Safety of probiotics that contain lactobacilli or bifidobacteria

Probiotics in clinical practice: an overview

The observation that intestinal bacterial microflora might be able to influence immune system surveillance through changed nutritional habits has raised awareness of the role of probiotics. These are live microorganisms that are able to reach the gastrointestinal tract and alter its microfloral composition, producing beneficial health effects when consumed in adequate amounts. Recent clinical trials have evaluated the clinical effectiveness of probiotics in the treatment and prevention of a wide range of acute and chronic gastrointestinal diseases, and also non-gastrointestinal diseases, such as atopy, respiratory infections, vaginitis and hypercholesterolaemia. Probiotic supplements are generally regarded as safe because the microorganisms they contain are identical to those found in human gastrointestinal and vaginal microflora. Guidelines on the use of probiotics in the clinical setting require periodical updates for the latest data to be included in clinical applications. The purpose of this clinical report is to review current evidence on the use of probiotics in a variety of gastrointestinal and non-gastrointestinal conditions.

Fate and effects of Camembert cheese micro-organisms in the human colonic microbiota of healthy volunteers after regular Camembert consumption

The objective of this study was to determine i) if Camembert cheese micro-organisms could be detected in fecal samples after regular consumption by human subjects and ii) the consequence of this consumption on global metabolic activities of the host colonic microbiota. An open human protocol was designed where 12 healthy volunteers were included: a 2-week period of fermented products exclusion followed by a 4-weeks Camembert ingestion period where 2x40 g/day of Camembert cheese was consumed. Stools were collected from the volunteers before consumption, twice during the ingestion period (2nd and 4th week) and once after a wash out period of 2 weeks. During the consumption of Camembert cheese, high levels of Lactococcus lactis and Leuconostoc mesenteroides were measured in fecal samples using real-time quantitative PCR, reaching median values of 8.2 and 7.5 Log(10) genome equivalents/g of stool. For Ln. mesenteroides, persistence was observed 15 days after the end of Camembert consumption. The survival of Geotrichum candidum was also assessed and the fecal concentration reached a median level of 7.1 Log(10) CFU/g in stools. Except a decreasing trend of the nitrate reductase activity, no significant modification was shown in the metabolic activities during this study.

The safety of Bacillus subtilis and Bacillus indicus as food probiotics

AIMS

To conduct in vitro and in vivo assessments of the safety of two species of Bacillus, one of which, Bacillus subtilis, is in current use as a food supplement.

METHODS AND RESULTS

Cultured cell lines, Caco-2, HEp-2 and the mucus-producing HT29-16E cell line, were used to evaluate adhesion, invasion and cytotoxicity. The Natto strain of B. subtilis was shown to be able to invade and lyse cells. Neither species was able to adhere significantly to any cell line. The Natto strain was also shown to form biofilms. No strain produced any of the known Bacillus enterotoxins. Disc-diffusion assays using a panel of antibiotics listed by the European Food Safety Authority (EFSA) showed that only Bacillus indicus carried resistance to clindamycin at a level above the minimum inhibitory concentration breakpoints set by the EFSA. In vivo assessments of acute and chronic dosing in guinea pigs and rabbits were made. No toxicity was observed in animals under these conditions.

CONCLUSIONS

Bacillus indicus and B. subtilis should be considered safe for oral use although the resistance of B. indicus to clindamycin requires further study.

SIGNIFICANCE AND IMPACT OF THE STUDY

The results support the use of B. subtilis and B. indicus strains as food supplements.

Lactobacillus rhamnosus R11 consumed in a food supplement survived human digestive transit without modifying microbiota equilibrium as assessed by real-time polymerase chain reaction

The aim of this study was to evaluate the survival of Lactobacillus rhamnosus R11 and Lactobacillus acidophilus R52 in the human digestive tract and their effects on the microbiota homeostasis. We designed an open human trial including 14 healthy volunteers. A 3-week exclusion period of fermented products was followed by a 12-day consumption period of 4 capsules daily containing 2 x 10(9)L. rhamnosus R11 and 1 x 10(8)L. acidophilus R52, and a 12-day wash-out period. The 2 strains and dominant bacterial groups of the microbiota were quantified by real-time polymerase chain reaction. At the end of the capsule consumption period, high levels of L. rhamnosus R11 were detected in faecal samples from all volunteers, reaching a mean value of 7.1 log(10) colony-forming unit (CFU) equivalents/g of stool. L. acidophilus R52 was detected in the stools of only 1 volunteer, reaching a maximum level of 6.1 log(10) CFU equivalents/g of stool. Dilution plating enumerations performed in parallel provided less consistent and generally lower levels. No significant effect of capsule consumption was observed on microbiota homeostasis for the dominant faecal populations. Mean values of 8.8, 9.2, 9.9 and 10.6 log(10) CFU equivalents/g of stool were obtained for the Clostridium coccoides, Bifidobacterium sp., Bacteroides sp. and Clostridium leptum groups, respectively.

A double blind randomized controlled trial of a probiotic combination in 100 patients with irritable bowel syndrome

OBJECTIVES

The purpose of this study was to evaluate the effects of a probiotic combination on symptoms in patients with irritable bowel syndrome (IBS).

METHODS

We investigated the efficiency of a probiotic dietary supplement, containing four strains of lactic acid bacteria, on symptoms of IBS. One hundred and sixteen patients with IBS fulfilling the Rome II criteria were randomized in a parallel group, double-blind study to receive a placebo or a probiotic combination (1 x 10(10) cfu once daily) for four weeks. The symptoms that were monitored weekly included discomfort, abdominal pain, and stool frequency and quality. Quality of life was assessed before and at the end of the treatment using the SF36 and FDD-quality-of-life questionnaires.

RESULTS

One hundred subjects completed the study (48 probiotic combination, 52 placebo). The probiotic combination was not superior to the placebo in relieving symptoms of IBS (42.6 versus 42.3% improvement). However, the decrease of abdominal pain between the first and the fourth week of treatment was significantly higher in probiotic treated patients (-41.9 versus -24.2%, P=0.048). Interesting findings from the IBS sub-groups were also observed such as a lower pain score at end point in patients with alternating bowel habits (P=0.023) and an increase of stool frequency in the constipated sub-group from the first week of probiotic treatment (P=0.043).

CONCLUSIONS

The probiotic combination was not significantly superior to the placebo in relieving symptoms of IBS. Despite the apparent high placebo response, interesting findings from IBS sub-groups were observed in the field of abdominal pain and stool frequency.

