Interactions between Staphylococcus aureus and lactic acid bacteria: An old story with new perspectives

A Living Microecological Hydrogel with Microbiota Remodeling and Immune Reinstatement for Diabetic Wound Healing

Dysregulated skin microbiota and compromised immune responses are the major etiological factors for non-healing diabetic wounds. Current antibacterial strategies fail to orchestrate immune responses and indiscriminately eradicate bacteria at the wound site, exacerbating the imbalance of microbiota. Drawing inspiration from the beneficial impacts that probiotics possess on microbiota, a living microecological hydrogel containing Lactobacillus plantarum and fructooligosaccharide (LP/FOS@Gel) is formulated to remodel dysregulated skin microbiota and reinstate compromised immune responses, cultivating a conducive environment for optimal wound healing. LP/FOS@Gel acts as an "evocator," skillfully integrating the skin microecology, promoting the proliferation of Lactobacillus, Ralstonia, Muribaculum, Bacillus, and Allobaculum, while eradicating colonized pathogenic bacteria. Concurrently, LP/FOS@Gel continuously generates lactic acid to elicit a reparative macrophage response and impede the activation of the nuclear factor kappa-B pathway, effectively alleviating inflammation. As an intelligent microecological system, LP/FOS@Gel reinstates the skin's sovereignty during the healing process and effectively orchestrates the harmonious dialogue between the host immune system and microorganisms, thereby fostering the healing of diabetic infectious wounds. These remarkable attributes render LP/FOS@Gel highly advantageous for pragmatic clinical applications.

Potential probiotic characteristics and genomic analysis of a new folate-producing lactic acid bacteria Lactiplantibacillus plantarum ZFM55

BACKGROUND

Folate is crucial for maintaining health, but humans are unable to synthesize folate and need to obtain it from food. Lactiplantibacillus plantarum can produce the necessary vitamin B for the human body, including folate. Whole genome sequencing technology can clarify the physiological characteristics of folate production in Lactiplantibacillus plantarum. In order to explore new Lactiplantibacillus plantarum that produce folate, the folate production and probiotic characteristics of Lactiplantibacillus plantarum ZFM55 isolated from infant feces were investigated, and whole genome sequencing was performed.

RESULTS

The folate synthesis ability of Lactiplantibacillus plantarum ZFM55 were measured, and its total folate production was 299.72 ± 28.81 ng mL-1. Subsequently, its probiotic properties were explored. The antibacterial test showed that its inhibition zone diameter against Staphylococcus aureus and Salmonella typhimurium was 15.5 ± 0.82 mm and 13.88 ± 0.98 mm, respectively. The tolerance test results indicated that it maintained good activity in simulated gastrointestinal tract and bile salt environments. In vitro intestinal simulation experiments had confirmed that Lactiplantibacillus plantarum ZFM55 can increase the abundance of beneficial bacteria such as Bifidobacteria in the intestine and inhibit the growth of harmful bacteria such as Escherichia_Shigella. Genomic sequencing indicated that the genetic material of Lactiplantibacillus plantarum ZFM55 contains one chromosome and three plasmids, and it has 20 genes related to folate synthesis, which explains its ability to produce folate.

CONCLUSION

This study reports a new potential probiotic that produces folate, and provides ideas for exploring probiotics with specific probiotic characteristics. © 2024 Society of Chemical Industry.

Inhibiting pathogenicity of vaginal Candida albicans by lactic acid bacteria and MS analysis of their extracellular compounds

Maintaining healthy vaginal microflora post-puberty is critical. In this study we explore the potential of vaginal lactic acid bacteria (LAB) and their extracellular metabolites against the pathogenicity of Candida albicans. The probiotic culture free supernatant (PCFS) from Lactobacillus crispatus, L. gasseri, and L. vaginalis exhibit an inhibitory effect on budding, hyphae, and biofilm formation of C. albicans. LGPCFS manifested the best potential among the LAB PCFS, inhibiting budding for 24 h and restricting hyphae formation post-stimulation. LGPCFS also pre-eminently inhibited biofilm formation. Furthermore, L. gasseri itself grew under RPMI 1640 stimulation suppressing the biofilm formation of C. albicans. The PCFS from the LAB downregulated the hyphal genes of C. albicans, inhibiting the yeast transformation to fungi. Hyphal cell wall proteins HWP1, ALS3, ECE1, and HYR1 and transcription factors BCR1 and CPH1 were downregulated by the metabolites from LAB. Finally, the extracellular metabolome of the LAB was studied by LC-MS/MS analysis. L.gasseri produced the highest antifungal compounds and antibiotics, supporting its best activity against C. albicans. Vaginal LAB and their extracellular metabolites perpetuate C. albicans at an avirulent state. The metabolites produced by these LAB in vitro have been identified, and can be further exploited as a preventive measure against vaginal candidiasis.

