On the safety of lactic acid bacteria from food

Safety considerations for dietary supplement manufacturers in the United States

Due to significant dietary supplement use in the US, product manufacturers must understand the importance of implementing a robust approach to establishing safety for all ingredients, including dietary ingredients, components, and finished dietary supplement products. Different regulatory pathways exist by which the safety of dietary ingredients can be established, and thus allowed to be marketed in a dietary supplement. For individual dietary ingredients, safety information may come from a variety of sources including history of safe use, presence of the ingredient in foods, and/or non-clinical and clinical data. On occasion safety data gaps are identified for a specific ingredient, particularly those of botanical origin. Modern toxicological methods and models can prove helpful in satisfying data gaps and are presented in this review. For finished dietary supplement products, issues potentially impacting safety to consider include claims, product labeling, overages, contaminants, residual solvents, heavy metals, packaging, and product stability. In addition, a safety assessment does not end once a product is marketed. It is important that manufacturers actively monitor and record the occurrence of adverse events reported in association with the use of their products, in accordance with the law. Herein, we provide a comprehensive overview of considerations for assessing dietary supplement safety.

Safety Assessment and Probiotic Potential Comparison of Bifidobacterium longum subsp. infantis BLI-02, Lactobacillus plantarum LPL28, Lactobacillus acidophilus TYCA06, and Lactobacillus paracasei ET-66

Bifidobacterium longum subsp. infantis BLI-02, Lactobacillus paracasei ET-66, Lactobacillus plantarum LPL28, and Lactobacillus acidophilus TYCA06, isolated from healthy breast milk, miso, and the healthy human gut, were assessed for safety in this study. BLI-02, LPL28, TYCA06, and ET-66 exhibited no antibiotic resistance and mutagenic activity in the Ames test at the highest dosage (5000 μg/plate). No genotoxicity was observed in micronucleus and chromosomal aberration assays in rodent spermatogonia at the maximum dosage of 10 g/kg body weight (BW). No acute and sub-chronic toxicity occurred in mice and rats at the maximum tested dosage of 10 g/kg BW and 1.5 g/kg BW, respectively. The lyophilized powder of these strains survived a low pH and high bile salt environment, adhering strongly to Caco-2 cells. Unique antimicrobial activities were noted in these strains, with BLI-02 demonstrating the best growth inhibition against Vibrio parahaemolyticus, LPL28 exhibiting the best growth inhibition against Helicobacter pylori, and ET-66 showing the best growth inhibition against Aggregatibacter actinomycetemcomitans. Based on the present study, the lyophilized powder of these four strains appears to be a safe probiotic supplement at tested dosages. It should be applicable for clinical or healthcare applications.

Isolation of bacterial consortia with probiotic potential from the rumen of tropical calves

Probiotics are live microorganisms that confer health benefits to their animal host by balancing the composition of its gastrointestinal microbiota and modulating its immune response. In this work, we studied bacterial consortia isolated from the rumen of 28- and 42-day-old calves to select those showing probiotic capacity. Consortia were characterized and their growth dynamics were determined in several growth media. The number of viable bacteria was larger in the Man, Rogosa and Sharpe broth (MRS) than in nutritive medium A (MNA) and the largest was for A3D42. Antibiotic susceptibility of bacterial consortia in MRS was higher than in MNA and the most susceptible samples were A1D28 and A3D42. In turn, A3D42 showed the highest tolerance to bile salts in MRS and MNA. Moreover, all bacterial consortia showed optimal growth at pH 5, 5.5, 6 and 7 in both media, while their temperature tolerance was higher in MRS. The antagonistic activity of bacterial consortia in MNA was higher than in MRS with A2D42 showing the best antagonistic activity for Pseudomona aureginosa (ATCC 9027) and Staphylococcus aureus (ATCC 6538) in MNA. Additionally, A1D42 and A2D42 in MRS and A3D42 in MNA had significant adhesion to mucins, and A1D42 in MRS had the highest. Regarding their species composition, all bacterial consortia in MRS belonged to the phylum Firmicutes, and the class Bacilli and bacterial consortia in MNA belonged to three phyla; Proteobacteria, Firmicutes, and Bacteroidetes. Lactobacillus casei, Lactobacillus rhamnosus, Lactobacillus fermentum, and Lactobacillus johnsonii were identified in all bacterial consortia in MRS broth. Based on these results, A1D42 and A3D42 grown in MRS showed the best potential as probiotics for calves, which could result in health benefits and improve their production.

Considerations for determining safety of probiotics: A USP perspective

A history of safe use is a backbone of safety assessments for many current probiotic species, however, there is no global harmonization regarding requirements for establishing probiotic safety for use in foods and supplements. As probiotic manufacturers are increasingly seeking to use new strains, novel species, and next-generation probiotics, justification based on a significant history of use may be challenged. There are efforts underway by a variety of stakeholders, including the United States Pharmacopeia (USP), to develop best practices guidelines for assessing the quality and safety of probiotics. A current initiative of the USP seeks to provide expert advice specific to safety considerations for probiotics. Toward this goal, this review provides a helpful summary guide to global regulatory guidelines. We question the suitability of traditional animal toxicology studies designed for testing chemicals for relevance in assessing probiotic safety. This includes discussion of the use of excessive dose levels, the length of repeated dose toxicity studies needed, and the most suitable animal species used in toxicology studies. In addition, the importance of proper manufacturing practices with regard to final product safety are also included. Thus, an outline of essential parameters of a comprehensive safety assessment for a probiotic are provided.

Anti-cancer activity of human gastrointestinal bacteria

Malignant neoplasm is one of the most incurable diseases among inflammatory diseases. Researchers have been studying for decades to win over this lethal disease and provide the light of hope to humankind. The gastrointestinal bacteria of human hold a complex ecosystem and maintain homeostasis. One hundred trillion microbes are residing in the gastrointestinal tract of human. Disturbances in the microbiota of human's gastrointestinal tract can create immune response against inflammation and also can develop diseases, including cancer. The bacteria of the gastrointestinal tract of human can secrete a variety of metabolites and bioproducts which aid in the preservation of homeostasis in the host and gut. During pathogenic dysbiosis, on the other hand, numerous microbiota subpopulations may increase and create excessive levels of toxins, which can cause inflammation and cancer. Furthermore, the immune system of host and the epithelium cell can be influenced by gut microbiota. Probiotics, which are bacteria that live in the gut, have been protected against tumor formation. Probiotics are now studied to see if they can help fight dysbiosis in cancer patients undergoing chemotherapy or radiotherapy because of their capacity to maintain gut homeostasis. Countless numbers of gut bacteria have demonstrated anti-cancer efficiency in cancer treatment, prevention, and boosting the efficiency of immunotherapy. The review article has briefly explained the anti-cancer immunity of gut microbes and their application in treating a variety of cancer. This review paper also highlights the pre-clinical studies of probiotics against cancer and the completed and ongoing clinical trials on cancers with the two most common and highly effective probiotics Lactobacillus and Bacillus spp.