Probiotics in infectious diarrhoea in children: are they indicated?

Infectious gastroenteritis continues to be a leading cause of mortality and morbidity worldwide. The cornerstone of treatment remains replacement of water and electrolyte losses with oral rehydration solution. Until a few years ago, probiotics were discussed primarily in the context of alternative medicine, but they are now entering mainstream medical practice since a decrease of the severity and duration of infectious gastroenteritis in approximately 24 hours has been shown for some strains. Therefore, probiotics are a potential add-on therapy in acute gastro-enteritis. The shortening of the duration of diarrhoea and the reduction in hospital stay result in a social and economic benefit. Evidence found in viral gastroenteritis is more convincing than in bacterial or parasitic infection. Mechanisms of action are strain specific and only those commercial products for which there is evidence of clinical efficacy should be recommended. Timing of administration is also of importance. In acute gastroenteritis, there is evidence for efficacy of some strains of lactobacilli (e.g. Lactobacillus caseii GG and Lactobacillus reuteri) and for Saccharomyces boulardii. Probiotics are "generally regarded as safe", but side effects such as septicaemia and fungaemia have very rarely been reported in high-risk situations. Although most studies conclude in a statistically significant shortening of the duration of diarrhea, the clinical relevance of this finding is limited. In conclusion, selected strains of probiotics result in a statistically significant but clinically moderate benefit in shortening the duration of diarrhoea caused by acute infectious gastroenteritis.

History of safe use as applied to the safety assessment of novel foods and foods derived from genetically modified organisms

Very few traditional foods that are consumed have been subjected to systematic toxicological and nutritional assessment, yet because of their long history and customary preparation and use and absence of evidence of harm, they are generally regarded as safe to eat. This 'history of safe use' of traditional foods forms the benchmark for the comparative safety assessment of novel foods, and of foods derived from genetically modified organisms. However, the concept is hard to define, since it relates to an existing body of information which describes the safety profile of a food, rather than a precise checklist of criteria. The term should be regarded as a working concept used to assist the safety assessment of a food product. Important factors in establishing a history of safe use include: the period over which the traditional food has been consumed; the way in which it has been prepared and used and at what intake levels; its composition and the results of animal studies and observations from human exposure. This paper is aimed to assist food safety professionals in the safety evaluation and regulation of novel foods and foods derived from genetically modified organisms, by describing the practical application and use of the concept of 'history of safe use'.

Studies with inulin-type fructans on intestinal infections, permeability, and inflammation

Symbiosis between host and gut bacteria can be optimized by prebiotics. Inulin-type fructans have been shown to improve the microbial balance of the intestinal ecosystem by stimulating the growth of bifidobacteria and lactobacilli. These changes have been associated with several health benefits, including the prevention of gastrointestinal and systemic infections in animal models and human studies. Inulin-type fructans induce changes of the intestinal mucosa characterized by higher villi, deeper crypts, increased number of goblet cells, and a thicker mucus layer on the colonic epithelium. Bacterial antagonism and competition of bifidobacteria and lactobacilli with pathogens, as well as the trophic effects on the intestinal epithelium, may explain the protective role of inulin against enteric infections. In contrast, studies with rats fed a low-calcium diet suggested a negative effect of prebiotics on intestinal barrier function. However, the adverse effect was clearly ascribed to the strong reduction of dietary calcium, as it could be reversed by oral administration of calcium. The adverse effect of a low-calcium diet on intestinal permeability has not been observed in humans. Inulin and oligofructose are now being tested in human studies aimed at prevention of bacterial translocation in critical health conditions. Mixtures of probiotics and prebiotics including inulin or oligofructose significantly reduced the rate of postoperative infections in liver transplant patients. Finally, inulin and oligofructose have proven useful to prevent mucosal inflammatory disorders in animal models and in patients with inflammatory bowel disease.

Effect of a fermented milk combining Lactobacillus acidophilus Cl1285 and Lactobacillus casei in the prevention of antibiotic-associated diarrhea: a randomized, double-blind, placebo-controlled trial

BACKGROUND

Antibiotic-associated diarrhea is an important problem in hospitalized patients. The use of probiotics is gaining interest in the scientific community as a potential measure to prevent this complication. The main objective of the present study was to assess the efficacy and safety of a fermented milk combining Lactobacillus acidophilus and Lactobacillus casei that is widely available in Canada, in the prevention of antibiotic-associated diarrhea.

METHODS

In this double-blind, randomized study, hospitalized patients were randomly assigned to receive either a lactobacilli-fermented milk or a placebo on a daily basis.

RESULTS

Among 89 randomized patients, antibiotic-associated diarrhea occurred in seven of 44 patients (15.9%) in the lactobacilli group and in 16 of 45 patients (35.6%) in the placebo group (OR 0.34, 95% CI 0.125 to 0.944; P=0.05). The median hospitalization duration was eight days in the lactobacilli group, compared with 10 days in the placebo group (P=0.09). Overall, the lactobacilli-fermented milk was well tolerated.

CONCLUSION

The daily administration of a lactobacilli-fermented milk was safe and effective in the prevention of antibiotic-associated diarrhea in hospitalized patients.

Examining the hygiene hypothesis: the Trial of Infant Probiotic Supplementation

The hygiene hypothesis suggests that the absence of infectious exposure at a critical point in immune system development leads to a greater risk for the later development of atopic disease. As a result, it may be possible to devise strategies that can block the onset of atopic diseases such as asthma. This paper outlines the rationale, background and design for the Trial of Infant Probiotic Supplementation study, which is designed to test the effectiveness of a daily infant probiotic supplement in the first 6 months of life in preventing the development of early markers of asthma.