Triple Cross-linked Dynamic Responsive Hydrogel Loaded with Selenium Nanoparticles for Modulating the Inflammatory Microenvironment via PI3K/Akt/NF-κB and MAPK Signaling Pathways

Modulating the inflammatory microenvironment can inhibit the process of inflammatory diseases (IDs). A tri-cross-linked inflammatory microenvironment-responsive hydrogel with ideal mechanical properties achieves triggerable and sustained drug delivery and regulates the inflammatory microenvironment. Here, this study develops an inflammatory microenvironment-responsive hydrogel (OD-PP@SeNPs) composed of phenylboronic acid grafted polylysine (PP), oxidized dextran (OD), and selenium nanoparticles (SeNPs). The introduction of SeNPs as initiators and nano-fillers into the hydrogel results in extra cross-linking of the polymer network through hydrogen bonding. Based on Schiff base bonds, Phenylboronate ester bonds, and hydrogen bonds, a reactive oxygen species (ROS)/pH dual responsive hydrogel with a triple-network is achieved. The hydrogel has injectable, self-healing, adhesion, outstanding flexibility, suitable swelling capacity, optimal biodegradability, excellent stimuli-responsive active substance release performance, and prominent biocompatibility. Most importantly, the hydrogel with ROS scavenging and pH-regulating ability protects cells from oxidative stress and induces macrophages into M2 polarization to reduce inflammatory cytokines through PI3K/AKT/NF-κB and MAPK pathways, exerting anti-inflammatory effects and reshaping the inflammatory microenvironment, thereby effectively treating typical IDs, including S. aureus infected wound and rheumatoid arthritis in rats. In conclusion, this dynamically responsive injectable hydrogel with a triple-network structure provides an effective strategy to treat IDs, holding great promise in clinical application.

Development of in vitro methods to model the impact of vaginal lactobacilli on Staphylococcus aureus biofilm formation on menstrual cups as well as validation of recommended cleaning directions

Introduction

Menstrual cups (MC) are a reusable feminine hygiene product. A recent publication suggested that Staphylococcus aureus (S. aureus) biofilms can form on MCs which may lead to increased risk of menstrual Toxic Shock Syndrome (mTSS). Additionally, there is concern that buildup of residual menses may contribute to microbial growth and biofilm formation further increasing mTSS risk. Quantitative and qualitative analysis of in vitro tests were utilized to determine if S. aureus biofilm could form on MC in the presence of the keystone species Lactobacillus after 12 h of incubation. The methodology was based on a modification of an anaerobic in vitro method that harnesses the keystone species hypothesis by including a representative of vaginal lactic acid bacteria.

Methods

MCs were incubated anaerobically for 12 h in Vaginal Defined Media (VDM) with the two morphologically distinct bacteria, Lactobacillus gasseri (L. gasseri) and S. aureus. Colony Forming Units (CFU) for each organism from the VDM broth and sonicated MC were estimated. In addition, a separate experiment was conducted where S. aureus was grown for 12 h in the absence of L. gasseri. Qualitative analysis for biofilm formation utilized micro-CT (µ-CT) and cryogenic scanning electron microscopy (Cryo-SEM).

Results

Samples collected from the media control had expected growth of both organisms after 12 h of incubation. Samples collected from VDM broth were similar to media control at the end of the 12-h study. Total S. aureus cell density on MC following sonication/rinsing was minimal. Results when using a monoculture of S. aureus demonstrated that there was a significant growth of the organism in the media control and broth as well as the sonicated cups indicating that the presence of L. gasseri was important for controlling growth and adherence of S. aureus. Few rod-shaped bacteria (L. gasseri) and cocci (S. aureus) could be identified on the MCs when grown in a dual species culture inoculum and no biofilm was noted via µ-CT and cryo-SEM. Additionally, efforts to model and understand the validity of the current labeled recommendations for MC cleaning in-between uses are supported.

