New insights in antibiotic resistance of Lactobacillus species from fermented foods

Anti-fungal effects of lactic acid bacteria from pickles on the growth and sterigmatocystin production of Aspergillus versicolor

Sterigmatocystin (STC) is an emerging mycotoxin that poses a significant threat to the food security of cereal crops. To mitigate STC contamination in maize, this study employed selected lactic acid bacteria as biocontrol agents against Aspergillus versicolor, evaluating their biocontrol potential and analyzing the underlying mechanisms. Lactiplantibacillus plantarum HJ10, isolated from pickle, exhibited substantial in vitro antifungal activity and passed safety assessments, including antibiotic resistance and hemolysis tests. In vivo experiments demonstrated that L. plantarum HJ10 significantly reduced the contents of A. versicolor and STC in maize (both >84 %). The impact of heat, enzymes, alkali, and other treatments on the antifungal activity of cell-free supernatant (CFS) was investigated. Integrated ultra-high-performance liquid chromatography (UPLC) and gas chromatography-mass spectrometry (GC-MS) analysis revealed that lactic acid, acetic acid, and formic acid are the key substances responsible for the in vitro antifungal activity of L. plantarum HJ10. These metabolites induced mold apoptosis by disrupting cell wall structure, increasing cell membrane fluidity, reducing enzyme activities, and disrupting energy metabolism. However, in vivo antagonism by L. plantarum HJ10 primarily occurs through organic acid production and competition for growth space and nutrients. This study highlights the potential of L. plantarum HJ10 in reducing A. versicolor and STC contamination in maize.

Food safety assessment and 28-day toxicity study of the synbiotic medical food consortium SBD121

The human gut microbiome plays a crucial role in immune function. The synbiotic consortium or Defined Microbial Assemblage™ (DMA™) Medical Food product, SBD121, consisting of probiotic microbes and prebiotic fibers was designed for the clinical dietary management of rheumatoid arthritis. A 28-day repeated administration study was performed to evaluate the oral toxicity of SBD121 in male and female rats (age/weight at study start: 60 days/156-264 g) administered levels of 0, 4.96 x 1010, 2.48 x 1011, or 4.96 x 1011 colony forming units (CFU)/kg-bw. No treatment related changes were observed in ophthalmological effects, mortality, morbidity, general health and clinical observations, urinalysis, hematology, serum chemistry, absolute or relative organ weights, gross necropsy, or histopathology. A significant decrease in body weight was reported in females in the low and high-concentration groups, which corresponded in part with a significant decrease in food consumption. Results of the functional observation battery indicated front grip strength was significantly greater in the high-concentration males compared to the controls; however, this effect was not considered adverse. Based on these findings, the administration of the Medical Food SBD121 to male and female rats has a no-observable adverse effect level (NOAEL) at the highest level tested of 4.96 x 1011 CFU/kg-bw.

Isolation and Characterization of Lactic Acid Bacteria With Probiotic Attributes From Different Parts of the Gastrointestinal Tract of Free-living Wild Boars in Hungary

Lactic acid bacteria (LAB) in the microbiota play an important role in human and animal health and, when used as probiotics, can contribute to an increased growth performance in livestock management. Animals living in their native habitat can serve as natural sources of microorganisms, so isolation of LAB strains from wild boars could provide the opportunity to develop effective probiotics to improve production in swine industry. In this study, the probiotic potential of 56 LAB isolates, originated from the ileum, colon, caecum and faeces of 5 wild boars, were assessed in vitro in details. Their taxonomic identity at species level and their antibacterial activity against four representative strains of potentially pathogenic bacteria were determined. The ability to tolerate low pH and bile salt, antibiotic susceptibility, bile salt hydrolase activity and lack of hemolysis were tested. Draft genome sequences of ten Limosilactobacillus mucosae and three Leuconostoc suionicum strains were determined. Bioinformatic analysis excluded the presence of any known acquired antibiotic resistance genes. Three genes, encoding mesentericin B105 and two different bacteriocin-IIc class proteins, as well as two genes with possible involvement in mesentericin secretion (mesE) and transport (mesD) were identified in two L. suionicum strains. Lam29 protein, a component of an ABC transporter with proved function as mucin- and epithelial cell-adhesion factor, and a bile salt hydrolase gene were found in all ten L. mucosae genomes. Comprehensive reconsideration of all data helps to select candidate strains to assess their probiotic potential further in animal experiments.

Probiotic bacteria of wild boar origin intended for piglets - An in vitro study

Using probiotics represents a potential solution to post-weaning diarrheal diseases in piglets on commercial farms. The gastrointestinal tract of wild boars serves as a promising reservoir of novel lactic acid bacteria with suitable probiotic characteristics. In this study, we isolated eight bacterial strains from the intestinal content of wild boars identified as representatives of the species Bifidobacterium apri, Lactobacillus amylovorus, and Ligilactobacillus salivarius. These isolates underwent in vitro analysis and characterisation to assess their biological safety and probiotic properties. Analysis of their full genome sequences revealed the absence of horizontally transferrable genes for antibiotic resistance. However, seven out of eight isolates harboured genes encoding various types of bacteriocins in their genomes, and bacteriocin production was further confirmed by mass spectrometry analysis. Most of the tested strains demonstrated the ability to inhibit the growth of selected pathogenic bacteria, produce exopolysaccharides, and stimulate the expression of interleukin-10 in porcine macrophages. These characteristics deem the isolates characterised in this study as potential candidates for use as probiotics for piglets during the post-weaning period.

Phenotypic and genotypic characterization of antimicrobial resistances reveals the effect of the production chain in reducing resistant lactic acid bacteria in an artisanal raw ewe milk PDO cheese

Antimicrobial resistance (AMR) is a significant public health threat, with the food production chain, and, specifically, fermented products, as a potential vehicle for dissemination. However, information about dairy products, especially raw ewe milk cheeses, is limited. The present study analysed, for the first time, the occurrence of AMRs related to lactic acid bacteria (LAB) along a raw ewe milk cheese production chain for the most common antimicrobial agents used on farms (dihydrostreptomycin, benzylpenicillin, amoxicillin and polymyxin B). More than 200 LAB isolates were obtained and identified by Sanger sequencing (V1-V3 16S rRNA regions); these isolates included 8 LAB genera and 21 species. Significant differences in LAB composition were observed throughout the production chain (P ≤ 0.001), with Enterococcus (e.g., E. hirae and E. faecalis) and Bacillus (e.g., B. thuringiensis and B. cereus) predominating in ovine faeces and raw ewe milk, respectively, along with Lactococcus (L. lactis) in whey and fresh cheeses, while Lactobacillus and Lacticaseibacillus species (e.g., Lactobacillus sp. and L. paracasei) prevailed in ripened cheeses. Phenotypically, by broth microdilution, Lactococcus, Enterococcus and Bacillus species presented the greatest resistance rates (on average, 78.2 %, 56.8 % and 53.4 %, respectively), specifically against polymyxin B, and were more susceptible to dihydrostreptomycin. Conversely, Lacticaseibacillus and Lactobacillus were more susceptible to all antimicrobials tested (31.4 % and 39.1 %, respectively). Thus, resistance patterns and multidrug resistance were reduced along the production chain (P ≤ 0.05). Genotypically, through HT-qPCR, 31 antimicrobial resistance genes (ARGs) and 6 mobile genetic elements (MGEs) were detected, predominating Str, StrB and aadA-01, related to aminoglycoside resistance, and the transposons tnpA-02 and tnpA-01. In general, a significant reduction in ARGs and MGEs abundances was also observed throughout the production chain (P ≤ 0.001). The current findings indicate that LAB dynamics throughout the raw ewe milk cheese production chain facilitated a reduction in AMRs, which has not been reported to date.

