Lactobacillus isolates from weaned piglets’ mucosa with inhibitory activity against common porcine pathogens

Acid resistance and response to pH-induced stress in two Lactobacillus plantarum strains with probiotic potential

Two new Lactobacillus plantarum strains, KR6-DSM 28780 and M5 isolated from sour turnip and traditional dried fresh cheese, respectively, were evaluated for species identity, antibiotic susceptibility, resistance to gastrointestinal conditions and adaptive response to low pH. Resistance mechanisms involved in the adaptation to acid-induced stress in these two strains were investigated by quantitative PCR of the atpA, cfa1, mleS and hisD genes. In addition to absence of antibiotic resistance, the two L. plantarum strains showed excellent survival rates at pH values as low as 2.4. Adaptive response to low pH was clearly observed in both strains; strain KR6 was superior to M5, as demonstrated by its ability to survive during 3 h incubation at pH 2.0 upon adaptation to moderately acidic conditions. In contrast, acid adaptation did not significantly affect the survival rate during simulated passage through the gastrointestinal tract. In both strains, induction of histidine biosynthesis (hisD) was upregulated during the acid adaptation response. In addition, significant upregulation of the cfa1 gene, involved in modulation of membrane fatty acid composition, was observed during the adaptation phase in strain KR6 but not in strain M5. Cells adapted to moderately acidic conditions also showed a significantly increased viability after the lyophilisation procedure, a cross-protection phenomenon providing additional advantage in probiotic application.

Human intestinal mucosa-associated Lactobacillus and Bifidobacterium strains with probiotic properties modulate IL-10, IL-6 and IL-12 gene expression in THP-1 cells

Lactobacilli and bifidobacteria are considered one of the permanent genera of the physiological human intestinal microbiota and represent an enormous pool of potential probiotic candidates. Approximately 450 isolates of presumptive Lactobacillus or Bifidobacterium strains were obtained from bioptic samples of colonic and ileal mucosa from 15 adolescents aged 12 to 18 years. On the basis of randomly amplified polymorphic DNA (RAPD)-PCR analysis, 20 strains were selected for further taxonomic classification and characterisation, as well as assessment of probiotic properties and safety. Importantly, selected strains showed the capability of colonising different parts of the intestine. The most frequently isolated species was Lactobacillus paracasei followed by Lactobacillus fermentum. The majority of isolates were susceptible to antimicrobials of human and veterinary importance, however, tetracycline and/or erythromycin resistance was observed in Lactobacillus plantarum and L. fermentum strains. Thirteen strains were able to ferment more than 19 different carbon sources and three out of five tested strains exerted antagonistic activity against several different indicator strains. Two Lactobacillus isolates (L. paracasei L350 and L. fermentum L930 bb) and one Bifidobacterium isolate (Bifidobacterium animalis subsp. animalis IM386) fulfilled in vitro selection criteria for probiotic strains and exhibited strong downregulation of pro-inflammatory cytokines IL-6 and IL-12 and upregulation of anti-inflammatory IL-10. The selected strains represent suitable candidates for further studies regarding their positive influence on host health and could play an important role in ameliorating the symptoms of inflammatory bowel diseases.

Detection and quantification of probiotic strain Lactobacillus gasseri K7 in faecal samples by targeting bacteriocin genes

Lactobacillus gasseri K7 is a probiotic strain that produces bacteriocins gassericin K7 A and K7 B. In order to develop a real-time quantitative PCR assay for the detection of L. gasseri K7, 18 reference strains of the Lactobacillus acidophilus group and 45 faecal samples of adults who have never consumed strain K7 were tested with PCR using 14 pairs of primers specific for gassericin K7 A and K7 B gene determinants. Incomplete gassericin K7 A or K7 B gene clusters were found to be dispersed in different lactobacilli strains as well as in faecal microbiota. One pair of primers was found to be specific for the total gene cluster of gassericin K7A and one for gassericin K7B. The real-time PCR analysis of faecal samples spiked with K7 strain revealed that primers specific for the gene cluster of the gassericin K7 A were more suitable for quantitative determination than those for gassericin K7 B, due to the lower detection level. Targeting of the gassericin K7 A or K7 B gene cluster with specific primers could be used for detection and quantification of L. gasseri K7 in human faecal samples without prior cultivation. The results of this study also present new insights into the prevalence of bacteriocin-encoding genes in gastrointestinal tract.

