Lactobacillus probiotics restore vaginal and gut microbiota of pregnant women with vaginal candidiasis

The development of probiotics has now included the areas along the gut-vaginal axis. We thus aimed to investigate the effects of lactobacilli probiotic to modulate and restore vaginal and gut microbiota of pregnant women with vaginal candidiasis (VC). A randomised, double-blind and placebo-controlled study was performed in 78 pregnant women with VC. Patients were randomised to either the probiotic (SynForU-HerCare) or placebo which were administered at baseline and continued for 8-weeks (two capsules/day of 9.5 log cfu/capsule). Microbiota profiles were assessed at time points of weeks-0, 4 and 8 for high vaginal swab and faecal samples. Shannon diversity index showed that after 8-weeks amid VC, a shift in microbial community compositional changes occurred in the high vaginal region at both genus (P=0.025) and species (P=0.044) levels, where the administration of probiotic prevented such a shift. These changes were mainly attributed to a decreased in abundance of Lactobacillus (P=0.042) accompanied by increased abundance of Prevotella (P=0.002) and Atopobium (P=0.002) in the placebo group while the probiotic group remained unchanged over time. The administration of probiotics also prevented a reduced abundance of faecal phylum Firmicutes after 8-weeks as seen in the placebo group (P<0.0001), which also showed reduction at subsequent taxonomic levels of class, family, genera and species. VC has not only altered the microbiota of vagina regions but also gut microbiota profiles, causing lessening of gut microbiota that are crucial for gut nutrient availability, protection and immunity. The administration of lactobacilli probiotics has prevented such a shift, leading to better modulated gut and vaginal microenvironment amid VC. The study was registered at ClinicalTrials.gov: identifier number NCT03940612.

Genomic, metabolomic, and functional characterisation of beneficial properties of Pediococcus pentosaceus ST58, isolated from human oral cavity

Bacteriocins produced by lactic acid bacteria are proteinaceous antibacterial metabolites that normally exhibit bactericidal or bacteriostatic activity against genetically closely related bacteria. In this work, the bacteriocinogenic potential of Pediococcus pentosaceus strain ST58, isolated from oral cavity of a healthy volunteer was evaluated. To better understand the biological role of this strain, its technological and safety traits were deeply investigated through a combined approach considering physiological, metabolomic and genomic properties. Three out of 14 colonies generating inhibition zones were confirmed to be bacteriocin producers and, according to repPCR and RAPD-PCR, differentiation assays, and 16S rRNA sequencing it was confirmed to be replicates of the same strain, identified as P. pentosaceus, named ST58. Based on multiple isolation of the same strain (P. pentosaceus ST58) over the 26 weeks in screening process for the potential bacteriocinogenic strains from the oral cavity of the same volunteer, strain ST58 can be considered a persistent component of oral cavity microbiota. Genomic analysis of P. pentosaceus ST58 revealed the presence of operons encoding for bacteriocins pediocin PA-1 and penocin A. The produced bacteriocin(s) inhibited the growth of Listeria monocytogenes, Enterococcus spp. and some Lactobacillus spp. used to determine the activity spectrum. The highest levels of production (6400 AU/ml) were recorded against L. monocytogenes strains after 24 h of incubation and the antimicrobial activity was inhibited after treatment of the cell-free supernatants with proteolytic enzymes. Noteworthy, P. pentosaceus ST58 also presented antifungal activity and key metabolites potentially involved in these properties were identified. Overall, this strain can be of great biotechnological interest towards the development of effective bio-preservation cultures as well as potential health promoting microbes.