Multidrug resistance profile in Lactobacillus delbrueckii: a food industry species with probiotic properties

Lactobacillus delbrueckii, a widely used lactic acid bacterium in the food industry, has been studied for its probiotic properties and reservoir of antibiotic-resistant genes, raising safety concerns for probiotic formulations and fermented products. This review consolidates findings from 60 articles published between 2012 and 2023, focusing on the global antibiotic resistance profile and associated genetic factors in L. delbrueckii strains. Resistance to aminoglycosides, particularly streptomycin, kanamycin, and gentamicin, as well as resistance to glycopeptides (vancomycin), fluoroquinolones (ciprofloxacin), and tetracyclines was predominant. Notably, although resistance genes have been identified, they have not been linked to mobile genetic elements, reducing the risk of dissemination. However, a significant limitation is the insufficient exploration of responsible genes or mobile elements in 80% of studies, hindering safety assessments. Additionally, most articles originated from Asian and Middle Eastern countries, with strains often isolated from fermented dairy foods. Therefore, these findings underscore the necessity for comprehensive analyses of new strains of L. delbrueckii for potential industrial and biotherapeutic applications and in combating the rise of antibiotic-resistant pathogens.

Bacteriocins: potentials and prospects in health and agrifood systems

Bacteriocins are highly diverse, abundant, and heterogeneous antimicrobial peptides that are ribosomally synthesized by bacteria and archaea. Since their discovery about a century ago, there has been a growing interest in bacteriocin research and applications. This is mainly due to their high antimicrobial properties, narrow or broad spectrum of activity, specificity, low cytotoxicity, and stability. Though initially used to improve food quality and safety, bacteriocins are now globally exploited for innovative applications in human, animal, and food systems as sustainable alternatives to antibiotics. Bacteriocins have the potential to beneficially modulate microbiota, providing viable microbiome-based solutions for the treatment, management, and non-invasive bio-diagnosis of infectious and non-infectious diseases. The use of bacteriocins holds great promise in the modulation of food microbiomes, antimicrobial food packaging, bio-sanitizers and antibiofilm, pre/post-harvest biocontrol, functional food, growth promotion, and sustainable aquaculture. This can undoubtedly improve food security, safety, and quality globally. This review highlights the current trends in bacteriocin research, especially the increasing research outputs and funding, which we believe may proportionate the soaring global interest in bacteriocins. The use of cutting-edge technologies, such as bioengineering, can further enhance the exploitation of bacteriocins for innovative applications in human, animal, and food systems.

Accounting for the health risk of probiotics

Probiotics have long been associated with a myriad of health benefits, so much so that their adverse effects whether mild or severe, are often neglected or overshadowed by the enormous volume of articles describing their beneficial effects in the current literature. Recent evidence has demonstrated several health risks of probiotics that warrant serious reconsideration of their applications and further investigations. This review aims to highlight studies that report on how probiotics might cause opportunistic systemic and local infections, detrimental immunological effects, metabolic disturbance, allergic reactions, and facilitating the spread of antimicrobial resistance. To offer a recent account of the literature, articles within the last five years were prioritized. The narration of these evidence was based on the nature of the studies in the following order of preference: clinical studies or human samples, in vivo or animal models, in situ, in vitro and/or in silico. We hope that this review will inform consumers, food scientists, and medical practitioners, on the health risks, while also encouraging research that will focus on and clarify the adverse effects of probiotics.

Microbiological Quality and Antimicrobial Resistance of Commercial Probiotic Products for Food-Producing Animals

Probiotics have been popularly used in livestock production as an alternative to antibiotics. This study aimed to investigate the microbiological quality and phenotypic and genotypic antimicrobial resistance of bacteria in probiotic products sold for food animals. A total of 45 probiotic products were examined for the number of viable cells, species, and antimicrobial susceptibility; the contamination of Escherichia coli and Salmonella; and the presence of 112 genes encoding resistance to clinically important antimicrobials and transferability of AMR determinants. The results showed that 29 of 45 products (64.4%) were incorrectly labeled in either number of viable cells or bacterial species. None of the tested products were contaminated with E. coli and Salmonella. A total of 33 out of 64 bacterial isolates (51.6%) exhibited resistance to at least one antimicrobial agent. Of the 45 products tested, 16 (35.5%) carried AMR genes. Almost all AMR genes detected in probiotic products were not correlated to the AMR phenotype of probiotic strains formulated in the products. Three streptomycin-resistant Lactobacillus isolates could horizontally transfer their AMR determinants. The findings demonstrated that the probiotic products could serve as reservoirs for the spread of AMR genes and may not yield benefits to animals as claimed. The need for the adequate quality control of probiotic products is highlighted.

Prevalence of antibiotic resistance in lactic acid bacteria isolated from traditional fermented Indian food products

The emergence of antimicrobial resistance (AMR) in lactic acid bacteria (LAB) raises questions on qualified presumptive safety status and poses challenge of AMR transmission in food milieu. This study focuses on isolation, identification and characterization of AMR in LAB prevalent in traditional fermented Indian food products. The analysis of 16SrRNA based phylogenetic tree showed placements of isolates among four different genera Lactobacillus, Enterococcus, Weissella and Leuconostoc. In E-strip gradient test of susceptibility to 14 different antibiotics, over 50% of isolates showed resistance to ampicillin, chloramphenicol, ciprofloxacin, erythromycin, kanamycin, linezolid, streptomycin, trimethoprim and vancomycin. A multivariate principal component analysis, an antibiogram and multiple antibiotic resistance index-values (> 0.2) indicated presence of multidrug-resistance among the isolates. This study reports prevalence of an alarmingly high rate of AMR LAB strains in traditional fermented foods and is important to regulators and public health authorities for developing strategies to control transmission in food systems.

Supplementary Information

The online version contains supplementary material available at 10.1007/s10068-023-01305-1.

Hazardous risk of antibiotic resistance genes: Host occurrence, distribution, mobility and vertical transmission from different environments to corn silage

Antibiotic resistance genes (ARGs) are one of the emerging contaminants posing a great deal of hazardous risk to public health. This study employed metagenomics and deciphered the potential risk of the antibiotic resistome and their vertical transfer to ensiled whole-crop corn silage harvested from six climate zones: 1. Warm temperate-fully humid-hot summer (Cfa), 2. Arid-desert-cold arid (BWk), 3. Snow-desert-cold summer (Dwc), 4. Snow-desert-hot summer (Dwa), 5. Arid-steppe-cold arid (BSk), and 6. Equatorial-desert (Aw) based on the Köppen-Geiger climate classification in China. The findings demonstrate a high diversity of ARGs, which is related to the drug classes of tetracycline, ciprofloxacin, lincosamide, fosfomycin, and beta lactam. Resistome variations are mostly related to variations in microbial composition and fermentation characteristics of the silages from different climate zones, which are indirectly influenced by environmental conditions. The most dominating ARGs in corn silage were tetM, acrA, H-NS, lnuA, emrR, and KpnG, which is primarily hosted by Klebsiella and Lactobacilli. There were 5 high-risk ARGs (tetM, bacA, SHV-1, dfrA17, and QnrS1) in silage from different climate zones, and the tetM was the most prevalent high-risk ARG. However, throughout the ensiling process, the abundance of ARGs, and mobile ARGs were reduced. The resistome contamination in silage from Tibet (Dwc) with high altitude and harsh environment was relatively low due to the low variety and abundance of ARGs, the low abundance of mobile ARGs and high-risk ARGs. In addition, most of the bacteria responsible for the silage fermentation were also found to be the hosts to the ARGs, although their abundance decreased after 90 d of silage fermentation. Hence, we alert the existence of ARGs-related biosafety risk in silages and call for more attention to the silage ARGs, their hosts, and mobile genetic elements in order to curtail their possible risk to public health.