In vitro inhibition of Clostridium difficile and Clostridium perfringens by commercial probiotic strains

Probiotics have gained importance in human and veterinary medicine to prevent and control clostridial enteric disease. Limited information is available on the ability of different probiotic bacteria used in food products to inhibit Clostridium difficile and Clostridium perfringens. The objective of this study was to examine the in vitro inhibitory effects of selected commercial bacterial strains on pathogenic clostridia and their growth characteristics under simulated gastrointestinal conditions. The inhibitory effects of 17 commercial strains of Lactobacillus (n = 16) and Bifidobacterium (n = 1) on the reference strains of C. difficile and C. perfringens were assessed by an agar well diffusion assay and by a broth culture inhibition assay using cell-free supernatant harvested at different growth phases, with and without pH neutralization. To study growth characteristics, probiotic strains were cultivated in different acid and bile environments, and growth in the modified media was compared to growth in standard medium. In the agar well diffusion assay, supernatant obtained from two probiotic strains inhibited the growth of both reference and clinical strains of C. perfringens. This effect as seen when supernatant was assessed with and without pH neutralization. Supernatants obtained from 10 probiotic strains inhibited C. difficile only when supernatant was added without pH neutralization. In the broth culture inhibition assay, growth of C. perfringens and C. difficile was inhibited by supernatant without pH neutralization from 5 and 10 probiotic strains, respectively. All potential probiotic strains were able to grow at pH 4.0 and in the presence of 0.15% and 0.3% bile but none were able to grow or survive at pH 2.0. Altogether five probiotic strains [Lactobacillus plantarum (n = 2), Lactobacillus rhamnosus (n = 2), Bifidobacterium animalis lactis (n = 1)] were shown to inhibit all strains of C. difficile and C. perfringens. The inhibitory effect was probiotic strain-specific. Two strains showed a pH-independent inhibitory effect likely due to production of either antibiotics or bacteriocins inhibiting C. perfringens only. These strains have favourable growth characteristics for use as probiotics and their efficacy as prophylactic or therapeutic measures against clostridial enteric disease should be further evaluated by clinical trials in animals.

Evaluation of Lactobacillus strains for selected probiotic properties

Eleven strains of Lactobacillus collected in the Culture Collection of Dairy Microorganisms (CCDM) were evaluated for selected probiotic properties such as survival in gastrointestinal fluids, antimicrobial activity, and competition with non-toxigenic Escherichia coli O157:H7 for adhesion on Caco-2 cells. The viable count of lactobacilli was reduced during 3-h incubation in gastric fluid followed by 3-h incubation in intestinal fluid. All strains showed antimicrobial activity and the three most effective strains inhibited the growth of at least 16 indicator strains. Antimicrobial metabolites of seven strains active against Lactobacillus and Clostridium indicator strains were found to be sensitive to proteinase K and trypsin, which indicates their proteinaceous nature. The degree of competitive inhibition of non-toxigenic E. coli O157:H7 adhesion on the surface of Caco-2 cells was strain-dependent. A significant decrease (P < 0.05) in the number of non-toxigenic E. coli O157:H7 adhering to Caco-2 cells was observed with all lactobacilli. Three strains were selected for additional studies of antimicrobial activity, i.e., Lactobacillus gasseri CCDM 215, Lactobacillus acidophilus CCDM 149, and Lactobacillus helveticus CCDM 82.