Role of gastrointestinal microbial populations, a terra incognita of the human body in the management of intestinal bowel disease and metabolic disorders

Intestinal bowel disease (IBD) is a chronic immune-mediated clinical condition that affects the gastrointestinal tract and is mediated by an inflammatory response. Although it has been extensively studied, the multifactorial aetiology of this disorder makes it difficult to fully understand all the involved mechanisms in its development and therefore its treatment. In recent years, the fundamental role played by the human microbiota in the pathogenesis of IBD has been emphasised. Microbial imbalances in the gut bacterial communities and a lower species diversity in patients suffering from inflammatory gastrointestinal disorders compared to healthy individuals have been reported as principal factors in the development of IBD. These served to support scientific arguments for the use of probiotic microorganisms in alternative approaches for the prevention and treatment of IBD. In a homeostatic environment, the presence of bacteria (including probiotics) on the intestinal epithelial surface activates a cascade of processes by which immune responses inhibited and thereby commensal organisms maintained. At the same time these processes may support activities against specific pathogenic bacteria. In dysbiosis, these underlying mechanisms will serve to provoke a proinflammatory response, that, in combination with the use of antibiotics and the genetic predisposition of the host, will culminate in the development of IBD. In this review, we summarised the main causes of IBD, the physiological mechanisms involved and the related bacterial groups most frequently associated with these processes. The intention was to enable a better understanding of the interaction between the intestinal microbiota and the host, and to suggest possibilities by which this knowledge can be useful for the development of new therapeutic treatments.

Safety and beneficial properties of bacteriocinogenic Pediococcus acidilactici and Pediococcus pentosaceus isolated from silage

The control of Listeria monocytogenes is a relevant goal for dairy products, a process that begins from the supply of feed and management of animals' health. In the present study, we evaluated the safety of two bacteriocinogenic Pediococcus strains and show that both can be considered as safe, based on their haemolytic activity, biogenic amine production and antibiotic resistance, all evaluated through phenotypical and biomolecular approaches. Both strains have shown potential as a producer of γ-aminobutiric acid (GABA) and carry an incomplete set of genes related to folate biosynthesis; both strains were able to adhere to Caco-2 cell lines with adhesion rates of 6·59% ± 3·73 and 0·84% ± 0·48. Laboratory prepared clover silage, inoculated with each bacteriocinogenic Pediococcus strain and contaminated with L. monocytogenes, proved the hypothesis for bioprotective effect of the tested strains, with the tested pathogen eliminated in the first 24 h of the experiment. These results indicate that evaluated strains can be potential beneficial candidates for application in silage production.

Bacteriocin production by Leuconostoc citreum ST110LD isolated from organic farm soil, a promising biopreservative

AIMS

The objective of this study was to isolate a bacteriocin-producing strain and to characterize the expressed bacteriocin for the control of Listeria monocytogenes with aim of biopreservation application.

METHODS AND RESULTS

Soil samples from a Korean organic farm were subjected to microbiological analysis for isolation of potential bacteriocinogenic LAB, based on a three-level approach, using L. monocytogenes ATCC 15313 as an indicator test micro-organism. From a total of 17 isolates with inhibitory potential, seven were confirmed to be bacteriocin producers. The selected isolates were differentiated based on their morphology, catalase reaction, sugar fermentation profile obtained by API50CHL and by RAPD-PCR generating two unique profiles. One of the isolates, ST110LD, a specific strong producer of anti-Listeria bacteriocins (12 800 AU ml^-1 ) was identified as Leuconostoc citreum. The proteinaceous nature of the inhibitory compound produced by Leuc. citreum ST110LD was confirmed through treatment with pepsin and α-chymotrypsin. Bacteriocin activity was observed to be not affected by the presence of milk, NaCl, SDS, Tween 80 or glycerol. Bacteriocin ST110LD effectively inhibited the growth of exponentially growing L. monocytogenes ATCC 15313 during a 10-h incubation period in BHI at 37°C. In addition, this bacteriocin showed specific inhibition of only Listeria spp., but did not inhibit the growth of beneficial cultures included in the microbial test panel for assessment of the spectrum of activity.

CONCLUSIONS

Leuconostoc citreum ST110LD was evaluated as safe bacterium strain, producing bacteriocin with high specificity against listerial and enterococcal species. Specificity of producer strain and expressed bacteriocin can be explored in biopreservation of different fermented food products or applied in biotherapy of antibiotic resistant listerial or enterococcal infections.