Intestinal Microbiomics and Metabolomics Insights into the Hepatoprotective Effects of Lactobacillus paracasei CCFM1222 Against the Acute Liver Injury in Mice

In recent years, acute liver injury (ALI) has received wide-range attention in the world due to its relatively high morbidity and mortality. This study aimed to explore the hepatoprotective effect of Lactobacillus paracasei CCFM1222 against lipopolysaccharide (LPS)-induced ALI mice and further elaborate its mechanism of action from the perspective of intestinal microbiomics and metabolomics. The results displayed that L. paracasei CCFM1222 pretreatment significantly decreased the serum ALT, and AST levels, inhibited the releases of hepatic TNF-α, IL-1β, and IL-6 levels, and activated the SOD, CAT, and GSH-Px activities in LPS-treated mice. The cecal short-chain fatty acid (SCFAs) levels were increased in LPS-treated mice with L. paracasei CCFM1222 pretreatment. In addition, L. paracasei CCFM1222 pretreatment remarkably shifted the intestinal microbiota composition, including the higher abundance of Faecalibaculum, Bifidobacterium, and lower abundance of the Prevotellaceae NK3B31 group, which is positively associated with the cecal propionic, butyric, valeric, isobutyric, and isovaleric acids. The metabolomics based on UPLC-QTOF/MS revealed that L. paracasei CCFM1222 pretreatment significantly regulated the composition of feces metabolites in LPS-treated mice, especially the potential biomarker-related butanoate metabolism, vitamin B6 metabolism, D-glutamine and D-glutamate metabolism, tryptophan metabolism, caffeine metabolism, arginine biosynthesis, arginine, and proline metabolism. Moreover, L. paracasei CCFM1222 pretreatment remarkably regulated the expression of gene-associated ALI (including Tlr4, Myd88, Nf-kβ, iNOS, Cox2, Iκ-Bα, Nrf2, and Sirt-1). In conclusion, these results suggest the possibility that L. paracasei CCFM1222 supplementation has beneficial effects on preventing the occurrence and development of ALI by inhibiting the inflammatory responses and altering intestinal microbiota composition and their metabolites.

Probiotic Lactobacillus and the potential risk of spreading antibiotic resistance: a systematic review

Background and purpose

Lactobacillus, the most popular probiotic, has recently gained more attention because it is a potential reservoir of antibiotic resistance. This review summarized and discussed the phenotypic-genotypic characteristics of antibiotic resistance.

Experimental approach

Google Scholar, PubMed, Web of Science, and Scopus were searched up to February 2022. The inclusion criteria were all studies testing antibiotic resistance of probiotic Lactobacillus strains present in human food supplementation and all human/animal model studies in which transferring antibiotic-resistant genes from Lactobacillus strains to another bacterium were investigated.

Findings/Results

Phenotypic and genotypic characterization of Lactobacillus probiotics showed that the most antibiotic resistance was against protein synthesis inhibitors (fourteen studies, 87.5%) and cell wall synthesis inhibitors (ten studies, 62.5%). Nine of these studies reported the transfer of antibiotic resistance from Lactobacillus probiotic as donor species to pathogenic bacteria and mostly used in vitro methods for resistance gene transfer.

Conclusion and implications

The transferability of resistance genes such as tet and erm in Lactobacillus increases the risk of spreading antibiotic resistance. Further studies need to be conducted to evaluate the potential spread of antibiotic resistance traits via probiotics, especially in elderly people and newborns.

Antibiotic Resistance and Probiotics: Knowledge Gaps, Market Overview and Preliminary Screening

Probiotics are among those products, the use of which is increasing, and they are available primarily as food/dietary supplements, as well as in the form of medicines. This study aims to assess the attitudes and practices of health professionals and students of health sciences, give a short overview of the probiotics currently on the market, and conduct a screening of five food supplements and one drug with respect to antibiotic resistance. Nearly half of the respondents in our survey state that probiotics have no side effects, while only 6.3% believe that the use of probiotics can lead to antibiotic resistance. In addition, more than 40% of the participants throw unused probiotics into municipal waste. The market analysis results indicate that probiotic products on the Serbian market have highly variable CFU counts, while the declared health claims cover numerous beneficial health effects, and they are sometimes even registered as medicines. Lactobacilli are frequently present in probiotic supplements, and are sold in pharmacies and online. The experimental results showed that antibiotic resistance is present in different types of lactobacilli in probiotic products. The risk of using probiotics, regardless of their beneficial health effects, should be taken into account in the future. An update to the regulations governing probiotics, including a stipulation for antimicrobial resistance (AMR) testing, should be established, and guidelines for their proper use and disposal put into place.

Harnessing the probiotic properties and immunomodulatory effects of fermented food-derived Limosilactobacillus fermentum strains: implications for environmental enteropathy

Introduction

Environmental enteropathy (EE), a chronic small intestine disease characterized by gut inflammation, is widely prevalent in low-income countries and is hypothesized to be caused by continuous exposure to fecal contamination. Targeted nutritional interventions using potential probiotic strains from fermented foods can be an effective strategy to inhibit enteric pathogens and prevent chronic gut inflammation.

Methods

We isolated potential strains from fermented rice water and lemon pickle and investigated their cell surface properties, antagonistic properties, adhesion to HT-29 cells, and inhibition of pathogen adherence to HT-29 cells. Bacteriocin-like inhibitory substances (BLIS) were purified, and in vivo, survival studies in Caenorhabditis elegans infected with Salmonella enterica MW116733 were performed. We further checked the expression pattern of pro and anti-inflammatory cytokines (IL-6, IL8, and IL-10) in HT-29 cells supplemented with strains.

Results

The strains isolated from rice water (RS) and lemon pickle (T1) were identified as Limosilactobacillus fermentum MN410703 and MN410702, respectively. Strains showed probiotic properties like tolerance to low pH (pH 3.0), bile salts up to 0.5%, simulated gastric juice at low pH, and binding to extracellular matrix molecules. Auto-aggregation of T1 was in the range of 85% and significantly co-aggregated with Klebsiella pneumoniae, S. enterica, and Escherichia coli at 48, 79, and 65%, respectively. Both strains had a higher binding affinity to gelatin and heparin compared to Bacillus clausii. Susceptibility to most aminoglycoside, cephalosporin, and macrolide classes of antibiotics was also observed. RS showed BLIS activity against K. pneumoniae, S. aureus, and S. enterica at 60, 48, and 30%, respectively, and the protective effects of BLIS from RS in the C. elegans infection model demonstrated a 70% survival rate of the worms infected with S. enterica. RS and T1 demonstrated binding efficiency to HT-29 cell lines in the 38-46% range, and both strains inhibited the adhesion of E. coli MDR and S. enterica. Upregulation of IL-6 and IL-10 and the downregulation of IL-8 were observed when HT-29 cells were treated with RS, indicating the immunomodulatory effects of the strain.

