Guidance on the assessment of bacterial susceptibility to antimicrobials of human and veterinary importance

The Occurrence of Colistin Resistance in Potential Lactic Acid Bacteria of Food-Producing Animals in India

The overuse of colistin, the last-resort antibiotic, has led to the emergence of colistin-resistant bacteria, which is a major concern. Lactic acid bacteria which are generally regarded as safe are known to be reservoirs of antibiotic resistance that possibly pose a threat to human and animal health. Therefore, this study assessed the prevalence of colistin antimicrobial resistance in livestock in India, that is lactic acid bacteria in healthy chickens, sheep, beef, and swine of Mysore. Diverse phenotypic and genotypic colistin resistance were examined among the lactic acid bacterial species (n = 84) isolated from chicken (n = 44), sheep (n = 16), beef (n = 14), and swine (n = 10). Hi-comb, double-disk diffusion tests, Minimum Inhibitory Concentration (MIC), and biofilm formation were assessed for phenotypic colistin resistance. Specific primers for colistin-resistant genes were used for the determination of genotypic colistin resistance. Around 20%, 18%, and 1% were colistin-resistant Lactobacillus, Enterococcus, and Pediococcus species, respectively. Among these, 66.67% exhibited MDR phenotypes, including colistin antibiotic. The identified resistant isolates are Levilactobacillus brevis LBA and LBB (2), Limosilactobacillus fermentum LBF (1), and Pediococcus acidilactici CHBI (1). The mcr-1 and mcr-3 genes were detected in Levilactobacillus brevis LBA, LBB, and Pediococcus acidilactici CHBI isolated from chicken and sheep intestines respectively. The study identified colistin resistance determinants in lactobacilli from food animals, emphasizing the need for enhanced surveillance and monitoring of resistance spread. These findings underscore colistin resistance as a significant medical concern and should be integrated into India's ongoing antimicrobial resistance monitoring programs.

Interference of gastrointestinal barriers with antibiotic susceptibility of foodborne pathogens: an in vitro case study of ciprofloxacin and tetracycline against Salmonella enterica and Listeria monocytogenes

Minimum inhibitory concentrations (MIC) assays are often questioned for their representativeness. Especially when foodborne pathogens are tested, it is of crucial importance to also consider parameters of the human digestive system. Hence, the current study aimed to assess the inhibitory capacity of two antibiotics, ciprofloxacin and tetracycline, against Salmonella enterica and Listeria monocytogenes, under representative environmental conditions. More specifically, aspects of the harsh environment of the human gastrointestinal tract (GIT) were gradually added to the experimental conditions starting from simple aerobic lab conditions into an in vitro simulation of the GIT. In this way, the effects of parameters including the anoxic environment, physicochemical conditions of the GIT (low gastric pH, digestive enzymes, bile acids) and the gut microbiota were evaluated. The latter was simulated by including a representative consortium of selected gut bacteria species. In this study, the MIC of the two antibiotics against the relevant foodborne pathogens were established, under the previously mentioned environmental conditions. The results of S. enterica highlighted the importance of the anaerobic environment when conducting such studies, since the pathogen thrived under such conditions. Inclusion of physicochemical barriers led to exactly opposite results for S. enterica and L. monocytogenes since the former became more susceptible to ciprofloxacin while the latter showed lower susceptibility towards tetracycline. Finally, the inclusion of gut bacteria had a bactericidal effect against L. monocytogenes even in the absence of antibiotics, while gut bacteria protected S. enterica from the effect of ciprofloxacin.

Comprehensive Metagenomic Analysis of Veterinary Probiotics in Broiler Chickens

Probiotics are widely used in broiler chickens to support the gut microbiome, gut health, and to reduce the amount of antibiotics used. Despite their benefits, there is concern over their ability to carry and spread antimicrobial resistance genes (ARGs), posing a significant public health risk. This study utilized next-generation sequencing to investigate ARGs in probiotics approved for poultry, focusing on their potential to be transferred via mobile genetic elements such as plasmids and phages. We examined the gut microbiome and resistome changes in 60 broiler chickens over their rearing period, correlating these changes with different probiotic treatments. Specific resistance mechanisms against critically important antibiotics were identified, including genes related to fluoroquinolone resistance and peptide antibiotic resistance. We also found genes with significant relevance to public health (aadK, AAC(6')-Ii) and multiple drug-resistance genes (vmlR, ykkC, ykkD, msrC, clbA, eatAv). Only one phage-encoded gene (dfrA43) was detected, with no evidence of plasmid or mobile genetic element transmission. Additionally, metagenomic analysis of fecal samples showed no significant changes corresponding to time or diet across groups. Our findings highlight the potential risks associated with the use of probiotics in poultry, particularly regarding the carriage of ARGs. It is crucial to conduct further research into the molecular genetics of probiotics to develop strategies that mitigate the risk of resistance gene transfer in agriculture, ensuring the safe and effective use of probiotics in animal husbandry.

Genomic and Phenotypic Safety Assessment of Probiotic Bacillus coagulans Strain JBI-YZ6.3

Spore-forming Bacillus coagulans has been widely recognized as an important probiotic, which is commonly used in products for human consumption and animal feeds. B. coagulans exhibits beneficial traits from both Bacillus and lactic acid-producing Lactobacillus. The present study evaluated the safety of the newly isolated B. coagulans strain JBI-YZ6.3, using combined genomic and phenotypic analysis approaches. The taxonomic classification based on genome sequence and biochemical tests identified strain JBI-YZ6.3 as B. coagulans. Comprehensive genome-based analyses established JBI-YZ6.3 as a novel strain of B. coagulans. Antibiotic susceptibility testing showed that the strain JBI-YZ6.3 was sensitive to a panel of fourteen antibiotics, and no genes related to antibiotic resistance were found in its genome. The spores of strain JBI-YZ6.3 exhibited tolerance to acid and bile salts, as well as stability at ambient and elevated conditions of temperature and relative humidity. There were no homologs of Bacillus toxin genes identified in the genome of JBI-YZ6.3, and the strain exhibited no cytotoxicity towards Vero cells and human peripheral blood mononuclear cells. In conclusion, findings from this study support the safety of B. coagulans strain JBI-YZ6.3, which can be developed into new probiotic products for preventive and therapeutic benefits in human and animal hosts.

A critical assessment of microbial-based antimicrobial sanitizing of inanimate surfaces in healthcare settings

The global rise in antimicrobial resistance (AMR) poses a significant public health threat, especially in healthcare settings, where controlling the spread of antimicrobial genes is crucial. While person-to-person transmission remains the primary route for healthcare-associated infections (HAIs), hospital surfaces serve as key reservoirs for antimicrobial-resistant microorganisms. Regular cleaning and disinfection of these surfaces are essential. Microbial-based products for sanitizing hospital surfaces have emerged as promising tools to combat HAIs and AMR. However, a review of 32 publications found inconsistencies and potential risks. A total of 15 publications included hospital-based trials, while the rest were either in vitro or in situ assays, reviews, book chapters, or commentaries. In most of the hospital-based studies, specific strains of applied microorganisms were not identified, and the term "probiotic" was inaccurately used. These products mainly featured spores from Bacillus and Priestia genera, which was mainly hypothesized to work through competitive exclusion. Most hospital-based studies have shown that the application of microbial-based products resulted in a significant reduction in pathogens on surfaces, thereby contributing to a decrease in the incidence of healthcare-associated infections (HAIs). Further research is however needed to understand the effectiveness, mechanisms of action, and safety of microbial-based sanitizing agents. Strain-level identification is crucial for safety assessments, yet many reviewed products lacked this information. Consequently, there is a need for rigorous safety evaluations within existing regulatory frameworks to ensure the efficacy and safety of microbial-based cleaning products in healthcare settings.

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.

Probiotic Pediococcus acidilactici Strains Exert Anti-inflammatory Effects by Regulating Intracellular Signaling Pathways in LPS-Induced RAW 264.7 Cells

This study investigated the anti-inflammatory effects of Pediococcus acidilactici strains isolated from fermented vegetables on lipopolysaccharide (LPS)-stimulated RAW 264.7 macrophages. In addition, the probiotic characteristics and safety were evaluated. Our results show that Ped. acidilactici strains possess high survivability in simulated gastrointestinal environments and strong attachment to HT-29 cells. All Ped. acidilactici strains exhibited γ-hemolysis and resistance to gentamicin, kanamycin, and streptomycin, a characteristic commonly observed in lactic acid bacteria. Treatment with Ped. acidilactici inhibited the expression of inducible nitric oxide synthase and cyclooxygenase-2, leading to a subsequent reduction in nitric oxide and prostaglandin E2 production. Furthermore, the strains downregulated interleukin (IL)-1β and IL-6 mRNA levels, ultimately suppressing their production. We demonstrated that Ped. acidilactici strains could modulate the activation of nuclear factor-κB, mitogen-activated protein kinase, and activator protein-1, which are known to regulate inflammatory responses. Consequently, the anti-inflammatory properties of Ped. acidilactici strains in this study support their potential application as therapeutic agents for inflammatory diseases, providing molecular insights into next-generation functional probiotic products.

Identification and Safety Assessment of Enterococcus casseliflavus KB1733 Isolated from Traditional Japanese Pickle Based on Whole-Genome Sequencing Analysis and Preclinical Toxicity Studies

The present study involves the precise identification and safety evaluation of Enterococcus casseliflavus KB1733, previously identified using 16S rRNA analysis, through whole-genome sequencing, phenotypic analysis, and preclinical toxicity studies. Analyses based on the genome sequencing data confirm the identity of KB1733 as E. casseliflavus and show that the genes related to vancomycin resistance are only present on the chromosome, while no virulence factor genes are present on the chromosome or plasmid. Phenotypic analyses of antibiotic resistance and hemolytic activity also indicated no safety concerns. A bacterial reverse mutation test showed there was no increase in revertant colonies of heat-killed KB1733. An acute toxicity test employing heat-killed KB1733 at a dose of 2000 mg/kg body weight in rats resulted in no deaths and no weight gain or other abnormalities in the general condition of the animals, with renal depression foci and renal cysts only occurring at the same frequency as in the control. Taking the background data into consideration, the effects on the kidneys observed in the current study were not caused by KB1733. Our findings suggest that KB1733 is non-pathogenic to humans/animals, although further studies involving repeated oral toxicity tests and/or clinical tests are required.