Nutritional factors influencing intestinal health of the neonate

Dietary nutrients are essential for gastrointestinal (GI) growth and function, and nutritional support of GI growth and development is a significant component of infant care. For healthy full-term neonates, nutritional provisions of the mother's milk and/or formula will support normal maturation of structure and function of the GI tract in most infants. The composition of breast milk affects GI barrier function and development of a competent mucosal immune system. The functional nutrients and other bioactive components of milk support a microenvironment for gut protection and maturation. However, premature infants struggle with feeding tolerance impairing normal GI function, leading to intestinal dysfunction and even death. The high prevalence worldwide of enteric diseases and dysfunction in neonates has led to much interest in understanding the role of nutrients and food components in the establishment and maintenance of a functioning GI tract. Neonates who do not receive enteral feeding as either mother's milk or formula are supported by total parental nutrition (TPN). The lack of enteral nutrition can compound intestinal dysfunction, leading to high morbidity and mortality in intestinally compromised infants. Reciprocally, enteral stimulation of an immature GI tract can also compound intestinal dysfunction. Therefore, further understanding of nutrient interactions with the mucosa is necessary to define nutritional requirements of the developing GI tract to minimize intestinal complications and infant morbidity. Piglet models of intestinal development and function are similar to humans, and this review summarizes recent findings regarding nutrient requirements for growth and maintenance of intestinal health. In particular, this article reviews the role of specific amino acids (arginine, glutamine, glutamate, and threonine), fatty acids (long chain polyunsaturated, medium chain, and short chain), various prebiotic carbohydrates (short-chain fructo-oligosaccharide, fructo--oligosaccharide, lacto-N-neotetraose, human milk oligosaccharide, polydextrose, and galacto-oligosaccharide), and probiotics that have been examined in the suckling piglet model of intestinal health.

The gut microbiome of kittens is affected by dietary protein:carbohydrate ratio and associated with blood metabolite and hormone concentrations

High-protein, low-carbohydrate (HPLC) diets are common in cats, but their effect on the gut microbiome has been ignored. The present study was conducted to test the effects of dietary protein:carbohydrate ratio on the gut microbiota of growing kittens. Male domestic shorthair kittens were raised by mothers fed moderate-protein, moderate-carbohydrate (MPMC; n 7) or HPLC (n 7) diets, and then weaned at 8 weeks onto the same diet. Fresh faeces were collected at 8, 12 and 16 weeks; DNA was extracted, followed by amplification of the V4–V6 region of the 16S rRNA gene using 454 pyrosequencing. A total of 384 588 sequences (average of 9374 per sample) were generated. Dual hierarchical clustering indicated distinct clustering based on the protein:carbohydrate ratio regardless of age. The protein:carbohydrate ratio affected faecal bacteria. Faecal Actinobacteria were greater (P< 0·05) and Fusobacteria were lower (P< 0·05) in MPMC-fed kittens. Faecal Clostridium, Faecalibacterium, Ruminococcus, Blautia and Eubacterium were greater (P< 0·05) in HPLC-fed kittens, while Dialister, Acidaminococcus, Bifidobacterium, Megasphaera and Mitsuokella were greater (P< 0·05) in MPMC-fed kittens. Principal component analysis of faecal bacteria and blood metabolites and hormones resulted in distinct clusters. Of particular interest was the clustering of blood TAG with faecal Clostridiaceae, Eubacteriaceae, Ruminococcaceae, Fusobacteriaceae and Lachnospiraceae; blood ghrelin with faecal Coriobacteriaceae, Bifidobacteriaceae and Veillonellaceae; and blood glucose, cholesterol and leptin with faecal Lactobacillaceae. The present results demonstrate that the protein:carbohydrate ratio affects the faecal microbiome, and highlight the associations between faecal microbes and circulating hormones and metabolites that may be important in terms of satiety and host metabolism.