Discussion

The potential strains identified could effectively inhibit enteric pathogens and prevent environmental enteropathy.

Promising biotherapeutic prospects of different probiotics and their derived postbiotic metabolites: in-vitro and histopathological investigation

BACKGROUND

Probiotics and their derived postbiotics, as cell-free supernatants (CFS), are gaining a solid reputation owing to their prodigious health-promoting effects. Probiotics play a valuable role in the alleviation of various diseases among which are infectious diseases and inflammatory disorders. In this study, three probiotic strains, Lactiplantibacillus plantarum, Lacticaseibacillus rhamnosus, and Pediococcus acidilactici, were isolated from marketed dietary supplements. The antimicrobial activity of the isolated probiotic strains as well as their CFS was investigated. The neutralized CFS of the isolated probiotics were tested for their antibiofilm potential. The anti-inflammatory activity of the isolated Lactobacillus spp., together with their CFS, was studied in the carrageenan-induced rat paw edema model in male Wistar rats. To the best of our knowledge, such a model was not previously experimented to evaluate the anti-inflammatory activity of the CFS of probiotics. The histopathological investigation was implemented to assess the anti-inflammatory prospect of the isolated L. plantarum and L. rhamnosus strains as well as their CFS.

RESULTS

The whole viable probiotics and their CFS showed variable growth inhibition of the tested indicator strains using the agar overlay method and the microtiter plate assay, respectively. When tested for virulence factors, the probiotic strains were non-hemolytic lacking both deoxyribonuclease and gelatinase enzymes. However, five antibiotic resistance genes, blaZ, ermB, aac(6')- aph(2"), aph(3'')-III, and vanX, were detected in all isolates. The neutralized CFS of the isolated probiotics exhibited an antibiofilm effect as assessed by the crystal violet assay. This effect was manifested by hindering the biofilm formation of the tested Staphylococcus aureus and Pseudomonas aeruginosa clinical isolates in addition to P. aeruginosa PAO1 strain. Generally, the cell cultures of the two tested probiotics moderately suppressed the acute inflammation induced by carrageenan compared to indomethacin. Additionally, the studied CFS relatively reduced the inflammatory changes compared to the inflammation control group but less than that observed in the case of the probiotic cultures treated groups.

CONCLUSIONS

The tested probiotics, along with their CFS, showed promising antimicrobial and anti-inflammatory activities. Thus, their safety and their potential use as biotherapeutics for bacterial infections and inflammatory conditions are worthy of further investigation.

Exploring the Inhibitory Activity of Selected Lactic Acid Bacteria against Bread Rope Spoilage Agents

In this study, a wide pool of lactic acid bacteria strains deposited in two recognized culture collections was tested against ropy bread spoilage bacteria, specifically belonging to Bacillus spp., Paenibacillus spp., and Lysinibacillus spp. High-throughput and ex vivo screening assays were performed to select the best candidates. They were further investigated to detect the production of active antimicrobial metabolites and bacteriocins. Moreover, technological and safety features were assessed to value their suitability as biocontrol agents for the production of clean-label bakery products. The most prominent inhibitory activities were shown by four strains of Lactiplantibacillus plantarum (NFICC19, NFICC 72, NFICC163, and NFICC 293), two strains of Pediococcus pentosaceus (NFICC10 and NFICC341), and Leuconostoc citreum NFICC28. Moreover, the whole genome sequencing of the selected LAB strains and the in silico analysis showed that some of the strains contain operons for bacteriocins; however, no significant evidence was observed phenotypically.

Characterization of Lactic Acid Bacteria Isolated from Spontaneously Fermented Sausages: Bioprotective, Technological and Functional Properties

Fermentation is one of the most ancient strategies to improve safety and extend shelf-life of the products. Starter cultures are mainly represented by lactic acid bacteria (LAB), which may also be bioprotective agents controlling the fermentation process, the native microbiota and pathogen outgrowth. This work aimed to select new LAB strains from spontaneously fermented sausages produced in different areas of Italy, which can be effective as starter cultures and bioprotective agents in fermented salami. The strains, mainly belonging to the Latilactobacillus sakei species, were characterized for their ability to inhibit major meat pathogens, the presence of antibiotic resistances and amine production. Moreover, technological performances, such as growth and acidification kinetics at increasing NaCl concentrations, were studied. As a result, new autochthonous Lat. sakei strains were obtained, lacking antibiotic resistance, possessing antimicrobial activity against Clostridium sporogenes, Listeria monocytogenes, Salmonella and Escherichia coli and with high growth performance under osmotic pressure. These strains have the potential for future application to improve the safety of fermented meats, even under conditions in which chemical preservatives are reduced or eliminated. Moreover, studies on autochthonous cultures are pivotal for guaranteeing specific characteristics of traditional products that represent an important cultural heritage.

Antimicrobial Susceptibility Data for Six Lactic Acid Bacteria Tested against Fifteen Antimicrobials

Antimicrobial resistance is a rising threat in the agrifood sector. The misuse of antibiotics exerts selective pressure, driving resistance mechanisms in bacteria, which could ultimately spread through many routes and render treatments for infectious diseases inefficient in humans and animals. Herein, we report antimicrobial susceptibility data obtained for six lactic acid bacteria, the members of which are commonly used in the food and feed chain. Fifteen antimicrobials were considered for the phenotypic testing: ampicillin, gentamicin, kanamycin, tetracycline, erythromycin, clindamycin, chloramphenicol, streptomycin, vancomycin, quinupristin-dalfopristin, bacitracin, sulfamethoxazole, ciprofloxacin, linezolid, and rifampicin. The reported dataset could be used for the comparison, generation, and reconsideration of new and/or existing cut-off values when considering lactic acid bacteria, particularly lactobacilli and pediococci.

Effects of cumin (Cuminum cyminum L.) essential oil and chronic heat stress on growth performance, carcass characteristics, serum biochemistry, antioxidant enzyme activity, and intestinal microbiology in broiler chickens

This study was conducted on 600 one-day-old male broiler chicks, using a 2 × 6 factorial design (ambient temperature, A x feed additive, F), for a period of 42 days. The chicks assigned to different groups were exposed to thermoneutral (TN, 24 ± 1 °C) and constant heat stress (HT, 36 ± 1 °C) conditions, and were only fed on a basal diet, and a basal diet supplemented with either 100 mg/kg chloramphenicol, 50 IU/kg α-tocopherol, or 200, 400, and 600 mg/kg of cumin essential oil (CEO). The results showed that heat stress adversely affected performance and carcass characteristics, and increased both the mortality rate and footpad lesions. Moreover, constant chronic heat stress showed negative effects on serum biochemistry and the intestinal microbiota, increased antioxidant activity in both the plasma and breast meat, and increased counts of the pathogenic microorganisms in the small intestine. On the other hand, dietary CEO supplementation positively affected these parameters. CEO had a slight effect on performance, carcass characteristics, mortality rate and the incidence of footpad lesions. When compared to the control group, it was determined that CEO generally had a positive effect on lipid peroxidation in the plasma and tissues and decreased antioxidant enzyme activity. Furthermore, CEO positively affected serum biochemistry and counts of beneficial microorganisms in the small intestine.