Infectivity of Lactobacillus rhamnosus and Lactobacillus paracasei isolates in a rat model of experimental endocarditis

The potential pathogenicity of selected (potentially) probiotic and clinical isolates of Lactobacillus rhamnosus and Lactobacillus paracasei was investigated in a rat model of experimental endocarditis. In addition, adhesion properties of the lactobacilli for fibrinogen, fibronectin, collagen and laminin, as well as the killing activity of the platelet-microbicidal proteins fibrinopeptide A (FP-A) and connective tissue activating peptide 3 (CTAP-3), were assessed. The 90 % infective dose (ID(90)) of the L. rhamnosus endocarditis isolates varied between 10(6) and 10(7) c.f.u., whereas four of the six (potentially) probiotic L. rhamnosus isolates showed an ID(90) that was at least 10-fold higher (10(8) c.f.u.) (P<0.001). In contrast, the two other probiotic L. rhamnosus isolates exhibited an ID(90) (10(6) and 10(7) c.f.u.) comparable to the ID(90) of the clinical isolates of this species investigated (P>0.05). Importantly, these two probiotic isolates shared the same fluorescent amplified fragment length polymorphism cluster type as the clinical isolate showing the lowest ID(90) (10(6) c.f.u.). L. paracasei tended to have a lower infectivity than L. rhamnosus (ID(90) of 10(7) to > or =10(8) c.f.u.). All isolates had comparable bacterial counts in cardiac vegetations (P>0.05). Except for one L. paracasei strain adhering to all substrates, all tested lactobacilli adhered only weakly or not at all. The platelet peptide FP-A did not show any microbicidal activity against the tested lactobacilli, whereas CTAP-3 killed the majority of the isolates. In general, these results indicate that probiotic lactobacilli display a lower infectivity in experimental endocarditis compared with true endocarditis pathogens. However, the difference in infectivity between L. rhamnosus endocarditis and (potentially) probiotic isolates could not be explained by differences in adherence or platelet microbicidal protein susceptibility. Other disease-promoting factors may exist in these organisms and warrant further investigation.

Probiotics: contributions to oral health

Probiotics have been extensively studied for their health-promoting effects. The main field of research has been in the gastrointestinal tract. However, in the past few years probiotics have also been investigated in the oral health perspective, which is the topic of the present review. We discuss the mechanisms of bacterial adhesion, potential of probiotics in oral cavity colonization, interspecies interactions, and possible effects on immunomodulation, and means of probiotic administration. We suggest that probiotic treatment of diseases other than dental caries and periodontal disease should also be systematically investigated. In general, hardly any randomized controlled trials have been conducted in this area and the studies on probiotics vs oral health are still in their cradle. Hence, much more investigations are called for before any evidence-based conclusions can be drawn: if or not probiotic therapy can be recommended for oral health purposes.

Acute infectious pediatric gastroenteritis: beyond oral rehydration therapy

Worldwide diarrheal diseases are a leading cause of childhood morbidity and mortality. Improvements in gastroenteritis management have reduced the annual number of pediatric deaths attributable to gastroenteritis from 5 million in 1982 to 2 million over 20 years. Recent advances are likely to contribute further to a reduction in morbidity and mortality secondary to acute infectious gastroenteritis. A new generation of vaccines against rotavirus is entering into routine use. Research into antisecretory agents has demonstrated that this class of medications may play a significant role in the future management of acute infectious gastroenteritis. A significant body of literature has recently emerged supporting the use of the antiemetic agent ondansetron. In developing countries, the routine use of zinc is now recommended by many experts, while, in developed countries, the use of probiotic agents has been associated with significant benefits in acute infectious gastroenteritis. Finally, more aggressive intravenous rehydration strategies are being employed; however, at present, limited data from randomized clinical trials are available to support its routine use.

The role of a probiotics mixture in the treatment of childhood constipation: a pilot study

Background

Inconsistent data exist about the efficacy of probiotics in the treatment of constipation. Several studies in adults with constipation showed positive effects of probiotics on constipation. Inconsistent data exist regarding the effect of a single probiotic strain in constipated children. The aim of this pilot study was to determine the effect of a mixture of probiotics containing bifidobacteria and lactobacilli in the treatment of childhood constipation.

Methods

Children aged 4–16 years with constipation as defined by the Rome III criteria were eligible for the study. During a 4 week period, children received a daily mix of 4 × 10⁹ colony forming units of a probiotic mixture (Ecologic^®Relief) containing Bifidobacteria (B.) bifidum, B. infantis, B. longum, Lactobacilli (L.) casei, L. plantarum and L. rhamnosus. Primary outcome measures were frequency of bowel movements (BMs) per week and stool consistency. Secondary outcome measures were number of faecal incontinence episodes per week, abdominal pain and side effects.

Results

Twenty children, 50% male, median age 8 (range 4–16) were included.

The frequency of BMs per week increased from 2.0 (1.0–5.0) to 4.2 (0.0–16.0) in week 2 (p = 0.10) and 3.8 (2.1–7.0) in week 4 (p = 0.13). In 12 children presenting with <3 BMs/week, BMs per week increased significantly from 1.0 (0.0–2.0) to 3.0 (0.0–7.0) in week 2 (p = 0.01) and 3.0 (0.0–10.0) in week 4 (p = 0.01). The stool consistency was reported as hard in 7 children at baseline, in 4 children at week 2 (p = 0.23) and in 6 children after 4 weeks of treatment (p = 1.00). A significant decrease in number of faecal incontinence episodes per week was found in the entire group: 4.0 (0.0–35.0) to 1.5 (0.0–14.0) in week 2 (p = 0.01) and 0.3 (0.0–7.0) in week 4 (p = 0.001). The presence of abdominal pain decreased significantly from 45% to 25% in week 2 (p = 0.04) and 20% at week 4 (p = 0.006). No side effects were reported.

Conclusion

This pilot study shows that a mixture of probiotics, has positive effects on symptoms of constipation. To confirm these findings, a large randomised placebo controlled trial is required.

Design of a multispecies probiotic mixture to prevent infectious complications in critically ill patients

BACKGROUND & AIMS

Although the potential for probiotics is investigated in an increasing variety of diseases, there is little or no consensus regarding the desired probiotic properties for a particular disease in question, nor about the final design of the probiotic. Specific strain selection procedures were undertaken to design a disease-specific multispecies probiotic.

METHODS

From a strain collection of 69 different lactic acid bacteria a primary selection was made of 14 strains belonging to different species showing superior survival in a simulated gastrointestinal environment. Functional tests like antimicrobial activity against a range of clinical isolates and cytokine inducing capacity in cultured human peripheral blood mononuclear cells were used to further identify potential strains.

RESULTS

Specific strains inhibited growth of clinical isolates whereas others superiorly induced the anti-inflammatory cytokine IL-10. Based on functional tests and general criteria regarding probiotic design and safety, a selection of the following six strains was made (Ecologic 641); Bifidobacterium bifidum, Bifidobacterium infantis, Lactobacillus acidophilus, Lactobacillus casei, Lactobacillus salivarius and Lactococcus lactis. Combination of these strains resulted in a wider antimicrobial spectrum, superior induction of IL-10 and silencing of pro-inflammatory cytokines as compared to the individual components.

CONCLUSIONS

Application of strict criteria during the design of a disease-specific probiotic prior to implementation in clinical trials may provide a rational basis for use of probiotics.