Genomic Characterization and Safety Assessment of Bifidobacterium breve BS2-PB3 as Functional Food

Our group had isolated Bifidobacterium breve strain BS2-PB3 from human breast milk. In this study, we sequenced the whole genome of B. breve BS2-PB3, and with a focus on its safety profile, various probiotic characteristics (presence of antibiotic resistance genes, virulence factors, and mobile elements) were then determined through bioinformatic analyses. The antibiotic resistance profile of B. breve BS2-PB3 was also evaluated. The whole genome of B. breve BS2-PB3 consisted of 2,268,931 base pairs with a G-C content of 58.89% and 2,108 coding regions. The average nucleotide identity and whole-genome phylogenetic analyses supported the classification of B. breve BS2-PB3. According to our in silico assessment, B. breve BS2-PB3 possesses antioxidant and immunomodulation properties in addition to various genes related to the probiotic properties of heat, cold, and acid stress, bile tolerance, and adhesion. Antibiotic susceptibility was evaluated using the Kirby-Bauer disk-diffusion test, in which the minimum inhibitory concentrations for selected antibiotics were subsequently tested using the Epsilometer test. B. breve BS2-PB3 only exhibited selected resistance phenotypes, i.e., to mupirocin (minimum inhibitory concentration/MIC >1,024 μg/ml), sulfamethoxazole (MIC >1,024 μg/ml), and oxacillin (MIC >3 μg/ml). The resistance genes against those antibiotics, i.e., ileS, mupB, sul4, mecC and ramA, were detected within its genome as well. While no virulence factor was detected, four insertion sequences were identified within the genome but were located away from the identified antibiotic resistance genes. In conclusion, B. breve BS2-PB3 demonstrated a sufficient safety profile, making it a promising candidate for further development as a potential functional food.

Characterization of Bacillus amyloliquefaciens PM415 as a potential bio-preserving probiotic

Animal feed is vulnerable to fungal infections, and the use of bio-preserving probiotics has received increasing attention. In contrast to Lactobacillus and Bifidobacteria spp., fewer Bacillus spp. have been recognized as antifungal probiotics. Therefore, our objective was to screen antifungal strains and provide more Bacillus candidates to bridge this gap. Here, we screened 56 bacterial strains for cyclic lipopeptide genes and conducted an antifungal assay with Aspergillus niger as a representative fungus. We found that a Bacillus strain Bacillus amyloliquefaciens PM415, isolated from pigeon manure, exhibited the highest fungal inhibition activity as demonstrated by the confrontation assay and morphological observation under scanning electron microscope (SEM). Preliminary safety assessment and probiotic characterization revealed its non-pathogenic feature and stress tolerance capability. Whole genome sequencing of Bacillus amyloliquefaciens PM415 revealed a genome size of 4.16 Mbp and 84 housekeeping genes thereof were used for phylogenetic analysis showing that it is most closely related to Bacillus amyloliquefaciens LFB112. The in silico analysis further supported its non-pathogenic feature at the genomic level and revealed potential biosynthetic gene clusters responsible for its antifungal property. RNA-seq analysis revealed genome-wide changes in transportation, amino acid metabolism, non-ribosomal peptides (NRPs) biosynthesis and glycan degradation during fungal antagonism. Our results suggest that Bacillus amyloliquefaciens PM415 is a safe and effective probiotic strain that can prevent fungal growth in animal feeds.

Heat-Killed Lactilactobacillus sakei WB2305 and Lactiplantibacillus plantarum WB2324 Inhibited LPS-Induced Inflammation in Human Airway Epithelial Cells

Asthma is characterized by inflammation of the airways, including the inflammatory and airway structural cells. Probiotics, which have diverse effects, even within the same species, are being studied to prevent and mitigate the severity of asthma. Lactilactobacillus sakei WB2305 and Lactiplantibacillus plantarum WB2324 were isolated from kimchi. These strains have acceptable probiotic properties and are safe. In addition, the anti-inflammatory potential of the heat-killed isolates against lipopolysaccharide (LPS)-induced inflammation in the human pulmonary epithelial cell line (A549) was investigated. The heat-killed Lact. sakei WB2305 and Lact. plantarum WB2324 reduced the chemokine and cytokines mRNA expression levels, as shown by the results of using real-time polymerase chain reaction. Western blotting results showed that the nuclear factor-kappa B (NF-κB) activation and mitogen-activated protein kinases (MAPK) signaling pathways were suppressed by treatment with the heat-killed strains. The production amounts of eotaxin, tumor necrosis factor-ɑ (TNF-α), and interleukin-6 (IL-6) were lower than those in LPS-only treated cells. Additionally, 2',7'-dichlorofluorescein diacetate (DCFH-DA) staining confirmed decreased reactive oxygen species (ROS) production in A549 cells. Therefore, the results of present study demonstrate the anti-inflammatory and anti-asthmatic activities of heat-killed Lact. sakei WB2305 and Lact. plantarum WB2324 in human airway epithelial cells.

Cell-Free Supernatant from a Strain of Bacillus siamensis Isolated from the Skin Showed a Broad Spectrum of Antimicrobial Activity

In recent years, the search for new compounds with antibacterial activity has drastically increased due to the spread of antibiotic-resistant microorganisms. In this study, we analyzed Cell-Free Supernatant (CFS) from Bacillus siamensis, assessing its potential antimicrobial activity against some of the main pathogenic microorganisms of human interest. To achieve this goal, we exploited the natural antagonism of skin-colonizing bacteria and their ability to produce compounds with antimicrobial activity. Biochemical and molecular methods were used to identify 247 strains isolated from the skin. Among these, we found that CFS from a strain of Bacillus siamensis (that we named CPAY1) showed significant antimicrobial activity against Staphylococcus aureus, Enterococcus faecalis, Streptococcus agalactiae, and Candida spp. In this study, we gathered information on CFS's antimicrobial activity and on its sensitivity to chemical-physical parameters. Time-kill studies were performed; anti-biofilm activity, antibiotic resistance, and plasmid presence were also investigated. The antimicrobial compounds included in the CFS showed resistance to the proteolytic enzymes and were heat stable. The production of antimicrobial compounds started after 4 h of culture (20 AU/mL). CPAY1 CFS showed antimicrobial activity after 7 h of bacteria co-culture. The anti-biofilm activity of the CPAY1 CFS against all the tested strains was also remarkable. B. siamensis CPAY1 did not reveal the presence of a plasmid and showed susceptibility to all the antibiotics tested.

Characterization of feline-originated probiotics Lactobacillus rhamnosus CACC612 and Bifidobacterium animalis subsp. lactis CACC789 and and evaluation of their host response

BACKGROUND

Probiotics are beneficial for animal health and new potential probiotics need to be characterized for their prospective use in improving animal health. In this study, 32 bacterial strains were isolated from a Norwegian forest cat (castrated, 12 years old) and a Persian cat (castrated, 10 years old), which were privately owned and had indoor access.

RESULTS

Lactobacillus rhamnosus CACC612 (CACC612) and Bifidobacterium animalis subsp. lactis CACC789 (CACC789) were selected as potential probiotics; characterization of the two strains showed equivalent acid tolerance, similar cell adhesion rates on the HT-29 monolayer cell line, and superior bile tolerance compared to Lactobacillus rhamnosus GG (LGG). Subsequently, they exhibited inhibitory effects against a broad spectrum of pathogenic bacteria, including E. coli (KCTC 2617), Salmonella Derby (NCCP 12,238), Salmonella Enteritidis (NCCP 14,546), Salmonella Typhimurium (NCCP 10,328), Clostridium difficile JCM 1296T. From evaluating host effects, the viability of the feline macrophage cell line (Fcwf-4) increased with the treatment of CACC612 or CACC789 (P < 0.05). The induced expression of immune-related genes such as IFN-γ, IL1β, IL2, IL4, and TNF-α by immune stimulation was significantly attenuated by the treatment of CACC612 or CACC789 (P < 0.05). When 52 clinical factors of sera from 21 healthy cats were analyzed using partial least squares discriminant analysis (PLS-DA), the animals were obviously clustered before and after feeding with CACC612 or CACC789. In addition, hemoglobin and mean corpuscular hemoglobin concentration (MCHC) significantly increased after CACC612 feeding (P < 0.05).

CONCLUSIONS

In this study, feline-originated probiotics were newly characterized and their potentially probiotic effects were evaluated. These results contribute to our understanding of the functional effects of feline-derived probiotics and support their industrial applications.

Assessment of Genomic and Metabolic Characteristics of Cholesterol-Reducing and GABA Producer Limosilactobacillus fermentum AGA52 Isolated from Lactic Acid Fermented Shalgam Based on "In Silico" and "In Vitro" Approaches

This study aimed to characterize the genomic and metabolic properties of a novel Lb. fermentum strain AGA52 which was isolated from a lactic acid fermented beverage called "shalgam." The genome size of AGA52 was 2,001,184 bp, which is predicted to carry 2024 genes, including 50 tRNAs, 3 rRNAs, 3 ncRNAs, 15 CRISPR repeats, 14 CRISPR spacers, and 1 CRISPR array. The genome has a GC content of 51.82% including 95 predicted pseudogenes, 56 complete or partial transposases, and 2 intact prophages. The similarity of the clusters of orthologous groups (COG) was analyzed by comparison with the other Lb. fermentum strains. The detected resistome on the genome of AGA52 was found to be intrinsic originated. Besides, it has been determined that AGA52 has an obligate heterofermentative carbohydrate metabolism due to the absence of the 1-phosphofructokinase (pfK) enzyme. Furthermore, the strain is found to have a better antioxidant capacity and to be tolerant to gastrointestinal simulated conditions. It was also observed that the AGA52 has antimicrobial activity against Yersinia enterocolitica ATCC9610, Bacillus cereus ATCC33019, Salmonella enterica sv. Typhimurium, Escherichia coli O157:h7 ATCC43897, Listeria monocytogenes ATCC7644, Klebsiella pneumoniae ATCC13883, and Proteus vulgaris ATCC8427. Additionally, AGA52 exhibited 42.74 ± 4.82% adherence to HT29 cells. Cholesterol assimilation (33.9 ± 0.005%) and GABA production capacities were also confirmed by "in silico" and "in vitro." Overall, the investigation of genomic and metabolic features of the AGA52 revealed that is a potential psychobiotic and probiotic dietary supplement candidate and can bring functional benefits to the host.