Characterization and Transferability of erm and tet Antibiotic Resistance Genes in Lactobacillus spp. Isolated from Traditional Fermented Milk

Lactobacillus is a widely used bacteria and consumed through various fermented foods and beverages. Strains have been shown to carry resistance genes and mobile genetic elements with their ability to transfer the resistance to sensitive pathogenic strains. To study this, 4 cultures of Lactobacillus were isolated from traditional fermented milk. The isolates were able to grow up to 4% (w/v) NaCl concentration and 45 °C temperature, and showed > 97% 16S rRNA gene similarities with Lactobacillus fermentum. All the isolates were phenotypically screened for the presence of antibiotic resistance. Minimum inhibitory concentration (MIC) as microbiological breakpoints were observed against a varied class of antibiotics. Isolates AKO 94.6, DVM 95.7, and NIFTEM 95.8 were explicitly resistant to ampicillin, ciprofloxacin and vancomycin with MIC well beyond the maximum range of 256 µg/ml in the E-strip test. While isolate SKL1 was sensitive to ampicillin and showed MIC at 0.25 µg/ml but resistant to streptomycin and trimethoprim (MIC > 256 µg/ml). Molecular characterization showed the presence of tet(M) gene in three isolates SKL1, DVM 95.7, and NIFTEM 95.8 which was chromosomally associated resistance determinants while erm(B) resistance gene was detected in isolates DVM 95.7 and NIFTEM 95.8 only which was a plasmid associated gene and could be transferrable conjugally. Gene for Tn916 family (xis) was also observed in isolates DVM 95.7 and NIFTEM 95.8. Transferability of antibiotic resistance to pathogenic recipient strains was examined in isolates DVM 95.7 and NIFTEM 95.8 in different food matrices. The highest conjugation frequency with ~ 10^-1 was obtained in alfalfa seed sprouts. This study reports the presence of acquired gene resistance in Lactobacillus species and dissemination to susceptible strains of bacteria in different food matrices. 16S rRNA gene sequences of isolates were uploaded to the NCBI GenBank database to retrieve the accession number.

Lactobacillus acidophilus novel strain, MJCD175, as a potential probiotic for oral health in dogs

The oral cavity is the second-largest habitat for microorganisms, and a well-balanced oral microbiome contributes to preventing dental disorders caused by pathogenic bacteria. Since humans and dogs have different lifestyles and oral microbiome structures, the present study aimed to develop novel probiotics for dogs. A total 53 Lactobacillus spp. were isolated from healthy dogs, and nine isolates were identified as Lactobacillus acidophilus according to 16S rRNA gene sequencing. According to the high antimicrobial activity against the dental caries-causing bacterium Streptococcus mutans, single or three mixed strains were orally administered to dogs for 4 weeks with concentration of 10⁸-10⁹ CFU/day. Intraoral swab samples were collected before and after the administration, and changes of oral pathogen were analyzed using quantitative PCR. Among them, Porphyromonas gingivalis, a critical factor of periodontitis, was significantly reduced in the single-strain administered group. Based on the acid and bile salts tolerance characteristics of isolates, systemic effects were also analyzed by comparing serum immunoglobulin and reproductive ability before and after the administration. However, no significant changes were observed in the serum IgG level and sperm quality. Overall, these in vitro and in vivo results suggest that L. acidophilus isolates from dogs, especially L. acidophilus MJCD175, could be promising probiotic candidates to support oral health without systemic adverse effects in dogs.

Emergence and spread of antibiotic-resistant foodborne pathogens from farm to table

Antibiotics have been overused and misused for preventive and therapeutic purposes. Specifically, antibiotics are frequently used as growth promoters for improving productivity and performance of food-producing animals such as pigs, cattle, and poultry. The increasing use of antibiotics has been of great concern worldwide due to the emergence of antibiotic resistant bacteria. Food-producing animals are considered reservoirs for antibiotic resistance genes (ARGs) and residual antibiotics that transfer from the farm through the table. The accumulation of residual antibiotics can lead to additional antibiotic resistance in bacteria. Therefore, this review evaluates the risk of carriage and spread of antibiotic resistance through food chain and the potential impact of antibiotic use in food-producing animals on food safety. This review also includes in-depth discussion of promising antibiotic alternatives such as vaccines, immune modulators, phytochemicals, antimicrobial peptides, probiotics, and bacteriophages.

ProbResist: a database for drug-resistant probiotic bacteria

Drug resistance remains a global threat, and the rising trend of consuming probiotic-containing foods, many of which harbor antibiotic resistant determinants, has raised serious health concerns. Currently, the lack of accessibility to location-, drug- and species-specific information of drug-resistant probiotics has hampered efforts to combat the global spread of drug resistance. Here, we describe the development of ProbResist, which is a manually curated online database that catalogs reports of probiotic bacteria that have been experimentally proven to be resistant to antibiotics. ProbResist allows users to search for information of drug resistance in probiotics by querying with the names of the bacteria, antibiotic or location. Retrieved results are presented in a downloadable table format containing the names of the antibiotic, probiotic species, resistant determinants, region where the study was conducted and digital article identifiers (PubMed Identifier and Digital Object Identifier) hyperlinked to the original sources. The webserver also presents a simple analysis of information stored in the database. Given the increasing reports of drug-resistant probiotics, an exclusive database is necessary to catalog them in one platform. It will enable medical practitioners and experts involved in policy making to access this information quickly and conveniently, thus contributing toward the broader goal of combating drug resistance.

Probiotic and Antioxidant Potential of the Lactobacillus Spp. Isolated from Artisanal Fermented Pickles

The present study was based on bacterial isolation with probiotic potential from artisanal fermented pickles. A total of 36 bacterial strains were isolated from 50 different artisanal fermented pickle samples. Nine isolates with promising probiotic potential (PCR99, PCR100, PCR118, PCR119, PCR121, PCR125, PCR137, PCR140 and PCR141) were selected. The strains showed varied protease, amylase, lipase and cellulase patterns. The isolated strains displayed varied responses towards various antibiotic classes, i.e., PCR140 showed resistance to penicillin G, polymyxin B, Metronidazole and Streptomycin. PCR140 showed highest resistance to bile salt concentrations (0.3% and 0.5%) and acidic conditions (pH 3 and pH 4) when exposed to mimicked gastrointestinal conditions. The cell viability against enzymes produced in stomach and intestines showed different patterns as pepsin was in the range of 94.32–91.22%, pancreatic resistance 97.32–93.11% and lysozyme resistance was detected at 99.12–92.55%. Furthermore, the auto-aggregation capability of isolated strains was in the range of 46.11–33.33% and cell surface hydrophobicity was in the range of 36.55–31.33%. PCR 140 showed maximum antioxidant activity in lyophilized cells as well as probiotic potential. A phylogenetic analysis based on 16S rRNA gene sequencing confirmed that PCR140 (NMCC91) with higher in vitro probiotic and antioxidant potential belongs to the genus Lactobacillus with 97% similarity with Lacticaseibacillus paracasei. This work demonstrated that the isolate PCR 140 (NMCC91) is suitable for use in food and medical industries.