SIGNIFICANCE AND IMPACT OF THE STUDY

To the best of our knowledge, this is the first report of bacteriocin produced by Leuc. citreum strain with highly specific antimicrobial activity against Listeria sp. and Enterococcus sp.

Molecular screening of beneficial and safety determinants from bacteriocinogenic lactic acid bacteria isolated from Brazilian artisanal calabresa

Despite of the beneficial relevance of several lactic acid bacteria (LAB) in the food industry, micro-organisms belonging to this group can determine spoilage in food products and carry a number of virulence and antibiotic resistance-related genes. This study aimed on the characterization of beneficial and safety aspects of five bacteriocinogenic LAB strains (Lactobacillus curvatus 12-named L. curvatus UFV-NPAC1), L. curvatus 36, Weissela viridescens 23, W. viridescens 31 and Lactococcus garvieae 36) isolated from an artisanal Brazilian calabresa, a traditional meat sausage. Regarding their beneficial aspects, all tested isolates were positive for mub, while EF226-cbp, EF1249-fbp and EF2380-maz were detected in at least one tested strain; none of the isolates presented map, EFTu or prgB. However, evaluated strains presented a variable pattern of virulence-related genes, but none of the strains presented gelE, cylA, efsA, cpd, int-Tn or sprE. Moreover, other virulence-related genes evaluated in this study were detected at different frequencies. L. curvatus 12 was generated positive results for ace, ccf, int, ermC, tetL, aac(6')-Ie-aph(2″)-Ia, aph(2″)-Ib, aph(2″)-Ic, bcrB, vanB and vanC2; L. curvatus 36: hyl, asa1, esp, int, ermC, tetK, aph(3')-IIIa, aph(2'')-Ic and vanC2; L. garvieae 32: asa1, ant(4')-Ia, aph(2'')-Ib, catA, vanA and vanC1; W. viridescens 23: esp, cob, ermB, aph(3')-IIIa, aph(2'')-Ic, vanA, vanB and vanC2; W. viridescens 31: hyl, esp, ermC, aph(3')-IIIa, aph(2'')-Ib, aph(2'')-Ic, catA, vanA and vanB. Despite presenting some beneficial aspects, the presence of virulence and antibiotic resistance genes jeopardize their utilization as starter or biopreservatives cultures in food products. Considering the inhibitory potential of these strains, an alternative would be the use of their bacteriocins as semi-purified or pure technological preparation. SIGNIFICANCE AND IMPACT OF THE STUDY: The food industry has a particular interest in using bacteriocinogenic lactic acid bacteria (LAB) as starter, probiotics and/or biopreservatives in different food products. Characterization of additional beneficial features is important to identify new, multifunctional potential probiotic strains. However, these strains can only be applied in food products only after being properly characterized according their potential negative aspects, such as virulence and antibiotic resistance genes. A wide characterization of beneficial and safety aspects of bacteriocinogenic LAB is determinant to guide the proper utilization of these strains, or their purified bacteriocins, by the food industry.

Beneficial and Safety Properties of a Corynebacterium vitaeruminis Strain Isolated from the Cow Rumen

