In Vitro Evaluation of Beneficial Properties of Bacteriocinogenic <Emphasis Type="Italic">Lactobacillus plantarum</Emphasis> ST8Sh

Lactobacillus plantarum ST8Sh, isolated from Bulgarian salami “shpek” and previously characterized as bacteriocin producer, was evaluated for its beneficial properties. Based on the PCR analysis, Lb. plantarum ST8Sh was shown to host a gene related to the production of adhesion proteins such as Mab, Mub, EF, and PrgB. Genetic and physiological tests suggest Lb. plantarum ST8Sh to represent a potential probiotic candidate, including survival in the presence of low levels of pH and high levels of ox bile, production of β-galactosidase, bile salt deconjugation, high level of hydrophobicity, functional auto- and co-aggregation properties, and adhesion to cell lines. Application of semi-purified bacteriocin produced by Lb. plantarum ST8Sh in combination with ciprofloxacin presented synergistic effect on inhibition of Listeria monocytogenes Scott A. Based on observed properties, Lb. plantarum ST8Sh can be considered as a potential probiotic candidate with additional bacteriocinogenic properties.     

Use of the mCherry Fluorescent Protein To Study Intestinal Colonization by Enterococcus mundtii ST4SA and Lactobacillus plantarum 423 in Mice

Lactic acid bacteria (LAB) are natural inhabitants of the gastrointestinal tract (GIT) of humans and animals, and some LAB species receive considerable attention due to their health benefits. Although many papers have been published on probiotic LAB, only a few reports have been published on the migration and colonization of the cells in the GIT. This is due mostly to the lack of efficient reporter systems. In this study, we report on the application of the fluorescent mCherry protein in the in vivo tagging of the probiotic strains Enterococcus mundtii ST4SA and Lactobacillus plantarum 423. The mCherry gene, encoding a red fluorescent protein (RFP), was integrated into a nonfunctional region on the genome of L. plantarum 423 by homologous recombination. In the case of E. mundtii ST4SA, the mCherry gene was cloned into the pGKV223D LAB/Escherichia coli expression vector. Expression of the mCherry gene did not alter the growth rate of the two strains and had no effect on bacteriocin production. Both strains colonized the cecum and colon of mice.     

Comparison of Campylobacter jejuni isolates from human, food, veterinary and environmental sources in Iceland using PFGE, MLST and fla-SVR sequencing

Aims: To evaluate the probiotic properties of strains isolated from smoked salmon and previously identified as bacteriocin producers. Methods and Results: Strains Lactobacillus curvatus ET06, ET30 and ET31, Lactobacillus fermentum ET35, Lactobacillus delbrueckii ET32, Pediococcus acidilactici ET34 and Enterococcus faecium ET05, ET12 and ET88 survived conditions simulating the gastrointestinal tract (GIT) and produced bacteriocins active against several strains of Listeria monocytogenes, but presented very low activity against other lactic acid bacteria (LAB). Cell‐free supernatants containing bacteriocins, added to 3‐h‐old cultures of L. monocytogenes 603, suppressed growth over 12 h. Auto‐aggregation was strain‐specific, and values ranged from 7·2% for ET35 to 12·1% for ET05. Various degrees of co‐aggregation with L. monocytogenes 603, Lactobacillus sakei ATCC 15521 and Enterococcus faecalis ATCC 19443 were observed. Adherence of the bacteriocinogenic strains to Caco‐2 cells was within the range reported for Lactobacillus rhamnosus GG, a well‐known probiotic. The highest levels of hydrophobicity were recorded for Lact. curvatus (61·9–64·6%), Lact. fermentum (78·9%), Lact. delbrueckii (43·7%) and Ped. acidilactici (51·3%), which are higher than the one recorded for Lact. rhamnosus GG (53·3%). These strains were highly sensitive to several antibiotics and affected by several drugs from different generic groups in a strain‐dependent manner. Conclusions: Smoked salmon is a rich source of probiotic LAB. All strains survived conditions simulating the GIT and produced bacteriocins active against various pathogens. Adherence to Caco‐2 cells was within the range reported for Lact. rhamnosus GG, a well‐known probiotic. In addition, the high hydrophobicity readings recorded define the strains as good probiotics. Significance and Impact of the Study: Smoked salmon contains a number of different probiotic LAB and could be marketed as having a potential beneficial effect.     