Safety Assessment of Levilactobacillus brevis KU15006: A Comprehensive Analysis of its Phenotypic and Genotypic Properties

Levilactobacillus brevis KU15006, isolated from kimchi, exhibits pathogen-antagonistic and anti-diabetic activities; however, the safety of this strain has not been assessed. In the present study, L. brevis KU15006 was evaluated to elucidate its safety as a probiotic strain using phenotypic and genotypic analyses. Its safety was assessed using a minimum inhibitory concentration test comprising nine antibiotics, 26 antibiotic resistance genes, a single conjugative element, virulence gene analysis, hemolysis, cell cytotoxicity, mucin degradation, and toxic metabolite production. L. brevis KU15006 exhibited equal or lower minimum inhibitory concentration for the nine antibiotics than the cut-off value established by the European Food Safety Authority. It did not harbor antibiotic resistance and virulence genes. L. brevis KU15006 lacked β-hemolysis, mucin degradation, cytotoxicity against Caco-2 cells, gelatin liquefaction, bile salt deconjugation, and toxic metabolite production abilities. Based on the results, L. brevis KU15006, which has antagonistic and anti-diabetic effects, could be marketed as a probiotic in the future.

Probiotic characterization of Bacillus smithii: Research advances, concerns, and prospective trends

Bacillus smithii is a thermophilic Bacillus that can be isolated from white wine, hot spring soil, high-temperature compost, and coffee grounds, with various biofunctions and wide applications. It is resistant to both gastric acid and high temperature, which makes it easier to perform probiotic effects than traditional commercial probiotics, so it can maintain good vitality during food processing and has great application prospects. This paper starts with the taxonomy and genetics and focuses on aspects, including genetic transformation, functional enzyme production, waste utilization, and application in the field of food science as a potential probiotic. According to available studies during the past 30 years, we considered that B. smithii is a novel class of microorganisms with a wide range of functional enzymes such as hydrolytic enzymes and hydrolases, as well as resistance to pathogenic bacteria. It is available in waste degradation, organic fertilizer production, the feed and chemical industries, the pharmaceutical sector, and food fortification. Moreover, B. smithii has great potentials for applications in the food industry, as it presents high resistance to the technological processes that guarantee its health benefits. It is also necessary to systematically evaluate the safety, flavor, and texture of B. smithii and explore its biological mechanism of action, which is of great value for further application in multiple fields, especially in food and medicine.

Isolation, characterization of Weissella confusa and Lactococcus lactis from different milk sources and determination of probiotic features

This study aimed to investigate the probiotic properties of Lactic Acid Bacteria (LAB) isolates derived from various milk sources. These isolates identified based on their morphological characteristics and 16S rRNA gene sequencing. Four strains of Lactococcus lactis and two strains of Weissella confusa were identified with over 96% 16S rRNA gene similarity according to the NCBI-BLAST results. The survival of the isolates was determined in low pH, pepsin, bile salts, and pancreatin, and their adhesion ability was assessed by in vitro cell adhesion assay, hydrophobicity, auto- and co-aggregation, and safety criteria were determined by hemolytic, gelatinase activities, and DNAse production ability tests. The results showed that the LAB isolates had different levels of resistance to various stress factors. L. lactis subsp. cremoris MH31 showed the highest resistance to bile salt, while the highest pH resistance was observed in L. lactis MH31 at pH 3.0. All the isolates survived in pepsin exposure at pH 3.0 for 3 h. The auto-aggregation test results showed that all strains exhibited auto-aggregation ranging from 84.9 to 91.4%. Co-aggregation percentage ranged from 19 - 54% and 17 - 57% against Escherichia coli ATCC 25922 and Staphylococcus aureus ATCC 29213, respectively. The hydrophobicity capacity of the LAB isolated ranged from 35-61%. These isolates showed different adhesion abilities to Caco-2 cells (81.5% to 92.6%). None of the isolates exhibited DNase, gelatinase and hemolytic activity (γ-hemolysis). All results indicate that these LAB strains have the potential to be used as probiotics.

Lacticaseibacillus paracasei AD22 Stress Response in Brined White Cheese Matrix: In Vitro Probiotic Profiles and Molecular Characterization

Functionalizing foods involve discovering and integrating new candidate health-promoting bacteria into the food matrix. This study aimed (i) to reveal the probiotic potential of autochthonous Lacticaseibacillus paracasei AD22 by a series of in vitro tests and molecular characterization and (ii) to evaluate its application to the matrix of brined white cheese, which is the most common cheese in Türkiye, in terms of survival and stress response. To evaluate in vitro probiotic characteristics, L. paracasei AD22 was exposed to functional, technological, and safety tests. Pilot scale production was conducted to integrate L. paracasei AD22 into the brined white cheese matrix. The expression levels of stress-related genes (dnaK, groES, ftsH, argH, and hsp20) were detected by reverse-transcriptase polymerase chain reaction to determine the transcriptional stress response during ripening. The presence of genes encoding stress-related proteins was determined by whole-genome sequence analysis using a subsystem approach; the presence of antibiotic resistance and virulence genes was determined by ResFinder4.1 and VirulenceFinder 2.0 databases. The BAGEL4 database determined the presence of bacteriocin clusters. L. paracasei AD22 was found to survive in pH 2 and medium with 12% NaCl and did not cause hemolysis. Adhesion of the strain to Caco2 cells was 76.26 ± 4.81% and it had coaggregation/autoaggregation properties. It was determined that L. paracasei AD22 exceeded 7 log cfu/g in the cheese matrix at the end of the ripening period. Total mesophilic aerobes decreased in the cheese inoculated with L. paracasei AD22 after the 45th day of ripening. While hsp20 and groES genes were downregulated during ripening, argH was upregulated. Both downregulation and upregulation were observed in dnaK and ftsH. Fold changes indicating the expression levels of dnaK, groES, ftsH, argH, and hsp20 genes were not statistically significant during ripening (p > 0.05). Whole-genome sequence profiles revealed that the strain did not contain antibiotic and virulence genes but bacteriocin clusters encoding Enterolysin A (Class III bacteriocin), Carnosine CP52 (class II bacteriocin), Enterocin X beta chain (Class IIc bacteriocin), and the LanT region. Subsystems approach manifested that the most functional part of the genomic distribution belonged to metabolism, protein processing, and stress response functions. The study findings highlight that L. paracasei AD22 will provide biotechnological innovation as a probiotic adjunct because it contains tolerance factors and probiotic characteristics to produce new functional foods.

Identification of safe putative probiotics from various food products

The objective of this study was to isolate, identify, and assess the safety and functionality in vitro of putative probiotic bacterial strains. Isolation procedures were based on standard methods using elective and selective media. The isolates were identified by comparative 16S rRNA sequencing analysis while their safety was determined according to the safety tests recommended by the FAO/WHO such as antibiotic resistance, hemolysin, and biogenic amine production. Most of the isolates did not pass the in vitro safety tests; therefore, only Lactiplantibacillus plantarum (from ant intestine and cheese), Lacticaseibacillus paracasei (from goat milk and kimchi), Enterococcus faecium (from chili doenjang and vegetables with kimchi ingredients), Limosilactobacillus fermentum (from saliva), and Companilactobacillus alimentarius (from kimchi) were identified and selected for further studies. The isolates were further differentiated by rep-PCR and identified to the strain level by genotypic (16S rRNA) and phenotypic (Gen III) approaches. Subsequently, the strain tolerance to acid and bile was evaluated resulting in good viability after simulated gastrointestinal tract passage. Adhesion to mucin in vitro and the presence of mub, mapA, and ef-tu genes confirmed the adhesive potential of the strains and the results of features associated with adhesion such as hydrophobicity and zeta potential extended the insights. This study reflects the importance of fermented and non-fermented food products as a promising source of lactic acid bacteria with potential probiotic properties. Additionally, it aims to highlight the challenges associated with the selection of safe strains, which often fail in the in vitro tests, thus hindering the possibilities of "uncovering" novel and safe probiotic strains.

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.

Safety assessment of five candidate probiotic lactobacilli using comparative genome analysis

Micro-organisms belonging to the Lactobacillus genus complex are often used for oral consumption and are generally considered safe but can exhibit pathogenicity in rare and specific cases. Therefore, screening and understanding genetic factors that may contribute to pathogenicity can yield valuable insights regarding probiotic safety. Limosilactobacillus mucosae LM1, Lactiplantibacillus plantarum SK151, Lactiplantibacillus plantarum BS25, Limosilactobacillus fermentum SK152 and Lactobacillus johnsonii PF01 are current probiotics of interest; however, their safety profiles have not been explored. The genome sequences of LM1, SK151, SK152 and PF01 were downloaded from the NCBI GenBank, while that of L. plantarum BS25 was newly sequenced. These genomes were then annotated using the Rapid Annotation using Subsystem Technology tool kit pipeline. Subsequently, a command line blast was performed against the Virulence Factor Database (VFDB) and the Comprehensive Antibiotic Resistance Database (CARD) to identify potential virulence factors and antibiotic resistance (AR) genes. Furthermore, ResFinder was used to detect acquired AR genes. The query against the VFDB identified genes that have a role in bacterial survivability, platelet aggregation, surface adhesion, biofilm formation and immunoregulation; and no acquired AR genes were detected using CARD and ResFinder. The study shows that the query strains exhibit genes identical to those present in pathogenic bacteria with the genes matched primarily having roles related to survival and surface adherence. Our results contribute to the overall strategies that can be employed in pre-clinical safety assessments of potential probiotics. Gene mining using whole-genome data, coupled with experimental validation, can be implemented in future probiotic safety assessment strategies.