Antibiotic susceptibility of Lactobacillus plantarum strains, isolated from katak

Several Lactobacillus species are accepted as microorganisms with Qualified Presumption of Safety (QPS) in the EFSA’s list. One of them, Lactobacillus plantarum is a widely distributed species with a proven probiotic potential and technological relevance. In addition, every strain must complete several requirements, before implementation. Antibiotic susceptibility is one of EFSA’s important criteria regarding the safety of probiotics. The reason is to avoid any possibility of antibiotic resistance genes transfer to opportunistic pathogens in the gut. In the present study 14 Lactobacillus plantarum strains were assessed for susceptibility to 21 antibiotics from different groups. A high number of resistant strains was determined toward 12 antibiotics (penicillins – penicillin, piperacillin; IIIth generation cephalosporins – cefotaxime, ceftriaxone, ceftazidime; glycopeptides – vancomycin; tetracyclines – tetracycline; aminoglycosides – gentamicin; macrolides – clarithromycin; quinolones – nalidixic acid, ciprofloxacin, levofloxacin). Concerning the other tested antibiotics, strain-specific antibiotic-sensitivity patterns were observed. Antibiotic resistance was also discussed as an advantage in the selection of probiotic strains, however only when it is not transferable. Estimated susceptibility patterns of some of tested candidate probiotic strains are also important, considering the use of the latter as agents accompanying antibiotic therapy

The issue of the correct use of probiotics in the absence of recommendations

Antibiotics are important for saving both human health and life. Antibiotics destroy all bacteria within their spectrum, because they do not distinguish between good and bad bacteria. Even if an antibiotic therapy lasts only a few days, it may cause diarrhoea and mycosis. Antibiotics destroy most bacterial species in the intestines. These changes may affect one’s whole life. Today it is a challenge for medicine to be able to manipulate the microbiome so as to restore normal relations between microorganisms. At present, when antibiotics are abused, probiotics are very often applied. However, as there are no recommendations, a lot of mistakes can be made when using them. Both drugs and dietary supplements can be classified as probiotics. Medicinal probiotics are subject to very strict registration requirements and their use is associated with a specific disease or ailment. Probiotic microorganisms must be classified according to their genus, species and strain. These preparations may contain one or more probiotic strains depending on its application. At present there are no established schemes or rules concerning the dosage of probiotic preparations. This issue arouses numerous controversies. It is assumed that the probiotic should be applied at a dose which proved to have a beneficial effect in tests conducted on humans. Patients usually make decisions on the choice and dosage of preparations themselves. Individualised probiotic therapy is the key to success. There is no universal preparation – a specific probiotic should be used in a particular clinical case.

Identification, Classification and Screening for γ-Amino-butyric Acid Production in Lactic Acid Bacteria from Cambodian Fermented Foods

Screening for various types of lactic acid bacteria (LAB) that form the biological agent γ-amino-butyric acid (GABA) is important to produce different kinds of GABA-containing fermented foods. So far, no GABA-producing LAB have been reported from Cambodian fermented foods. Most small-scale fermentations and even some industrial processes in this country still rely on indigenous LAB. The application of GABA-producing autochthonous starters would allow the production of Cambodian fermented foods with an additional nutritional value that meet the population's dietary habits and that are also more attractive for the international food market. Matrix-assisted laser desorption/ionizing time-of-flight mass spectrometry (MALDI-TOF MS) and partial 16S rDNA sequencing were used to identify 68 LAB isolates from Cambodian fermented foods. These isolates were classified and grouped with (GTG)5 rep-PCR, resulting in 50 strains. Subsequently, all strains were investigated for their ability to produce GABA by thin layer chromatography. GABA-positive strains were further analyzed by the GABase assay. Of the six GABA-positive LAB strains-one Lactobacillus futsaii, two Lactobacillus namurensis, and three Lactobacillus plantarum strains-two Lactobacillus plantarum strains produced high amounts of GABA (20.34 mM, 16.47 mM). These strains should be further investigated for their potential application as GABA-producing starter cultures in the food applications.

Lactobacilli intra-tracheal administration protects from Pseudomonas aeruginosa pulmonary infection in mice - a proof of concept

The spreading of antibiotic resistance is a major public health issue, which requires alternative treatments to antibiotics. Lactobacilli have shown abilities to prevent pneumonia in clinical studies when given by oral route, certainly through the gut-lung axis involvement. Rationally, respiratory administration of lactobacilli has been developed and studied in murine model, to prevent from respiratory pathogens. It allows a direct effect of probiotics into the respiratory system. To our knowledge, no study has ever focused on the effect of probiotic intra-respiratory administration to prevent from Pseudomonas aeruginosa (PA) pneumonia, a major respiratory pathogen associated with high morbidity rates. In this study, we evaluated the beneficial activity of three Lactobacillus strains (Lactobacillus fermentum K.C6.3.1E, Lactobacillus zeae Od.76, Lactobacillus paracasei ES.D.88) previously screened by ourselves and known to be particularly efficient in vitro in inhibiting PAO1 virulence factors. Cytotoxic assays in alveolar epithelial cell line A549 were performed, followed by the comparison of two lactobacilli prophylactic protocols (one or two administrations) by intra-tracheal administration in a C57BL/6 murine model of PA pneumonia. A549 cells viability was improved from 23 to 75% when lactobacilli were administered before PAO1 incubation, demonstrating a protective effect (P<0.001). A significant decrease of 2 log of PAO1 was observed 4 h after PAO1 instillation (3×10⁶ cfu/mouse) in both groups receiving lactobacilli (9×10⁶ cfu/mouse) compared to PAO1 group (P<0.05). One single prophylactic administration of lactobacilli significantly decreased the secretion by 50% in bronchoalveolar lavages of interleukin (IL)-6 and tumour necrosis factor-α compared to PAO1. No difference of secretion was observed for the IL-10 secretion, whatever the prophylactic study design. This is the first study highlighting that direct lung administration of Lactobacillus strains protect against PA pneumonia. Next step will be to decipher the mechanisms involved before developing this novel approach for human applications.

