The evaluation of a mupirocin-based selective medium for the enumeration of bifidobacteria from probiotic animal feed

Physiological and genomic characterization of Lactiplantibacillus plantarum isolated from Indri indri in Madagascar

AIMS

Indri indri is a lemur of Madagascar which is critically endangered. The analysis of the microbial ecology of the intestine offers tools to improve conservation efforts. This study aimed to achieve a functional genomic analysis of three Lactiplantibacillus plantarum isolates from indris.

METHODS AND RESULTS

Samples were obtained from 18 indri; 3 isolates of Lp. plantarum were obtained from two individuals. The three isolates were closely related to each other, with <10 single nucleotide polymorphisms, suggesting that the two individuals shared diet-associated microbes. The genomes of the three isolates were compared to 96 reference strains of Lp. plantarum. The three isolates of Lp. plantarum were not phenotypically resistant to antibiotics but shared all 17 genes related to antimicrobial resistance that are part of the core genome of Lp. plantarum. The genomes of the three indri isolates of Lp. plantarum also encoded for the 6 core genome genes coding for enzymes related to metabolism of hydroxybenzoic and hydroxycinnamic acids. The phenotype for metabolism of hydroxycinnamic acids by indri isolates of Lp. plantarum matched the genotype.

CONCLUSIONS

Multiple antimicrobial resistance genes and gene coding for metabolism of phenolic compounds were identified in the genomes of the indri isolates, suggesting that Lp. plantarum maintains antimicrobial resistance in defense of antimicrobial plant secondary pathogens and that their metabolism by intestinal bacteria aids digestion of plant material by primate hosts.

Fucosylated Human Milk Oligosaccharides Drive Structure-Specific Syntrophy between Bifidobacterium infantis and Eubacterium hallii within a Modeled Infant Gut Microbiome

SCOPE

Fucosylated human milk oligosaccharides (fHMOs) are metabolized by Bifidobacterium infantis and promote syntrophic interactions between microbiota that colonize the infant gut. The role of fHMO structure on syntrophic interactions and net microbiome function is not yet fully understood.

METHODS AND RESULTS

Metabolite production and microbial populations are tracked during mono- and co-culture fermentations of 2'fucosyllactose (2'FL) and difucosyllactose (DFL) by two B. infantis strains and Eubacterium hallii. This is also conducted in an in vitro modeled microbiome supplemented by B. infantis and/or E. hallii. Metabolites are quantified by high performance liquid chromatography. Total B. infantis and E. hallii populations are quantified through qRT-PCR and community composition through 16S amplicon sequencing. Differential metabolism of 2'FL and DFL by B. infantis strains gives rise to strain- and fHMO structure-specific syntrophy with E. hallii. Within the modeled microbial community, fHMO structure does not strongly alter metabolite production in aggregate, potentially due to functional redundancy within the modeled community. In contrast, community composition is dependent on fHMO structure.

CONCLUSION

Whereas short chain fatty acid production is not significantly altered by the specific fHMO structure introduced to the modeled community, specific fHMO structure influences the composition of the gut microbiome.

Development of a selective medium for the enumeration of lactic acid bacteria and bifidobacteria in food products

This study was conducted to develop a selective medium for enumerating LAB and Bifidobacteria in food samples. Thirteen media were evaluated to determine their suitability for selectively enumerating LAB (17 bacilli and 7 cocci) and Bifidobacteria (12 strains) under aerobic and anaerobic conditions. When BL, BCP, and mMRS were supplemented with propionic acid (5 ml/l) and adjusted to pH 5, the growth of all indicator microorganisms was inhibited; however, these media also inhibited the growth of certain LAB and Bifidobacterial strains. Using propionic acid, the pH levels of BL, BCP, and mMRS were adjusted to pH 5.2, 6.0, and 6.0, respectively. These media inhibited the growth of all indicator microorganisms, whereas they did not inhibit any of the LAB and Bifidobacteria strains under anaerobic conditions. Overall, BLP (pH 5.8) lacking blood showed significantly higher bacterial counts compared with other media in food products. Further analyses indicated that BLP (pH 5.8) was the most suitable medium for enumerating LAB and Bifidobacteria in food.

Supplementary Information

The online version contains supplementary material available at 10.1007/s10068-022-01202-z.

Reduction of multiple antibiotics from the waste water using coated glutathione S-transferase producing biocatalyst

Oxytetracycline is widely used in veterinary and human medicine. It has been detected in wastewater from pharmaceuticals, hospitals and domestic wastewater. In recent years, much more attention has been directed towards glutathione transferases (GSTs) because of their bio-transforming ability of antibiotics. In this study, 19 Lactobacillus strains were initially screened for the production of GSTs and five strains were selected for biotransformation of oxytetracycline. Among the strains, L. fermentum LA6 improved oxytetracyline degradation than other strains. It was subjected to optimize GST production and optimum growth was achieved after 24 h incubation at 32 ± 2 °C and 200 mg/L initial oxytetracycline concentration. The biocatalyst was immobilized and antibiotic degradation efficiency was analyzed. The immobilized culture of L. fermentum LA6 improved biodegradation of oxytetracycline in the wastewater. At 50 mg/L initial antibiotic concentration, 53.2 ± 2.8% oxytetracycline degradation was achieved, however, it improved at 200 mg/L antibiotic concentration in the culture medium (89.1 ± 4.3%) after 24 h. The chemical oxygen demand (COD) of the wastewater decreased significantly after treatment. At 200 mg/L oxytetracycline concentration, COD removal was considerably high (93.6 ± 5.3 mg/L) than 150 mg/L oxytetracycline concentration in the medium. Antibiotic removal efficiency in immobilized form revealed that this method is highly suitable for the removal of antibiotics from the wastewater.

Novel microaerobic agar plate method delivers highly selective and accurate enumeration of probiotic lactobacilli in freeze-dried blends containing bifidobacteria

The enumeration of viable bacteria is an essential metric in the dietary supplement and food industry to ensure quality of probiotic products. However, selective enumeration of lactobacilli in probiotic freeze-dried blends containing bifidobacteria is difficult to achieve with current Lactobacillus-specific agars (i.e., Rogosa and LAMVAB). Using a panel of Bifidobacterium and Lactobacillus commercial probiotic species, we found that Rogosa agar failed to inhibit all bifidobacteria while LAMVAB agar suppressed several lactobacilli. This prompted us to develop an alternative method of selection, hereby referred to as Lactobacillus Micro-Aerobic (LMA) method, which promotes growth under controlled microaerobic conditions (6-12% O₂, 5-8% CO₂) to leverage the different oxygen sensitivities of lactobacilli and bifidobacteria. Validation using pure cultures and multi-strain blends of 4 Bifidobacterium and 10 Lactobacillus species showed that LMA effectively suppressed all bifidobacteria and accurately enumerated all lactobacilli when compared to control methods. These results demonstrate the superior efficacy of modulating the redox environment to select for Lactobacillus within a Bifidobacterium-rich background, as opposed to applying acid and antibiotic pressures.