Corynebacterium vitaeruminis MRU4 was isolated from the cow rumen and was differentiated from other isolates by rep-PCR and RAPD and identified by 16S rRNA sequencing. This strain presented higher survival rates for low pH and bile salts treatments, and it was able to survive and multiply in simulated gastric and intestinal environments. C. vitaeruminis MRU4 had a 53.2% auto-aggregation rate, 42.4% co-aggregation rate with Listeria monocytogenes Scott A, 41.6% co-aggregation rate with Enterococcus faecalis ATCC 19443, 10.0% co-aggregation rate with Lactobacillus sakei ATCC 15521, and 98.2% cell surface hydrophobicity rate. PCR analysis showed the presence of EFTu and map genes. The strain possessed positive results for deconjugation of bile salts (taurocholic acid, taurodeoxycholic acid, glycocholic acid, and glycodeoxycholic acid) and positive results for β-galactosidase activity and lactose assimilation activity (glucose of 8.15 ± 0.01 CFU/ml and lactose of 9.24 ± 0.02 CFU/ml). No virulence was observed by phenotypical tests. C. vitaeruminis MRU4 was resistant to oxacillin, gentamicin, erythromycin, clindamycin, sulfa/trimethoprim, and rifampicin by the disc diffusion method and showed resistance just for vancomycin by the Etest® strips test. The strain was negative for 50 tested virulence and resistance genes based on performed PCR. Based on our knowledge, this is the first report regarding the beneficial potential of one C. vitaeruminis strain.

Potential beneficial properties of bacteriocin-producing lactic acid bacteria isolated from smoked salmon

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.

In vitro study of beneficial properties and safety of lactic acid bacteria isolated from Portuguese fermented meat products

Many lactic acid bacteria produce bacteriocins with a rather broad spectrum of inhibition, which could offer potential applications in food preservation. Bacteriocin production by starter cultures may bring advantage to these strains in competitive interactions with pathogenic bacteria from the food matrix. The objective of this study was to determine the safety of beneficial strains (Lactobacillus plantarum ST202Ch and ST216Ch, Enterococcus faecium ST211Ch, and Lactobacillus sakei ST22Ch, ST153Ch and ST154Ch) previously isolated from fermented meat products and characterised as bacteriocin producers. Auto-aggregation was strain-specific, and values of 28.97, 27.86 and 28.56% were recorded for L. sakei ST22Ch, ST153Ch and ST154Ch, respectively, 16.95 and 14.58% for L. plantarum ST202Ch and ST216Ch, respectively, and 12.77% for E. faecium ST211Ch. Various degrees of co-aggregation between 28.85 and 44.76% for Listeria monocytogenes 211 and 409, and between 23.60 to 34.96% for E. faecium ATCC 19443 were observed. According to the results of the diffusion method, the studied strains demonstrated susceptibility to penicillin G, ampicillin, amoxicillin, amoxicillin/clavulonic acid, imipenem, linezolid, and tetracycline. In addition, the susceptibility of the six strains to various non-antibiotic commercial drugs was examined. Production of β-galactosidase by L. sakei ST22Ch, ST153Ch and ST154Ch, L. plantarum ST202Ch and ST216Ch, and E. faecium ST211Ch was confirmed by employing sterile filter paper discs impregnated with o-nitrophenyl-β-D-galactopyranose. A statistically significant (P<0.001) inhibition of Mycobacterium tuberculosis growth by bacteriocins produced by L. plantarum ST202Ch (38.3%) and ST216Ch (48.6%), L. sakei ST153Ch (16.2%) and ST154Ch (16.1%), and E. faecium ST211Ch (21.7%) was observed. As determined by the polymerase chain reaction, the tested strains showed a low virulence gene profile.

Purification and characterization of the bacteriocin produced by Lactobacillus sakei MBSa1 isolated from Brazilian salami

AIMS

The study aimed at determining the biochemical characteristics of the bacteriocin produced by Lactobacillus sakei MBSa1, isolated from salami, correlating the results with the genetic features of the producer strain.

METHODS AND RESULTS

Identification of strain MBSa1 was performed by 16S rDNA sequencing. The bacteriocin was tested for spectrum of activity, heat and pH stability, mechanism of action, molecular mass and amino acid sequence when purified by cation-exchange and reversed-phase HPLC. Genomic DNA was tested for bacteriocin genes commonly present in Lact. sakei. Bacteriocin MBSa1 was heat-stable, unaffected by pH 2·0 to 6·0 and active against all tested Listeria monocytogenes strains. Maximal production of bacteriocin MBSa1 (1600 AU ml(-1)) in MRS broth occurred after 20 h at 25°C. The molecular mass of produced bacteriocin was 4303·3 Da, and the molecule contained the SIIGGMISGWAASGLAG sequence, also present in sakacin A. The strain contained the sakacin A and curvacin A genes but was negative for other tested sakacin genes (sakacins T-α, T-β, X, P, G and Q).