The Probiotic Potential and Metabolite Characterization of Bioprotective Bacillus and Streptomyces for Applications in Animal Production

Probiotics are increasingly recognized for their potential in managing bacterial challenges in animal production. This study aimed to evaluate the probiotic potential of Bacillus and Streptomyces strains, specifically their bioprotective ability against Salmonella. In agar inhibition assays, these bacteria supported Salmonella-inhibition zones, ranging from 2.5 ± 0.5 to 6.3 ± 2.0 mm. Analyses of antimicrobial metabolites revealed their capacity to produce compounds with anti-Salmonella properties, except for Bacillus subtilis MLB2. When Salmonella was exposed to lyophilized metabolites, inhibition occurred in both liquid (at concentrations between 250 and 500 g/L) and solid cultures (at 500 g/L). To confirm their probiotic potential, the S. griseus and Bacillus strains underwent evaluations for antimicrobial resistance, bile salt tolerance, auto- and co-aggregation, pH resistance, and their ability to adhere to and inhibit Salmonella in Caco-2 cells. These assessments confirmed their probiotic potential. The probiotic strains were further encapsulated and subjected to simulated swine and poultry digestion. They demonstrated survival potential through the gastrointestinal tract and significantly reduced the Salmonella population. Thus, these strains exhibit considerable promise for producing biotechnological products aimed at controlling Salmonella in animal production. This approach ensures the health and hygiene of farming facilities, mitigates the spread of zoonotic bacteria, and contributes positively to public health.

In vitro safety and functional characterization of the novel Bacillus coagulans strain CGI314

Introduction

Bacillus coagulans species have garnered much interest in health-related functional food research owing to their desirable probiotic properties, including pathogen exclusion, antioxidant, antimicrobial, immunomodulatory and food fermentation capabilities coupled with their tolerance of extreme environments (pH, temperature, gastric and bile acid resistance) and stability due to their endosporulation ability.

Methods

In this study, the novel strain Bacillus coagulans CGI314 was assessed for safety, and functional probiotic attributes including resistance to heat, gastric acid and bile salts, the ability to adhere to intestinal cells, aggregation properties, the ability to suppress the growth of human pathogens, enzymatic profile, antioxidant capacity using biochemical and cell-based methods, cholesterol assimilation, anti-inflammatory activity, and attenuation of hydrogen peroxide (H2O2)-induced disruption of the intestinal-epithelial barrier.

Results

B. coagulans CGI314 spores display resistance to high temperatures (40°C, 70°C, and 90°C), and gastric and bile acids [pH 3.0 and bile salt (0.3%)], demonstrating its ability to survive and remain viable under gastrointestinal conditions. Spores and the vegetative form of this strain were able to adhere to a mucous-producing intestinal cell line, demonstrated moderate auto-aggregation properties, and could co-aggregate with potentially pathogenic bacteria. Vegetative cells attenuated LPS-induced pro-inflammatory cytokine gene expression in HT-29 intestinal cell lines and demonstrated broad antagonistic activity toward numerous urinary tract, intestinal, oral, and skin pathogens. Metabolomic profiling demonstrated its ability to synthesize several amino acids, vitamins and short-chain fatty acids from the breakdown of complex molecules or by de novo synthesis. Additionally, B. coagulans CGI314's strong antioxidant capacity was demonstrated using enzyme-based methods and was further supported by its cytoprotective and antioxidant effects in HepG2 and HT-29 cell lines. Furthermore, B. coagulans CGI314 significantly increased the expression of tight junction proteins and partially ameliorated the detrimental effects of H2O2 induced intestinal-epithelial barrier integrity.

Discussion

Taken together these beneficial functional properties provide strong evidence for B. coagulans CGI314 as a promising potential probiotic candidate in food products.

Antibiotic Resistance Characterization and Molecular Characteristics of Enterococcus Species Isolated from Combination Probiotic Preparations in China

Enterococci can act as reservoirs for antibiotic-resistant genes that are potentially at risk of being transferred to other bacteria that inhabit in the gastrointestinal tract. The aim of this study was to determine the phenotypic and molecular characteristics of antibiotic-resistant enterococci isolated from probiotic preparations. In total, we isolated 15 suspected Enterococcus species from 5 compound probiotics, which were identified by 16S rDNA as 12 Enterococcus faecium and 3 Enterococcus faecalis. Determination of antimicrobial susceptibility by the microdilution broth method showed widespread resistance to sulfamethoxazole (100%), norfloxacin (99.3%), azithromycin (99.3%), gentamicin (86.7%), and chloramphenicol (20%). Whole genome sequencing of five resistant strains revealed that all had circular DNA chromosomes and that E. faecium J-1-A to J-4-A contained a plasmid, while E. faecalis J-5-A did not. The results of the resistance gene analysis revealed that each strain contained approximately 30 resistance genes, with the antibiotic resistance genes and the multidrug resistance efflux pump genes mdtG, lmrC, and lmrD detected in all strains. The chloramphenicol resistance genes ykkC and ykkD were first identified in E. faecalis. And there were 21, 19, 21, 21, and 29 virulence factors involved in strains, respectively. Further analysis of the gene islands (GIs) revealed that each strain contained more than 10 GIs. The above results confirm the existence of hidden dangers in the safety of probiotics and remind us to carefully select probiotic preparations containing enterococcal strains to avoid the potential spread of resistance and pathogenicity.

Safety Assessment and Probiotic Potential Comparison of Bifidobacterium longum subsp. infantis BLI-02, Lactobacillus plantarum LPL28, Lactobacillus acidophilus TYCA06, and Lactobacillus paracasei ET-66

Bifidobacterium longum subsp. infantis BLI-02, Lactobacillus paracasei ET-66, Lactobacillus plantarum LPL28, and Lactobacillus acidophilus TYCA06, isolated from healthy breast milk, miso, and the healthy human gut, were assessed for safety in this study. BLI-02, LPL28, TYCA06, and ET-66 exhibited no antibiotic resistance and mutagenic activity in the Ames test at the highest dosage (5000 μg/plate). No genotoxicity was observed in micronucleus and chromosomal aberration assays in rodent spermatogonia at the maximum dosage of 10 g/kg body weight (BW). No acute and sub-chronic toxicity occurred in mice and rats at the maximum tested dosage of 10 g/kg BW and 1.5 g/kg BW, respectively. The lyophilized powder of these strains survived a low pH and high bile salt environment, adhering strongly to Caco-2 cells. Unique antimicrobial activities were noted in these strains, with BLI-02 demonstrating the best growth inhibition against Vibrio parahaemolyticus, LPL28 exhibiting the best growth inhibition against Helicobacter pylori, and ET-66 showing the best growth inhibition against Aggregatibacter actinomycetemcomitans. Based on the present study, the lyophilized powder of these four strains appears to be a safe probiotic supplement at tested dosages. It should be applicable for clinical or healthcare applications.

Novel Strain Leuconostoc lactis DMLL10 from Traditional Korean Fermented Kimchi as a Starter Candidate for Fermented Foods

Leuconostoc lactis strain DMLL10 was isolated from kimchi, a fermented vegetable, as a starter candidate through safety and technological assessments. Strain DMLL10 was susceptible to ampicillin, chloramphenicol, clindamycin, erythromycin, gentamicin, kanamycin, streptomycin, and tetracycline. It did not show any hemolytic activity. Regarding its phenotypic results related to its safety properties, genomic analysis revealed that strain DMLL10 did not encode for any toxin genes such as hemolysin found in the same genus. It did not acquire antibiotic resistance genes either. Strain DMLL10 showed protease activity on agar containing NaCl up to 3%. The genome of DMLL10 encoded for protease genes and possessed genes associated with hetero- and homo-lactic fermentative pathways for lactate production. Finally, strain DMLL10 showed antibacterial activity against seven common foodborne pathogens, although bacteriocin genes were not identified from its genome. These results indicates that strain DMLL10 is a novel starter candidate with safety, enzyme activity, and bacteriocin activity. The complete genomic sequence of DMLL10 will contribute to our understanding of the genetic basis of probiotic properties and allow for assessment of the effectiveness of this strain as a starter or probiotic for use in the food industry.

Unveiling the Probiotic Potential of the Anaerobic Bacterium Cetobacterium sp. nov. C33 for Enhancing Nile Tilapia (Oreochromis niloticus) Cultures

The bacterium strain Cetobacterium sp. C33 was isolated from the intestinal microbial content of Nile tilapia (O. niloticus) under anaerobic conditions. Given that Cetobacterium species are recognized as primary constituents of the intestinal microbiota in cultured Nile tilapia by culture-independent techniques, the adaptability of the C33 strain to the host gastrointestinal conditions, its antibacterial activity against aquaculture bacterial and its antibiotic susceptibility were assessed. The genome of C33 was sequenced, assembled, annotated, and subjected to functional inference, particularly regarding pinpointed probiotic activities. Furthermore, phylogenomic comparative analyses were performed including closely reported strains/species relatives. Comparative genomics with closely related species disclosed that the isolate is not phylogenetically identical to other Cetobacterium species, displaying an approximately 5% sequence divergence from C. somerae and a 13% sequence divergence from Cetobacterium ceti. It can be distinguished from other species through physiological and biochemical criteria. Whole-genome annotation highlighted that Cetobacterium sp. nov. C33 possesses a set of genes that may contribute to antagonism against competing bacteria and has specific symbiotic adaptations in fish. Additional in vivo experiments should be carried out to verify favorable features, reinforcing its potential as a probiotic bacterium.