Characterization of Some Microorganisms from Human Stool Samples and Determination of Their Effects on CT26 Colorectal Carcinoma Cell Line

The present study aimed to isolate and identify the potential probiotic, pathobiont, and pathogenic microorganisms in the stool samples of 12 healthy individuals and evaluate their in vitro effects on cancer formation. A total of 83 strains were isolated from the stool samples and identified using MALDI-Biotyper. Fourteen of the isolates were identified as Candida spp., three isolates were identified as Cryptococcus neoformans, 55 isolates were identified as lactic acid bacteria, and the remaining isolates belonged to different 11 bacterial genera. Important microbial properties for cancer prevention and some probiotic properties were examined. All strains maintained their viability under acidic conditions and in media containing bile salts. Of the bacterial strains, 62.5% were resistant to ampicillin, chloramphenicol, gentamicin, erythromycin, kanamycin, penicillin, streptomycin, tetracycline, and vancomycin. All yeast strains were resistant to ketoconazole and susceptible to nystatin. The susceptibility of the strains to fluconazole, voriconazole, amphotericin B, and itraconazole varied. Fifty-nine percent of the strains produced EPS and 21.7% showed proteolytic activity (PA). Of the strains, 15.7% both produced exopolysaccharides (EPS) and had PA. The antioxidant activity (AOA) varied depending on the strains. The pathobiont and pathogenic microorganisms promoted tumor formation, while potential probiotic microorganisms had a suppressive effect on tumor formation (P > 0.01). One yeast (Candida kefyr MK17) and three lactic acid bacteria strains (Lacticaseibacillus paracasei MK73, Lactiplantibacillus plantarum MK55, Limosilactobacillus mucosae MK45) have superior potential thanks to their anticarcinogenic properties as well as tolerance to gastrointestinal tract conditions. Stool samples of each individual contain various potential probiotic, pathobiont, and pathogenic microorganisms.

Anti-Inflammatory Effects of Limosilactobacillus fermentum KGC1601 Isolated from Panax ginseng and Its Probiotic Characteristics

We investigated the potential probiotic properties of Limosilactobacillus fermentum KGC1601 isolated from Panax ginseng. Ginseng cultivated in an experimental field of the Korea Ginseng Research Institute was fermented, followed by single colony selection from MRS agar. We performed 16s-rRNA sequencing and whole-genome analysis to identify L. fermentum and evaluate the biosafety parameters of this strain, respectively. We confirmed this strain was susceptible to six antibiotics, as proposed by the European Food Safety Authority, did not produce biogenic amines, and did not exhibit any hemolytic activity. Acid resistance and bile salt tolerance, which are essential properties of a probiotic agent, were investigated. Notably, distinguishing properties of this strain were that it exhibited excellent bile salt tolerance and anti-inflammatory effects. The excellent bile salt tolerance was confirmed by scanning electron microscopy. Through qRT-PCR and ELISA studies, it was revealed that L. fermentum KGC1601 pre-treatment up-regulates anti-inflammatory cytokines and down-regulates pro-inflammatory cytokines in RAW 264.7 cells. Consequently, we suggested that L. fermentum KGC1601 can be safely used as a potential anti-inflammatory functional probiotic agent.

Postbiotics as the new frontier in food and pharmaceutical research

Food is the essential need of human life and has nutrients that support growth and health. Gastrointestinal tract microbiota involves valuable microorganisms that develop therapeutic effects and are characterized as probiotics. The investigations on appropriate probiotic strains have led to the characterization of specific metabolic byproducts of probiotics named postbiotics. The probiotics must maintain their survival against inappropriate lethal conditions of the processing, storage, distribution, preparation, and digestion system so that they can exhibit their most health effects. Conversely, probiotic metabolites (postbiotics) have successfully overcome these unfavorable conditions and may be an appropriate alternative to probiotics. Due to their specific chemical structure, safe profile, long shelf-life, and the fact that they contain various signaling molecules, postbiotics may have anti-inflammatory, immunomodulatory, antihypertensive properties, inhibiting abnormal cell proliferation and antioxidative activities. Consequently, present scientific literature approves that postbiotics can mimic the fundamental and clinical role of probiotics, and due to their unique characteristics, they can be applied in an oral delivery system (pharmaceutical/functional foods), as a preharvest food safety hurdle, to promote the shelf-life of food products and develop novel functional foods or/and for developing health benefits, and therapeutic aims. This review addresses the latest postbiotic applications with regard to pharmaceutical formulations and commercial food-based products. Potential postbiotic applications in the promotion of host health status, prevention of disease, and complementary treatment are also reviewed.

Incidence of virulence determinants and antibiotic resistance in lactic acid bacteria isolated from food products

Background: Lactic acid bacteria (LAB) confer beneficial health effects in humans. However, the safety of these bacteria and their potential to spread resistance in the environment must be evaluated. Materials & methods: Fifty-three LAB were isolated from different food samples and assessed for the prevalence of virulence determinants and antibiotic resistance profile. Results: Multiple resistance was reported for Lactobacillus brevis MIM04, having revealed phenotypic resistance to vancomycin (MIC >128 μg/ml), ampicillin, cefotaxime, oxacillin and gentamicin. Virulence traits (cylA, gelE, esp and agg) were detected using specific primers. Enterococcus faecium CHE32, Lactobacillus plantarum CHE37 and E. faecium MLK68 lack virulence genes, possess antimicrobial activity and survive in low pH and bile salt conditions. Conclusion: Isolated LAB revealed probiotic properties.

Study on the effect of sublethal concentrations of antimicrobials on the growth and development of probiotic lactobacilli

The objective of this study was to investigate the effect of sublethal concentrations of 5 antibiotics (tetracycline, erythromycin, penicillin G, lincomycin, ciprofloxacin) and 2 preservatives (benzoic and sorbic acid) on the growth and development of 8 probiotic Lactobacillus strains. All lactobacilli were subjected to a large range of concentrations, growth curves were plotted and MICs were determined for each antimicrobial. The results showed correlation between the sublethal concentrations and the growth rate of the studied microorganisms. Based on the obtained data two groups of strains could be defined – sensitive and relatively resistant. The first group includes L. bulgaricus S2. L. bulgaricus S4. L. bulgaricus S19 and L. gasseri S20. The most resistant of this group was L. gasseri S20. The second group showed more sensitivity and the most affected by the antimicrobials was L. bulgaricus S28.

Assessing the drug resistance profiles of oral probiotic lozenges

Background

Probiotic lozenges have been developed to harvest the benefits of probiotics for oral health, but their long-term consumption may encourage the transfer of resistance genes from probiotics to commensals, and eventually to disease-causing bacteria.

Aim

To screen commercial probiotic lozenges for resistance to antibiotics, characterize the resistance determinants, and examine their transferability in vitro.

Results

Probiotics of all lozenges were resistant to glycopeptide, sulfonamide, and penicillin antibiotics, while some were resistant to aminoglycosides and cephalosporins. High minimum inhibitory concentrations (MICs) were detected for streptomycin (>128 µg/mL) and chloramphenicol (> 512 µg/mL) for all probiotics but only one was resistant to piperacillin (MIC = 32 µg/mL). PCR analysis detected erythromycin (erm(T), ermB or mefA) and fluoroquinolone (parC or gyr(A)) resistance genes in some lozenges although there were no resistant phenotypes. The dfrD, cat-TC, vatE, aadE, vanX, and aph(3")-III or ant(2")-I genes conferring resistance to trimethoprim, chloramphenicol, quinupristin/dalfopristin, vancomycin, and streptomycin, respectively, were detected in resistant probiotics. The rifampicin resistance gene rpoB was also present. We found no conjugal transfer of streptomycin resistance genes in our co-incubation experiments.

Conclusion

Our study represents the first antibiotic resistance profiling of probiotics from oral lozenges, thus highlighting the health risk especially in the prevailing threat of drug resistance globally.