Discussion

The data support continued safe use of the Tampax® cup when used and maintained as recommended.

Growth and Non-Thermal Inactivation of Staphylococcus aureus in Sliced Dry-Cured Ham in Relation to Water Activity, Packaging Type and Storage Temperature

Dry-cured ham (DCH) could support the growth of Staphylococcus aureus as a halotolerant bacterium, which may compromise the shelf-stability of the product according to the growth/no growth boundary models and the physicochemical parameters of commercial DCH. In the present study, the behavior of S. aureus is evaluated in sliced DCH with different water activity (a_w 0.861-0.925), packaged under air, vacuum, or modified atmosphere (MAP), and stored at different temperatures (2-25 °C) for up to 1 year. The Logistic and the Weibull models were fitted to data to estimate the primary kinetic parameters for the pathogen Log₁₀ increase and Log₁₀ reduction, respectively. Then, polynomial models were developed as secondary models following their integration into the primary Weibull model to obtain a global model for each packaging. Growth was observed for samples with the highest a_w stored at 20 and 25 °C in air-packaged DCH. For lower a_w, progressive inactivation of S. aureus was observed, being faster at the lowest temperature (15 °C) for air-packaged DCH. In contrast, for vacuum and MAP-packaged DCH, a higher storage temperature resulted in faster inactivation without a significant effect of the product a_w. The results of this study clearly indicate that the behavior of S. aureus is highly dependent on factors such as storage temperature, packaging conditions and product a_w. The developed models provide a management tool for evaluating the risk associated with DCH and for preventing the development of S. aureus by selecting the most appropriate packaging according to a_w range and storage temperature.

Interspecies Interactions within the Host: the Social Network of Group B Streptococcus

Group B Streptococcus (GBS) is a pervasive neonatal pathogen accounting for a combined half a million deaths and stillbirths annually. The most common source of fetal or neonatal GBS exposure is the maternal microbiota. GBS asymptomatically colonizes the gastrointestinal and vaginal mucosa of 1 in 5 individuals globally, although its precise role in these niches is not well understood. To prevent vertical transmission, broad-spectrum antibiotics are administered to GBS-positive mothers during labor in many countries. Although antibiotics have significantly reduced GBS early-onset neonatal disease, there are several unintended consequences, including an altered neonatal microbiota and increased risk for other microbial infections. Additionally, the incidence of late-onset GBS neonatal disease remains unaffected and has sparked an emerging hypothesis that GBS-microbe interactions in developing neonatal gut microbiota may be directly involved in this disease process. This review summarizes our current understanding of GBS interactions with other resident microbes at the mucosal surface from multiple angles, including clinical association studies, agriculture and aquaculture observations, and experimental animal model systems. We also include a comprehensive review of in vitro findings of GBS interactions with other bacterial and fungal microbes, both commensal and pathogenic, along with newly established animal models of GBS vaginal colonization and in utero or neonatal infection. Finally, we provide a perspective on emerging areas of research and current strategies to design microbe-targeting prebiotic or probiotic therapeutic intervention strategies to prevent GBS disease in vulnerable populations.

Antimicrobial and immunoregulatory effects of Lactobacillus delbrueckii 45E against genitourinary pathogens

BACKGROUND

Lactobacilli are essential microbiota that maintain a healthy, balanced vaginal environment. Vaginitis is a common infection in women during their reproductive years. Many factors are associated with vaginitis; one of them is the imbalance of microbiota in the vaginal environment. This study aimed to evaluate the antimicrobial properties of Lactobacillus delbrueckii 45E (Ld45E) against several species of bacteria, namely, Group B Streptococcus (GBS), Escherichia coli, Klebsiella spp., and Candida parapsilosis, as well as to determine the concentration of interleukin-17 (IL-17) in the presence of Ld45E.