Microbial Metabolic Capacity for Intestinal Folate Production and Modulation of Host Folate Receptors

Microbial metabolites, including B complex vitamins contribute to diverse aspects of human health. Folate, or vitamin B9, refers to a broad category of biomolecules that include pterin, para-aminobenzoic acid (pABA), and glutamate subunits. Folates are required for DNA synthesis and epigenetic regulation. In addition to dietary nutrients, the gut microbiota has been recognized as a source of B complex vitamins, including folate. This study evaluated the predicted folate synthesis capabilities in the genomes of human commensal microbes identified in the Human Microbiome Project and folate production by representative strains of six human intestinal bacterial phyla. Bacterial folate synthesis genes were ubiquitous across 512 gastrointestinal reference genomes with 13% of the genomes containing all genes required for complete de novo folate synthesis. An additional 39% of the genomes had the genetic capacity to synthesize folates in the presence of pABA, an upstream intermediate that can be obtained through diet or from other intestinal microbes. Bacterial folate synthesis was assessed during exponential and stationary phase growth through the evaluation of expression of select folate synthesis genes, quantification of total folate production, and analysis of folate polyglutamylation. Increased expression of key folate synthesis genes was apparent in exponential phase, and increased folate polyglutamylation occurred during late stationary phase. Of the folate producers, we focused on the commensal Lactobacillus reuteri to examine host-microbe interactions in relation to folate and examined folate receptors in the physiologically relevant human enteroid model. RNAseq data revealed segment-specific folate receptor distribution. Treatment of human colonoid monolayers with conditioned media (CM) from wild-type L. reuteri did not influence the expression of key folate transporters proton-coupled folate transporter (PCFT) or reduced folate carrier (RFC). However, CM from L. reuteri containing a site-specific inactivation of the folC gene, which prevents the bacteria from synthesizing a polyglutamate tail on folate, significantly upregulated RFC expression. No effects were observed using L. reuteri with a site inactivation of folC2, which results in no folate production. This work sheds light on the contributions of microbial folate to overall folate status and mammalian host metabolism.

Oncolytic Bacteria and their potential role in bacterium-mediated tumour therapy: a conceptual analysis

As the human microbiota has been confirmed to be of great significance in maintaining health, the dominant bacteria in them have been applied as probiotics to treat various diseases. After the detection of bacteria in tumours, which had previously been considered a sterile region, these bacteria have been isolated and genetically modified for use in tumour therapy. In this review, we sum up the main types of bacteria used in tumour therapy and reveal the mechanisms of both wild type and engineered bacteria in eliminating tumour cells, providing potential possibilities for newly detected, genetically modified, tumour-associated bacteria in anti-tumour therapy.

Effects of chlortetracycline alone or in combination with direct fed microbials on nursery pig growth performance and antimicrobial resistance of fecal Escherichia coli

A total of 300 nursery pigs (initially 5.9 ± 0.05 kg BW) were used in a 42-d growth trial to evaluate the effects of feeding a therapeutic level of chlortetracycline (CTC) with or without direct fed microbials (DFM) on growth performance and antimicrobial resistance (AMR) of fecal Escherichia coli. CTC is a broad-spectrum in-feed antibiotic commonly used in the swine industry. Weaned pigs (~21 d of age) were allotted to pens based on initial BW and fed a common starter diet for 4 d. Pens were then blocked by BW and allotted to dietary treatments in a completely randomized block design. Dietary treatments were arranged in a 2 × 3 factorial consisting of combinations of CTC (none vs. 400 mg/kg from days 0 to 42) and DFM (0 vs. 0.05% DFM 1 vs. 0.05% DFM 2). Fecal samples were collected from three randomly selected pigs from each pen on days 0, 21, and 42 for E. coli isolation and AMR determination. Overall, pigs fed diets containing CTC had improved (P < 0.001) ADG, ADFI, and BW compared to those not fed CTC with no evidence for any effect of either DFM 1 or DFM 2. Regardless of CTC, inclusion of DFM 2 in diets improved (P < 0.05) ADFI from days 0 to 14 and on day 14 BW compared to diets that did not include DFM 2. The addition of CTC with or without DFMs to nursery pig diets increased (P < 0.05) the probability of AMR to tetracycline and ceftiofur of fecal E. coli isolates, but this resistance generally decreased (P < 0.05) over time. A decrease (P < 0.05) in AMR to ampicillin and tetracycline (TET) throughout the trial was observed, while resistance to ceftriaxone decreased (P < 0.020) from days 0 to 21 and increased from days 21 to 42 amongst dietary treatments regardless of CTC or DFM inclusion in the diet. A CTC × DFM × day interaction (P < 0.015) was observed for streptomycin, whereby from days 21 to 42 AMR increased in diets containing either CTC or DFM 1 alone, but the combination decreased resistance. There was no evidence for any effect of DFMs on AMR of fecal E. coli isolates to any other antibiotics evaluated. In conclusion, therapeutic levels of added CTC with or without DFM inclusion improved nursery pig performance, but increased AMR of fecal E. coli isolates to TET and ceftiofur. A moderate improvement in intake and day 14 BW was observed when DFM 2 was included in the diet with or without CTC, but, except for streptomycin, there was no evidence that added dietary DFMs affected resistance of fecal E. coli to antibiotics.

Multilocus sequence typing of Carnobacterium maltaromaticum strains associated with fish disease and dairy products

AIMS

Carnobacterium maltaromaticum is a lactic acid bacterium of technological interest in the field of dairy ripening and food bioprotection and is generally recognized as safe in the United States. As it is associated with fish infections, the European Food Safety Agency did not include this species in the qualified presumption safety list of micro-organisms. This implies that the risk assessment for the species has to be performed at the strain level.