Antibiotic susceptibility of Lactobacillus plantarum strains, isolated from katak

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

Lactic acid bacteria and bifidobacteria deliberately introduced into the agro-food chain do not significantly increase the antimicrobial resistance gene pool

Lactic acid bacteria (LAB) and bifidobacteria may serve as reservoirs of antimicrobial resistance, but the risk posed by strains intentionally introduced into the agro-food chain has not yet been thoroughly investigated. The aim of our study was to evaluate whether probiotics, starter and protective cultures, and feed additives represent a risk to human health. In addition to commercial strains of LAB and bifidobacteria, isolates from human milk or colostrum, intestinal mucosa or feces, and fermented products were analyzed. Phenotypic susceptibility data of 474 strains showed that antimicrobial resistance was more common in intestinal isolates than in commercial strains. Antimicrobial resistance genes (ARGs) and mobile genetic elements (MGEs) were characterized in the whole genome sequences of 1114 strains using comparative genomics. Intrinsic ARGs were abundant in enterococci, bifidobacteria, and lactococci but were considered non-risky due to the absence of MGEs. The results revealed that 13.8% of commercial strains contained acquired ARGs, most frequently for tetracycline. We associated 75.5% of the acquired ARGs with known or novel MGEs, and their potential for transmission was assessed by examining metagenomic sequences. We confirmed that ARGs and MGEs were not as abundant or diverse in commercial strains as in human intestinal isolates or isolates from human milk, suggesting that strains intentionally introduced into the agro-food chain do not pose a significant threat. However, attention should be paid especially to individual probiotic strains containing elements that have been shown to have high potential for transferability in the gut microbiota.Abbreviations: ARG, antimicrobial resistance gene; ICE, integrative and conjugative element; IME, integrative and mobilizable element; LAB, lactic acid bacteria; MDR, multidrug resistance; MIC, minimum inhibitory concentration; MGE, mobile genetic element; TRRPP, tetracycline-resistant ribosomal protection protein; WGS, whole genome sequences.

Safety Assessment of Lactiplantibacillus (formerly Lactobacillus) plantarum Q180

The safety of the probiotic strain Q180, which exerts postprandial lipid-lowering effects, was bioinformatically and phenotypically evaluated. The genome of strain Q180 was completely sequenced, and single circular chromosome of 3,197,263 bp without any plasmid was generated. Phylogenetic and related analyses using16S rRNA gene and whole-genome sequences revealed that strain Q180 is a member of Lactiplantibacillus (Lp., formerly Lactobacillus) plantarum. Antimicrobial resistance (AMR) genes were bioinformatically analyzed using all Lp. plantarum genomes available in GenBank, which showed that AMR genes are present differently depending on Lp. plantarum strains. Bioinformatic analysis demonstrated that some mobile genetic elements such as prophages and insertion sequences were identified in the genome of strain Q180, but because they did not contain harmful genes such as AMR genes and virulence factor (VF)- and toxin-related genes, it was suggested that there is no transferability of harmful genes. The minimum inhibition concentrations of seven tested antibiotics suggested by the European Food Safety Authority guidelines were slightly lower than or equal to the microbiological cut-off values for Lp. plantarum. Strain Q180 did not show hemolytic and gelatinase activities and biogenic amine-producing ability. Taken together, this study demonstrated the safety of strain Q180 in terms of absence of AMR genes and VF- and toxin-related genes as a probiotic strain.

Evaluation of Tetracycline Resistance and Determination of the Tentative Microbiological Cutoff Values in Lactic Acid Bacterial Species

Lactic acid bacteria (LAB) are widely used as probiotics in the food industry owing to their beneficial effects on human health. However, numerous antibiotic resistance genes have been found in LAB strains, especially tetracycline resistance genes. Notably, the potential transferability of these genes poses safety risks. To comprehensively evaluate tetracycline resistance in LAB, we determined the tetracycline susceptibility patterns of 478 LAB strains belonging to four genera and eight species. By comparing phenotypes with genotypes based on genome-wide annotations, five tetracycline resistance genes, tet(M), tet(W/N/W), tet(L), tet(S), and tet(45), were detected in LAB. Multiple LAB strains without tetracycline resistance genes were found to be resistant to tetracycline at the currently recommended cutoff values. Thus, based on the minimum inhibitory concentrations of tetracycline for these LAB strains, the species-specific microbiological cutoff values for Lactobacillus (para)gasseri, Lactobacillus johnsonii, and Lactobacillus crispatus to tetracycline were first developed using the Turnidge, Kronvall, and eyeball methods. The cutoff values for Lactiplantibacillus plantarum were re-established and could be used to better distinguish susceptible strains from strains with acquired resistance. Finally, we verified that these five genes play a role in tetracycline resistance and found that tet(M) and tet(W/N/W) are the most widely distributed tetracycline resistance genes in LAB.

Aggrandizement of fermented cucumber through the action of autochthonous probiotic cum starter strains of Lactiplantibacillus plantarum and Pediococcus pentosaceus

Purpose

Cucumber fermentation is traditionally done using lactic acid bacteria. The involvement of probiotic cultures in food fermentation guarantees enhanced organoleptic properties and protects food from spoilage.

Methods

Autochthonous lactic acid bacteria were isolated from spontaneously fermented cucumber and identified to species level. Only strains adjudged as safe for human consumption were examined for their technological and functional characteristics. Strain efficiency was based on maintaining high numbers of viable cells during simulated GIT conditions and fermentation, significant antioxidant activity, EPS production, nitrite degradation, and antimicrobial ability against Gram-positive and Gram-negative foodborne pathogens.

Result

Two strains, Lactiplantibacillus plantarum NPL 1258 and Pediococcus pentosaceus NPL 1264, showing a suite of promising functional and technological attributes, were selected as a mixed-species starter for carrying out a controlled lactic acid fermentations of a native cucumber variety. This consortium showed a faster lactic acid-based acidification with more viable cells, at 4% NaCl and 0.2% inulin (w/v) relative to its constituent strains when tested individually. Sensory evaluation rated the lactofermented cucumber acceptable based on texture, taste, aroma, and aftertaste.

Conclusion

The results suggest that the autochthonous LAB starter cultures can shorten the fermentation cycle and reduce pathogenic organism’ population, thus improving the shelf life and quality of fermented cucumber. The development of these new industrial starters would increase the competitiveness of production and open the country’s frontiers in the fermented vegetable market.