CONCLUSIONS

In the studied conditions, Lact. sakei MBSa1 produced sakacin A, a class II bacteriocin, with anti-Listeria activity.

SIGNIFICANCE AND IMPACT OF THE STUDY

The study covers the purification and characterization of the bacteriocin produced by a lactic acid bacteria isolated from salami (Lact. sakei MBSa1), linking genetic and expression information. Its heat-resistance, pH stability in acid conditions (pH 2·0-6·0) and activity against L. monocytogenes food isolates bring up a potential technological application to improve food safety.

Technological properties of bacteriocin-producing lactic acid bacteria isolated from Pico cheese an artisanal cow's milk cheese

AIM

Evaluate technologically relevant properties from bacteriocin-producing strains to use as starter/adjunct cultures in cheese making.

METHODS AND RESULTS

Eight isolates obtained from Pico cheese produced in Azores (Portugal) were found to produce bacteriocins against Listeria monocytogenes and three isolates against Clostridium perfringens. They were identified as Lactococcus lactis and Enterococcus faecalis and submitted to technological tests: growth at different conditions of temperature and salt, acid production, proteolysis, lipolysis, coexistence, enzymatic profile and autolytic capacity. Safety evaluation was performed by evaluating haemolytic, gelatinase and DNase activity, resistance to antibiotics and the presence of virulence genes. Some isolates presented good technological features such as high autolytic activity, acid and diacetyl production. Lactococcus lactis was negative for all virulence genes tested and inhibit the growth of all Lactic acid bacteria (LAB) isolates. Enterococci were positive for the presence of some virulence genes, but none of the isolates were classified as resistant to important antibiotics.

CONCLUSIONS

The bacteriocin-producing Lc. lactis present good potential for application in food as adjunct culture in cheese production. The study also reveals good technological features for some Enterococcus isolates.

SIGNIFICANCE AND IMPACT OF THE STUDY

Bacteriocin-producing strains presented important technological properties to be exploited as new adjunct culture for the dairy industry, influencing flavour development and improve safety.

Isolation and identification of bacteriocinogenic strain of Lactobacillus plantarum with potential beneficial properties from donkey milk

AIMS

The goal of this study was to isolate and characterize a lactic acid bacteria (LAB) from donkey milk with potential beneficial properties.

METHODS AND RESULTS

Lactic acid bacteria were isolated from donkey milk and identified based on physiological, biochemical and molecular methods. The isolate that presented highest bacteriocin potential (Lactobacillus plantarum LP08AD) was evaluated for the production of bacteriocin, including stability in the presence of various enzymes, surfactants, salts, pH and temperatures. Bactericidal effect of bacteriocin LP08AD on Listeria monocytogenes, Enterococcus faecium and Lactobacillus curvatus was shown for actively growing and stationary cells. Similar growth and bacteriocin production were observed when strain LP08AD was cultured in MRS broth at 30°C or 37°C. Bacteriocin LP08AD adhered at low levels on the producer cells (200 AU ml(-1) ). The presence of plantaricin W gene on the genomic DNA was recorded based on PCR. Good growth for strain LP08AD was recorded in MRS broth with pH from 5·0 to 9·0 and LP08AD grew well in the absence of oxbile or concentration below 0·8%. Lact. plantarum LP08AD was applied to the small intestinal epithelial polarized monolayers of H4, PSIc1 and CLAB and demonstrated low attachment ability on all cell lines studied, with values with a similar behaviour for cells from human and pig origin.

CONCLUSIONS

Bacteriocin-producing Lact. plantarum LP08AD might be useful in the design of novel functional foods with potential probiotic or biopreservation properties.