METHODS AND RESULTS

Multilocus sequence typing (MLST) is a tool that (i) potentially allows to discriminate strains isolated from diseased fish from apathogenic strains and (ii) to assess the genetic relatedness between both groups of strains. In this study, we characterized by MLST 21 C. maltaromaticum strains including 16 strains isolated from diseased fish and 5 apathogenic dairy strains isolated from cheese. The resulting population structure was investigated by integrating these new data to the previously published population structure (available at http://pubmlst.org), which represents an overall of 71 strains.

CONCLUSIONS

This analysis revealed that none of the strains isolated from diseased fish is assigned to a clonal complex containing cheese isolates, and that 11 strains exhibit singleton genotypes suggesting that the population of diseased fish isolates is not clonal.

SIGNIFICANCE AND IMPACT OF THE STUDY

This study thus provides a population structure of C. maltaromaticum that could serve in the future as a reference that could contribute to the risk assessment of C. maltaromaticum strains intended to be used in the food chain.

Bio-protective potential of lactic acid bacteria: Effect of Lactobacillus sakei and Lactobacillus curvatus on changes of the microbial community in vacuum-packaged chilled beef

OBJECTIVE

This study was to determine the bacterial diversity and monitor the community dynamic changes during storage of vacuum-packaged sliced raw beef as affected by Lactobacillus sakei and Lactobacillus curvatus.

METHODS

L. sakei and L. curvatus were separately incubated in vacuumed-packaged raw beef as bio-protective cultures to inhibit the naturally contaminating microbial load. Dynamic changes of the microbial diversity of inoculated or non-inoculated (control) samples were monitored at 4°C for 0 to 38 days, using polymerase chain reaction-denaturing gradient gel electrophoresis (PCR-DGGE).

RESULTS

The DGGE profiles of DNA directly extracted from non-inoculated control samples highlighted the order of appearance of spoilage bacteria during storage, showing that Enterbacteriaceae and Pseudomonas fragi emerged early, then Brochothrix thermosphacta shared the dominant position, and finally, Pseudomonas putida showed up became predominant. Compared with control, the inoculation of either L. sakei or L. curvatus significantly lowered the complexity of microbial diversity and inhibited the growth of spoilage bacteria (p<0.05). Interestingly, we also found that the dominant position of L. curvatus was replaced by indigenous L. sakei after 13 d for L. curvatus-inoculated samples. Plate counts on selective agars further showed that inoculation with L. sakei or L. curvatus obviously reduced the viable counts of Enterbacteraceae, Pseudomonas spp. and B. thermosphacta during later storage (p< 0.05), with L. sakei exerting greater inhibitory effect. Inoculation with both bio-protective cultures also significantly decreased the total volatile basic nitrogen values of stored samples (p<0.05).

CONCLUSION

Taken together, the results proved the benefits of inoculation with lactic acid bacteria especially L. sakei as a potential way to inhibit growth of spoilage-related bacteria and improve the shelf life of vacuum-packaged raw beef.

Lactobacillus-derived extracellular vesicles enhance host immune responses against vancomycin-resistant enterococci

Background

Probiotic bacteria are known to modulate host immune responses against various pathogens. Recently, extracellular vesicles (EVs) have emerged as potentially important mediators of host-pathogen interactions. In this study, we explored the role of L. plantarum derived EVs in modulating host responses to vancomycin-resistant Enterococcus faecium (VRE) using both Caenorhabditis elegans and human cells.

Results

Our previous work has shown that probiotic conditioning C. elegans with L. acidophilus NCFM prolongs the survival of nematodes exposed to VRE. Similarly, L. plantarum WCFS1 derived extracellular vesicles (LDEVs) also significantly protected the worms against VRE infection. To dissect the molecular mechanisms of this EV-induced protection, we found that treatment of C. elegans with LDEVs significantly increased the transcription of host defense genes, cpr-1 and clec-60. Both cpr-1 and clec-60 have been previously reported to have protective roles against bacterial infections. Incubating human colon-derived Caco-2 cells with fluorescent dye-labeled LDEVs confirmed that LDEVs could be transported into the mammalian cells. Furthermore, LDEV uptake was associated with significant upregulation of CTSB, a human homologous gene of cpr-1, and REG3G, a human gene that has similar functions to clec-60.

Conclusions

We have found that EVs produced from L. plantarum WCFS1 up-regulate the expression of host defense genes and provide protective effects on hosts. Using probiotic-derived EVs instead of probiotic bacteria themselves, this study provides a new direction to treat antimicrobial resistant pathogens, such as VRE.

Electronic supplementary material

The online version of this article (doi:10.1186/s12866-017-0977-7) contains supplementary material, which is available to authorized users.

Characterization of Antibiotic Resistance Genes from Lactobacillus Isolated from Traditional Dairy Products

Lactobacilli are widely used as starter cultures or probiotics in yoghurt, cheese, beer, wine, pickles, preserved food, and silage. They are generally recognized as safe (GRAS). However, recent studies have shown that some lactic acid bacteria (LAB) strains carry antibiotic resistance genes and are resistant to antibiotics. Some of them may even transfer their intrinsic antibiotic resistance genes to other LAB or pathogens via horizontal gene transfer, thus threatening human health. A total of 33 Lactobacillus strains was isolated from fermented milk collected from different areas of China. We analyzed (1) their levels of antibiotic resistance using a standardized dilution method, (2) their antibiotic resistance gene profiles by polymerase chain reaction (PCR) using gene-specific primers, and (3) the transferability of some of the detected resistance markers by a filter mating assay. All Lactobacillus strains were found to be resistant to vancomycin, but susceptible to gentamicin, linezolid, neomycin, erythromycin, and clindamycin. Their susceptibilities to tetracycline, kanamycin, ciprofloxacin, streptomycin, quinupristin/dalfopristin, trimethoprim, ampicillin, rifampicin, and chloramphenicol was different. Results from our PCR analysis revealed 19 vancomycin, 10 ciprofloxacin, and 1 tetracycline-resistant bacteria that carried the van(X), van(E), gyr(A), and tet(M) genes, respectively. Finally, no transferal of the monitored antibiotic resistance genes was observed in the filter mating assay. Taken together, our study generated the antibiotic resistance profiles of some milk-originated lactobacilli isolates and preliminarily assessed their risk of transferring antibiotic gene to other bacteria. The study may provide important data concerning the safe use of LAB.