Functional Characterization of Potential Probiotic Lactic Acid Bacteria Isolated from <Emphasis Type="Italic">Kalarei</Emphasis> and Development of Probiotic Fermented Oat Flour

Considerable variations among probiotics with respect to their health benefitting attributes fuel the research on bioprospecting of proficient probiotic strains from various ecological niches especially the poorly unexplored ones. In the current study, kalarei, an indigenous cheese-like fermented milk product, and other dairy-based sources like curd and raw milk were used for isolation of lactic acid bacteria (LAB). Among 34 LAB isolates, 7 that could withstand simulated gastrointestinal (GI) conditions were characterized for functional probiotic attributes, viz. adhesion ability, aggregation and coaggregation, extracellular enzyme producing capability, antibacterial activity against pathogens and antibiotic resistance. The isolate M-13 (from kalarei) which exhibited most of the desirable probiotic functional properties was identified as Lactobacillus plantarum based on 16S ribosomal DNA sequence analysis and designated as L. plantarum M-13. The sequence was submitted to GenBank (accession number KT592509). The study presents the first ever report of isolation of potential probiotic LAB, i.e. L. plantarum M-13 from indigenous food kalarei, and its application for development of potential probiotic fermented oat flour (PFOF). PFOF was analysed for parameters like viability of L. plantarum M-13, acidity and pH. Results show that PFOF serves as a good matrix for potential probiotic L. plantarum M-13 as it supported adequate growth of the organism (14.4 log cfu/ml after 72 h of fermentation). In addition, appreciable acid production by L. plantarum M-13 and consequential pH reduction indicates the vigorous and active metabolic status of the potential probiotic organism in the food matrix. Thus, study shows that fermented oat flour may possibly be developed as a potential probiotic carrier especially in view of the problems associated with dairy products as probiotic vehicles.     

<Emphasis Type="Italic">Lactobacillus plantarum</Emphasis> and Its Probiotic and Food Potentialities

The number of studies claiming probiotic health effects of Lactobacillus plantarum is escalating. Lb. plantarum is a lactic acid bacterium found in diverse ecological niches, highlighting its particular capabilities of adaptation and genome plasticity. Another function that needs to be underlined is the capabilities of Lb. plantarum to produce diverse and potent bacteriocins, which are antimicrobial peptides with possible applications as food preservative or antibiotic complementary agents. Taken together, all these characteristics design Lb. plantarum as a genuine model for academic research and viable biological agent with promising applications. The present review aims at shedding light on the safety of Lb. plantarum and run through the main studies underpinning its beneficial claims. The mechanisms explaining probiotic-related features are discussed.     

Characterization of the three selected probiotic strains for the application in food industry

Previously selected bacterial probiotic strains Enterococcus faecium L3, Lactobacillus plantarum L4 and Lactobacillus acidophilus M92 have shown their potential as functional starter cultures in silage, white cabbage and milk fermentation. Therefore, the phenotypic and genotypic characteristics important for their application in food industry were investigated. Pulsed-field gel electrophoresis (PFGE) of NotI digested genomic DNA, in combination with physiological traits determined by API tests, made a useful tool for identification of these probiotic strains and differentiation among them. Lyophilized probiotic cells remained viable during 75 days of storage at −20, +4 and +15°C, while fresh concentrated cells remained viable only at −20°C with addition of glycerol as cryoprotectant. After the lyophilization with addition of skim milk as lyoprotectant, the viability of L. acidophilus M92, L. plantarum L4 and E. faecium L3 was reduced by only 0.37, 0.44 and 0.50 log, respectively. Furthermore, probiotic strains L. acidophilus M92, L. plantarum L4, and E. faecium L3, demonstrated anti-Salmonella activity, and L. acidophilus M92 having also antilisterial activity demonstrated by in vitro competition test. Overnight cultures and cell-free supernatants of the three probiotic strains exerted also an antagonistic effect against the Gram-positive and Gram-negative test microorganisms examined, demonstrated by the agar-well diffusion test. The inhibition of Listeria monocytogenes, Salmonella typhimurium, Yersinia enterocolitica, and Acinetobacter calcoaceticus obtained, achieved by the neutralized, 5-fold concentrated supernatant of L. plantarum L4, may be the result of its bacteriocinogenic activity. On the basis of these results, the application of the three examined probiotic strains may become a point of great importance in respect of food safety.     