SIGNIFICANCE AND IMPACT OF THE STUDY

To the best of our knowledge, this is the first report on detection and characterization of bacteriocinogenic Lact. plantarum from donkey milk. The strain LP08AD shows to have potential beneficial properties, as demonstrated by the use of noncancerogenic cell lines.

A class IIa peptide from Enterococcus mundtii inhibits bacteria associated with otitis media

Peptide ST4SA, produced by Enterococcus mundtii ST4SA, inhibits the growth of Acinetobacter baumannii, Enterococcus faecalis, Enterococcus faecium, Staphylococcus aureus, Streptococcus pneumoniae and Gram-positive bacteria isolated from patients diagnosed with middle ear infections. The peptide adsorbed at a level of 94% to S. pneumoniae 40, Pseudomonas aeruginosa 25 and E. faecium HKLHS. Low concentrations of peptide ST4SA (51200 arbitrary units (AU)/mL) caused DNA and enzyme leakage from target cells, whilst 1638400AU/mL caused cell lysis. No decrease in antimicrobial activity was observed when tested on solid medium with human blood as base. Peptide ST4SA revealed a similar level of activity compared with tetracycline (30 microg), but much higher activity compared with nasal sprays, aminoglycosides, cephalosporins, fluoroquinolones, lincosamides, macrolides, nitroimidazole, penicillin, quinolones, sulphonamides, chloramphenicol, furazolidone, fusidic acid, rifampicin, trimethoprim, trimethoprim/sulfamethoxazole and vancomycin when tested in vitro. Peptide ST4SA dissipates the proton-motive force and may be used in the treatment of multidrug-resistant strains where antibiotics are excluded from cells by efflux pumps dependent on the membrane proton gradient.

The antimicrobial activity of copper and copper alloys against nosocomial pathogens and Mycobacterium tuberculosis isolated from healthcare facilities in the Western Cape: an in-vitro study

Clinical isolates of meticillin-resistant Staphylococcus aureus (MRSA), Klebsiella pneumoniae, Pseudomonas aeruginosa, Acinetobacter baumannii, Candida albicans and Mycobacterium tuberculosis (MTB) were tested against copper (Cu) and its alloys. Stainless steel and polyvinylchloride (PVC) were used as controls. The amount of Cu required to inhibit test isolates at room temperature (24 degrees C) and at 4 degrees C was determined. At room temperature, Cu, DZR Brass (Cu 62%, Pb 2.5%, arsenate 0.13% and Zn 22.5%) and Brass 70/30 (Cu 70% and zinc 30%) inhibited C. albicans and K. pneumoniae at 60 min; nickel silver (NiAg) inhibited C. albicans at 60 min and K. pneumoniae at 270 min. P. aeruginosa was inhibited by Brass 70/30 and nickel silver (NiAg) at 180 min and at 270 min by Cu and DZR. Cu and DZR inhibited A. baumannii at 180 min while the other alloys were effective at 360 min. Stainless steel and PVC showed little or no inhibitory activity. Two M. tuberculosis strains, one isoniazid resistant (R267) and the other multidrug resistant (R432), demonstrated growth inhibition with Cu of 98% and 88% respectively compared with PVC; the other alloys were less active. Time to positivity (TTP) for R267 was >15 days with Cu and 11 days for the other alloys; with R432 it was 5 days. Effective inhibition of nosocomial pathogens and MTB by Cu and alloys was best when the Cu content was >55%.

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 CC(50), ranged from 38 to 3776 microg ml(-1). Bacteriocin bacST284BZ revealed high activity (EC(50) = 735 microg 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.

Probiotic properties of Lactococcus lactis ssp. lactis HV219, isolated from human vaginal secretions

AIMS

To determine the resistance of Lactococcus lactis ssp. lactis HV219 to acids, bile, antibiotics, inflammatory drugs and spermicides, compare adsorption of the strain to bacteria and Caco-2 cells under stress, and evaluate the antimicrobial activity of bacteriocin HV219.