Potential of bacteriocin-producing lactic acid bacteria for safety improvements of traditional Thai fermented meat and human health

Lactic acid bacteria (LAB) are very important in converting of agricultural products into safe, delicious and shelf stable foods for human consumption. The preservative activity of LAB in foods is mainly attributed to the production of anti-microbial metabolites such as organic acids and bacteriocins which enables them to grow and control the growth of pathogens and spoilage microorganisms. Besides ensuring safety, bacteriocin-producing LAB with their probiotic potentials could also be emerging as a means to develop functional meat products with desirable health benefits. Nevertheless, to be qualified as a candidate probiotic culture, other prerequisite probiotic properties of bacteriocin-producing LAB have to be assessed according to regulatory guidelines for probiotics. Nham is an indigenous fermented sausage of Thailand that has gained popularity and acceptance among Thais. Since Nham is made from raw meat and is usually consumed without cooking, risks due to undesirable microorganisms such as Salmonella spp., Staphylococcus aureus, and Listeria monocytogenes, are frequently observed. With an ultimate goal to produce safer and healthier product, our research attempts on the development of a variety of new Nham products are discussed.

A proposed framework for an appropriate evaluation scheme for microorganisms as novel foods with a health claim in Europe

This paper concerns the procedure and the scientific approach to obtain market authorization for a microorganism to be recognized as a novel food with a health claim. Microorganisms that have not been traditionally used during food production in Europe prior to 1997 are considered as novel foods, which should undergo an in-depth characterization and safety assessment before being authorized on the European market. If a novel food bacterium is claimed to provide a beneficial effect on health, these claims must also be investigated before they can be authorized. Some requirements to obtain novel food certification are shared with those required to obtain a health claim. Although regulation exists that deals with these issues for foods in general, bacteria in food raise a specific set of questions that are only minimally addressed in official documentation. We propose a framework and suggest a list of criteria that should be assessed to obtain marketing authorization and health claim for a bacterium in accordance with European health policy.

Effect of Long-Term Consumption of Lactobacillus paracasei SD1 on Reducing Mutans streptococci and Caries Risk: A Randomized Placebo-Controlled Trial

Background: A previous study revealed Lactobacillus paracasei SD1, a probiotic strain, could reduce mutans streptococci (MS). The aim of this study was to evaluate the long-term effects of L. paracasei SD1 on the colonization of MS, and whether caries lesions developed. Methods: After informed consent, 122 children were recruited and randomly assigned to the probiotic or control groups. The probiotic group received milk-powder containing L. paracasei SD1 and the control group received standard milk-powder once daily for six months. Salivary MS and lactobacilli were enumerated using differential culture at baseline and at three-month intervals for 12 months. The persistence of L. paracasei SD1 was investigated using AP-PCR for DNA-fingerprinting. Oral health was examined at baseline and at the end of the study according to WHO criteria. Results: The long-term consumption could prolong colonization of L. paracasei SD1. Significantly reduced MS counts and increased lactobacilli levels were found among children in the probiotic group. There were less caries lesions in the probiotic group at the end of the study. A significant reduction of the development of new caries lesions (4.5 times) was observed in the high caries risk group but not in the low caries risk group. Conclusions: Results demonstrate that the long-term daily ingestion of the human-derived probiotic L. paracasei SD1 significantly reduces the number of MS and caries risk in the high caries group.

Effect of Probiotics Containing Lactobacillus paracasei SD1 on Salivary Mutans Streptococci and Lactobacilli in Orthodontic Cleft Patients: A Double-Blinded, Randomized, Placebo-Controlled Study

Objective

(1) To investigate the effect of probiotic bacterium Lactobacillus paracasei SDA on the level of salivary mutans streptococci and lactobacilli, and (2) the oral persistence of L. paracasei SD1 in orthodontically treated nonsyndromic cleft lip and palate patients.

Design

Double-blinded, randomized, placebo-controlled study.

Participants

A total of 30 orthodontically treated nonsyndromic cleft lip and palate patients (aged 19.22 ± 3.66 years): 15 in the intervention group (A) and 15 in the control group (B).

Interventions

Milk with or without L. paracasei SD1. Average daily consumption of milk in both groups was 50 mL for 4 weeks.

Main Outcome Measures

Salivary mutans streptococci and lactobacilli were enumerated using a quantitative differential culture at baseline and once a week after the end of the administration period for 4 weeks. The persistence of L. paracasei SD1 was traced using arbitrarily primed polymerase chain reaction of the DNA fingerprinting.

Results

A statistically significant reduction in mutans streptococci counts occurred in group A, in contrast to group B ( P < .001). A significant increase of lactobacilli numbers was found in group A ( P < .001), and L. paracasei SD1 could be detected up to 4 weeks following cessation of dosing.

Conclusions

The probiotic milk powder containing L. paracasei SD1 could reduce mutans streptococci counts and was apparently able to colonize the oral cavity of the orthodontically treated cleft lip and palate patients. However, the potentially beneficial influence of the probiotic milk on the complex oral microflora justifies further studies with a larger group of volunteers.

Oral immunization with recombinant Lactococcus lactis delivering a multi-epitope antigen CTB-UE attenuates Helicobacter pylori infection in mice

Urease is an essential virulence factor and colonization factor for Helicobacter pylori (H. pylori) and is considered as an excellent vaccine candidate antigen. However, conventional technologies for preparing an injectable vaccine require purification of the antigenic protein and preparation of an adjuvant. Lactococcus lactis NZ9000 (L. lactis) could serve as an antigen-delivering vehicle for the development of edible vaccine. In previous study, we constructed a multi-epitope vaccine, designated CTB-UE, which is composed of the mucosal adjuvant cholera toxin B subunit (CTB), three Th cell epitopes and two B-cell epitopes from urease subunits. To develop a novel type of oral vaccine against H. pylori, genetically modified L. lactis strains were established to secrete this epitope vaccine extracellularly in this study. Oral prophylactic immunization with recombinant L. lactis significantly elicited humoral anti-urease antibody responses (P < 0.001) and reduced the gastric colonization of H. pylori from 7.14 ± 0.95 to 4.68 ± 0.98 log10 CFU g(-1) stomach. This L. lactis oral vaccine offers a promising vaccine candidate for the control of H. pylori infection.