Antimicrobial plant secondary metabolites, MDR transporters and antimicrobial resistance in cereal-associated lactobacilli: is there a connection?

Cereal-associated lactobacilli resist antimicrobial plant secondary metabolites. This study aimed to identify multi-drug-resistance (MDR) transporters in isolates from mahewu, a Zimbabwean fermented cereal beverage, and to determine whether these MDR-transporters relate to resistance against phenolic compounds and antibiotics. Comparative genomic analyses indicated that all seven mahewu isolates harbored multiple MATE and MFS MDR proteins. Strains of Lactiplantibacillus plantarum and Limosilactobacillus fermentum encoded for the same gene, termed mahewu phenolics resistance gene mprA, with more than 99% nucleotide identity, suggesting horizontal gene transfer. Strains of Lp. plantarum were more resistant than strains of Lm. fermentum to phenolic acids, other antimicrobials and antibiotics but the origins of strains were not related to resistance. The resistance of several strains exceeded EFSA thresholds for several antibiotics. Analysis of gene expression in one strain each of Lp. plantarum and Lm. fermentum revealed that at least one MDR gene in each strain was over-expressed during growth in wheat, sorghum and millet relative to growth in MRS5 broth. In addition, both strains over-expressed a phenolic acid reductase. The results suggest that diverse lactobacilli in mahewu share MDR transporters acquired by lateral gene transfer, and that these transporters mediate resistance to secondary plant metabolites and antibiotics.

Draft Genome Sequence of Bifidobacterium pseudocatenulatum Bif4, Isolated from Healthy Infant Feces

We report the 2.24-Mb draft genome sequence of Bifidobacterium pseudocatenulatum Bif4, isolated from a fecal sample from a healthy infant. The specific annotations revealed genes predictive of its probiotic attributes.

We report the 2.24-Mb draft genome sequence of Bifidobacterium pseudocatenulatum Bif4, isolated from a fecal sample from a healthy infant. The specific annotations revealed genes predictive of its probiotic attributes.

Enhancing the prebiotic effect of cellulose biopolymer in the gut by physical structuring via particle size manipulation

Cellulose is generally recognised as dietary fibre with no limit of permissible quantity in food, and its consumption may modulate digesta content and impact positively on the gastrointestinal physiology and gut microflora. However, cellulose in its native form possessed inherent undesirable physical properties, making it unattractive for food applications. Here, we postulate that by changing cellulose size to nanometric scale, its prebiotic effect would be altered and fermented differently in contrast with micro size cellulose by the gut microbiome and promote the yield of metabolites such as short chain fatty acids (SCFAs). Using faecal matter from three healthy human donors as microbial source, in vitro fermentation of variable size fractions of cellulose from the same were fermented under anaerobic conditions, and SCFAs as well Bifidobacterium selectively isolated and analysed. The increase in production of acetate (194%), butyrate (224%) and propionate (211%) after 24 h of fermentation was significantly promoted by the size reduction and revealed size-dependent relationship as exemplified R² values >0.83. Consequently, gavaging rats with nanometric size cellulose (125 nm) significantly (p < 0.05) increased these SCFAs yields as well Bifidobacterium counts in contrast with both control and the micro scale size cellulose. Therefore, engineered nanocellulose might have beneficial physiological impact on the gut with improved prebiotic effect.

Condensed tannins decreased the growth performance and impaired intestinal immune function in on-growing grass carp (Ctenopharyngodon idella)

The present study investigated the effects of condensed tannins (CT) on intestinal immune function in on-growing grass carp (Ctenopharyngodon idella). A total of 540 healthy grass carp were fed six diets containing different levels of CT (0, 10·00, 20·00, 30·00, 40·00 and 50·00 g/kg diet) for 70 d and then challenged with Aeromonas hydrophila for 14 d. The results showed that, compared with the control group, dietary CT (1) induced intestinal histopathological lesions and aggravated enteritis; (2) decreased lysozyme and acid phosphatase activities, complement 3 (C3), C4 and IgM contents and down-regulated the Hepcidin, liver-expressed antimicrobial peptide (LEAP)-2A, LEAP-2B, Mucin2 and β-defensin-1 mRNA levels in the proximal intestine (PI), mid intestine (MI) and distal intestine (DI) (P < 0·05); (3) down-regulated the mRNA levels of anti-inflammatory cytokines transforming growth factor (TGF)-β1, TGF-β2 (not in MI and DI), IL-4/13A (not IL-4/13B), IL-10 and IL-11 partly correlated with target of rapamycin (TOR) signalling; and (4) up-regulated the mRNA levels of pro-inflammatory cytokines interferon-γ2, IL-1β, IL-6, IL-8 (not in PI), IL-12p35, IL-12p40, IL-15 and IL-17D partly related to NF-κB signalling in the intestine of on-growing grass carp. Overall, the results indicated that CT could impair the intestinal immune function, and its potential regulation mechanisms were partly associated with the TOR and NF-κB signalling pathways. Finally, based on the percentage weight gain and enteritis morbidity, the maximum allowable levels of CT for on-growing grass carp (232·22-890·11 g) were estimated to be 18·6 and 17·4 g/kg diet, respectively.

Metabolism of the predominant human milk oligosaccharide fucosyllactose by an infant gut commensal

A number of bifidobacterial species are found at a particularly high prevalence and abundance in faecal samples of healthy breastfed infants, a phenomenon that is believed to be, at least partially, due to the ability of bifidobacteria to metabolize Human Milk Oligosaccharides (HMOs). In the current study, we isolated a novel strain of Bifidobacterium kashiwanohense, named APCKJ1, from the faeces of a four-week old breastfed infant, based on the ability of the strain to utilise the HMO component fucosyllactose. We then determined the full genome sequence of this strain, and employed the generated data to analyze fucosyllactose metabolism in B. kashiwanohense APCKJ1. Transcriptomic and growth analyses, combined with metabolite analysis, in vitro hydrolysis assays and heterologous expression, allowed us to elucidate the pathway for fucosyllactose metabolism in B. kashiwanohense APCKJ1. Homologs of the key genes for this metabolic pathway were identified in particular in infant-derived members of the Bifdobacterium genus, revealing the apparent niche-specific nature of this pathway, and allowing a broad perspective on bifidobacterial fucosyllactose and L-fucose metabolism.