Safety of <Emphasis Type="Italic">Lactobacillus plantarum</Emphasis> ST8Sh and Its Bacteriocin

Total DNA extracted from Lb. plantarum ST8Sh was screened for the presence of more than 50 genes related to production of biogenic amines (histidine decarboxylase, tyrosine decarboxylase, and ornithine decarboxylase), virulence factors (sex pheromones, gelatinase, cytolysin, hyaluronidase, aggregation substance, enterococcal surface protein, endocarditis antigen, adhesion of collagen, integration factors), and antibiotic resistance (vancomycin, tetracycline, erythromycin, gentamicin, chloramphenicol, bacitracin). Lb. plantarum ST8Sh showed a low presence of virulence genes. Only 13 genes were detected (related to sex pheromones, aggregation substance, adhesion of collagen, tetracycline, gentamicin, chloramphenicol, erythromycin, but not to vancomycin, and bacitracin) and may be considered as indication of safety for application in fermented food products. In addition, interaction between Lb. plantarum ST8Sh and drugs from different groups were determined in order to establish possible application of the strain in combination with commercial drugs. Cytotoxicity of the semi-purified bacteriocins produced by Lb. plantarum ST8Sh was depended on applied concentration—highly cytotoxic when applied at 25 μg/mL and no cytotoxicity at 5 μg/mL.     

Characterization of lactic acid bacteria isolated from sourdoughs for Cornetto, a traditional bread produced in Basilicata (Southern Italy)

A total of 41 strains of lactic acid bacteria (LAB) isolated from durum wheat sourdoughs used to produce Cornetto di Matera bread, were identified by SDS-PAGE of whole cell proteins (WCP) and screened for acid production ability, antimicrobial activity and exopolysaccharide (EPS) production. The isolates were identified as Lactobacillus plantarum (49%), Leuconostoc mesenteroides (17%), Lactobacillus curvatus (15%), Lactobacillus paraplantarum (12%), Weissella cibaria (5%) and Lactobacillus pentosus (2%). Several strains of Lb. plantarum and Leuc. mesenteroides showed a high acid production ability. The antagonistic activity was tested using an agar-spot deferred antagonism assay against a set of five indicators. The species had different profiles of inhibition. Lb. plantarum had the largest spectrum of inhibition, while no isolates of W. cibaria and Leuc. mesenteroides showed antimicrobial activity. No strains had antimicrobial activity against Bacillus cereus. The inhibitory activity of five strains was confirmed to be sensitive to proteolytic enzymes and thus potentially due to bacteriocin production. All Leuc. mesenteroides and W. cibaria strains produced EPS from sucrose. Some Lb. plantarum and Lb. paraplantarum strains produced EPS from different sugars in solid media. EPS production in liquid media was different within the species, with the highest production in liquid media containing glucose and maltose. A defined strain starter culture (W. cibaria DBPZ1006, Lb. plantarum DBPZ1015 and S. cerevisiae MTG10) was selected on the basis of technological properties and tested in model sourdough fermentations.     

Quantitative Appraisal of the Probiotic Attributes and In Vitro Adhesion Potential of Anti-listerial Bacteriocin-producing Lactic Acid Bacteria