Antimicrobial susceptibilities of Lactobacillus, Pediococcus and Lactococcus human isolates and cultures intended for probiotic or nutritional use

OBJECTIVES

To determine MICs of 16 antimicrobials representing all major classes for 473 taxonomically well-characterized isolates of lactic acid bacteria (LAB) encompassing the genera Lactobacillus, Pediococcus and Lactococcus. To propose tentative epidemiological cut-off (ECOFF) values for recognizing intrinsic and acquired antimicrobial resistances in numerically dominant species.

METHODS

On the basis of depositors' information, LAB were grouped in categories of probiotic, nutritional, probiotic or nutritional research, human and animal isolates and tested for their antibiotic susceptibilities by broth microdilution using LAB susceptibility test medium (LSM). Tentative ECOFFs were defined according to the recommendations of the European Committee on Antimicrobial Susceptibility Testing. Isolates showing acquired antimicrobial resistance(s) were selected for PCR-based detection of resistance gene(s) and in vitro conjugative transfer experiments.

RESULTS

Tentative ECOFF values of 13 antibiotics were determined for up to 12 LAB species. Generally, LAB were susceptible to penicillin, ampicillin, ampicillin/sulbactam, quinupristin/dalfopristin, chloramphenicol and linezolid. LAB exhibited broad or partly species-dependent MIC profiles of trimethoprim, trimethoprim/sulfamethoxazole, vancomycin, teicoplanin and fusidic acid. Three probiotic Lactobacillus strains were highly resistant to streptomycin. Although erythromycin, clindamycin and oxytetracycline possessed high antimicrobial activities, 17 Lactobacillus isolates were resistant to one or more of these antibiotics. Eight of them, including six probiotic and nutritional cultures, possessed erm(B) and/or tet(W), tet(M) or unidentified members of the tet(M) group. In vitro intra- and interspecies filter-mating experiments failed to show transfer of resistance determinants.

CONCLUSIONS

Finding of acquired resistance genes in isolates intended for probiotic or nutritional use highlights the importance of antimicrobial susceptibility testing in documenting the safety of commercial LAB.

Special circumstances: trophic feeds, necrotizing enterocolitis and bronchopulmonary dysplasia

There are many unresolved issues regarding how to feed the extremely-low-birth-weight (ELBW) infant. Trophic feedings of small volumes of breast milk or formula do not appear to increase the incidence of necrotizing enterocolitis (NEC). For prevention of NEC, breast milk, antenatal steroids and fluid restriction each confers a benefit. Because the incidence of NEC is relatively low, to determine if a particular prevention strategy is effective, large numbers of infants would need to be enrolled in a prospective, randomized controlled trial, and such trials are rare. Candidate therapies for NEC prevention that warrant further study include oral immunoglobulins, probiotics, long-chain polyunsaturated fatty acids and arginine. Suboptimal nutrition in ELBW infants is common in the early postnatal period. This is also the most critical time for the development of bronchopulmonary dysplasia, when even brief periods of malnutrition have significant effects on lung development and growth.

Potential uses of probiotics in the neonate

Probiotics are specific microbes that, when consumed, contribute to the management of disease or to reducing the risk of disease. Probiotic bacteria have been shown to have several effects that might be of benefit to the neonate, including: modulating the establishment of intestinal microbiota, degrading antigens, promoting mucosal barrier functions and inhibiting mucosal pathogen adherence, and enhancing the maturation of the innate and adaptive immune systems. Results from clinical trials suggest that specific probiotics might be useful in reducing the risk of necrotising enterocolitis and infectious disease in infancy. In addition, probiotic supplementation commenced in the neonatal period might reduce the risk of atopic disease in later life. These data are preliminary, and a number of issues need to be resolved before general guidelines regarding the use of probiotics in the neonatal period can be given.

Characterization of Lactobacillus plantarum PH04, a potential probiotic bacterium with cholesterol-lowering effects

The bacterium Lactobacillus plantarum PH04 was isolated from infant feces and tested positive for bile/acid tolerance and bile salt hydrolase activity. It was evaluated as a potential probiotic with cholesterol-lowering effect. Bile salt hydrolase activity was nine times greater in stationary phase than in exponential phase cells and increased when the cells were exposed to conjugated bile salts. L. plantarum PH04 was resistant to seven of nine antibiotics tested and did not produce beta-glucuronidase. L. plantarum PH04 was fed to hypercholesterolemic mice at numbers of 10(7) CFU per mouse per day for 14 days. Compared with a control group, the serum cholesterol and triglycerides were respectively 7 and 10% lower in the group fed L. plantarum PH04, and fecal lactic acid bacteria increased while no any significant differences (P<0.05) in body weight, visceral weigh index or bacteria translocation between two groups were observed. The results indicated that L. plantarum PH04 might be effective as a probiotic with cholesterol-lowering activities.

Probiotics for prevention of recurrent urinary tract infections in women: a review of the evidence from microbiological and clinical studies

Recurrent urinary tract infections (UTIs) afflict a great number of women around the world. The use of probiotics, especially lactobacilli, has been considered for the prevention of UTIs. Since lactobacilli dominate the urogenital flora of healthy premenopausal women, it has been suggested that restoration of the urogenital flora, which is dominated by uropathogens, with lactobacilli may protect against UTIs. This review is based on a search of PubMed for relevant articles. Many in vitro studies, animal experiments, microbiological studies in healthy women, and clinical trials in women with UTIs have been carried out to assess the effectiveness and safety of probiotics for prophylaxis against uropathogens. Most of them had encouraging findings for some specific strains of lactobacilli. Lactobacillus rhamnosus GR-1 and L. reuteri RC-14 (previously called L. fermentum RC-14) seemed to be the most effective among the studied lactobacilli for the prevention of UTIs. L. casei shirota and L. crispatus CTV-05 have also shown efficacy in some studies. L. rhamnosus GG did not appear to be quite as effective in the prevention of UTIs. The evidence from the available studies suggests that probiotics can be beneficial for preventing recurrent UTIs in women; they also have a good safety profile. However, further research is needed to confirm these results before the widespread use of probiotics for this indication can be recommended.