Dissect the mode of action of probiotics in affecting host-microbial interactions and immunity in food producing animals

Prophylactic antimicrobials have been widely used in food animal production with the aim to prevent infectious diseases, enhance feed efficiency, and promote growth. However, the extensive use of antimicrobials in food animal production systems has led to the emergence of antimicrobial resistant pathogens, which are potential threats to human and animal health. Probiotics have been proposed to be a promising alternative of prophylactic antimicrobials, with potential beneficial effects on the host animal by improving the balance of intestinal microbiota and host immunity. Although an increasing body of evidence shows that probiotics could directly or indirectly affect gut microbiota and host immune functions, the lack of the understanding of how probiotics influence host-microbial interaction and immunity is one of the reasons for controversial findings from many animal trials, especially in food production animals. Therefore, in this review we focused on the most recent (last ten years) studies on how gut microbiota and host immune function changes in response to probiotics in food production animals (swine, poultry, and ruminant). In addition, the relationship between microbial changes and host immune function was illustrated, and how such relationship differs among animal species was further compared. Moreover, the future directions concerning the mechanisms of how probiotics modulate host-microbial interactions and host immunity were highlighted, which may assist in the optimal supplementation strategy to maximize the efficacy of probiotics to improve animal gut health and productivity.

Tracking the Taxonomy of the Genus Bifidobacterium Based on a Phylogenomic Approach

For decades, bacterial taxonomy has been based on in vitro molecular biology techniques and comparison of molecular marker sequences to measure the degree of genetic similarity and deduce phylogenetic relatedness of novel bacterial species to reference microbial taxa. Due to the advent of the genomic era, access to complete bacterial genome contents has become easier, thereby presenting the opportunity to precisely investigate the overall genetic diversity of microorganisms. Here, we describe a high-accuracy phylogenomic approach to assess the taxonomy of members of the genus Bifidobacterium and identify apparent misclassifications in current bifidobacterial taxonomy. The developed method was validated by the classification of seven novel taxa belonging to the genus Bifidobacterium by employing their overall genetic content. The results of this study demonstrate the potential of this whole-genome approach to become the gold standard for phylogenomics-based taxonomic classification of bacteria.IMPORTANCE Nowadays, next-generation sequencing has given access to genome sequences of the currently known bacterial taxa. The public databases constructed by means of these new technologies allowed comparison of genome sequences between microorganisms, providing information to perform genomic, phylogenomic, and evolutionary analyses. In order to avoid misclassifications in the taxonomy of novel bacterial isolates, new (bifido)bacterial taxons should be validated with a phylogenomic assessment like the approach presented here.

Probiotic and functional characterization of bifidobacteria of Indian human origin

AIMS

To identify and characterize the probiotic and functional attributes of bifidobacteria isolated from human sources by in vitro methods.

METHODS AND RESULTS

Twelve isolates of bifidobacteria were obtained from different human sources viz; human milk, infant and adult faeces. The preliminary identification of isolates was done using genus-specific PCR followed by species level identification using 16S rRNA sequencing. All the isolates invariably showed potential probiotic characteristics. Finally, three most promising isolates were subjected to safety evaluation and were found to be safe. These were further evaluated for their potential functional characteristics like, antioxidative, antimutagenic and cholesterol assimilation. The isolates viz; NBIF-5 (73·55 ± 0·03%) and NBIF-7 (64·06 ± 0·03%) assimilated significantly higher cholesterol than NBIF-2. The maximum antioxidative activity was observed in NBIF-2 (56·56 ± 0·28% of radical inhibition). High percentage antimutagenicity scores of 52·41 ± 2·25% and 53·68 ± 1·98% against sodium azide (NaN3) were shown by NBIF-2 and NBIF-7 respectively.

CONCLUSIONS

Three strains (NBIF-2, NBIF-5 and NBIF-7) were found to be endowed with appreciable probiotic and functional activities.

SIGNIFICANCE AND IMPACT OF THE STUDY

With growing demands for probioitcs and bifidobacteria being prominent ones, new strains of diversified origin have the potential to be explored for commercial and functional applications and thus can be added to the existing commercially available strains of this genera.

Effects of Brevibacillus brevis FJAT-1501-BPA on growth performance, faecal microflora, faecal enzyme activities and blood parameters of weaned piglets

A feeding expriment was performed to investigate the effects of dietary supplementation with Brevibacillus brevis FJAT-1501-BPA fermentation on the growth performance, faecal microflora, faecal enzyme activities and blood parameters of weaned piglets. A total of 150 weaned piglets were randomly assigned to different treatments groups, which were fed the same basic diet supplemented with 10, 1, 0.1, 0.01 and 0 % B. brevis FJAT-1501-BPA fermentation. The results showed that a diet supplemented with 10 % B. brevis FJAT-1501-BPA fermentation could significantly increase the final body weight (P < 0.05) and decrease feed to gain ratio, which was 37.1 % lower than that of the control group. The addition of B. brevis FJAT-1501-BPA exhibited a trend of reducing the contents of the Escherichia coli, Lactobacillus and Salmonella compared with the control. During the 35 day experimental period, cellulase and protease activities were significantly increased by the dietary inclusion of the B. brevis FJAT-1501-BPA fermentation (P < 0.05). The cellulase activity for piglets fed diet containing 1 % B. brevis FJAT-1501-BPA fermentation, 21.8 U/g, was highest among the different treatments. The protease activity for piglets fed diet containing 10 % B. brevis FJAT-1501-BPA fermentation, 50.4 U/g, was highest among the different treatments. The amylase and hemicellulase activities for piglets fed diet containing 10 % B. brevis FJAT-1501-BPA fermentation were significantly higher than those on the control diet and other treatments (P < 0.05). Moreover, usage of feed dietary supplementation with B. brevis FJAT-1501-BPA had positive effects on levels of enzymes and minerals in blood. The alkaline phosphatase, alanine aminotransferase, Fe and Mg concentrations for weaned piglets fed diet containing B. brevis FJAT-1501-BPA fermentation were significantly higher than for those on the control diet (P < 0.05). Furthermore, concentration of IgG in serum was higher in weaned piglets fed diet containing 1 % B. brevis FJAT-1501-BPA fermentation compared to other treatments. These results indicated that feeding with B. brevis FJAT-1501-BPA has the potential to improve growth performance, faecal microflora, faecal enzyme activities and blood parameters of weaned piglets.