Mucosal Bacteria Modulate Candida albicans Virulence in Oropharyngeal Candidiasis

Oropharyngeal candidiasis (OPC) is the most prevalent oral infection in immunocompromised patients, primarily associated with Candida albicans. Increasing evidence points to a significant role of mucosal bacteria on the transition of C. albicans from commensal to pathogenic. In this work, we hypothesized that changes in the abundance or composition of the mucosal bacterial microbiota induced by dietary sucrose during the development of OPC can modulate C. albicans virulence. C. albicans burdens and mucosal lesions were evaluated in a mouse cortisone immunosuppression model amended with sucrose. We also analyzed the mucosal bacterial composition using 16S rRNA gene sequencing and culture methods. In immunocompetent mice, sucrose significantly increased total bacterial burdens and reduced alpha diversity, by increasing the relative abundance of mitis group streptococci. In immunocompromised mice, C. albicans infection was associated with a significantly reduced bacterial alpha diversity due to an increase in the relative abundance of enterococci. When exposed to dietary sucrose, these mice had reduced C. albicans burdens and reduced bacterial alpha diversity, associated with an increase in the relative abundance of Lactobacillus. SparCC correlation networks showed a significant negative correlation between Lactobacillus and Enterococcus in all Candida-infected mice. Depletion of lactobacilli with antibiotic treatment partially restored C. albicans burdens in mice receiving sucrose. In coculture in vitro experiments, mouse oral Lactobacillus johnsonii isolates inhibited growth of Enterococcus faecalis isolates and C. albicans. These results support the hypothesis that the sucrose-induced attenuation of C. albicans virulence was a result of changes in the mucosal bacterial microbiome characterized by a reduction in enterococci and an increase in lactobacilli. IMPORTANCE By comparing Candida albicans virulence and the mucosal bacterial composition in a mouse oral infection model, we were able to dissect the effects of the host environment (immunosuppression), infection with C. albicans, and local modulating factors (availability of sucrose as a carbon source) on the mucosal bacterial microbiome and its role on fungal virulence. We showed that changes in endogenous microbial communities in response to sucrose can lead to attenuation of fungal disease. We also showed that Lactobacillus johnsonii may curtail Candida virulence both by inhibiting its growth and by inhibiting the growth of potentially synergistic bacteria such as enterococci. Our results support the concept that Candida pathogenesis should be viewed in the contexts of both a susceptible host and a mucosal bacterial microbiota conducive to virulence.

Molecular identification and in vitro evaluation of probiotic functional properties of some Egyptian lactic acid bacteria and yeasts

BACKGROUND

The health-promoting effects along with global economic importance of consuming food products supplemented with probiotic microorganisms encouraged the researchers to discover new probiotics.

RESULTS

Fourteen lactic acid bacterial isolates were identified as Enterococcus mediterraneensis, Lactobacillus fermentum, and Streptococcus lutetiensis by 16S rRNA gene sequencing, and in vitro characterized for their actual probiotic potential. All E. mediterraneensis isolates were resistant to clindamycin, whereas Lb. fermentum isolates were resistant to ampicillin, clindamycin, and vancomycin. The E. mediterraneensis and Lb. fermentum isolates displayed high overall digestive survival, ranged from 1.35 ± 0.06 to 32.73 ± 0.84% and from 2.01 ± 0.01 to 23.9 ± 1.85%, respectively. All isolates displayed cell surface hydrophobicity, ranged between 15.44 ± 6.72 and 39.79 ± 2.87%. The strongest auto-aggregation capability, higher than 40%, was observed for most E. mediterraneensis and Lb. fermentum isolates. The E. mediterraneensis isolates (L2, L12, and L15), Lb. fermentum (L8, L9, and L10), and Strep. lutetiensis (L14) exhibited the greatest co-aggregation with Salmonella typhimurium, Escherichia coli O157:H7, Staphylococcus aureus, and Bacillus cereus. Fifty-seven and fourteen hundredth percent of E. mediterraneensis isolates could be considered bacteriocinogenic against E. coli O157:H7, B. cereus, and S. aureus.

CONCLUSION

This study is the first one to isolate Enterococcus mediterraneensis in Egypt and to characterize it as new species of probiotics globally. According to the results, E. mediterraneensis (L2, L12, and L15), Lb. fermentum (L8, L9, and L10), and Strep. lutetiensis (L14) are the most promising in vitro probiotic candidates.

Molecular Analysis of Bacterial Isolates From Necrotic Wheat Leaf Lesions Caused by Xanthomonas translucens, and Description of Three Putative Novel Species, Sphingomonas albertensis sp. nov., Pseudomonas triticumensis sp. nov. and Pseudomonas foliumensis sp. nov

Xanthomonas translucens is the etiological agent of the wheat bacterial leaf streak (BLS) disease. The isolation of this pathogen is usually based on the Wilbrink's-boric acid-cephalexin semi-selective medium which eliminates 90% of other bacteria, some of which might be novel species. In our study, a general purpose nutrient agar was used to isolate 49 bacterial strains including X. translucens from necrotic wheat leaf tissues. Maximum likelihood cluster analysis of 16S rRNA sequences grouped the strains into 10 distinct genera. Pseudomonas (32.7%) and Pantoea (28.6%) were the dominant genera while Xanthomonas, Clavibacter and Curtobacterium had 8.2%, each. Erwinia and Sphingomonas had two strains, each. BLAST and phylogenetic analyses of multilocus sequence analysis (MLSA) of specific housekeeping genes taxonomically assigned all the strains to validly described bacterial species, except three strains (10L4B, 12L4D and 32L3A) of Pseudomonas and two (23L3C and 15L3B) of Sphingomonas. Strains 10L4B and12L4D had Pseudomonas caspiana as their closest known type strain while strain 32L3A was closest to Pseudomonas asturiensis. Sphingomonas sp. strains 23L3C and 15L3B were closest to S. faeni based on MLSA analysis. Our data on MLSA, whole genome-based cluster analysis, DNA-DNA hybridization and average nucleotide identity, matrix-assisted laser desorption/ionization-time-of-flight, chemotaxonomy and phenotype affirmed that these 5 strains constitute three novel lineages and are taxonomically described in this study. We propose the names, Sphingomonas albertensis sp. nov. (type strain 23L3C^T = DOAB 1063^T = CECT 30248^T = LMG 32139^T), Pseudomonas triticumensis sp. nov. (type strain 32L3A^T = DOAB 1067^T = CECT 30249^T = LMG 32140^T) and Pseudomonas foliumensis sp. nov. (type strain 10L4B^T = DOAB 1069^T = CECT 30250^T = LMG 32142^T). Comparative genomics of these novel species, relative to their closest type strains, revealed unique repertoires of core secretion systems and secondary metabolites/antibiotics. Also, the detection of CRISPR-Cas systems in the genomes of these novel species suggests an acquired mechanism for resistance against foreign mobile genetic elements. The results presented here revealed a cohabitation, within the BLS lesions, of diverse bacterial species, including novel lineages.

Insight into phenotypic and genotypic differences between vaginal Lactobacillus crispatus BC5 and Lactobacillus gasseri BC12 to unravel nutritional and stress factors influencing their metabolic activity

The vaginal microbiota, normally characterized by lactobacilli presence, is crucial for vaginal health. Members belonging to L. crispatus and L. gasseri species exert crucial protective functions against pathogens, although a total comprehension of factors that influence their dominance in healthy women is still lacking. Here we investigated the complete genome sequence and comprehensive phenotypic profile of L. crispatus strain BC5 and L. gasseri strain BC12, two vaginal strains featured by anti-bacterial and anti-viral activities. Phenotype microarray (PM) results revealed an improved capacity of BC5 to utilize different carbon sources as compared to BC12, although some specific carbon sources that can be associated to the human diet were only metabolized by BC12, i.e. uridine, amygdalin, tagatose. Additionally, the two strains were mostly distinct in the capacity to utilize the nitrogen sources under analysis. On the other hand, BC12 showed tolerance/resistance towards twice the number of stressors (i.e. antibiotics, toxic metals etc.) with respect to BC5. The divergent phenotypes observed in PM were supported by the identification in either BC5 or BC12 of specific genetic determinants that were found to be part of the core genome of each species. The PM results in combination with comparative genome data provide insights into the possible environmental factors and genetic traits supporting the predominance of either L. crispatus BC5 or L. gasseri BC12 in the vaginal niche, giving also indications for metabolic predictions at the species level.