METHODS

The probiotic characteristics of Ld45E were evaluated by examining its morphology, pH tolerance, adhesive ability onto HeLa cells, hemolytic activity, antibiotic susceptibility, and autoaggregation ability. Then, the antimicrobial activity of Ld45E was determined using Ld45E culture, cell-free supernatant, and crude bacteriocin solution. Co-aggregation and competition ability assays against various pathogens were conducted. The immunoregulatory effects of Ld45E were analyzed by measuring the proinflammatory cytokine IL-17. A p-value less than 0.05 was considered statistical significance.

RESULTS

Ld45E is 3-5 mm in diameter and round with a flat-shaped colony. pH 4 and 4.5 were the most favorable range for Ld45E growth within 12 h of incubation. Ld45E showed a strong adhesion ability onto HeLa cells (86%) and negative hemolytic activities. Ld45E was also sensitive to ceftriaxone, cefuroxime, ciprofloxacin, and doxycycline. We found that it had a good autoaggregation ability of 80%. Regarding antagonistic properties, Ld45E culture showed strong antimicrobial activity against GBS, E. coli, and Klebsiella spp. but only a moderate effect on C. parapsilosis. Cell-free supernatant of Ld45E exerted the most potent inhibitory effects at 40 °C against all genital pathogens, whereas bacteriocin showed a robust inhibition at 37 °C and 40 °C. The highest co-aggregation affinity was observed with GBS (81%) and E. coli (40%). Competition ability against the adhesion of GBS (80%), E. coli (76%), Klebsiella (72%), and C. parapsilosis (58%) was found. Ld45E was able to reduce the induction of the proinflammatory protein IL-17.

CONCLUSIONS

Ld45E possessed antimicrobial and immunoregulatory properties, with better cell-on-cell activity than supernatant activity. Thus, Ld45E is a potential probiotic candidate for adjunct therapy to address vaginal infections.

Probiotic disruption of quorum sensing reduces virulence and increases cefoxitin sensitivity in methicillin-resistant Staphylococcus aureus

Therapies which target quorum sensing (QS) systems that regulate virulence in methicillin-resistant Staphylococcus aureus (MRSA) are a promising alternative to antibiotics. QS systems play a crucial in the regulation of MRSA antibiotic resistance, exotoxin production, antioxidant protection and immune cell evasion, and are therefore attractive therapeutic targets to reduce the virulence of a pathogen. In the present work the the effects of bioactive peptides isolated from two strains of lactic acid bacteria were tested against antibiotic resistance, carotenoid production, resistance to oxidative killing and biofilm structure in two clinical MRSA isolates. The results obtained from fractional-inhibitory concentration assays with bulk and semi-purified bioactive molecules showed a significant synergistic effect increasing cefoxitin mediated killing of MRSA. This was coupled to a six-fold decrease of the major membrane pigment staphyloxanthin, and a 99% increase in susceptibility to oxidative stress mediated killing. Real-time quantitative PCR analysis of the QS-genes agrA and luxS, showed differential expression between MRSA strains, and a significant downregulation of the hemolysin gene hla. Light microscopy and scanning electron microscopy revealed alteration in biofilm formation and clustering behavior. These results demonstrate that bioactive metabolites may be effectively applied in tandem with beta-lactam antibiotics to sensitize MRSA to cefoxitin. Moreover, these results shown that several key QS-controlled virulence mechanisms are diminished by probiotic metabolites.

Probiotics in vaginal health

Bacterial vaginosis, a type of vaginal inflammation, can be considered the main reason for abnormal discharges of the vagina and vaginal dysbiosis during reproductive years. Epidemiological investigations of females suffering from vaginitis demonstrated that at least 30% to 50% of all women had Bacterial vaginosis (BV). One of the fields of treatment is the use of probiotics, probiotics are commonly defined as viable microorganisms (yeasts or bacteria) that can positively affect the health of their hosts. They are used in foods, notably fermented milk products, and medicine-related products. The development of new probiotic strains is aimed at more active advantageous organisms. Lactobacillus species are the dominant bacteria in a normal vagina that can decrease the pH of the vagina by the production of lactic acid. A number of lactobacilli types can produce hydrogen peroxide as well. The presence of hydrogen peroxide-induced low pH can prevent the growth of several other microorganisms. The vaginal flora of BV cases can modify by replacing the Lactobacillus species with a high density of anaerobic bacteria (i.e. Mobiluncus sp. Bacteroides sp.), Mycoplasma hominis, and Gardnerella vaginalis. More vaginal infections are treated with medications, while there is a possibility of recurrence and chronic infection because of the adverse effects on the indigenous lactobacilli. Probiotics and prebiotics have shown capacities for optimizing, maintaining, and restoring the vaginal microflora. Therefore, biotherapeutics can offer alternative approaches to reduce infections of the vagina and thus promote consumers' health.