Microbiological and physical-chemical characteristics of the Peruvian fermented beverage "Chicha de siete semillas": Towards the selection of strains with acidifying properties

Traditional fermented beverages have been consumed worldwide for centuries. Such is the case of "Chicha de siete semillas" which is originally from the province of Huanta, in Ayacucho, Peru. In this work we have analyzed the chemical composition and bacterial diversity of products manufactured from six producers, who have used different combinations of cereals, pseudocereals, legumes and aromatic herbs, although maize was present in all of them. The fermented beverages had a low pH, mainly due to the production of lactic acid, whereas ethanol was, in general, present in low concentrations. Most of the products were rich in GABA, the content of biogenic amines being very low, as corresponds to a product with a short maturation time (less than 4 days). A metataxonomic analysis revealed that Streptococcaceae and Leuconostocaceae families were dominant in the majority of the beverages, Streptococcus spp. and Leuconostoc spp. being the representative genera, respectively. The result was corroborated by culture-dependent techniques, since these were the most abundant genera isolated and identified in all samples, with Streptococcus macedonicus and Leuconostoc lactis as representative species. In lower proportions other isolates were identified as Lactobacillus delbrueckii, Lactiplantibacillus plantarum, Furfurilactobacillus rossiae, Weissella confusa and Enterococcus faecium. The genetic profile of 26 S. macedonicus isolates was determined by RAPD-PCR and REP-PCR, showing five different patterns distinguishable with the first technique. One representative strain from each genetic pattern was further characterized and used to ferment a maize-based matrix (with saccharose) in order to know their technological potential. All strains were able to ferment the beverage at 30 °C in a short time (about 6 h) reaching a pH below 4.5 and they remained viable after 24 h; the main organic acid contributing to the pH decrease was lactic acid. Therefore, S. macedonicus is a good candidate for being part of a putative starter culture, since it is a species well adapted to this cereal-based food niche.

Bacillus subtilis RBT-7/32 and Bacillus licheniformis RBT-11/17 as New Promising Strains for Use in Probiotic Feed Additives

The normal functioning of a gastrointestinal microflora in poultry and livestock is of significant importance, since its imbalance negatively influences an organism's functions. In this study, the UV mutagenesis and selection were used to obtain two Bacillus strains possessing antagonistic activity towards Escherichia coli and Staphylococcus aureus, and their potential as a probiotic feed additive was evaluated. Compared to the parental strains, the ability of B. subtilis RBT-7/32 and B. licheniformis RBT-11/17 strains to suppress E. coli increased by 77 and 63%, respectively; the corresponding ability of these strains to suppress S. aureus increased by 80 and 79%, respectively. RBT-11/17 could not utilize microcrystalline cellulose and carboxymethyl cellulose, whereas cellulolytic activity of RBT-7/32 was doubled compared to the initial strain. The amylolytic activity of new strains was increased by 40%. Cultivation of strains on media containing soybean, pea, and corn meal did not provide any difference in the biomass production compared to the control. The heating of a water suspension of a dried biomass of the strains for 10-20 min at 80 and 100 °C or incubation in water solutions of citric, ascorbic, acetic, and formic acids (pH 3.0) for 3 and 24 h at 40 °C did not provide any negative influence on the spore survivability. Both strains were evaluated for their resistance to a number of veterinary antibiotics. Thus, RBT-7/32 and RBT-11/17 strains have good prospects for use in feed additives.

Assessment of probiotic properties of lactic acid bacteria isolated from an artisanal Colombian cheese

Lactic Acid Bacteria play an important role in the milk fermentation processes of traditional cheeses and have become an important target for the development of novel cheese cultures because of their ability to confer health benefits. This study aimed to evaluate the probiotic potential of 12 Lactic Acid Bacteria (LAB) strains previously isolated and molecularly identified from an artisanal Colombian Double-Cream Cheese. Probiotic properties, including safety (hemolysis and sensibility to antibiotics), pH and bile salt tolerance, auto-aggregation, cell surface hydrophobicity, antibacterial activity, and exopolysaccharide production, were examined. None of the strains were hemolytic, and Pediococcus (16, 18) and Lactobacillus (28, 29) were found to be sensitive to all antibiotics. Moreover, all the strains tolerated pH (3.0, 6.5 and 8.0) and bile salt conditions (0.3, 0.6 and 1.0 % w/v). Pediococcus pentosaceus (16), Leuconostoc citreum (17), Pediococcus acidilactici (18), Enterococcus faecium (21,22), Enterococcus faecalis (24) and Limosilactobacillus fermentum (29) exhibited medium autoaggregation and affinity to chloroform. Six of the strains exhibited a ropy exopolysaccharide phenotype. Antibacterial activity against foodborne pathogens, Salmonella Typhimurium ATCC 14028, Listeria monocytogenes ATCC 19111, Escherichia coli ATCC 25922 and Staphylococcus aureus ATCC 25923, was found to be strain dependent, with the strains 16, 18, 21, 26, 28 and 29 presenting a higher inhibition (>4 mm) against all of them. According to Principal Component Analysis, P. pentosaceus (16), Leu. mesenteroides (26), L. casei (28), L. fermentum (29), and E. faecium (21) showed strong probiotic properties. Our findings suggest that five strains out of the 12 sampled strains are potential probiotics that could be used in the processing of traditional dairy products on an industrial scale to improve their quality.

Antimicrobial and Mycotoxin Reducing Properties of Lactic Acid Bacteria and Their Influence on Blood and Feces Parameters of Newborn Calves

The aim of this study was to evaluate the influence of in acid whey (AW) multiplied Lactiplantibacillus plantarum LUHS135 (L.pl135), Lacticaseibacillus paracasei LUHS244 (L.pc244), and their biomass combination on newborn calves' feces and blood parameters. Additionally, the antimicrobial and mycotoxin-reducing properties and the resistance to antibiotics of the tested lactic acid bacteria (LAB) strains were analyzed. In order to ensure effective biomass growth in AW, technological parameters for the supplement preparation were selected. Control calves were fed with a standard milk replacer (SMR) and treated groups (from the 2nd day of life until the 14th day) were supplemented with 50 mL of AWL.pl135, AWL.pc244, and AWL.pl135×L.pc244 (25 mL AWL.pl135 + 25 mL AWL.pc244) in addition to SMR. It was established that L.pl135 and L.pc244 possess broad antimicrobial activities, are non-resistant to the tested antibiotics, and reduce mycotoxin concentrations in vitro. The optimal duration established for biomass growth was 48 h (LAB count higher than 7.00 log10 CFU mL-1 was found after 48 h of AW fermentation). It was established that additional feeding of newborn calves with AWL.pl135, AWL.pc244, and AWL.pl135×L.pc244 increased lactobacilli (on average by 7.4%), and AWL.pl135 and AWL.pc244 reduced the numbers of Enterobacteriaceae in calves' feces. The tested supplements also reduced the lactate concentration (on average, by 42.5%) in calves' blood. Finally, the tested supplements had a positive influence on certain health parameters of newborn calves; however, further research is needed to validate the mechanisms of the beneficial effects.

Effects of Synbiotic Lacticaseibacillus paracasei, Bifidobacterium breve, and Prebiotics on the Growth Stimulation of Beneficial Gut Microbiota

The gut microbiota is a complex community of microorganisms that plays a vital role in maintaining overall health, and is comprised of Lactobacillus and Bifidobacterium. The probiotic efficacy and safety of Lacticaseibacillus paracasei and Bifidobacterium breve for consumption were confirmed by in vitro experiments. The survival rate of the probiotics showed a significant decline in in vitro gut tract simulation; however, the survival rate was more than 50%. Also, the probiotics could adhere to Caco-2 cell lines by more than 90%, inhibit the pathogenic growths, deconjugate glycocholic acid and taurodeoxycholic acid through activity of bile salt hydrolase (BSH) proteins, and lower cholesterol levels by over 46%. Regarding safety assessment, L. paracasei and B. breve showed susceptibility to some antibiotics but resistance to vancomycin and were examined as γ-hemolytic strains. Anti-inflammatory properties of B. breve with Caco-2 epithelial cell lines showed the significantly highest value (p < 0.05) for interleukin-10. Furthermore, probiotics and prebiotics (inulin, fructooligosaccharides, and galactooligosaccharides) comprise synbiotics, which have potential effects on the increased abundance of beneficial microbiota, but do not affect the growth of harmful bacteria in feces samples. Moreover, the highest concentration of short chain fatty acid was of acetic acid, followed by propionic and butyric acid.

Limosilactobacillus vaginalis Exerts Bifidogenic Effects: A Novel Postbiotic Strategy for Infant Prebiotic Supplementation

Infant microbiota shaping strictly influences newborns' well-being and long-term health, and babies born by cesarean-section and formula-fed generally show low microbial gut diversity and are more prone to develop various disorders. The supplementation with beneficial microbes of vaginal origin or derivatives (postbiotics, including heat-inactivated cells) represents a valid strategy to drive the correct gut microbiota shaping. Here, we explored for the first time the bifidogenic activity of a heat-killed vaginal strain (Limosilactobacillus vaginalis BC17), in addition to the assessment of its safety. L. vaginalis BC17 whole genome was sequenced by Nanopore technology and highlighted the absence of antibiotic resistance genes and virulence factors, indicating the strain safety profile for human health. MIC values confirmed that L. vaginalis BC17 is susceptible to widely employed antibiotics. Heat-killed BC17 cells significantly enhanced the planktonic growth of Bifidobacterium spp. For the first time, stimulating effects were observed also toward biofilm formation of bifidobacteria and their pre-formed biofilms. Conversely, heat-killed BC17 cells exerted antibacterial and anti-biofilms activities against Gram-positive and Gram-negative pathogens. Lyophilized heat-killed BC17 cells were formulated in a sunflower oil suspension (1010 heat-killed cell/g) intended for infant oral intake. This possessed optimal technological (i.e., re-dispersibility and stability) and functional properties (i.e., bifidogenic activity) that were maintained even after pre-digestion in acidic conditions.