Estimation of bile tolerance, endurance to gastric and intestinal environment and adhesion potential to intestinal cells are significant selection criteria for probiotic lactic acid bacteria (LAB). In this paper, the probiotic potential of native bacteriocin-producing LAB isolated previously from indigenous source has been determined through quantitative approaches. Among fifteen anti-listerial bacteriocin-producing native LAB, ten strains were found to be bile tolerant. The presence of bile salt hydrolase (bsh) gene in native Lactobacillus plantarum strains was detected by PCR and confirmed by nucleic acid sequencing of a representative amplicon. Interestingly, three native LAB strains exhibited significant viability in simulated gastric fluid, analogous to the standard LAB Lactobacillus rhamnosus GG, while an overwhelming majority of the native LAB strains demonstrated the ability to survive and remain viable in simulated intestinal fluid. Quantitative adhesion assays based on conventional plating method and a fluorescence-based method revealed that the LAB isolates obtained from dried fish displayed significant in vitro adhesion potential to human adenocarcinoma HT-29 cells, and the adhesion level was comparable to some of the standard probiotic LAB strains. The present study unravels putative probiotic attributes in certain bacteriocin-producing LAB strains of non-human origin, which on further in vivo characterization could find specific applications in probiotic food formulations targeted for health benefits.     

Functional Properties of <Emphasis Type="Italic">Lactobacillus plantarum</Emphasis> Strains Isolated from Maasai Traditional Fermented Milk Products in Kenya

Lactobacillus plantarum was the major species among the lactic acid bacterial strains isolated from traditional fermented milk of the Maasai in Kenya. Selected strains were characterized for their functional properties using in vitro standard procedures. All strains expressed acid tolerance at pH 2.0 after 2-h exposure of values that ranged from 1% to 100%, while bile tolerance of acid-stressed cells at 0.3% oxgal varied from 30% to 80%. In vitro adhesion to the mucus-secreting cell line HT 29 MTX and binding capacity to extracellular protein matrices was demonstrated for several strains. The four strains tested in a simulated stomach duodenum passage survived with recovery rates ranging from 17% to 100%. Strains were intrinsically resistant to several antibiotics tested. From these in vitro studies, a number of Lb. plantarum strains isolated from the Maasai traditional fermented milk showed probiotic potential. The strains are good candidates for multifunctional starter culture development.     

Diversity of lactic acid bacteria from Miang,a traditional fermented tea leaf in northern Thailand and their tannin-tolerant ability in tea extract

The microbiota of lactic acid bacteria (LAB) in thirty-five samples of Miang, a traditional fermented tea leaf product, collected from twenty-two different regions of eight provinces in upper northern Thailand was revealed through the culture-dependent technique. A total of 311 presumptive LAB strains were isolated and subjected to clustering analysis based on repetitive genomic element-PCR (rep-PCR) fingerprinting profiles. The majority of the strains belonged to the Lactobacillus genera with an overwhelming predominance of the Lb. plantarum group. Further studies of species-specific PCR showed that 201 of 252 isolates in the Lb. plantarum group were Lb. plantarum which were thus considered as the predominant LAB in Miang, while the other 51 isolates belonged to Lb. pentosus. In contrast to Lb. plantarum, there is a lack of information on the tannase gene and the tea tannin-tolerant ability of Lb. pentosus. Of the 51 Lb. pentosus isolates, 33 were found to harbor the genes encoding tannase and shared 93-99% amino acid identity with tannase obtained from Lb. pentosus ATCC 8041^T. Among 33 tannase gene-positive isolates, 23 isolates exhibited high tannin- tolerant capabilities when cultivated on de Man Rogosa and Sharpe agar-containing bromocresol purple (0.02 g/L, MRS-BCP) supplemented with 20% (v/v) crude tea extract, which corresponded to 2.5% (w/v) tannins. These Lb. pentosus isolates with high tannin-tolerant capacity are expected to be the high potential strains for functional tannase production involved in Miang fermentation as they will bring about certain benefits and could be used to improve the fermentation of tea products.     

Screening from pickled vegetables the potential probiotic strains of lactic acid bacteria able to inhibit the Salmonella invasion in mice

Aims: To screen from pickled vegetables the potential probiotic lactic acid bacteria (LAB) strains with antagonistic activity against Salmonella invasion in host. Methods and Results: Probiotic properties including acid and bile tolerance as well as inhibition on pathogenic bacteria were used for screening of LAB strains from pickled vegetables. Two strains, i.e Pediococcus pentosaceus MP12 and Lactobacillus plantarum LAP6, were selected and further assayed for their activities against Salmonella invasion in mouse liver and spleen. For these two LAB strains, strain LAP6 was able to adhere to the mouse intestinal epithelium cells. Conclusions: In screening of the probiotic strains able to inhibit the Salmonella invasion in host, factors other than the adherence to host intestinal epithelium may contribute some roles. Significance and Impact of the Study: Probiotic LAB strains with activity against Salmonella invasion in host could be isolated from vegetable origins. These strains may be used for vegetable processing.     