Probiotics: from research to consumer

Intestinal microflora has metabolic, trophic and protective functions, and can be modified in pathological conditions and by the exogenous administration of probiotics. Probiotics are defined as living microorganisms which resist gastric, bile, and pancreatic secretions, attach to epithelial cells and colonize the human intestine. In the last twenty years research has been focused on the identification of the role of planktonic flora and adhesive bacteria in health and disease, and on the requisite of bacterial strains to become probiotic product which can be marketed. Probiotics can be commercialized either as nutritional supplements, pharmaceuticals or foods, but the marketing as a pharmaceutical product requires significant time, complex and costly research, and the demonstration of a well-defined therapeutic target. This review examines the sequential steps of research which, from the identification of a possible probiotic strain, lead to its production and marketing, summarizing the whole process existing behind its development, through its growth in laboratory, the studies performed to test its resistance to human secretions and stability, microencapsulation technologies, and safety tests.

Évaluation d'une préparation pour nourrissons à teneur réduite en protéines et enrichie en probiotiques, en relais de l'allaitement maternel

Besides assuring growth and development in early infancy, human breast milk plays a key role in preventing infections, in particular by favouring the growth of bifidobacteria. The development of infant formulas containing probiotic agents consequently represents a significant advance in the provision of an optimal alternative to breast feeding when this is not feasible. A further concern is to avoid an excessively high protein content relative to breast milk, potentially favouring obesity in later life.

OBJECTIVES

The objective of this open Multicenter comparative study was to demonstrate that a new infant formula, characterized by a reduced protein content and the presence of a probiotic agent, was as effective as conventional formulas in assuring growth during the first months of life.

POPULATION AND METHODS

The study population comprised full-term healthy infants with an age at inclusion of 1-28 days, whose mothers no longer wished to continue breast feeding or were unable to breast feed. The test formula (GE), enriched with Bifidobacterium lactis, had a protein content of 1.5 g/100 ml. The primary end point was daily weight gain from day 0 to day 90. Secondary end points were daily increase in height and cranial circumference, overall and gastrointestinal tolerance and formula acceptability. A total of 203 infants were included in the analysis, 117 receiving GE and 86 the formula habitually prescribed by the paediatrician.

RESULTS

Daily gains in weight, height and cranial circumference did not differ significantly between the groups. The rates of overall and gastrointestinal adverse events were comparable in the two groups and the acceptability of GE was consistently good, similar to that of the standard formulas.

CONCLUSION

The results of this study demonstrated that the new probiotic infant formula GE has equivalent efficacy to conventional formulas in achieving growth in early infancy, and is well tolerated.

Summary of probiotic activities of Bifidobacterium lactis HN019

The bacterium, Bifidobacterium lactis HN019, has been studied for a variety of traits important to its ability to function as a probiotic. Publications documenting identity, safety, antipathogenic effects, immune enhancement, and intestinal colonization are reviewed. Most studies documenting immune effects are short term in duration (< or =6 wk feeding periods), so longer term trials would be useful to determine to what extent effects are sustained. One year-long trial feeding both galacto-oligosaccharides and HN019 in children 1 to 3 years of age provided evidence for improved growth and reduction in infection incidence. HN019 is a well-characterized probiotic strain with documented probiotic effects of meaningful magnitude especially in the area of immune system modulation.

Absence of efficacy of nonviable Lactobacillus acidophilus for the prevention of traveler's diarrhea: a randomized, double-blind, controlled study

BACKGROUND

Diarrhea is the most common illness associated with international tourism. We evaluated the efficacy of a probiotic preparation of nonviable Lactobacillus acidophilus (hereafter referred to as LA) for the prevention of traveler's diarrhea.

METHODS

We conducted a randomized, double-blind, controlled trial. Travelers were randomized to receive either LA or placebo twice daily from 1 day before their departure to 3 days after their return. On each day of the trip and the week following the return, travelers had to record the number and consistency of stools and their adherence to the treatment. Diarrhea was defined as > or =3 unformed stools in a 24-h period.

RESULTS

From January 2001 to September 2004, a total of 174 subjects were randomized to each treatment group. Half of the travelers went to West Africa, and organized tours or backpacking were the most common modes of traveling. The incidence of diarrhea did not differ between the 2 groups; it was 61.4 cases per 100 person-months in the LA group (95% confidence interval [CI], 44.1-85.5) and 43.4 cases per 100 person-months in the placebo group (95% CI, 30.0-62.9) (P=.14). Adjustment for travel duration and other variables did not reveal any difference between the 2 groups (adjusted hazard ratios comparing the LA and placebo groups were 1.43 [95% CI, 0.87-2.36] in an intent-to-treat analysis and 1.38 [95% CI, 0.79-2.39] in an efficacy analysis).

CONCLUSIONS

There was no beneficial effect of treatment with LA for the prevention of travelers' diarrhea. More studies are required to assess the efficacy of other specific probiotics (e.g., a Lactobacillus rhamnosus GG preparation) for preventing traveler's diarrhea.

Beneficial lactobacilli in food and feed: long-term use, biodiversity and proposals for specific and realistic safety assessments

Lactobacilli have played a crucial role in the production of fermented products for millennia. Their probiotic effects have recently been studied and used in new products. Isolated cases of lactobacillemia have been reported in at-risk populations, but lactobacilli present an essentially negligible biological risk. We analyzed the current European guidelines for safety assessment in food/feed and conclude that they are not relevant for the Lactobacillus genus. We propose new specific guidelines, beginning by granting a 'long-standing presumption of safety' status to Lactobacillus genus based on its long history of safe use. Then, based on the available body of knowledge and intended use, only such tests as are useful will be necessary before attributing 'qualified presumption of safety' status.

Probiotic lactobacilli and bacteraemia in Stockholm

The objective of the present study was to determine the incidence of lactobacilli-induced bacteraemia in Stockholm, Sweden, between January 1998 and March 2004, and to identify the possible presence of probiotic strains. Isolated strains were checked for growth on selective lactobacilli-agar and the biochemical profiles were determined. The lactobacilli strains were further analysed with molecular methodologies to ascertain eventual similarities with the probiotic strains Lactobacillus paracasei subsp. paracasei F19 (LMG P 17806), Lactobacillus acidophilus NCFB 1748 and Lactobacillus rhamnosus GG (ATCC 53103). The minimum inhibitory concentrations of selected antimicrobial agents were determined by the agar dilution method. The incidence of bacteraemia cases caused by lactobacilli remained at the same level during the study period and constituted to <1% of the total number of bacteraemia cases each y. L. paracasei subsp. paracasei F19, L. acidophilus NCFB 1748 and L. rhamnosus GG were not identified in any of the samples.

Probiotic use in clinical practice: what are the risks?