Bifidobacteria strains isolated from stools of iron deficient infants can efficiently sequester iron

BACKGROUND

Bifidobacteria is one of the major gut commensal groups found in infants. Their colonization is commonly associated with beneficial effects to the host through mechanisms like niche occupation and nutrient competition against pathogenic bacteria. Iron is an essential element necessary for most microorganisms, including bifidobacteria and efficient competition for this micronutrient is linked to proliferation and persistence. For this research we hypothesized that bifidobacteria in the gut of iron deficient infants can efficiently sequester iron. The aim of the present study was to isolate bifidobacteria in fecal samples of iron deficient Kenyan infants and to characterize siderophore production and iron internalization capacity.

RESULTS

Fifty-six bifidobacterial strains were isolated by streaking twenty-eight stool samples from Kenyan infants, in enrichment media. To target strains with high iron sequestration mechanisms, a strong iron chelator 2,2-dipyridyl was supplemented to the agar media. Bifidobacterial isolates were first identified to species level by 16S rRNA sequencing, yielding B. bifidum (19 isolates), B. longum (15), B. breve (11), B. kashiwanohense (7), B. pseudolongum (3) and B. pseudocatenulatum (1). While most isolated bifidobacterial species are commonly encountered in the infantile gut, B. kashiwanohense was not frequently reported in infant feces. Thirty strains from culture collections and 56 isolates were characterized for their siderophore production, tested by the CAS assay. Siderophore activity ranged from 3 to 89% siderophore units, with 35 strains (41%) exhibiting high siderophore activity, and 31 (36%) and 20 (23%) showing intermediate or low activity. The amount of internalized iron of 60 bifidobacteria strains selected for their siderophore activity, was in a broad range from 8 to118 μM Fe. Four strains, B. pseudolongum PV8-2, B. kashiwanohense PV20-2, B. bifidum PV28-2a and B. longum PV5-1 isolated from infant stool samples were selected for both high siderophore activity and iron internalization.

CONCLUSIONS

A broad diversity of bifidobacteria were isolated in infant stools using iron limited conditions, with some strains exhibiting high iron sequestration properties. The ability of bifidobacteria to efficiently utilize iron sequestration mechanism such as siderophore production and iron internalization may confer an ecological advantage and be the basis for enhanced competition against enteropathogens.

Insights into bread melanoidins: fate in the upper digestive tract and impact on the gut microbiota using in vitro systems

Bread melanoidins are partially degraded in the small intestine and induce a dramatic decrease of enterobacteria during batch fermentation.

Toxicological effects of dietary nickel chloride on intestinal microbiota

This study was designed to evaluate the toxicological effect of dietary nickel chloride (NiCl2) on the counts of intestinal bacteria and diversity of microorganisms in broilers. Plate counting and polymerase chain reaction-denaturing gradient gel electrophoresis (PCR-DGGE) assays were used. A total of 240 one-day-old avian broilers chicks were divided into four equal groups and kept on corn-soybean basal diet along with supplementation of 0, 300, 600 and 900 mg/kg NiCl2 for 42 days. Samples were taken at 21 and 42 days of age during the experiment. The bacterial count results showed that dietary NiCl2 in the range of 300 to 900 mg/kg decreased the counts of Bifidobacterium spp. and Lactobacillus, increased Escherichia coli (E. coli) and Enterococcus spp. in the ileum and cecum. PCR-DGGE analysis showed that bacterial band numbers, profile similarity, and the Shannon index of the ileum and cecum were all decreased in the 300, 600, and 900 mg/kg groups at 21 and 42 days of age. In conclusion, dietary NiCl2 affected the amount and diversity of intestinal microbiota in the ileum and cecum of broilers. This finding implies that NiCl2 has toxicological effect on the intestinal ecosystem and, possibly functions.

Evaluation of culture media for selective enumeration of bifidobacteria and lactic acid bacteria

The purpose of this study was to test the suitability of Transgalactosylated oligosaccharides-mupirocin lithium salt (TOS-MUP) and MRS-clindamycin-ciprofloxacin (MRS-CC) agars, along with several other culture media, for selectively enumerating bifidobacteria and lactic acid bacteria (LAB) species commonly used to make fermented milks. Pure culture suspensions of a total of 13 dairy bacteria strains, belonging to eight species and five genera, were tested for growth capability under various incubation conditions. TOS-MUP agar was successfully used for the selective enumeration of both Bifidobacterium animalis subsp. lactis BB-12 and B. breve M-16 V. MRS-CC agar showed relatively good selectivity for Lactobacillus acidophilus, however, it also promoted the growth of Lb. casei strains. For this reason, MRS-CC agar can only be used as a selective medium for the enumeration of Lb. acidophilus if Lb. casei is not present in a product at levels similar to or exceeding those of Lb. acidophilus. Unlike bifidobacteria and coccus-shaped LAB, all the lactobacilli strains involved in this work were found to grow well in MRS pH 5.4 agar incubated under anaerobiosis at 37 °C for 72 h. Therefore, this method proved to be particularly suitable for the selective enumeration of Lactobacillus spp.

Microbiological quality and characteristics of probiotic products in China

BACKGROUND

Probiotics are widely used in the food industry and medicine fields in China, but few studies have been conducted to evaluate the actual microbial amounts and species in probiotic products, which may conflict with the labels and mislead consumers to choose inappropriate foods or medicines.

RESULTS

Twenty commercial dairy products and eight commercial 'healthcare' samples were collected from markets in China and tested using culture-dependent and culture-independent methods. The results suggested that the total bacterial counts of most commercial products met the minimum quantitative requirement of the Chinese national standard (6.00 log colony-forming units g(-1) ). However, the bacterial counts of specific species were inconsistent with the labelling. In parallel, denaturing gradient gel electrophoresis analysis indicated that some probiotic-containing products were wrongly labelled; no Bifidobacterium species were detected in the products claiming to contain bifidobacteria, and the probiotic characteristics (antimicrobial activity, acid resistance and bile resistance) of some isolates had degraded. Moreover, some contaminating bacteria, e.g. Enterobacter sp., Klebsiella sp. and Serratia sp., were also detected in these products.

CONCLUSION

The combination of culture-dependent and culture-independent methods was proven to quickly and conveniently detect the microbial diversity in probiotic products, and more effort is required to regulate the probiotic market in China.

Comparison of two oral probiotic preparations in a randomized crossover trial highlights a potentially beneficial effect of Lactobacillus paracasei NCC2461 in patients with allergic rhinitis

Background

There is promising but conflicting evidence to recommend the addition of probiotics to foods for prevention and treatment of allergy. Based on previous studies with fermented milk containing Lactobacillus paracasei NCC2461, we aimed to compare the effect of a powder form of the latter probiotic with the effect of a blend of Lactobacillus acidophilus ATCC SD5221 and Bifidobacterium lactis ATCC SD5219 in patients with allergic rhinitis.