Update on antibiotic resistance in foodborne Lactobacillus and Lactococcus species

Lactobacilli represent a major Lactic Acid Bacteria (LAB) component within the complex microbiota of fermented foods obtained from meat, dairy, and vegetable sources. Lactococci, on the other hand, are typical of milk and fermented dairy products, which in turn represent the vast majority of fermented foods. As is the case for all species originating from the environment, foodborne lactobacilli and lactococci consist of natural, uncharacterized strains, whose biodiversity depends on geographical origin, seasonality, animal feeding/plant growth conditions. Although a few species of opportunistic pathogens have been described, lactobacilli and lactococci are mostly non-pathogenic, Gram-positive bacteria displaying probiotic features. Since antibiotic resistant (AR) strains do not constitute an immediate threat to human health, scientific interest for detailed studies on AR genes in these species has been greatly hindered. However, increasing evidence points at a crucial role for foodborne LAB as reservoir of potentially transmissible AR genes, underlining the need for further, more detailed studies aimed at identifying possible strategies to avoid AR spread to pathogens through fermented food consumption. The availability of a growing number of sequenced bacterial genomes has been very helpful in identifying the presence/distribution of mobile elements associated with AR genes, but open questions and knowledge gaps still need to be filled, highlighting the need for systematic and datasharing approaches to implement both surveillance and mechanistic studies on transferability of AR genes. In the present review we report an update of the recent literature on AR in lactobacilli and lactococci following the 2006 EU-wide ban of the use of antibiotics as feed additives in animal farming, and we discuss the limits of the present knowledge in evaluating possible risks for human health.

Microbial characterization of probiotics--advisory report of the Working Group "8651 Probiotics" of the Belgian Superior Health Council (SHC)

When ingested in sufficient numbers, probiotics are expected to confer one or more proven health benefits on the consumer. Theoretically, the effectiveness of a probiotic food product is the sum of its microbial quality and its functional potential. Whereas the latter may vary much with the body (target) site, delivery mode, human target population, and health benefit envisaged microbial assessment of the probiotic product quality is more straightforward. The range of stakeholders that need to be informed on probiotic quality assessments is extremely broad, including academics, food and biotherapeutic industries, healthcare professionals, competent authorities, consumers, and professional press. In view of the rapidly expanding knowledge on this subject, the Belgian Superior Health Council installed Working Group "8651 Probiotics" to review the state of knowledge regarding the methodologies that make it possible to characterize strains and products with purported probiotic activity. This advisory report covers three main steps in the microbial quality assessment process, i.e. (i) correct species identification and strain-specific typing of bacterial and yeast strains used in probiotic applications, (ii) safety assessment of probiotic strains used for human consumption, and (iii) quality of the final probiotic product in terms of its microbial composition, concentration, stability, authenticity, and labeling.

Effects of a probiotic fermented milk on functional constipation: a randomized, double-blind, placebo-controlled study

BACKGROUND AND AIM

Evidence suggests that probiotics reduce certain constipation-related symptoms. Lactobacillus casei strain Shirota has never been tested as treatment for functional constipation in otherwise-healthy subjects. To evaluate the efficacy of this probiotic among adults with functional constipation was aimed.

METHODS

Subjects with functional constipation (Rome II-defined) were randomized to intake L.  casei strain Shirota fermented milk or placebo once daily for 4 weeks under double-blind condition. Primary outcomes were constipation severity and stool frequency; secondary outcomes were stool consistency and quantity.

RESULTS

In intent-to-treat population, compared with baseline, constipation severity and stool frequency improved in both probiotic (n = 47) and control groups (n = 43), but improvements were comparable in both groups at week 4 (α = 5% level). In probiotic group, stool consistency and quantity at week 4 improved significantly versus baseline but not versus control. Considering that the study agent is non-pharmaceutical and the purpose of supplementation is for long-term effect, re-evaluation at α = 10% was conducted, which showed significant improvement in constipation severity at week 4 (P = 0.058). Magnitude of the probiotic effect on stool consistency was small but grew over time, d = 0.19, 95% confidence interval 0.00-0.35 (Week 4), d = 0.29, 95% confidence interval 0.11-0.52 (postintervention). Post-hoc exploratory analysis suggests incomplete evacuation may decrease with probiotic intake.

CONCLUSIONS

Four-week administration of L.  casei strain Shirota did not alleviate constipation severity or stool frequency, consistency, and quantity when compared with control. With re-evaluation at α = 10% level, improvement in constipation severity was significant at week 4. To obtain conclusive results, further studies with longer intervention are warranted.

Synbiotics, probiotics or prebiotics in infant formula for full term infants: a systematic review

BACKGROUND

Synbiotics, probiotics or prebiotics are being added to infant formula to promote growth and development in infants. Previous reviews (2007 to 2011) on term infants given probiotics or prebiotics focused on prevention of allergic disease and food hypersensitivity. This review focused on growth and clinical outcomes in term infants fed only infant formula containing synbiotics, probiotics or prebiotics.

METHODS

Cochrane methodology was followed using randomized controlled trials (RCTs) which compared term infant formula containing probiotics, prebiotics or synbiotics to conventional infant formula with / without placebo among healthy full term infants. The mean difference (MD) and corresponding 95% confidence intervals (CI) were reported for continuous outcomes, risk ratio (RR) and corresponding 95% CI for dichotomous outcomes. Where appropriate, meta-analysis was performed; heterogeneity was explored using subgroup and sensitivity analyses. If studies were too diverse a narrative synthesis was provided.

RESULTS

Three synbiotic studies (N = 475), 10 probiotics studies (N = 933) and 12 prebiotics studies (N = 1563) were included. Synbiotics failed to significantly increase growth in boys and girls. Use of synbiotics increased stool frequency, had no impact on stool consistency, colic, spitting up / regurgitation, crying, restlessness or vomiting. Probiotics in formula also failed to have any significant effect on growth, stool frequency or consistency. Probiotics did not lower the incidence of diarrhoea, colic, spitting up / regurgitation, crying, restlessness or vomiting. Prebiotics in formula did increase weight gain but had no impact on length or head circumference gain. Prebiotics increased stool frequency but had no impact on stool consistency, the incidence of colic, spitting up / regurgitation, crying, restlessness or vomiting. There was no impact of prebiotics on the volume of formula tolerated, infections and gastrointestinal microflora. The quality of evidence was compromised by imprecision, inconsistency of results, use of different study preparations and publication bias.