Polydextrose enrichment of infant formula demonstrates prebiotic characteristics by altering intestinal microbiota, organic acid concentrations, and cytokine expression in suckling piglets

Oligosaccharides, the 3rd-most abundant component in human milk, are virtually absent from infant formulas and from the cow milk on which most are based. In breast-fed infants, human milk oligosaccharides (HMO) act as both receptor analogs, interfering with pathogen adhesion, and as prebiotics, stimulating the growth of certain commensal bacteria (e.g. bifidobacteria) and supporting the innate immunity. To further align the functional properties of infant formula with those of human milk, polydextrose (PDX) is proposed as a substitute for HMO. To determine the prebiotic functionality of PDX, 1-d-old pigs were fed a cow milk-based formula supplemented with increasing concentrations of PDX (0, 1.7, 4.3, 8.5, or 17 g/L) for 18 d (n = 13). Additional reference groups included pigs sampled at d 0 and sow-reared pigs sampled at d 18 (n = 12). Ileal Lactobacilli CFU, but not Bifidobacteria, increased linearly with increasing PDX (P = 0.02). The propionic acid concentration in digesta linearly increased with the PDX level (P = 0.045) and lactic acid increased linearly by 5-fold with increasing PDX (P = 0.001). Accordingly, digesta pH decreased linearly (P < 0.05) as PDX increased, with a maximal reduction approaching 0.5 pH units in pigs fed 17 g/L. Expression of TNFα, IL-1β, and IL-8 showed a negative quadratic pattern in response to PDX supplementation, declining at intermediate concentrations and rebounding at higher concentrations of PDX. In summary, PDX enrichment of infant formula resulted in a prebiotic effect by increasing ileal lactobacilli and propionic and lactic acid concentrations and decreasing pH with associated alterations in ileal cytokine expression.

New topics and limits related to the use of beneficial microbes in pig feeding

Reports highlighting the positive effects of probiotics on the performance of pigs or on in vitro traits are now quite frequent, but the use of probiotics in feed compounds has not been widespread. Prerequisites for the healthy and efficient growth of young pigs are the rapid maturation of the gut mucosa and the mucosa-associated lymphoid tissue, and the formation of a local stable and complex bacterial community. In neonatal pigs, suckling and the maternal environment shape the gut microbiota. Later, when weaning stress causes a transient drop in favourable bacteria, the oral supply of microbes could contribute to re-establish the microbiota balance. Some strains isolated from piglets were tested for their ability to settle in the intestine. After weaning, piglets experience new and often unfavourable bacteria. Probiotics have been investigated to contrast the enteropathogens, owing to their properties (production of antibacterial molecules, competition on adhesion sites, stimulation of immune response, etc.). Data in general show that their oral administration can be favourable or, at least, innocuous. However, two cases are presented here, where a probiotic given to pigs already combating enteropathogens impaired pig health, and this could be explained by their effect on the immune response. A more tolerogenic response of the host is expected when beneficial bacteria directly contrast the pathogens, probiotics are claimed to directly modulate or even activate the immune system. For one probiotic divergent effects on growth and health are presented, and these differences may be due to different experimental details or different starting microbiological environments. Scarce data are available on specific immune responses induced by commensal microbes in pigs, and on the interaction of resident microbiota with orally supplied probiotics. Increased knowledge of the role of commensal microbiota in the gut and in the pig metabolism, helps in selecting the best bacteria and in designing the best feeding strategies for improving the efficacy and the reliability of their oral use.

Specific degradation of the mucus adhesion-promoting protein (MapA) of Lactobacillus reuteri to an antimicrobial peptide

The intestinal flora of mammals contains lactic acid bacteria (LAB) that may provide positive health effects for the host. Such bacteria are referred to as probiotic bacteria. From a pig, we have isolated a Lactobacillus reuteri strain that produces an antimicrobial peptide (AMP). The peptide was purified and characterized, and it was unequivocally shown that the AMP was a well-defined degradation product obtained from the mucus adhesion-promoting protein (MapA); it was therefore termed AP48-MapA. This finding demonstrates how large proteins might inherit unexpected pleiotropic functions by conferring antimicrobial capacities on the producer. The MapA/AP48-MapA system is the first example where a large protein of an intestinal LAB is shown to give rise to such an AMP. It is also of particular interest that the protein that provides this AMP is associated with the binding of the bacterium producing it to the surface/lining of the gut. This finding gives us new perspective on how some probiotic bacteria may successfully compete in this environment and thereby contribute to a healthy microbiota.