Safety and probiotic functionality of isolated goat milk lactic acid bacteria

Purpose

Lactic acid bacteria (LAB) are traditionally employed in the food industry. LAB strains from goat milk may also present probiotic potential, and it is fundamental to study the safety and functionality aspects which are desirable for their use in food. The objective of this study was to verify the probiotic potential of lactic bacteria isolated from goat milk.

Methods

The presence of safety-related virulence factors (hemolytic activity, gelatinase production, coagulase, and sensitivity to antibiotics) as well as functionality (exopolysaccharide (EPS) production, proteolytic activity, autoaggregation, gas production, survival in the gastrointestinal tract, and antimicrobial activity against bacteria that impair oral health) were determined.

Result

The selected LAB strains are safe against the evaluated parameters and have characteristics of possible probiotic candidates. Especially L. plantarum (DF60Mi) and Lactococcus lactis (DF04Mi) have potential to be added to foods because they have better resistance to simulated gastrointestinal conditions. In addition, they are isolated with already proven antimicrobial activity against Listeria monocytogenes, an important food-borne pathogen. DF60Mi was able to produce EPS (exopolysaccharides). LS2 and DF4Mi strains, both Lactococcus lactis subsp. lactis, demonstrated antimicrobial activity against S. mutans ATCC 25175, a recurrent microorganism in oral pathologies, mainly caries.

Conclusion

This study provides subsidies for future exploration of the potentialities of these LAB strains for both the development of new functional foods and for application in oral health.

     

Screening for potential probiotic from spontaneously fermented non-dairy foods based on in vitro probiotic and safety properties

The aim of this study was to screen potential probiotic lactic acid bacteria from Chinese spontaneously fermented non-dairy foods by evaluating their probiotic and safety properties. All lactic acid bacteria (LAB) strains were identified by 16S rRNA gene sequencing. The in vitro probiotic tests included survival under low pH and bile salts, cell surface hydrophobicity, auto-aggregation, co-aggregation, antibacterial activity, and adherence ability to cells. The safety properties were evaluated based on hemolytic activity and antibiotic resistance profile. The salt tolerance, growth in litmus milk, and acidification ability were examined on selected potential probiotic LAB strains to investigate their potential use in food fermentation. A total of 122 strains were isolated and identified at the species level by 16S rRNA gene sequencing and included 62 Lactobacillus plantarum, 40 Weissella cibaria, 12 Lactobacillus brevis, 6 Weissella confusa, and 2 Lactobacillus sakei strains. One W. cibaria and nine L. plantarum isolates were selected based on their tolerance to low pH and bile salts. The hydrophobicity, auto-aggregation, co-aggregation, and antagonistic activities of these isolates varied greatly. All of the 10 selected strains showed multiple antibiotic resistance phenotypes and no hemolytic activity. The highest adhesion capacity to SW480 cells was observed with L. plantarum SK1. The isolates L. plantarum SK1, CB9, and CB10 were the most similar strains to Lactobacillus rhamnosus GG and selected for their high salt tolerance and acidifying activity. The results revealed strain-specific probiotic properties were and potential probiotics that can be used in the food industry.     

Identification and probiotic properties of lactobacilli isolated from two different fermented beverages

Purpose

Scientific information regarding the microbial content and functional aspects of fermented beverages traditionally produced in certain parts of Europe are scarce. However, such products are believed to have some health benefits and might contain functional bacterial strains, such as probiotics. The aim of the study was to identify such lactic acid bacteria strains isolated from water kefir and, for the first time, from braga, a Romanian fermented beverage made of cereals.

Methods

Lactic acid bacteria (LAB) were identified to species level based on (GTG)₅-PCR fingerprinting and 16S rRNA gene sequencing. Selected strains were screened for their antibacterial activity and probiotic potential.