Probiotic characterization of Bacillus species strains isolated from an artisanal fermented milk product Dahi

Dahi, an artisanal fermented milk product, widely consumed in Pakistan, is microbiologically diverse, and many bacterial communities await investigation. The current study is first to present probiotic assessment of Bacillus species strains isolated from dahi. Based on 49 identified strains assessed, only 6 strains, i.e., Bacillus licheniformis QAUBL19, QAUBL1901, and QAUBL1902; Bacillus mycoides QAUBM19 and QAUBM1901; and Bacillus subtilis QAUBSS1 were having prominent persistence in the simulated gastrointestinal fluids, being non-hemolytic, with no DNase activity. Probiotic characteristics, cholesterol-assimilating, and carbohydrate-fermenting capabilities were assessed for all the strains. These six strains each showed variant cholesterol assimilating abilities. B. licheniformis QAUBL19 retaining most desired probiotic traits presented both notable cholesterol assimilating and bile salt hydrolase activities. It can be used as a probiotic of choice with hypocholesterolemia ability. B. subtilis QAUBSS1 showed wide carbohydrate fermentation ability and strongest antibacterial potential. It is likely to be considered a probiotic for living beings and starter culture for fermentation of food/feed.

Diversity of the Microbiota of Traditional Izmir Tulum and Izmir Brined Tulum Cheeses and Selection of Potential Probiotics

High-throughput DNA sequencing (HTS) was used to study the microbial diversity of commercial traditional Izmir Tulum (IT) and Izmir Brined Tulum (IBT) cheeses from Izmir, Türkiye. Simultaneously, cultivation-dependent methods were used to isolate, identify and characterize bacterial strains displaying probiotic potential. At the phylum level, Firmicutes dominated the microbiota of both cheese types comprising >98% of the population. Thirty genera were observed, with Streptococcus being the most abundant genus and with Streptococcus thermophilus and S. infantarius subsp. infantarius being the most abundant species. Genera, including Bifidobacterium and Chryseobacterium, not previously associated with IT and IBT, were detected. IT cheeses displayed higher operational taxonomic units (OTUs; Richness) and diversity index (Simpson) than IBT cheeses; however, the difference between the diversity of the microbiota of IT and IBT cheese samples was not significant. Three Lacticaseibacillus paracasei strains isolated from IBT cheeses exhibited probiotic characteristics, which included capacity to survive under in vitro simulated gastrointestinal conditions, resistance to bile salts and potential to adhere to HT-29 human intestinal cells. These findings demonstrate that Tulum cheeses harbor bacterial genera not previously reported in this cheese and that some strains display probiotic characteristics.

Microbiota and its antibiotic resistance profile in avocado Guatemalan fruits (Persea nubigena var. guatemalensis) sold at retail markets of Ibarra city, northern Ecuador

Introduction

Avocados are typically sold in unsanitary conditions at the retail markets in Ecuador, which can raise the risk of microbial contamination. These microorganisms could exhibit multi-antibiotic resistance (MAR), being a serious threat concern to human health. In this study, we aimed to evaluate the microbiota and its antibiotic resistance profile in avocado Guatemalan fruits (Persea nubigena var. guatemalensis), at ripe stage: immature, firm light green (ready to eat in 4 days), peel (AFPE) and pulp (AFPU), and mature intense green (ready to eat) peel (AMPE) and pulp (AMPU), to gain baseline information on the prevalence of MAR bacteria.

Methods

Culture-independent (16S rRNA metagenomics) and culture-dependent approach (to detect specific indicator microorganisms) were used. Moreover, antibiotic susceptibility of selected target indicator bacteria was assessed providing information about the antibiotic resistance (AR) among the groups.

Results

Based on 16S rRNA gene metagenomic analysis, over 99.78% of reads were classified as bacteria in all samples. Shannon diversity index varies from 1.22 to 2.22, with the highest bacterial population assigned to AFPE samples (1327 species). The highest microbial counts of indicator Staphylococcus spp. (STAPHY), Enterobacter spp. (ENT), and Listeria spp. (LIST), were detected in AMPE samples. Thirty percent of the selected STAPHYs, and 20.91% of Enterobacter (ENT) clones were resistant to various classes of antibiotics. The MAR index varies between 0.25 to 0.88 and was clone-, and fruit ripe stage-dependent.

Conclusions

The results indicated that ready to eat avocados contained detectable levels of MAR bacteria, including methicillin resistant (MR)-STAPHY, which may act as a potential vector for the spread of antibiotic resistance. To achieve the increase of the production and marketing of Fuerte cultivar in Ecuador, it is vitally important to consider valuable strategies to protect the fruits at the early ripe stage in future. Thus, it is crucial to set up efficient control measures and develop coordinated strategies to guarantee the microbiological quality of the food.

Production of GABA in milk fermented by Bifidobacterium adolescentis strains selected on the bases of their technological and gastrointestinal performance

There is an increasing interest in producing foods enriched in gamma-aminobutyric acid (GABA), due to their purported health promoting attributes. GABA is the main inhibitor neurotransmitter of the central nervous system, and several microbial species are capable to produce it through decarboxylation of glutamate. Among them, several lactic acid bacteria species have been previously investigated as an appealing alternative to produce GABA enriched foods via microbial fermentation. In this work we report for the first time an investigation into the possibility of utilizing high GABA-producing Bifidobacterium adolescentis strains as a mean to produce fermented probiotic milks naturally enriched in GABA. To this end, in silico and in vitro analyses were conducted in a collection of GABA-producing B. adolescentis strains, with the main goal to scrutinize their metabolic and safety traits, including antibiotic resistance patterns, as well as their technological robustness and performance to survive a simulated gastrointestinal passage. One of the strains, IPLA60004, exhibited better survival to lyophilization and cold storage (for up to 4 weeks at 4 °C), as well as survival to gastrointestinal passage, as compared to the other strains under investigation. Besides, the elaboration of milk drinks fermented with this strain, yielded products with the highest GABA concentration and viable bifidobacterial cell counts, achieving conversion rates of the precursor, monosodium glutamate (GMS), up to 70 %. To our knowledge, this is the first report on the elaboration of GABA enriched milks through fermentation with B. adolescentis.

Novel, non-colonizing, single-strain live biotherapeutic product ADS024 protects against Clostridioides difficile infection challenge in vivo

BACKGROUND

The Centers for Disease Control and Prevention estimate that Clostridioides difficile (C. difficile) causes half a million infections (CDI) annually and is a major cause of total infectious disease death in the United States, causing inflammation of the colon and potentially deadly diarrhea. We recently reported the isolation of ADS024, a Bacillus velezensis (B. velezensis) strain, which demonstrated direct in vitro bactericidal activity against C. difficile, with minimal collateral impact on other members of the gut microbiota. In this study, we hypothesized that in vitro activities of ADS024 will translate in vivo to protect against CDI challenge in mouse models.

AIM

To investigate the in vivo efficacy of B. velezensis ADS024 in protecting against CDI challenge in mouse models.

METHODS

To mimic disruption of the gut microbiota, the mice were exposed to vancomycin prior to dosing with ADS024. For the mouse single-dose study, the recovery of ADS024 was assessed via microbiological analysis of intestinal and fecal samples at 4 h, 8 h, and 24 h after a single oral dose of 5 × 108 colony-forming units (CFU)/mouse of freshly grown ADS024. The single-dose study in miniature swine included groups that had been pre-dosed with vancomycin and that had been exposed to a dose range of ADS024, and a group that was not pre-dosed with vancomycin and received a single dose of ADS024. The ADS024 colonies [assessed by quantitative polymerase chain reaction (qPCR) using ADS024-specific primers] were counted on agar plates. For the 28-d miniature swine study, qPCR was used to measure ADS024 levels from fecal samples after oral administration of ADS024 capsules containing 5 × 109 CFU for 28 consecutive days, followed by MiSeq compositional sequencing and bioinformatic analyses to measure the impact of ADS024 on microbiota. Two studies were performed to determine the efficacy of ADS024 in a mouse model of CDI: Study 1 to determine the effects of fresh ADS024 culture and ADS024 spore preparations on the clinical manifestations of CDI in mice, and Study 2 to compare the efficacy of single daily doses vs dosing 3 times per day with fresh ADS024. C. difficile challenge was performed 24 h after the start of ADS024 exposure. To model the human distal colon, an anerobic fecal fermentation system was used. MiSeq compositional sequencing and bioinformatic analyses were performed to measure microbiota diversity changes following ADS024 treatment. To assess the potential of ADS024 to be a source of antibiotic resistance, its susceptibility to 18 different antibiotics was tested.

RESULTS

In a mouse model of CDI challenge, single daily doses of ADS024 were as efficacious as multiple daily doses in protecting against subsequent challenge by C. difficile pathogen-induced disease. ADS024 showed no evidence of colonization based on the observation that the ADS024 colonies were not recovered 24 h after single doses in mice or 72 h after single doses in miniature swine. In a 28-d repeat-dose study in miniature swine, ADS024 was not detected in fecal samples using plating and qPCR methods. Phylogenetic analysis performed in the human distal colon model showed that ADS024 had a selective impact on the healthy human colonic microbiota, similarly to the in vivo studies performed in miniature swine. Safety assessments indicated that ADS024 was susceptible to all the antibiotics tested, while in silico testing revealed a low potential for off-target activity or virulence and antibiotic-resistance mechanisms.

CONCLUSION

Our findings, demonstrating in vivo efficacy of ADS024 in protecting against CDI challenge in mouse models, support the use of ADS024 in preventing recurrent CDI following standard antibiotic treatment.