Methods

A double-blind, randomized, cross-over study, involving 31 adults with allergic rhinitis to grass pollen, was performed outside the grass pollen season (registration number: NCT01233154). Subjects received each product for 4-weeks in two phases separated by a wash-out period of 6 to 8 weeks. A nasal provocation test was performed before and after each 4-week product intake period, and outcome parameters (objective and subjective clinical symptoms; immune parameters) were measured during and/or 24 hours after the test.

Results

Out of the 31 subject enrolled, 28 completed the study. While no effect was observed on nasal congestion (primary outcome), treatment with NCC2461 significantly decreased nasal pruritus (determined by VAS), and leukocytes in nasal fluid samples, enhanced IL-5, IL-13 and IL-10 production by peripheral blood mononuclear cells in an allergen specific manner and tended to decrease IL-5 secretion in nasal fluid, in contrast to treatment with the blend of L. acidophilus and B. lactis.

Conclusions

Despite short-term consumption, NCC2461 was able to reduce subjective nasal pruritus while not affecting nasal congestion in adults suffering from grass pollen allergic rhinitis. The associated decrease in nasal fluid leukocytes and IL-5 secretion, and the enhanced IL-10 secretion in an allergen specific manner may partly explain the decrease in nasal pruritus. However, somewhat unexpected systemic immune changes were also noted. These data support the study of NCC2461 consumption in a seasonal clinical trial to further demonstrate its potentially beneficial effect.

Evaluation of adhesion properties and antibacterial activities of the infant gut commensal Bifidobacterium bifidum PRL2010

Bifidobacteria are extensively exploited by the food industry as health-promoting microorganisms. However, very little is known about the molecular mechanisms responsible for these beneficial activities, or the molecular players that sustain their ability to colonize and persist within the human gut. Here, we have investigated the enteric adaptation features of the gut commensal Bifidobacterium bifidum PRL2010, originally isolated from infant feces. This strain was able to survive under gastrointestinal challenges, while it was shown to adhere to human epithelial intestinal cell monolayers (Caco 2 and HT-29), thereby inhibiting adhesion of pathogenic bacteria such as Escherichia coli and Cronobacter sakazakii.

Prevalence and characterization of Clostridium perfringens from the faecal microbiota of elderly Irish subjects

The aim of this study was to investigate the diversity and composition of the intestinal microbiota of elderly subjects using a combination of culture-dependent techniques and 16S rRNA gene amplicon sequencing. The study was performed as part of the ELDERMET project, in which 368 faecal samples were assessed for viable numbers of Bifidobacterium spp., Lactobacillus spp. and Enterobacteriaceae on selective agar. However, the Bifidobacterium selective medium used also supported the growth of Clostridium perfringens, which appeared as distinct colonies and were subsequently characterized phenotypically and genotypically. All the isolates were confirmed as toxin biotype A producers. In addition, three isolates tested also had the genetic determinants for the β2 toxin. Of the 368 faecal samples assessed, C. perfringens was detected in 28 samples (7.6%). Moreover, C. perfringens was observed in samples from subjects in all the residence locations assessed but was most prevalent in subjects from long-stay residential care, with 71.4% of the samples (63.2% of the subjects) being from this residence location, and with a shedding level in excess of 10(6) c.f.u. (g faeces)(-1). Microbiota profiling revealed some significant compositional changes across both the family and genus taxonomic levels between the C. perfringens-positive and -negative datasets. Levels of culturable Bifidobacterium spp. and Lactobacillus spp. were significantly (P<0.05) lower in the C. perfringens-positive samples. Sequence-based methods also confirmed a significant difference in the Bifidobacterium spp. level (P<0.05) between both datasets. Taken together, these data suggest that a high viable count [>10(6) c.f.u. (g faeces)(-1)] of C. perfringens in stool samples may be indicative of a less healthy microbiota in the intestine of elderly people in long-stay residential care.

Effect of dietary vanadium on intestinal microbiota in broiler

The purpose of this 42-day study was to examine the effect of dietary vanadium on intestinal microorganism diversity in the duodenum, ileum, cecum, and rectum segments of broilers by the plate count and polymerase chain reaction-denaturing gradient gel electrophoresis (DGGE). A total of 420 1-day-old avian broilers were divided into six groups and fed on a control diet or the same diet supplemented with vanadium at the doses of 5, 15, 30, 45, and 60 mg/kg in the form of ammonium metavanadate. In comparison with control group, the dietary vanadium at the doses of 45 and 60 mg/kg could decrease the counts of Bifidobacterium spp. in the intestinal tract at 21 and 42 days of age. With increasing level in dietary vanadium, the counts of Escherichia coli were significantly increased in the ileum, cecum, and rectum and were decreased in the duodenum at 21 and 42 days of age. However, the counts of Lactobacilli were decreased in the cecum and rectum and increased in the ileum of 45 and 60 mg/kg groups. The colonization of these three bacteria could be affected by dietary vanadium. DGGE analysis showed that the number of bands in duodenum, ileum, cecum, and rectum were obviously decreased in the 30, 45, and 60 mg/kg groups at 21 and 42 days of age. In conclusion, the dietary vanadium in excess of 30 mg/kg could alter the amount and diversity of intestinal bacteria in broilers, implying that the structure and initial balance in the intestinal microbiota were disrupted.

Comparison of the kinetics of intestinal colonization by associating 5 probiotic bacteria assumed either in a microencapsulated or in a traditional, uncoated form

BACKGROUND

Beneficial findings concerning probiotics are increasing day by day. However, one of the most important parameters able to significantly affect the probiotic value of a microorganism is its survival during the transit through the stomach and the duodenum. Some techniques may be applied that aim to improve this parameter, but microencapsulation of bacterial cells remains one of the most important. A recent study assessed the kinetics of intestinal colonization by a mixture of 2 probiotic strains, given either in a microencapsulated or in a traditional, uncoated form.