METHODS AND RESULTS

Bacteriocin HV219 activity against Gram-positive and Gram-negative bacteria was confirmed by leakage of DNA and beta-galactosidase, and atomic force microscopy. Adsorption of bacteriocin HV219 to bacteria is influenced by pH, temperature, surfactants and salts. Initially, only 3% of HV219 cells adhered to Caco-2 cells. However, after 2 h, adherence increased to 7%. Strain HV219 and Listeria monocytogenes ScottA did not compete for colonization. Strain HV219 is sensitive to most antibiotics tested, but resistant to amikacin, ceftazidime, nalidixic acid, metronidazole, neomycin, oxacillin, streptomycin, sulphafurazole, sulphamethoxazole, sulphonamides, tetracycline and tobramycin. Ibuprofen, ciprofloxacin, diklofenak and nonoxylol-9 inhibited the growth of strain HV219.

CONCLUSION

Strain HV219 is resistant to hostile conditions in the intestinal tract, including therapeutic levels of specific antibiotics and binds to Caco-2 cells, but not in competition with L. monocytogenes.

SIGNIFICANCE AND IMPACT OF THE STUDY

Strain HV219 will only be effective as probiotic if taken with specific antibiotics and not with anti-inflammatory drugs and spermicides.

Comparison of bacteriocins produced by lactic-acid bacteria isolated from boza, a cereal-based fermented beverage from the Balkan Peninsula

Boza is a low-pH and low-alcohol cereal-based beverage produced in the Balkan Peninsula. From a total population of 9 x 10(6) colony-forming units ml(-1), four isolates (JW3BZ, JW6BZ, JW11BZ, and JW15BZ) produced bacteriocins active against a broad spectrum of Gram-positive bacteria. Bacteriocin JW15BZ inhibited the growth of Klebsiella pneumoniae. The producer strains were identified as Lactobacillus plantarum (strains JW3BZ and JW6BZ) and L. fermentum (strains JW11BZ and JW15BZ). The spectrum of antimicrobial activity, characteristics, and mode of action of these bacteriocins were compared with bacteriocins previously described for lactic-acid bacteria isolated from boza.

The effect of prebiotics on production of antimicrobial compounds, resistance to growth at low pH and in the presence of bile, and adhesion of probiotic cells to intestinal mucus

AIMS

Screening of five bile salt-resistant and low pH-tolerant lactic acid bacteria for inhibitory activity against lactic acid bacteria and bacterial strains isolated from the faeces of children with HIV/AIDS. Determining the effect of prebiotics and soy milk-base on cell viability and adhesion of cells to intestinal mucus.

METHODS AND RESULTS

Lactobacillus plantarum 423, Lactobacillus casei LHS, Lactobacillus salivarius 241, Lactobacillus curvatus DF 38 and Pediococcus pentosaceus 34 produced the highest level of antimicrobial activity (12,800 AU ml(-1)) when grown in MRS broth supplemented with 2% (m/v) dextrose. Growth in the presence of Raftilose Synergy1, Raftilose L95 and Raftiline GR did not lead to increased levels of antimicrobial activity. Cells grown in the presence of Raftilose Synergy1 took longer to adhere to intestinal mucus, whilst cells grown in the absence of prebiotics showed a linear rate of binding.

CONCLUSIONS

A broad range of gram-positive and gram-negative bacteria were inhibited. Dextrose stimulated the production of antimicrobial compounds. Adhesion to intestinal mucus did not increase with the addition of prebiotics.

SIGNIFICANCE AND IMPACT OF THE STUDY

The strains may be incorporated in food supplements for HIV/AIDS patients suffering from gastro-intestinal disorders.