Novel Starter Strain Enterococcus faecium DMEA09 from Traditional Korean Fermented Meju

The Enterococcus faecium strain DMEA09 was previously isolated from traditional Korean fermented meju. The objective of the current study was to investigate the traits of E. faecium strain DMEA09 as a starter candidate, focusing on its safety and technological properties. Regarding its safety, the DMEA09 strain was found to be sensitive to nine antibiotics (ampicillin, chloramphenicol, erythromycin, gentamicin, kanamycin, streptomycin, tetracycline, tylosin, and vancomycin) by showing lower minimum inhibitory concentrations (MICs) than the cut-off values suggested by the European Union Food Safety Authority for these nine antibiotics. However, its MIC value for clindamycin was twice as high as the cut-off value. A genomic analysis revealed that strain DMEA09 did not encode the acquired antibiotic resistance genes, including those for clindamycin. The DMEA09 strain did not show hemolysis as a result of analyzing α- and β-hemolysis. It did not form biofilm either. A genomic analysis revealed that strain DMEA09 did not encode for any virulence factors including hemolysin. Most importantly, multilocus sequence typing revealed that the clonal group of strain DMEA09 was distinguished from clinical isolates. Regarding its technological properties, strain DMEA09 could grow in the presence of 6% salt. It showed protease activity when the salt concentration was 3%. It did not exhibit lipase activity. Its genome possessed 37 putative protease genes and salt-tolerance genes for survivability under salt conditions. Consequently, strain DMEA09 shows safe and technological properties as a new starter candidate. This was confirmed by genome analysis.

The Impacts of Acidophilic Lactic Acid Bacteria on Food and Human Health: A Review of the Current Knowledge

The need to improve the safety/quality of food and the health of the hosts has resulted in increasing worldwide interest in acidophilic lactic acid bacteria (LAB) for the food, livestock as well as health industries. In addition to the use of acidophilic LAB with probiotic potential for food fermentation and preservation, their application in the natural disposal of acidic wastes polluting the environment is also being investigated. Considering this new benefit that has been assigned to probiotic microorganisms in recent years, the acceleration in efforts to identify new, efficient, promising probiotic acidophilic LAB is not surprising. One of these effots is to determine both the beneficial and harmful compounds synthesized by acidophilic LAB. Moreover, microorganisms are of concern due to their possible hemolytic, DNase, gelatinase and mucinolytic activities, and the presence of virulence/antibiotic genes. Hence, it is argued that acidophilic LAB should be evaluated for these parameters before their use in the health/food/livestock industry. However, this issue has not yet been fully discussed in the literature. Thus, this review pays attention to the less-known aspects of acidophilic LAB and the compounds they release, clarifying critical unanswered questions, and discussing their health benefits and safety.

Probiotics as an Alternative to Antibiotics: Genomic and Physiological Characterization of Aerobic Spore Formers from the Human Intestine

A total of thirty-two aerobic spore former strains were isolated from intestinal samples of healthy children and analyzed for their hemolytic and antibiotic-resistant activities. Four strains selected as non-hemolytic and sensitive to all antibiotics recommended as relevant by regulatory agencies were short-listed and evaluated for their in silico and in vitro probiotic potentials. The four selected strains were assigned to the Bacillus velezensis (MV4 and MV11), B. subtilis (MV24), and Priestia megaterium (formerly Bacillus megaterium) (MV30) species. A genomic analysis indicated that MV4, MV11, and MV24 contained a homolog of the gene coding for the fibrinolytic enzyme nattokinase while only MV30 encoded a glutamic acid decarboxylase essential to synthesize the neurotransmitter GABA. All four strains contained gene clusters potentially coding for new antimicrobials, showed strong antioxidant activity, formed biofilm, and produced/secreted quorum-sensing peptides able to induce a cytoprotective stress response in a model of human intestinal (HT-29) cells. Altogether, genomic and physiological data indicate that the analyzed strains do not pose safety concerns and have in vitro probiotic potentials allowing us to propose their use as an alternative to antibiotics.

Propionibacteria as promising tools for the production of pro-bioactive scotta: a proof-of-concept study

Dairy propionibacteria are Gram positive Actinomycetota, routinely utilized as starters in Swiss type cheese making and highly appreciated for their probiotic properties and health promoting effects. In this work, within the frame of a circular economy approach, 47 Propionibacterium and Acidipropionibacterium spp. were isolated from goat cheese and milk, and ewe rumen liquor, and characterized in view of their possible utilization for the production of novel pro-bioactive food and feed on scotta, a lactose rich substrate and one of the main by-products of the dairy industry. The evaluation of the Minimum Inhibitory Concentration (MIC) of 13 among the most common antibiotics in clinical practice revealed a general susceptibility to ampicillin, gentamycin, streptomycin, vancomycin, chloramphenicol, and clindamycin while confirming a lower susceptibility to aminoglycosides and ciprofloxacin. Twenty-five isolates, that proved capable of lactose utilization as the sole carbon source, were then characterized for functional and biotechnological properties. Four of them, ascribed to Propionibacterium freudenreichii species, and harboring resistance to bile salts (growth at 0.7-1.56 mM of unconjugated bile salts), acid stress (>80% survival after 1 h at pH 2), osmostress (growth at up to 6.5% NaCl) and lyophilization (survival rate > 80%), were selected and inoculated in scotta. On this substrate the four isolates reached cell densities ranging from 8.11 ± 0.14 to 9.45 ± 0.06 Log CFU mL-1 and proved capable of producing different vitamin B9 vitamers after 72 h incubation at 30°C. In addition, the semi-quantitative analysis following the metabolomics profiling revealed a total production of cobalamin derivatives (vitamin B12) in the range 0.49-1.31 mg L-1, thus suggesting a full activity of the corresponding biosynthetic pathways, likely involving a complex interplay between folate cycle and methylation cycle required in vitamin B12 biosynthesis. These isolates appear interesting candidates for further ad-hoc investigation regarding the production of pro-bioactive scotta.

Antibiotic Susceptibility Testing and Establishment of Tentative Species-Specific Microbiological Cut-off Values for Bifidobacteria Isolated from Chinese Population

Bifidobacteria are commonly used as probiotics in the food industry. The resistance of Bifidobacterium species to antibiotics is closely linked to food safety. However, we still lack a system for the safety evaluation of antibiotic resistance in bifidobacteria, and genus-level microbiological cut-off values remain in use for the determination of phenotypic resistance of Bifidobacterium strains to a given antibiotic. Here, we collected a total of 422 gut-derived bifidobacterial strains isolated from Chinese population and identified their phenotypic resistance profiles against ampicillin, amoxicillin, ciprofloxacin, chloramphenicol, clindamycin, erythromycin, rifampicin, tetracycline, trimethoprim, and vancomycin. Different Bifidobacterium species were found to have varying tolerances to the same antibiotic; therefore, we further established species-specific cut-off values for bifidobacterial species to ten antibiotics. Species-specific rather than genus-specific cut-off values for species belonging to the same taxon were considered more suitable to determine the phenotypic resistance of a Bifidobacterium strain. Moreover, a comprehensive scanning of antibiotic resistance genes in all Bifidobacterium strains tested revealed that the existence of the tetracycline resistance gene tet(W) and the erythromycin/clindamycin resistance gene ErmX is closely related to host phenotypes. Our findings provide guidance and reference values at both phenotype and genotype levels for the safe application of bifidobacteria in the food industry and the development of probiotic resistance evaluation standards.

Staphylococcus equorum plasmid pKS1030-3 encodes auxiliary biofilm formation and trans-acting gene mobilization systems

The foodborne bacterium Staphylococcus equorum strain KS1030 harbours plasmid pSELNU1, which encodes a lincomycin resistance gene. pSELNU1 undergoes horizontal transfer between bacterial strains, thus spreading antibiotic resistance. However, the genes required for horizontal plasmid transfer are not encoded in pSELNU1. Interestingly, a relaxase gene, a type of gene related to horizontal plasmid transfer, is encoded in another plasmid of S. equorum KS1030, pKS1030-3. The complete genome of pKS1030-3 is 13,583 bp long and encodes genes for plasmid replication, biofilm formation (the ica operon), and horizontal gene transfer. The replication system of pKS1030-3 possesses the replication protein-encoding gene repB, a double-stranded origin of replication, and two single-stranded origins of replication. The ica operon, relaxase gene, and a mobilization protein-encoding gene were detected in pKS1030-3 strain-specifically. When expressed in S. aureus RN4220, the ica operon and relaxase operon of pKS1030-3 conferred biofilm formation ability and horizontal gene transfer ability, respectively. The results of our analyses show that the horizontal transfer of pSELNU1 of S. equorum strain KS1030 depends on the relaxase encoded by pKS1030-3, which is therefore trans-acting. Genes encoded in pKS1030-3 contribute to important strain-specific properties of S. equorum KS1030. These results could contribute to preventing the horizontal transfer of antibiotic resistance genes in food.

Antibacterial and Antibiofilm Effects of Lactobacilli Strains against Clinical Isolates of Pseudomonas aeruginosa under Conditions Relevant to Cystic Fibrosis

Therapy of lung infections sustained by Pseudomonas aeruginosa in cystic fibrosis (CF) patients is challenging due to the presence of a sticky mucus in the airways and the ability of the bacterium to form biofilm, which exhibits increased antibiotic tolerance. A lung-directed bacteriotherapy through the airway administration of probiotics could represent an alternative approach to probiotic diet supplementation to improve the benefits and clinical outcomes of this kind of intervention in CF patients. This study aims to evaluate the ability of probiotic strains to grow in artificial sputum medium (ASM), mimicking the CF lung microenvironment, and to affect the planktonic and biofilm growth of CF clinical strains of P. aeruginosa in the same conditions. The results demonstrate that Lacticaseibacillus rhamnosus and Lactiplantibacillus plantarum (LP) can grow in ASM. LP inhibited the planktonic growth of P. aeruginosa, while both lactobacilli reduced the pre-formed biofilm of P. aeruginosa. Interestingly, LP was demonstrated to reduce the amount of polysaccharides in the extracellular matrix of P. aeruginosa biofilms and to potentiate the antibiofilm effects of tobramycin. Overall, the results indicated that LP is a promising candidate as an adjuvant in the antimicrobial therapy of P. aeruginosa infections in CF patients.