METHODS

A comparison between the intestinal colonization by associating 5 microencapsulated bacteria and the same uncoated strains was performed by a double-blind, randomized, cross-over study. The study (December 2007 to January 2009) involved 53 healthy volunteers. In particular, subjects were divided into 2 groups: group A (27 subjects) was given a mix of probiotic strains Probiotical S.p.A. (Novara, Italy), Lactobacillus acidophilus LA02 (DSM 21717), Lactobacillus rhamnosus LR04 (DSM 16605), L. rhamnosus GG, or LGG (ATCC 53103), L. rhamnosus LR06 (DSM 21981), and Bifidobacterium lactis BS01 (LMG P-21384) in an uncoated form, whereas group B (26 subjects) received the same strains microencapsulated with a gastroprotected material. The uncoated strains were administered at 5×10⁹ cfu/strain/d (a total of 25×10⁹ cfu/d) for 21 days, whereas the microencapsulated bacteria were given at 1×10⁹ cfu/strain/d (a total of 5×10⁹ cfu/d) for 21 days. At the end of the first period of supplementation with probiotics, a 3-week wash-out phase was included in the study setting. At the end of the wash-out period, the groups crossed over their treatment regimen; that is, group A was administered the microencapsulated bacteria and group B the uncoated bacteria. The administered quantities of each strain were the same as the first treatment. A quantitative evaluation of intestinal colonization by probiotics, either microencapsulated or uncoated, was undertaken by examining fecal samples at the beginning of the study (time 0), after 10 days and after 21 days of each treatment period. In particular, fecal total Lactobacilli, heterofermentative Lactobacilli, and total Bifidobacteria were quantified at each checkpoint. A genomic analysis of an appropriate number of colonies was performed to quantify individual L. rhamnosus strains among heterofermentative Lactobacilli.

RESULTS

A statistically significant increase in the fecal amounts of total Lactobacilli, heterofermentative Lactobacilli, and total Bifidobacteria was registered in both groups at the end of each supplementation period compared with d₀ or d₄₂ (group A: P=0.0002, P=0.0001, and P<0.0001 at d₂₁, P=0.0060, P=0.0069, and P<0.0001 at d₆₃ for total Lactobacilli, heterofermentative Lactobacilli, and Bifidobacteria, respectively; group B: P=0.0002, P=0.0006, and P<0.0001 at d₂₁, P=0.0015, P=0.0016, and P<0.0001 at d₆₃ for total Lactobacilli, heterofermentative Lactobacilli, and Bifidobacteria, respectively), confirming the ability of each strain in the administered composition to colonize the human gut, whether supplemented in a gastroprotected or in a traditional freeze-dried form. On the contrary, subjects receiving microencapsulated bacteria reported a kinetics of intestinal colonization that was entirely comparable with those who were given uncoated strains at a 5 times higher amount.

CONCLUSIONS

The microencapsulation technique used in this study is a valid approach aimed to significantly improve the survival of strains during gastroduodenal transit, thus enhancing their probiotic value and allowing the use of a 5 times lower amount.

Reduction of antibiotics using microorganisms containing glutathione S-transferases under immobilized conditions

The degradation of several antibiotics (tetracycline, sulfathiazole, ampicillin) was performed with immobilized bacterial cells containing the glutathione S-transferases (GSTs). Antibiotics in animal feed contaminated wastewater usually inhibit the growth of microorganisms that treat the wastewater, so a bio-friendly treatment method is required. Therefore, we have shown that the inhibitory effects of antibiotics on bacteria were reduced by microorganisms containing detoxifying enzyme GSTs by using a cell immobilizing method in a bioreactor. The initial concentrations of tetracycline, sulfathiazole and ampicillin were 100mg/L, 100mg/L and 50mg/L respectively, which are typical of the range detected in pig feed in Korea. In the results, we observed the removal efficiency of tetracycline to be almost 70% with Staphylococcus epidermidis in the bioreactor, suggesting that this method of antibiotic removal is worthy of further study.

Production of the antimicrobial peptides Caseicin A and B by Bacillus isolates growing on sodium caseinate

AIMS

The aim of this study was to identify Bacillus isolates capable of degrading sodium caseinate and subsequently to generate bioactive peptides with antimicrobial activity.

METHODS AND RESULTS

Sodium caseinate (2.5% w/v) was inoculated separately with 16 Bacillus isolates and allowed to ferment overnight. Protein breakdown in the fermentates was analysed using gel permeation-HPLC (GP-HPLC) and screened for peptides (<3-kDa) with MALDI-TOF mass spectrometry. Caseicin A (IKHQGLPQE) and caseicin B (VLNENLLR), two previously characterized antimicrobial peptides, were identified in the fermentates of both Bacillus cereus and Bacillus thuringiensis isolates. The caseicin peptides were subsequently purified by RP-HPLC and antimicrobial assays indicated that the peptides maintained the previously identified inhibitory activity against the infant formula pathogen Cronobacter sakazakii.

CONCLUSIONS

We report a new method using Bacillus sp. to generate two previously characterized antimicrobial peptides from casein.

SIGNIFICANCE AND IMPACT OF THE STUDY

This study highlights the potential to exploit Bacillus sp. or the enzymes they produce for the generation of bioactive antimicrobial peptides from bovine casein.

Correlation of rRNA gene amplicon pyrosequencing and bacterial culture for microbial compositional analysis of faecal samples from elderly Irish subjects

AIMS

The aim of this investigation was to establish the degree of correlation between measurements from culture-dependent microbiological techniques and from next generation sequencing technologies.

METHODS AND RESULTS

Data generated by both techniques were collected from faecal samples from 185 elderly Irish people involved in the ongoing ELDERMET study (http://eldermet.ucc.ie). The results for three groups of intestinal bacteria were compared. Bifidobacterium sp., Lactobacillus sp. and Enterobacteriaceae were enumerated on selective media through culture-dependent techniques, whereas proportions of these bacteria were determined through sequencing technology against the background of other bacteria. The Spearman's rank correlation coefficient determined a good correlation between results from culture-dependent microbiology and culture-independent techniques for all three bacterial groups assessed (correlation coefficients for Bifidobacterium sp., Lactobacillus sp. and Enterobacteriaceae were 0·380, 0·366 and 0·437, respectively).

CONCLUSION

Correlation between the two methods implies that a single method is capable of profiling intestinal Bifidobacterium, Lactobacillus and Enterobacteriaceae populations. However, both methods have advantages that justify their use in tandem.

SIGNIFICANCE AND IMPACT OF THE STUDY

This is the first extensive study to compare bacterial counts from culture-dependent microbiological techniques and from next generation sequencing technologies.