Results

Eight isolates belonging to seven Lactobacillus species were recovered from the two drinks. The identification of LAB involved in the fermentation of braga (Lactobacillus plantarum, Lactobacillus fermentum, and Lactobacillus delbrueckii) is firstly reported here. Five of the Lactobacillus isolates showed antibacterial activity against pathogenic bacteria, including Listeria monocytogenes, Escherichia coli, Staphylococcus aureus, and Salmonella enterica. Moreover, most of them showed a good resistance to pH 2.5 and some survived at high concentrations of bile salts (up to 2%). Two L. plantarum isolates were able to inhibit all the indicator strains, and showed the best viability (about 70%) after a sequential treatment simulating the passage through the gastrointestinal tract.

Conclusion

Based on the results, the most promising candidates for designing new probiotic products are: L. plantarum BR9 from braga and L. plantarum CR1 from water kefir.

     

Characterization and electrotransformation of <Emphasis Type="Italic">Lactobacillus plantarum</Emphasis> and <Emphasis Type="Italic">Lactobacillus paraplantarum</Emphasis> isolated from fermented vegetables

Aims of the study were to characterize two Lactobacillus plantarum-related strains, Lact. plantarum and Lactobacillus paraplantarum isolated from fermented vegetables and, for their potential use as starter strains, compare their growth in various food matrices. Species-level identification of the strains belonging to the Lact. plantarum group was performed by multiplex-PCR with species-specific primers and generation of distinct genotypic profiles was carried out by PFGE-based DNA-fingerprinting. Growth profiles were determined in various food and feed matrices. Compared to Lact. plantarum, Lact. paraplantarum reached higher cell densities in all plant-based matrices and MRS broth. On the contrary to the good growth in plant-based matrices and MRS, poor growth was observed in unprocessed milk. Supplemented lactose did not improve the growth of either tested strain, while predigestion of milk proteins with Lactobacillus helveticus or addition of casitone proved to be an effective means to enhance growth. To find out the applicability of molecular methods, the strains were transformed with replicative plasmids by electroporation. To our knowledge, this is a first report of the electrotransformation of Lact. paraplantarum with a recombinant plasmid.     

Design of a low-cost culture medium based in whey permeate for biomass production of enological Lactobacillus plantarum strains

The production of malolactic starter cultures requires the obtention of suitably large biomass at low-cost. In this work it was possible to obtain a good amount of biomass, at laboratory scale, of two enological strains of Lb. plantarum, by formulating a culture medium based on whey permeate (WP), a by-product of the cheese industry usually disposed as waste, when this was supplemented with yeast extract (Y), salts (S) and Tween 80 (T) (WPYST). Bacteria grown in WPYST medium exhibited good tolerance to stress conditions of synthetic wine (pH 3.5, ethanol 13% vol/vol). However, when WPYST was added with 8% vol/vol ethanol, cultures inoculated in synthetic wine, showed a lower viability and capacity to consume L-malic acid than when they were cultured in WPYST without ethanol. Subsequently, strains grown in WPYST were inoculated in sterile wine samples (final stage of alcoholic fermentation) of the red varietals Merlot and Pinot noir, and incubated at laboratory scale. Cultures from WPYST, inoculated in Pinot noir wine, showed a better performance than bacteria grown in MRS broth, and exhibited a consumption of L-malic acid higher than 90%. However, cultures from WPYST or from MRS broth, inoculated in sterile Merlot wine, showed a lower survival. This study allowed the formulation of a low-cost culture medium, based on a by-product of the food industry, which showed to be adequate for the growth of two enological strains of Lb. plantarum, suggesting their potentiality for application in the elaboration of malolactic starter cultures.     