AUTHORS' CONCLUSIONS

There is not enough evidence to state that supplementation of term infant formula with synbiotics, probiotics or prebiotics does result in improved growth or clinical outcomes in term infants. There is no data available to establish if synbiotics are superior to probiotics or prebiotics.

Genotypic characterization and safety assessment of lactic acid bacteria from indigenous African fermented food products

Background

Indigenous fermented food products play an essential role in the diet of millions of Africans. Lactic acid bacteria (LAB) are among the predominant microbial species in African indigenous fermented food products and are used for different applications in the food and biotechnology industries. Numerous studies have described antimicrobial susceptibility profiles of LAB from different parts of the world. However, there is limited information on antimicrobial resistance profiles of LAB from Africa. The aim of this study was to characterize 33 LAB previously isolated from three different African indigenous fermented food products using (GTG)₅-based rep-PCR, sequencing of the 16S rRNA gene and species-specific PCR techniques for differentiation of closely related species and further evaluate their antibiotic resistance profiles by the broth microdilution method and their haemolytic activity on sheep blood agar plates as indicators of safety traits among these bacteria.

Results

Using molecular biology based methods and selected phenotypic tests such as catalase reaction, CO₂ production from glucose, colonies and cells morphology, the isolates were identified as Lactobacillus delbrueckii, Lactobacillus fermentum, Lactobacillus ghanensis, Lactobacillus plantarum, Lactobacillus salivarius, Leuconostoc pseudomesenteroides, Pediococcus acidilactici, Pediococcus pentosaceus and Weissella confusa. The bacteria were susceptible to ampicillin, chloramphenicol, clindamycin and erythromycin but resistant to vancomycin, kanamycin and streptomycin. Variable sensitivity profiles to tetracycline and gentamicin was observed among the isolates with Lb. plantarum, Lb. salivarius, W. confusa (except strain SK9-5) and Lb. fermentum strains being susceptible to tetracycline whereas Pediococcus strains and Lb. ghanensis strains were resistant. For gentamicin, Leuc. pseudomesenteroides, Lb. ghanensis and Ped. acidilactici strains were resistant to 64 mg/L whereas some W. confusa and Lb. plantarum strains had a MIC value of 16 mg/L and 32 mg/L respectively. No β-haemolytic activity was observed, however, α-haemolytic activity was observed in 27% (9) of the strains comprising Lb. salivarius (6), W. confusa (2) and Lb. delbrueckii (1) isolates.

Conclusions

The resistance to kanamycin and vancomycin is probably an intrinsic feature since similar observations were reported in the literature for LAB. Low prevalence of pathogenicity indicator traits were observed among the isolates especially with the presence of poor haemolytic activities and they could therefore be considered as interesting candidates for selection of starter cultures or probiotics for different applications.

Lactobacillus rhamnosus bacteremia: an emerging clinical entity

Lactobacillus spp. are ubiquitous commensals of the normal human flora that are only occasionally found in clinical infections. Their role in human disease is established for infectious endocarditis but is controversial for other infections. We sought to characterize clinically associated Lactobacillus spp. We conducted a retrospective study, which consisted of the screening of Lactobacillus isolates obtained in our laboratory from January 2004 to December 2009. The polymerase chain reaction (PCR) assay was selected as the gold standard method. The isolates were first identified using API Coryne strips, matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS), and 16S rRNA gene sequencing. Lactobacillus tuf gene-based identification was used when the 16S rRNA results were inconclusive. Among the 60 strains of Lactobacillus spp. obtained in our laboratory, L. rhamnosus was the most commonly isolated species and was found in blood cultures from 16 patients. Combined with 45 patients reported in the literature, we found that patients presenting with L. rhamnosus bacteremia experienced nosocomial infections associated with both immunosuppression (66 %) and catheters (83 %).

Biocontainment strategies for live lactic acid bacteria vaccine vectors

Stability is an important issue when engineering bacteria for use as live vaccine vectors. For the majority of live bacterial vaccines, the antigen-encoding gene is either plasmid located or integrated into the chromosome. Regardless, several safety concerns can be raised for both instances. One concern when using plasmid-encoded antigens is the transfer of antibiotic resistance markers. Alternatively, for chromosomal integrated antigens however, the concern focuses on the spread and possible release of genetically-modified microorganisms (GMM) into the environment, which is problematic. Their recombinant nature calls for a proper bio-containment strategy to be implemented or in place before any realistic attempt at releasing a live bacterial vaccine. No examples of human bacterial vaccines causing problems among animals have been found in the literature but the possibility exists and has to be both tested and evaluated before release of a live bacterial vaccine. The ideal GMM for use in humans should therefore contain the minimal amount of foreign DNA and must not include an antibiotic resistance marker. Furthermore, the possibilities of transgene horizontal transfer must be minimized, and GMM lethality for biocontainment should be achieved in an unconfined environment.

The Lactobacillus flora in vagina and rectum of fertile and postmenopausal healthy Swedish women

Background

Lactobacillus species are the most often found inhabitants of vaginal ecosystem of fertile women. In postmenopausal women with low oestrogen levels, Lactobacillus flora is diminishing or absent. However, no studies have been performed to investigate the correlation between oestrogen levels and the lactobacilli in the gut. The aim of the present study was to investigate the relation in healthy women between vaginal and rectal microbial flora as well as possible variations with hormone levels.

Methods

Vaginal and rectal smears were taken from 20 healthy fertile women, average 40 years (range 28-49 years), in two different phases of the menstrual cycle, and from 20 postmenopausal women, average 60 years (range 52-85 years). Serum sex hormone levels were analyzed. Bacteria from the smears isolated on Rogosa Agar were grouped by Randomly Amplified Polymorphic DNA and identified by multiplex PCR and partial 16S rRNA gene sequencing.

Results

Lactobacillus crispatus was more often found in the vaginal flora of fertile women than in that of postmenopausal (p = 0.036). Fifteen of 20 fertile women had lactobacilli in their rectal smears compared to 10 postmenopausal women (p = 0.071). There was no correlation between the number of bacteria in vagina and rectum, or between the number of bacteria and hormonal levels. Neither could any association between the presence of rectal lactobacilli and hormonal levels be found.

Conclusion

Lactobacillus crispatus was more prevalent in the vaginal flora of fertile women, whereas the Lactobacillus flora of rectum did not correlate to the vaginal flora nor to hormonal levels.