Probiotics have been advocated for the prevention and treatment of a wide range of diseases, and there is strong evidence for their efficacy in some clinical scenarios. Probiotics are now widely used in many countries by consumers and in clinical practice. Given the increasingly widespread use of probiotics, a thorough understanding of their risks and benefits is imperative. In this article we review the safety of probiotics and discuss areas of uncertainty regarding their use. Although probiotics have an excellent overall safety record, they should be used with caution in certain patient groups-particularly neonates born prematurely or with immune deficiency. Because of the paucity of information regarding the mechanisms through which probiotics act, appropriate administrative regimens, and probiotic interactions, further investigation is needed in these areas. Finally, note that the properties of different probiotic species vary and can be strain-specific. Therefore, the effects of one probiotic strain should not be generalized to others without confirmation in separate studies. Careful consideration should be given to these issues before patients are advised to use probiotic supplements in clinical practice.

Probiotics in primary care pediatrics

Probiotics are live microorganisms that help stabilize and balance intestinal microflora. Although these organisms are ubiquitous and have been used in the production of foods, probiotics have been used more frequently for therapeutic purposes, including the treatment and prevention of pediatric diseases. This article reviews the proposed mechanisms of the beneficial effects of probiotics, potential uses of these organisms in pediatric care, and promising future directions for their application.

Use of probiotics in children with acute diarrhea

Probiotics, defined as microbial cell preparations or components of microbial cells that have a beneficial effect on the health and well being of the host, have traditionally been used to treat and prevent a variety of infections. Beneficial effects of probiotics in acute infectious diarrhea in children seem to be: (i) moderate; (ii) strain-dependent; (iii) dose dependent; (iv) significant in watery diarrhea and viral gastroenteritis, but non-existent in invasive, bacterial diarrhea; and (v) more evident when treatment with probiotics is initiated early in the course of disease. Three large, randomized controlled trials (RCTs) provide evidence of a very modest effect (statistically significant, but of questionable clinical importance) of some probiotic strains (Lactobaccillus GG, Lactobaccillus reuteri, Bifodobacterium lactis) on the prevention of community-acquired diarrhea. We have found conflicting evidence from four RCTs on the efficacy of Lactobacillus GG and B. bifidum and Streptococcus thermophilus in the prevention of nosocomial diarrhea in children. Two RCTs in children provide evidence of a moderate beneficial effect of Lactobacillus GG in the prevention of antibacterial-associated diarrhea (AAD), but results in adults are conflicting. Data on the efficacy of other probiotic strains in AAD in children are very limited. In conclusion, to date, the most extensively studied and best documented clinical application of probiotics in children is for the treatment of acute watery diarrhea of rotaviral or presumably viral etiology. Studies documenting effects in other types of diarrheal diseases in children are limited, although some preliminary results are promising. The effects of different probiotic microorganisms are not equal. Only very few probiotic strains have been tested rigorously in RCTs. Many questions remain to be answered. Future clinical trials should evaluate carefully selected, precisely defined probiotic strains and address clinically important endpoints.

Small intestinal bacterial overgrowth: roles of antibiotics, prebiotics, and probiotics

Small intestinal bacterial overgrowth is common in intestinal failure. Its occurrence relates to alterations in intestinal anatomy, motility, and gastric acid secretion. Its presence may contribute to symptoms, mucosal injury, and malnutrition. Relationships between bacterial overgrowth and systemic sepsis are of potential importance in the intestinal failure patient because the direct translocation of bacteria across the intestinal epithelium may contribute to systemic sepsis: a phenomenon that has been well established in experimental animal models. The accurate diagnosis of bacterial overgrowth continues to present a number of challenges in clinical practice and especially so among patients with intestinal failure. The management of patients with bacterial overgrowth remains, for the most part, primarily empiric and comprises antibiotic therapy and correction of any associated nutritional deficiencies. Although evidence from experimental animal studies consistently indicates that probiotics exert barrier-enhancing, antibacterial, immune-modulating, and anti-inflammatory effects, which all could be benefits in small intestinal bacterial overgrowth and intestinal failure, their role in human beings remains to be evaluated adequately.

Clinical safety of Lactobacillus casei shirota as a probiotic in critically ill children

OBJECTIVE

Diarrhea is frequently observed among critically ill children (CIC) admitted for intensive care. There is increasing evidence that probiotics decrease the incidence of acute infectious and nosocomial and antibiotic induced diarrhea amongst children hospitalized in nonintensive care settings. Despite theoretic advantages for the use of probiotics in CIC, safety has remained a concern in this vulnerable group. The objective of this study was to establish clinical safety (invasive infection/colonization) of Lactobacillus casei shirota (LCS) used as a probiotic in CIC.

METHODS

Prospective, descriptive pilot study on children admitted to a pediatric intensive care unit. Data regarding safety were collected on the initial recruits to a randomized controlled trial aimed to study the effects of LCS on stool frequency and consistency in CIC. Safety was assessed by bacteriologic surveillance for LCS in surface swabs and endotracheal aspirates (colonization) as well as blood, urine, and sterile body fluid cultures (invasive infection/bacteremia).

RESULTS

Safety data were available on 28 patients. LCS was cultured from the feces of five of the six study subjects who opened bowels during their stay on the pediatric intensive care unit. There was no evidence of either colonization or bacteremia with LCS in bacteriologic cultures obtained from study subjects. The preparation was well tolerated with no apparent side effects.

CONCLUSIONS

Our pilot safety study suggests that the use of LCS as a probiotic in enterally fed CIC is safe.

Living drugs for gastrointestinal diseases: the case for probiotics

Nonpathogenic micro-organisms may contain or produce molecules of potential therapeutic interest. This led to the concept of using ingested living micro-organisms to produce and transport these molecules to targets in the proximal or distal intestine. Several characteristics of this pharmacological approach are very original: potential for in vivo production of active molecules, for targeting immune cells, for presenting immunogenic molecules in a microbial context, for duodenal delivery using bile sensitivity. Probiotics have been studied for some decades and more recently worm eggs have also received some interest. This paper summarizes facts (especially results of randomized controlled trials and pharmacokinetic studies), and ideas about the use of probiotics to treat or prevent gastrointestinal diseases. The safety of this approach (exceptional cases of infections have been observed), and the potential for using new agents or genetically modified micro-organisms (ongoing trials in humans with Crohn's disease) are also discussed.