Insights into physiological and genetic mupirocin susceptibility in bifidobacteria

Mupirocin is an antibiotic commonly used in selective media for the isolation of bifidobacteria. However, little is known about the genetic traits responsible for bifidobacterial resistance to mupirocin. Our investigation demonstrates that all of the bifidobacteria tested exhibit a phenotype of generally high resistance to this antibiotic. The genotypic reason for bifidobacterial mupirocin resistance was further characterized by sequencing of the isoleucyl-tRNA synthetase gene (ileS) coupled with three-dimensional modeling of the encoded protein and cloning of the ileS gene of Bifidobacterium bifidum PRL2010 in a mupirocin-sensitive Escherichia coli strain. These analyses revealed key amino acid residues of the IleS protein that apparently are crucial for conferring a mupirocin resistance phenotype to bifidobacteria.

Influence of isomalto-oligosaccharides on intestinal microbiota in rats

AIMS

Isomalto-oligosaccharides (IMO) with α(1 --> 6) and α(1 --> 4) glucosidic linkages are produced by enzymatic conversion of starch. IMO are only partially digestible but data on their influence on intestinal microbiota are limited. It was the aim of this study to investigate the effect of IMO diet on intestinal microbiota and short-chain fatty acids production (SCFA) in rats.

METHODS AND RESULTS

Three groups of F344 rats, each consisting of six animals, were fed IMO, inulin or a control diets for six weeks. A qualitative assessment of the intestinal microbiota was achieved by PCR-denaturing gradient gel electrophoresis (DGGE). Major bacterial taxa were quantified by quantitative PCR (qPCR), and SCFA were measured using gas chromatography. Quantitative PCR demonstrated that lactobacilli were one of the dominant bacterial taxa in faecal samples from rats. IMO increased the number of lactobacilli and the total number of intestinal bacteria in rats fed IMO compared with animals receiving control and inulin diets. Furthermore, PCR-DGGE with lactobacilli-specific primers showed an altered biodiversity of lactobacilli in rats fed IMO compared with control diet.

CONCLUSIONS

IMO selectively stimulates lactobacilli and increases their diversity in rats.

SIGNIFICANCE AND IMPACT OF STUDY

  Isomalto-oligosaccharides specifically stimulate growth of intestinal lactobacilli in a rat model system.

Diversity of Lactobacillus and Bifidobacterium in feces of herbivores, omnivores and carnivores

The Lactobacillus and Bifidobacterium population in the feces of 26 animals (16 species) were studied by culture-dependent and culture-independent techniques. Lactobacilli were detected from a few herbivores, all carnivores and some omnivores. Lactobacillus johnsonii, Lactobacillus reuteri, Lactobacillus salivarius, Lactobacillus vaginalis and Lactobacillus ingluviei were the most dominant lactobacilli in carnivores. These species were, however, not predominant in herbivores and omnivores. Lactobacillus brevis, Lactobacillus casei, Lactobacillus parabuchneri, Lactobacillus plantarum, Lactobacillus sakei, Leuconostoc mesenteroides and Leuconostoc pseudomesenteroides, usually present in raw plant material, were present in omnivores but not in carnivores. Bifidobacteria were detected in only four herbivores and two omnivores. Bifidobacterium pseudolongum was the only Bifidobacterium species detected in herbivores. Bifidobacteria detected in the two omnivores are phylogenetically not closely related to known species and are possible novel species in the genus.

Evaluation of the intestinal colonization by microencapsulated probiotic bacteria in comparison with the same uncoated strains

BACKGROUND

Beneficial findings concerning probiotics are increasing day by day. However, one of the most important parameter which affects the probiotic activity of a microorganism is its survival during the gastroduodenal transit. Some microencapsulation techniques could be applied to bacterial cells to improve this parameter.

METHODS

A comparison between the intestinal colonization by microencapsulated bacteria and the same not microencapsulated strains has been conducted in a double blind, randomized, cross-over study. The study (April to July 2005) involved 44 healthy volunteers. In particular, participants were divided into 2 groups: group A (21 participants) received a mix of probiotic strains Lactobacillus plantarum LP01 (LMG P-21021) and Bifidobacterium breve BR03 (DSM 16604) in an uncoated form, group B (23 participants) was given the same strains microencapsulated with a gastroresistant material. The not microencapsulated strains were administered at 5 x 10(9) colony forming units/strain/d for 21 days, whereas the microencapsulated bacteria were given at 1 x 10(9) colony forming units/strain/d for 21 days. At the end of the first period of treatment with probiotics a 3 weeks washout phase has been included in the study protocol. At the end of the washout period the groups were crossed: in detail, group A had the microencapsulated and group B the uncoated bacteria. The administered amounts of each strain were the same as the first treatment. The quantitative evaluation of intestinal colonization by strains microencapsulated or not microencapsulated was made by fecal samples examination at the beginning of the clinical trial, after 10 and 21 days of each treatment period. In particular, fecal heterofermentative Lactobacilli and Bifidobacteria have been counted.

RESULTS

A statistically significant increase in the fecal amounts of Lactobacilli and Bifidobacteria was recorded in both groups at the end of each treatment compared with d0 or d42 (P<0.0001 and P<0.0001 at d21, P<0.0001 and P<0.0001 at d63 for Lactobacilli and Bifidobacteria, respectively), confirming the ability of the 2 strains to colonize the human gut, either in a gastroprotected form or not. Participants treated with the microencapsulated bacteria reported a kinetics of intestinal colonization quite similar to participants who received not coated strains.

CONCLUSIONS

Probiotics are able to exert many different beneficial effects on the human host. These effects are mediated by the number of viable cells which reach the gut. The microencapsulation technique used in this study is a valid strategy to significantly improve gastroresistance of strains, thus enhancing their probiotic activity and allowing the use of a 5 times lower amount.

New selective medium for selection of bifidobacteria from human feces

This work reports an alternative selective medium for reliable and efficient isolation of human fecal bifidobacteria. It uses a base commercially available, does not need pH adjustment and can be autoclaved with its additives. It provides a useful alternative for fecal bifidobacteria isolation.

Exploring the diversity of the bifidobacterial population in the human intestinal tract

Although the health-promoting roles of bifidobacteria are widely accepted, the diversity of bifidobacteria among the human intestinal microbiota is still poorly understood. We performed a census of bifidobacterial populations from human intestinal mucosal and fecal samples by plating them on selective medium, coupled with molecular analysis of selected rRNA gene sequences (16S rRNA gene and internally transcribed spacer [ITS] 16S-23S spacer sequences) of isolated colonies. A total of 900 isolates were collected, of which 704 were shown to belong to bifidobacteria. Analyses showed that the culturable bifidobacterial population from intestinal and fecal samples include six main phylogenetic taxa, i.e., Bifidobacterium longum, Bifidobacterium pseudocatenulatum, Bifidobacterium adolescentis, Bifidobacterium pseudolongum, Bifidobacterium breve, and Bifidobacterium bifidum, and two species mostly detected in fecal samples, i.e., Bifidobacterium dentium and Bifidobacterium animalis subp. lactis. Analysis of bifidobacterial distribution based on age of the subject revealed that certain identified bifidobacterial species were exclusively present in the adult human gut microbiota whereas others were found to be widely distributed. We encountered significant intersubject variability and composition differences between fecal and mucosa-adherent bifidobacterial communities. In contrast, a modest diversification of bifidobacterial populations was noticed between different intestinal regions within the same individual (intrasubject variability). Notably, a small number of bifidobacterial isolates were shown to display a wide ecological distribution, thus suggesting that they possess a broad colonization capacity.