Genetic and phenotypic assessments for the safety of probiotic Bacillus clausii 088AE

In this study, we report on whole genome sequence analysis of clinically documented, commercial probiotic Bacillus clausii 088AE and genome features contributing to probiotic properties. The whole genome sequence of B. clausii 088AE generated a single scaffold of 4,598,457 bp with 44.74 mol% G + C. This assembled genome sequence annotated by the RAST resulted in 4371 coding genes, 75 tRNAs, and 22 rRNAs. Gene ontology classification indicated 39.5% proteins with molecular function, 44.24% cellular component, and 16.25% proteins involved in biological processes. In taxonomic analysis, B. clausii 088AE shared 99% identity with B. clausii DSM 8716. The gene sequences related to safety and genome stability such as antibiotic resistance (840), virulence factors (706), biogenic amines (1), enterotoxin (0), emetic toxin (0), lanthipeptides (4), prophage (4) and clustered regularly interspaced short palindromic repeats (CRISPR) sequences (11), were identified and evaluated for safety and functions. The absence of functional prophage sequences and the presence of CRISPR indicated an advantage in genome stability. Moreover, the presence of genome features contributing to probiotic characteristics such as acid, and bile salt tolerance, adhesion to the gut mucosa, and environmental resistance ensure the strains survivability when consumed as a probiotic. In conclusion, the absence of risks associated with sequences/genes in the B. clausii 088AE genome and the presence of essential probiotic traits confirm the strain to be safe for use as a probiotic.

Isolation, Characterization, and Comparative Genomics of the Novel Potential Probiotics from Canine Feces

Lactic acid bacteria (LAB) are commonly used as probiotics; however, not all LAB strains have the same beneficial effects. To successfully use LAB as probiotics in canines, LAB species should originate from the canine intestinal tract as they display host specificity. The objective of this study was to investigate the phenotypic and genomic traits of potential probiotic LAB isolated from canine fecal samples. Twenty LAB samples were evaluated for their potential probiotic characteristics including resistance to low pH, bile salts, hydrophobicity, auto-aggregation, co-aggregation, adhesion to epithelia or mucosa, and production of inhibitory compounds. Additionally, we evaluated their safety and other beneficial effects on canine health, such as DPPH free radical scavenging, and β-galactosidase. Four strains demonstrated potential probiotic characteristics and were selected: Enterococcus hirae Pom4, Limosilactobacillus fermentum Pom5, Pediococcus pentosaceus Chi8, and Ligilactobacillus animalis FB2. Safety evaluations showed that all strains lacked hemolytic activity, could not produce biogenic amines, and did not carry any pathogenic genes. In addition, L. fermentum Pom5 and P. pentosaceus Chi8 displayed susceptibility to all antibiotics and concordant with the absence of antibiotic resistance genes. Based on their phenotypic and genomic characteristics, L. fermentum Pom5 and P. pentosaceus Chi8 were identified as potential probiotic candidates for canines.

Bifidobacterium breve PRL2020: Antibiotic-Resistant Profile and Genomic Detection of Antibiotic Resistance Determinants

Antibiotics are one of the greatest scientific achievements of modern medicine, but excessive use is creating challenges for the future of medicine. Antibiotic resistance (AR) is thought to cause changes in bowel habits and an increased risk of gastroenteritis, but it may also increase the risk of overweight, obesity, autoimmune and atopic diseases, and a low response to vaccines and cancer, likely mediated by antibiotic-induced gut dysbiosis. Probiotic add-on therapy could partially prevent antibiotic-induced gut dysbiosis, but their antibiotic sensitivity features likely limits this potential. The EFSA (European Food Safety Authority) guidelines consider the use of probiotics whose antibiotic-resistant profile could be transferable an important hazard. Recently, a strain of B. breve (PRL2020) has shown to be resistant to amoxicillin and amoxicillin-clavulanate (AC) by applying the microdilution protocol according EFSA guidelines. After verifying that horizontal gene transfer is unlikely to take place, this feature suggests its concomitant use with these specific antibiotics. The results of our tests demonstrated that the strain PRL2020 is indeed endowed with amoxicillin- and AC-resistant properties and that it is also insensitive to ampicillin. In-depth analysis of the annotated genome sequence of B. breve PRL2020 was employed to query the Comprehensive Antibiotic Resistance Database (CARD) using Resistance Gene Identifier (RGI) software (version 5.2.1). The similarity among the AR determinants found was studied through nucleotide sequence alignment, and it was possible to verify not only the absence of genes explaining these features in the flanking regions but also the presence of genetic sequences (rpoB and erm(X)) putatively responsible for rifampicin and erythromycin resistance. Both features are not phenotypically expressed, and for these antibiotics, the strain is within the EFSA limits. Analysis of the flanking regions of these genes revealed possible mobile elements upstream and downstream only in the case of the erm(X) gene, but the features of the Insertion Sequences (IS) are described as not to cause horizontal transfer. Our findings on strain PRL2020 demonstrate that its AR profile is compatible with antibiotics when taken with the aim of reducing the risk of dysbiosis.

Probiotic Properties and Antioxidant Activity In Vitro of Lactic Acid Bacteria

The properties of probiotics such as lactic acid bacteria (LAB) have been widely studied over the last decades. In the present study, four different LAB species, namely Lactobacillus gasseri ATCC 33323, Lacticaseibacillus rhamnosus GG ATCC 53103, Levilactobacillus brevis ATCC 8287, and Lactiplantibacillus plantarum ATCC 14917, were investigated in order to determine their ability to survive in the human gut. They were evaluated based on their tolerance to acids, resistance to simulated gastrointestinal conditions, antibiotic resistance, and the identification of genes encoding bacteriocin production. All four tested strains demonstrated high resistance to simulated gastric juice after 3 h, and the viable counts revealed declines in cell concentrations of less than 1 log cycle. L. plantarum showed the highest level of survival in the human gut, with counts of 7.09 log CFU/mL. For the species L. rhamnosus and L. brevis, the values were 6.97 and 6.52, respectively. L. gasseri, after 12 h, showed a 3.96 log cycle drop in viable counts. None of the evaluated strains inhibited resistance to ampicillin, gentamicin, kanamycin, streptomycin, erythromycin, clindamycin, tetracycline, or chloramphenicol. With regard to bacteriocin genes, the Pediocin PA gene was identified in Lactiplantibacillus plantarum ATCC 14917, Lacticaseibacillus rhamnosus GG ATCC 53103, and Lactobacillus gasseri ATCC 33323. The PlnEF gene was detected in Lactiplantibacillus plantarum ATCC 14917 and Lacticaseibacillus rhamnosus GG ATCC 53103. The Brevicin 174A and PlnA genes were not detected in any bacteria. Moreover, the potential antioxidant activity of LAB's metabolites was evaluated. At the same time, the possible antioxidant activity of metabolites of LAB was first tested using the free radical DDPH^• (a, a-Diphenyl-β-Picrylhydrazyl) and then evaluated with regard to their radical scavenging activity and inhibition against peroxyl radical induced DNA scission. All strains showed antioxidant activity; however, the best antioxidant activity was achieved by L. brevis (94.47%) and L. gasseri (91.29%) at 210 min. This study provides a comprehensive approach to the action of these LAB and their use in the food industry.

Antimicrobial Resistance of Lactic Acid Bacteria from Nono, a Naturally Fermented Milk Product

BACKGROUND

Antimicrobial resistance (AMR) is one of the biggest threats to public health. The food chain has been recognised as a vehicle for transmitting AMR bacteria. However, information about resistant strains isolated from African traditional fermented foods remains limited. Nono is a traditional, naturally fermented milk product consumed by many pastoral communities across West Africa. The main aim of this study was to investigate and determine the AMR patterns of lactic acid bacteria (LAB) involved in the traditional fermentation of milk for Nono production, and the presence of transferable AMR determinants.

METHODS

One hundred (100) LAB isolates from Nono identified in a previous study as Limosilactobacillus fermentum, Lactobacillus delbrueckii, Streptococcus thermophilus, Streptococcus infantarius, Lentilactobacillus senioris, Leuconostoc pseudomesenteriodes, and Enterococcus thailandicus were investigated. The minimum inhibitory concentration (MIC) was determined for 18 antimicrobials using the micro-broth dilution method. In addition, LAB isolates were screened for 28 antimicrobial resistance genes using PCR. The ability of LAB isolates to transfer tetracycline and streptomycin resistance genes to Enterococcus faecalis was also investigated.

RESULTS

The experiments revealed variable antimicrobial susceptibility according to the LAB isolate and the antimicrobial tested. The tetracycline resistance genes tet(S) and tet(M) were detected in isolates Ent. thailandicus 52 and S. infantarius 10. Additionally, aad(E) encoding resistance to streptomycin was detected in Ent. thailandicus 52. The conjugation experiments suggested that the tet(S) and aad(E) genes were transferable in vitro from isolate Ent. thailandicus 52 to Ent. faecalis JH2-2.

SIGNIFICANCE AND IMPACT

Traditional fermented foods play a significant role in the diet of millions of people in Africa, yet their contribution to the burden of AMR is largely unknown. This study highlights that LAB involved in traditionally fermented foods could be potential reservoirs of AMR. It also underscores the relevant safety issues of Ent. thailandicus 52 and S. infantarius 10 for use as starter cultures as they carry transferable AMR genes. Starter cultures are an essential aspect of improving the safety and quality attributes of African fermented foods. However, AMR monitoring is an important safety aspect in the selection of starter cultures for improving traditional fermentation technologies.