Prevention of histamine formation in cheese by bacteriocin-producing lactic Acid bacteria

The susceptibility of 13 amine-forming lactobacilli to several bacteriocins was investigated by an agar diffusion assay. All strains were susceptible to nisin and to five bacteriocins of enterococcal origin. Pediocin PA-1, bavaricin A, lactococcin A, and a bacteriocin from Enterococcus faecalis 1061 did not show inhibitory activity. Two bacteriocin-producing enterococci and a nisin-producing Lactococcus lactis strain were employed as starters in separate cheese-making experiments. Outgrowth of histamine producer Lactobacillus buchneri St2A, which was added to the milk at levels of up to 190 CFU/ml, was almost completely inhibited. No histamine formation was detected in the cheeses made with bacteriocin-producing starters. In the control cheese without bacteriocin, St2A reached levels of 1.1 x 10(sup8) CFU/g, and 200 mg of histamine per kg was found after 4 months of ripening. To our knowledge, this is the first report of bacteriocin-mediated inhibition of histamine formation in foods.

Comparison of expression vectors in Lactobacillus reuteri strains

The synthesis of heterologous proteins in lactobacilli is strongly influenced by the promoter selected for the expression. In addition, the activity of the promoters themselves may vary among different bacterial hosts. Three different promoters were investigated for their capability to drive enhanced green fluorescent protein (EGFP) expression in Lactococcus lactis spp. cremoris MG1363, in Lactobacillus reuteri DSM 20016(T) and in five L. reuteri strains isolated from chicken crops. The promoters of the Lactobacillus acidophilus surface layer protein gene (slp), L. acidophilus lactate dehydrogenase gene (ldhL) and enterococcal rRNA adenine N-6-methyltransferase gene (ermB) were fused to the coding sequence of EGFP and inserted into the backbone of the pTRKH3 shuttle vector (pTRKH3-slpGFP, pTRKH3-ldhGFP, pTRKH3-ermGFP). Besides conventional analytical methods, a new quick fluorimetric approach was set up to quantify the EGFP fluorescence in transformed clones using the Qubit() fluorometer. ermB proved to be the most effective promoter in L. reuteri isolates, producing 3.90 x 10(-7) g of fluorescent EGFP (mL OD(stationary culture))(-1). Under the same conditions, the ldhL promoter produced 2.66 x 10(-7) g of fluorescent EGFP (mL OD(stationary culture))(-1). Even though the slp promoter was efficient in L. lactis spp. cremoris MG1363, it was nearly inactive both in L. reuteri DSM 20016(T) and in L. reuteri isolates.

Isolation, characterization, and evaluation of wild isolates of Lactobacillus reuteri from pig feces

Lactic acid bacteria (LAB) are a well-used probiotics for health improvements in both humans and animals. Despite of several benefits, non-host-specific LAB showed poor probiotics effects due to difficulty in colonization and competition with normal flora. Therefore, the feasibility of porcine LAB isolates was evaluated as a probiotics. Ten of 49 Lactobacillus spp. isolates harbored 2 approximately 10 kb plasmid DNA. Seven strains were selected based on the safety test, such as hemolytic activity, ammonia, indole, and phenylalanine production. After safety test, five strains were selected again by several tests, such as epithelial adherence, antimicrobial activity, tolerance against acid, bile, heat, and cold-drying, and production of acid and hydrogen peroxide. Then, enzyme profiles (ZYM test) and antibiotics resistance were analyzed for further characterization. Five Lactobacillus reuteri isolates from pig feces were selected by safety and functional tests. The plasmid DNA which was able to develop vector system was detected in the isolates. Together with these approaches, pig-specific Lactobacillus spp. originated from pigs were selected. These strains may be useful tools to develop oral delivery system.

Biopreservation of refrigerated and vacuum-packed Dicentrarchus labrax by lactic acid bacteria

Two lactic acid bacteria (LAB) were selected from 100 LAB isolated from various sea products to examine their use in Dicentrarchus labrax preservation. The isolates, tentatively named strain nr 3 and 7, were identified as Lactobacillus plantarum and L. pentosus, respectively. They showed antagonistic activity against psychrotroph, pathogenic, and coliform bacteria. The antagonistic activity of strain 3 was suggested to be by bacteriocins since activity was abolished by protease treatment, while that of strain 7 was due to the effect of pH decrease caused by the produced organic acids. Their use prevented total volatile basic nitrogen contents (TVB-N) and trimethylamine (TMA) to some extent, suggesting that inoculation could extend the period of storage.

Oral vaccination of mice against Helicobacter pylori with recombinant Lactococcus lactis expressing urease subunit B

To determine whether a protective immune response could be elicited by oral delivery of a recombinant live bacterial vaccine, Helicobacter pylori urease subunit B (UreB) was expressed for extracellular expression in food-grade bacterium Lactococcus lactis. The UreB-producing strains were then administered orally to mice, and the immune response to UreB was examined. Orally vaccinated mice produced a significant UreB-specific serum immunoglobulin G (IgG) response. Specific anti-UreB IgA responses could be detected in the feces of mice immunized with the secreting lactococcal strain. Mice vaccinated orally were significantly protected against gastric Helicobacter infection following a challenge with H. pylori strain SS1. In conclusion, mucosal vaccination with L. lactis expressing UreB produced serum IgG and UreB-specific fecal IgA, and prevented gastric infection with H. pylori.

Oral vaccination of mice against Helicobacter pylori with recombinant Lactococcus lactis expressing urease subunit B

To determine whether a protective immune response could be elicited by oral delivery of a recombinant live bacterial vaccine, Helicobacter pylori urease subunit B (UreB) was expressed for extracellular expression in food-grade bacterium Lactococcus lactis. The UreB-producing strains were then administered orally to mice, and the immune response to UreB was examined. Orally vaccinated mice produced a significant UreB-specific serum immunoglobulin G (IgG) response. Specific anti-UreB IgA responses could be detected in the feces of mice immunized with the secreting lactococcal strain. Mice vaccinated orally were significantly protected against gastric Helicobacter infection following a challenge with H. pylori strain SS1. In conclusion, mucosal vaccination with L. lactis expressing UreB produced serum IgG and UreB-specific fecal IgA, and prevented gastric infection with H. pylori.