Antibiotic susceptibility testing of Bifidobacterium thermophilum and Bifidobacterium pseudolongum strains: Broth microdilution vs. agar disc diffusion assay

There is urgent need for having available suitable methods and data regarding the susceptibility levels of antibiotic resistant and sensitive strains of bifidobacteria. Based on a defined standard operation procedure, agar disc diffusion and broth microdilution were compared in order to evaluate the antimicrobial susceptibility profiles of 82 B. pseudolongum and 80 B. thermophilum strains mainly originating from the meat production chain. The methods that were assessed showed interpretable agreement within this study. The disc diffusion zone diameters are highly reproducible making the method a useful alternative to broth microdilution for antimicrobial susceptibility screening of bifidobacteria.

Antibiotic susceptibility of Bifidobacterium thermophilum and Bifidobacterium pseudolongum isolates from animal sources

The widespread use of antimicrobial substances has led to resistant populations of microorganisms in several ecosystems. In animal husbandry, the application of antibiotics has contributed to resistance development in pathogenic and commensal bacteria. These strains or their resistance genes can be spread along several ecological routes, including the food chain. Antibiotic resistance is important in terms of the safety of industrial strains, such as probiotics for food and feed. Bifidobacterium thermophilum and Bifidobacterium pseudolongum are known to comprise the major part of the bifidobacterial microbiota in the gut and feces of cattle and pigs. In this study, the antimicrobial susceptibility in bifidobacterial isolates of these species was investigated. Isolates from the beef and pork production chain were identified and typed to strain level, and the antimicrobial susceptibility level was tested to a set of antibiotics. Isolates with low susceptibility levels were screened by PCR for already described resistance genes. Strains atypically resistant to clindamycin, erythromycin, and tetracycline were determined. The resistance genes tet(O), tet(W), and erm(X) were detected in the bifidobacterial species that were examined.

Screening of Bacillus strains as potential probiotics and subsequent confirmation of the in vivo effectiveness of Bacillus subtilis MA139 in pigs

A total of 124 samples were collected from the intestine of broiler chickens, piglet faeces, fermented foods, soils and Chinese herbs. More than 750 strains of aerobic, spore-forming bacteria were isolated from these samples. The inhibitory activity of these spore-forming strains against Escherichia coli K88, E. coli K99, Salmonella typhimurium and Staphylococcus aureus was assessed using a disc plate diffusion assay. The six bacilli with the largest inhibition zones against the four indicator bacteria were chosen and assessed for their resistance to unfavorable conditions within simulated gut environments. The strain Bacillus subtilis MA139 showed full resistance to pH 2, 0.3% bile salts and exhibited the highest antimicrobial activity. Based on these results, B. subtilis MA139 was selected as a potential probiotic and fed to piglets at concentrations of 2.2 x 10(5), 2.2 x 10(6) or 2.2 x 10(7) CFU/g of feed during a 28-day feeding trial. A negative control consisting of the basal diet with no additives and a positive control consisting of the basal diet supplemented with 16 g/ton flavomycin were also included. Ninety piglets between 35 and 40 days old were used in the in vivo animal trials. B. subtilis MA139 enhanced daily gain (P = 0.10) and feed conversion (P = 0.03) compared with the negative control. The performance of pigs fed B. subtilis MA139 supplemented diets did not differ from that of pigs fed the antibiotic diet. There was a significant increase in Lactobacilli cell counts (P = 0.02) and a numerical decrease in E. coli counts (P = 0.05) in the faecal samples of pigs fed B. subtilis MA139 with 2.2 x 10(5) CFU/g of feed. The overall results of this study show that the use of initial co-culture with indicator pathogens, a disc plate diffusion assay and simulated gut environment tolerance tests is one of effective methods of screening Bacillus for probiotic use and that B. subtilis MA139 is a promising alternative to antibiotics for use as a feed additive in piglet diets.

Enumeration and identification of pediococci in powder-based products using selective media and rapid PFGE

In this study, pediococci selective medium (PSM) was evaluated for the enumeration of Pediococcus acidilactici and Pediococcus pentosaceus from probiotic animal feed and silage inoculants. PSM is based on the complex basal medium MRS supplemented with cysteine hydrochloride, novobiocin, vancomycin, and nystatin. No significant change in electivity was observed when pediococci where recovered from culture or powder-based products following incubation at 37 degrees C under anaerobic conditions for 24 h. The medium was suitable for the enumeration of pediococci in samples also containing bacilli, bifidobacteria, enterococci, lactobacilli, lactococci, propionibacteria, streptococci, and yeast components. However, to inhibit Lactobacillus plantarum and Lactobacillus casei, ampicillin was added and the revised medium, termed PSM+A, was also considered to be suitably elective for pediococci recovered from powder. In addition, a rapid PFGE protocol is presented, which allows Pediococcus species and strain verification from colonies in less than 3 days.

Bifidobacterium-selective isolation and enumeration from chicken caeca by a modified oligosaccharide antibiotic-selective agar medium

AIMS

To determine the efficacy and selectivity of an acidified, antibiotic-selective, oligosaccharide-containing media for enumerating Bifidobacterium spp. from chicken caeca samples.

METHODS AND RESULTS

Transoligosaccharide propionate agar medium (TOS) modified by addition of mupirocin (50 microg ml-1) and glacial acetic acid (1%, v/v), did not inhibit the growth of bifidobacteria compared with the control media yet inhibited the growth of Lactobacillus acidophilus, Lactobacillus gallinarum, Lactobacillus helveticus and Streptococcus gordonii.

CONCLUSIONS

Addition of mupirocin (50 microg ml-1) and glacial acetic acid (1%, v/v) to TOS (TOS-AM50), is an effective selective medium for isolation and enumeration of Bifidobacterium spp. from chicken caeca samples.

SIGNIFICANCE AND IMPACT OF THE STUDY

The development of an intestinal bifidobacteria-selective media contributes to the study of probiotics and prebiotics in poultry and potentially other species.