Nutritional care of the patient with constipation

Chronic constipation is defined as a symptom-based disorder based on the presence for at least 3 months in the last year of unsatisfactory defecation characterized by infrequent stools, difficult stool passage, or both. On the other hand, the presence of clinically important abdominal discomfort or pain associated with constipation defines irritable bowel syndrome (IBS) with constipation. Intake of dietary fibre and bulking agents (psyllium) may be effective in alleviating chronic constipation in patients without slow colonic transit or disordered constipation. On the other hand, fibre may improve stool consistency in patients with IBS with constipation, but it is considered to be not effective in improving abdominal pain, distension or bloating. Probiotics may be effective in relieving constipation; however, the effect of lactic acid bacteria ingestion may be dependent on the bacterial strain used and the population being studied. Lactulose, which is a substrate for lactic acid bacteria (prebiotic), is effective to treat patients with chronic constipation.

Soluble factors from Lactobacillus GG activate MAPKs and induce cytoprotective heat shock proteins in intestinal epithelial cells

Conditioned media from the probiotic Lactobacillus GG (LGG-CM) induce heat shock protein (Hsp) expression in intestinal epithelial cells. LGG-CM induces both Hsp25 and Hsp72 in a time- and concentration-dependent manner. These effects are mediated by a low-molecular-weight peptide that is acid and heat stable. DNA microarray experiments demonstrate that Hsp72 is one of the most highly upregulated genes in response to LGG-CM treatment. Real-time PCR and electrophoretic mobility shift assay confirm that regulation of Hsp induction is at least in part transcriptional in nature, involving heat shock factor-1. Although Hsps are not induced for hours after exposure, transient exposure to LGG-CM is sufficient to initiate the signal for Hsp induction, suggesting that signal transduction pathways may be involved. Experiments confirm that LGG-CM modulates the activity of certain signaling pathways in intestinal epithelial cells by activating MAP kinases. Inhibitors of p38 and JNK block the expression of Hsp72 normally induced by LGG-CM. Functional studies indicate that LGG-CM treatment of gut epithelial cells protects them from oxidant stress, perhaps by preserving cytoskeletal integrity. By inducing the expression of cytoprotective Hsps in gut epithelial cells, and by activating signal transduction pathways, the peptide product(s) secreted by LGG may contribute to the beneficial clinical effects attributed to this probiotic.

Probiotics under the regulatory microscope

This review examines current knowledge regarding the safety of probiotic bacteria in man. Tighter and more comprehensive standards and regulations will be developed as probiotic therapy moves from a limited number of products used in the food industry, into more defined therapeutic categories and more complex organisms. A new framework considering probiotics as nonspecific promoters of mucosal immunity, defines probiotic characteristics and the clinical circumstances in which it is used. For example, those with immune deficiency taking a high dose of viable bacteria may have an increased risk. A wider range of bacteria is now being used, sometimes in territories other than the gut mucosa. The question of competition with multiple isolates must be addressed, as does the use of nonselected faecal isolates. Transfer of antibiotic resistance with probiotics acting as a 'shuttle' needs clarification. These issues are addressed and reviewed as probiotics evolve into a new therapeutic arena.

Review article: bifidobacteria as probiotic agents -- physiological effects and clinical benefits

Bifidobacteria, naturally present in the dominant colonic microbiota, represent up to 25% of the cultivable faecal bacteria in adults and 80% in infants. As probiotic agents, bifidobacteria have been studied for their efficacy in the prevention and treatment of a broad spectrum of animal and/or human gastrointestinal disorders, such as colonic transit disorders, intestinal infections, and colonic adenomas and cancer. The aim of this review is to focus on the gastrointestinal effects of bifidobacteria as probiotic agents in animal models and man. The traditional use of bifidobacteria in fermented dairy products and the GRAS ('Generally Recognised As Safe') status of certain strains attest to their safety. Some strains, especially Bifidobacterium animalis strain DN-173 010 which has long been used in fermented dairy products, show high gastrointestinal survival capacity and exhibit probiotic properties in the colon. Bifidobacteria are able to prevent or alleviate infectious diarrhoea through their effects on the immune system and resistance to colonization by pathogens. There is some experimental evidence that certain bifidobacteria may actually protect the host from carcinogenic activity of intestinal flora. Bifidobacteria may exert protective intestinal actions through various mechanisms, and represent promising advances in the fields of prophylaxis and therapy.

Bifidobacterial lipoglycan as a new cause for false-positive platelia Aspergillus enzyme-linked immunosorbent assay reactivity

We previously hypothesized that a lipoglycan of Bifidobacterium bifidum subsp. pennsylvanicum cross-reacts with the Platelia Aspergillus (PA) enzyme-linked immunosorbent assay (ELISA) based on the presence of galactofuranosyl epitopes in the cell wall (M. A. S. H. Mennink-Kersten, R. R. Klont, A. Warris, H. J. M. Op den Camp, and P. E. Verweij, Lancet 363:325-327, 2004). We tested this hypothesis by testing bacterial suspensions of different bifidobacterial species and other gram-positive and -negative bacteria with the PA ELISA, which is used to detect circulating galactomannan for the serodiagnosis of invasive aspergillosis. Furthermore, neonatal fecal samples were enumerated for bifidobacteria by fluorescence in situ hybridization (FISH) and tested for PA ELISA reactivity. All bifidobacteria, except B. infantis and B. adolescentis, showed reactivity 6- to 600-fold higher compared to the controls (i.e., Micrococcus luteus and Propionibacterium freudenreichii, which contain a cell wall lipomannan). Eggerthella lenta showed a 25-fold-higher reactivity. ELISA reactivity was clearly shown to be associated with bacterial lipoglycans containing a beta-1,5-galactofuranosyl chain. All neonatal feces showed PA ELISA reactivity and associated numbers of bifidobacteria. Since high concentrations of bifidobacteria are present in the human gut, these bacteria or excreted lipoglycan may cause false serum PA ELISA reactivity in selected patient groups, especially neonates.

A probiotic mixture alleviates symptoms in irritable bowel syndrome patients: a controlled 6-month intervention

BACKGROUND

Irritable bowel syndrome is a gastrointestinal disorder of unknown aetiology. The effect of probiotics in this syndrome remains unclear.

AIM

To investigate whether a probiotic mixture containing Lactobacillus rhamnosus GG, L. rhamnosus LC705, Bifidobacterium breve Bb99 and Propionibacterium freudenreichii ssp. shermanii JS is effective in alleviating irritable bowel syndrome symptoms.

METHODS

A total of 103 patients fulfilling the Rome I or II criteria took part in this 6-month, randomized, double-blind placebo-controlled trial. The patients received a probiotic capsule or a placebo capsule daily. Gastrointestinal symptoms and bowel habits were recorded.