Manufacture of Cheddar cheese using probiotic Lactobacillus plantarum K25 and its cholesterol-lowering effects in a mice model

The probiotic adjunct Lactobacillus plantarum K25 was inoculated into milk to produce probiotic cheese. The effect of Lb. plantarum K25 on cheese composition, microbiological growth and survival during the manufacturing and ripening period, primary and secondary proteolysis during cheese ripening, and the in vivo cholesterol-lowering ability of the probiotic cheese were investigated. The results showed that the use of adjunct Lb. plantarum K25 in Cheddar cheese did not affect the cheese components including moisture, protein, fat, salt content and the pH value of cheese. During the whole ripening period, the probiotic adjunct maintained its viability, suggesting the effectiveness of Cheddar cheese as a vehicle for delivery of probiotic bacteria. No significant differences were observed in water-soluble nitrogen, 70?% ethanol-soluble nitrogen, 5?% phosphotungstic acid-soluble nitrogen, free amino acids and urea-PAGE patterns between the control and probiotic cheeses. Assessment of the in vivo cholesterol-lowering property of cheese with Lb. plantarum K25 showed that the levels of serum total cholesterol, low-density lipoprotein cholesterol and triglycerides decreased significantly, and the level of serum high-density lipoprotein cholesterol increased in mice fed with the probiotic cheese. The results indicated the potential function as a dietary item of the probiotic cheese with Lb. plantarum K25 to reduce the risk of cardiovascular diseases.     

Boza, a natural source of probiotic lactic acid bacteria

Aims: To evaluate the probiotic properties of strains isolated from boza, a traditional beverage produced from cereals. Methods and Results: The strains survived low pH conditions (pH 3·0), grew well at pH 9·0 and were not inhibited by the presence of 0·3% (w/v) oxbile. Cytotoxicity levels of the bacteriocins, expressed as CC₅₀, ranged from 38 to 3776 μg ml^?1. Bacteriocin bacST284BZ revealed high activity (EC₅₀ = 735 μg ml^?1) against herpes simplex virus type 1. Growth of Mycobacterium tuberculosis was 69% repressed after 5 days in the presence of bacST194BZ. Various levels of auto‐cell aggregation and co‐aggregation with Listeria innocua LMG 13568 were observed. Adhesion of the probiotic strains to HT‐29 cells ranged from 18 to 22%. Conclusions: Boza is a rich source of probiotic lactic acid bacteria. All strains survived conditions simulating the gastrointestinal tract and produced bacteriocins active against a number of pathogens. Adherence to HT‐29 and Caco‐2 cells was within the range reported for Lactobacillus rhamnosus GG, a well‐known probiotic. In addition, the high hydrophobicity readings recorded define the strains as good probiotics. Significance and Impact of the Study: Boza contains a number of different probiotic lactic acid bacteria and could be marketed as a functional food product.     

Distribution of antimicrobial‐resistant lactic acid bacteria in natural cheese in Japan

To determine and compare the extent of contamination caused by antimicrobial‐resistant lactic acid bacteria (LAB) in imported and domestic natural cheeses on the Japanese market, LAB were isolated using deMan, Rogosa and Sharpe (MRS) agar and MRS agar supplemented with six antimicrobials. From 38 imported and 24 Japanese cheeses, 409 LAB isolates were obtained and their antimicrobial resistance was tested. The percentage of LAB resistant to dihydrostreptomycin, erythromycin, and/or oxytetracycline isolated from imported cheeses (42.1%) was significantly higher than that of LAB resistant to dihydrostreptomycin or oxytetracycline from cheeses produced in Japan (16.7%; P = 0.04). Antimicrobial resistance genes were detected in Enterococcus faecalis (tetL, tetM, and ermB; tetL and ermB; tetM) E. faecium (tetM), Lactococcus lactis (tetS), Lactobacillus (Lb.), casei/paracasei (tetM or tetW), and Lb. rhamnosus (ermB) isolated from seven imported cheeses. Moreover, these E. faecalis isolates were able to transfer antimicrobial resistance gene(s). Although antimicrobial resistance genes were not detected in any LAB isolates from Japanese cheeses, Lb. casei/paracasei and Lb. coryniformis isolates from a Japanese farm‐made cheese were resistant to oxytetracycline (minimal inhibitory concentration [MIC], 32 µg/mL). Leuconostoc isolates from three Japanese farm‐made cheeses were also resistant to dihydrostreptomycin (MIC, 32 to > 512 µg/mL). In conclusion, the present study demonstrated contamination with antimicrobial‐resistant LAB in imported and Japanese farm‐made cheeses on the Japanese market, but not in Japanese commercial cheeses.