactulose, and probiotics on intestinal bacteria in the treatment of HE. Intestinal ammonia arises from aminoacids after bacterial de-amination and not from urea making urease-positive bacteria irrelevant. Antibiotics are not preferred in the treatment of HE, since ammonia-producing antibiotic-resistant bacteria may survive and replace ammonia-producing antibiotic-susceptible bacteria. Intestinal prebiotics are carbohydrate-like compounds, such as lactulose and resistant starch, that beneficially affects host's health in a different manner than normal food. In the small bowel prebiotics are not absorbed and digested, but are fermented in the colon by colonic bacteria. Fermentation of prebiotics yields lactic, acetic and butyric acids, as well as gas especially hydrogen (H2). The massive H2 volumes cause rapid intestinal hurry and thus massive amounts of colonic bacteria, not only urease-positive bacteria, but also deaminating bacteria, are removed and intestinal uptake of toxic bacterial metabolites, e.g., ammonia, reduced. As living non-pathogenic micro-organisms, probiotics beneficially affect the host's health by fermenting non-absorbed sugars, especially in the small bowel. Thus, they reduce the substrate of the other bacteria, and simultaneously they create a surplus of fermentation products which may affect the non-probiotic flora. Regarding the fermentation products (lactic acid, ethanol, acetic acid and CO2) five groups of probiotic micro-organisms are known. It is argued that probiotic, CO2-producing (facultatively) heterolactic lactobacilli, i.e., lactobacilli, that produce both lactic acid and CO2 from sugars, such as glucose, are preferred in the treatment of HE. Our ideas concur with the practice guidelines regarding HE as formulated by Blei, Cordoba and the Practice Parameters Committee of the American College of Gastroenterology, and does not alter the final conclusion of Solga as regards the beneficial use in future treatment of HE.