RESULTS

At the end the total symptom score (abdominal pain + distension + flatulence + borborygmi) was 7.7 (95% CI: -13.9 to -1.6) points lower in the probiotic group (P = 0.015). This represents a median reduction of 42% in the symptom score of the probiotic group compared with 6% in the placebo group. In individual symptoms, borborygmi was milder in the probiotic group (P = 0.008), and for the rest of the symptoms there was a non-significant trend.

CONCLUSIONS

The results indicate that this probiotic mixture is effective in alleviating irritable bowel syndrome symptoms. Considering the high prevalence of irritable bowel syndrome and the lack of effective therapies, even a slight reduction in symptoms could have positive public health consequences.

Antibiotic susceptibility patterns and resistance genes of starter cultures and probiotic bacteria used in food

A survey of starter and probiotic cultures was carried out to determine the current antibiotic resistance situation in microbial food additives in Switzerland. Two hundred isolates from 90 different sources were typed by molecular and other methods to belong to the genera Lactobacillus (74 samples), Staphylococcus (33 samples), Bifidobacterium (6 samples), Pediococcus (5 samples), or were categorized as lactococci or streptococci (82 samples). They were screened for phenotypic resistances to 20 antibiotics by the disk diffusion method. Twenty-seven isolates exhibiting resistances that are not an intrinsic feature of the respective genera were further analyzed by microarray hybridization as a tool to trace back phenotypic resistances to specific genetic determinants. Their presence was finally verified by PCR amplification or Southern hybridization. These studies resulted in the detection of the tetracycline resistance gene tet(K) in 5 Staphylococcus isolates used as meat starter cultures, the tetracycline resistance gene tet(W) in the probiotic cultures Bifidobacterium lactis DSM 10140 and Lactobacillus reuteri SD 2112 (residing on a plasmid), and the lincosamide resistance gene lnu(A) (formerly linA) in L. reuteri SD 2112.

The probiotic approach: an alternative treatment option in urology

OBJECTIVE

The prophylactic and therapeutic use of probiotic microorganisms is a wide and still controversial field. The review paper is aimed to summarize recent findings on the health-benefiting effects of probiotics in urological diseases. The use of certain beneficial strains against urogenital infections, bladder cancer recurrence and renal stone formation is discussed.

METHODS

Literature search of PubMed documented publications and abstracts from meetings.

RESULTS

Various clinical trials have now been performed which substantiate the beneficial effects of the probiotic strains L. rhamnosus GR-1, L. fermentum RC-14 and L. crispatus CTV-05 against urogenital infections, such as urinary tract infections and bacterial vaginosis. The potential of L. casei Shirota to reduce the recurrence rate of bladder cancer is one of the most intriguing examples for the use of probiotics in medical practice. The use of O. formigenes in the prevention of calcium oxalate stone disease was only recently suggested and needs to be further investigated.

CONCLUSION

Clinical trials increasingly provide a profound scientific basis for the use of probiotics in medicinal practice including urology. Efforts to make probiotic products available which are validated according to the guidelines recommended by the WHO and FAO and produced according to Good Manufacturing Practice will contribute to the acceptance of probiotic therapy by both the physicians and the patients.

Alternative treatments for Clostridium difficile disease: what really works?

Vancomycin and metronidazole have been used for treating Clostridium difficile-associated disease (CDAD) for the past 25 years, but approximately 20 % of patients develop recurrent disease. The increasing incidence of nosocomial outbreaks, cases of recurrent CDAD and other complications (toxic megacolon, ileus, sepsis) has fuelled the search for different types of treatments. As the understanding of the pathogenesis of this disease has matured, newer treatment strategies that take advantage of these mechanisms have been developed. This review will describe such treatments and examine the evidence for each strategy.

Lactobacilli – bacteria–host interactions with special regard to the urogenital tract

Lactobacilli are part of the commensal human mucosal flora. Their application as probiotics in dairy products such as yoghurt has increased during the last century since a health promoting effect has been reported. Much work has been done to study the effects of these bacteria on the immune system and epithelial cells, mainly focused on the intestinal mucosa as the field of first contact. This review is aimed to present and discuss results concerning interactions of lactobacilli and immune system or epithelial cells with focus to urogenital mucosa.

Lactobacillus rhamnosus GG bacteremia associated with probiotic use in a child with short gut syndrome

Probiotic agents are increasingly used for the treatment and prevention of a variety of infectious and inflammatory conditions. They are generally safe, but complications of probiotic use can occur. In this report, we describe bacteremia after ingestion of a Lactobacillus rhamnosus GG probiotic tablet in a child with short gut syndrome. We used sequencing of the ribosomal operon region and strain typing with pulsed field electrophoresis of the isolates to show identity between the tablet and bloodstream isolates.

Bile-mediated aminoglycoside sensitivity in Lactobacillus species likely results from increased membrane permeability attributable to cholic acid

Few studies have been conducted on antimicrobial resistance in lactobacilli, presumably because of their nonpathogenic nature as anaerobic commensals. We assessed resistance in 43 type strains and isolates representing 14 species by using agar disk diffusion and MIC analysis in MRS medium. Most noteworthy were two general phenotypes displayed by nearly every strain tested: (i) they were more susceptible (up to 256-fold in some cases) to the deconjugated bile acid cholic acid than to the conjugate taurocholic or taurodeoxycholic acid, and (ii) they became susceptible to aminoglycosides when assayed on agar medium containing 0.5% fractionated bovine bile (ox gall). Two-dimensional MIC analyses of one representative strain, Lactobacillus plantarum WCFS1, at increasing concentrations of ox gall (0 to 30.3 mg/ml) displayed corresponding decreases in resistance to all of the aminoglycosides tested and ethidium bromide. This effect was clinically relevant, with the gentamicin MIC decreasing from >1,000 to 4 mug/ml in just 3.8 mg of ox gall per ml. In uptake studies at pH 6.5, [G-3H]gentamicin accumulation increased over control levels when cells of this strain were exposed to bile acids or reserpine but not when they were exposed to carbonyl cyanide m-chlorophenylhydrazone. The effect was dramatic, particularly with cholic acid, increasing up to 18-fold, whereas only modest increases, 3- and 5-fold, could be achieved with taurocholic acid and ox gall, respectively. Since L. plantarum, particularly strain WCFS1, is known to encode bile salt hydrolase (deconjugation) activity, our data indicate that mainly cholic acid, but not taurocholic acid, effectively permeabilizes the membrane to aminoglycosides. However, at pHs approaching neutral conditions in the intestinal lumen, aminoglycoside resistance due to membrane impermeability may be complemented by a potential efflux mechanism.