Characterization of a 3944 Da bacteriocin, produced by Enterococcus mundtii ST15, with activity against Gram-positive and Gram-negative bacteria

Strain ST15, isolated from soy beans, and identified as Enterococcus mundtii, produces a 3944 Da bacteriocin that inhibits the growth of Lactobacillus sakei, Enterococcus faecalis, Bacillus cereus, Propionibacterium sp., Clostridium tyrobutyricum, Acinetobacter baumanii, Klebsiella pneumoniae, Pseudomonas aeruginosa, Staphylococcus aureus, Streptococcus pneumoniae and Streptococcus caprinus. Bacteriocin ST15 is inactivated by proteinase K, pronase, pepsin, protease and Triton X-114, but not when treated with catalase, alpha-amylase, Triton X-100, SDS, Tween 20, Tween 80, urea and EDTA. No change in activity was recorded after 2 h at pH values between 2.0 and 12.0, and after treatment at 100 degrees C for 90 min. Activity was, however, lost after treatment at 121 degrees C for 20 min. The mode of activity is bactericidal. The highest level of activity (51200 AU ml(-1)) was recorded when cells were grown in MRS broth, pH 6.5. Bacteriocin ST15 differs from other broad-spectrum bacteriocins described for Enterococcus spp. by being active against Gram-negative bacteria and by being smaller.

Effect of medium components on bacteriocin production by Lactobacillus plantarum strains ST23LD and ST341LD, isolated from spoiled olive brine

Bacteriocin ST23LD levels of 2930AU/OD were recorded in MRS broth (pH of 6.5) and in the presence of tryptone and yeast extract as sole nitrogen sources. Growth in MRS broth at an initial pH of 6.0 yielded only 1460AU/OD bacteriocin ST23LD. Activities of 5861AU/OD were recorded with maltose (20, 30 and 40 g/l) as sole carbon source and 9036AU/OD with the addition of 2.0-10.0 g/l KH2PO4. Bacteriocin ST341LD levels of 2850 and 2841AU/OD were recorded in MRS broth at an initial pH of 6.0 or 5.5, respectively. Only 709AU/OD was recorded in the same medium with an initial pH of 6.5. Bacteriocin ST341LD production was stimulated by the presence of tryptone. However, glucose at 10 and 40 g/l, or the presence of 5.0 or 10.0 g/l K2HPO4, resulted in a 50% reduction of bacteriocin activity. Glycerol in the growth medium repressed bacteriocin production. No increased bacteriocin production was recorded in medium supplemented with vitamins.

Screening of lactic-acid bacteria from South African barley beer for the production of bacteriocin-like compounds

Strains of Lactobacillus paracasei subsp. paracasei (strain ST11BR), L. pentosus (strain ST151BR), L. plantarum (strain ST13BR), and Lactococcus lactis subsp. lactis (strain ST34BR) producing bacteriocin-like peptides were isolated from barley beer produced in the Western, Northern and Eastern provinces of South Africa. The peptides (bacST11BR, bacST151BR, bacST13BR and bacST34BR) lost their activity after treatment with proteinase K, a proteinase, papain, chymotrypsin, trypsin, pepsin and pronase, but not when they were treated with alpha-amylase, suggesting that the peptides are not glycosylated. The peptides inhibited the growth of Lactobacillus casei, L. sakei, Pseudomonas aeruginosa, Escherichia coli and Enterococcus faecalis, but not Enterobacter cloacae, Lactobacillus bulgaricus subsp. delbrueckii, L. plantarum, L. salivarius, Listeria innocua, Staphylococcus aureus, Streptococcus uberis, S. agalactiae, S. caprinus and S. pneumoniae. Peptides bacST11BR and bacST13BR differed from the other 2 peptides by failing to kill Klebsiella pneumoniae and one of the E. coli strains. Peptides were stable after 2 h of incubation at pH 2.0-12.0, and after 90 min at 100 degrees C. When autoclaved (121 degrees C, 20 min), only bacST13BR lost its activity. The bacteriocin-like peptides were produced at a growth temperature of 30 degrees C, but not at 37 degrees C.