Amphiphilic sodium alginate-polylysine hydrogel with high antibacterial efficiency in a wide pH range

Bacterial infection is a major pathological factor leading to persistent wounds. With the aging of population, wound infection has gradually become a global health-issue. The wound site environment is complicated, and the pH changes dynamically during healing. Therefore, there is an urgent need for new antibacterial materials that can adapt to a wide pH range. To achieve this goal, we developed a thymol-oligomeric tannic acid/amphiphilic sodium alginate-polylysine hydrogel film, which exhibited excellent antibacterial efficacy in the pH range from 4 to 9, achieving the highest achievable 99.993 % (4.2 log units) and 99.62 % (2.4 log units) against Gram-positive Staphylococcus aureus and Gram-negative Escherichia coli, respectively. The hydrogel films exhibited excellent cytocompatibility, suggesting that the materials are promising as a novel wound healing material without the concern of biosafety.

Emergence of infectious diseases and role of advanced nanomaterials in point-of-care diagnostics: a review

Infectious outbreaks are the foremost global public health concern, challenging the current healthcare system, which claims millions of lives annually. The most crucial way to control an infectious outbreak is by early detection through point-of-care (POC) diagnostics. POC diagnostics are highly advantageous owing to the prompt diagnosis, which is economical, simple and highly efficient with remote access capabilities. In particular, utilization of nanomaterials to architect POC devices has enabled highly integrated and portable (compact) devices with enhanced efficiency. As such, this review will detail the factors influencing the emergence of infectious diseases and methods for fast and accurate detection, thus elucidating the underlying factors of these infections. Furthermore, it comprehensively highlights the importance of different nanomaterials in POCs to detect nucleic acid, whole pathogens, proteins and antibody detection systems. Finally, we summarize findings reported on nanomaterials based on advanced POCs such as lab-on-chip, lab-on-disc-devices, point-of-action and hospital-on-chip. To this end, we discuss the challenges, potential solutions, prospects of integrating internet-of-things, artificial intelligence, 5G communications and data clouding to achieve intelligent POCs.

pH Responsive Antibacterial Hydrogel Utilizing Catechol-Boronate Complexation Chemistry

Bacteria such as Methicillin-resistant Staphylococcus aureus (MRSA) causes acidic microenvironment during infection. A biomaterial that exhibits tunable antimicrobial property in a pH dependent manner is potentially attractive. Herein, we presented a novel antibacterial hydrogel consisting of pH responsive and reversible catechol-boronate linkage formed between intrinsically bactericidal chlorinated catechol (catechol-Cl) and phenylboronic acid. Fourier transformed infrared spectroscopy (FTIR), oscillatory rheometry, and Johnson Kendall Roberts (JKR) contact mechanics testing confirmed the formation and dissociation of the complex in a pH dependent manner. When the hydrogel was treated with an acidic buffer (pH 3), the hydrogel exhibited excellent antimicrobial property against multiple strains of Gram-positive and negative bacteria including MRSA (up to 4 log₁₀ reduction from 10⁸ colony forming units/mL). At an acidic pH, catechol-Cl was unbound from the phenylboronic acid and available for killing bacteria. Conversely, when the hydrogel was treated with a basic buffer (pH 8.5), the hydrogel lost its antimicrobial property but also became non-cytotoxic. At a basic pH, the formation of catechol-boronate complex effectively reduce the exposure of the cytotoxic catechol-Cl to the surrounding. When further incubating the hydrogel in an acidic pH, the reversible complex dissociated to re-expose catechol-Cl and the hydrogel recovered its antibacterial property. Overall, the combination of catechol-Cl and phenylboronic acid provide a new strategy for designing hydrogels with pH responsive antibacterial activity and reduced cytotoxicity.

Heme cross-feeding can augment Staphylococcus aureus and Enterococcus faecalis dual species biofilms

The contribution of biofilms to virulence and as a barrier to treatment is well-established for Staphylococcus aureus and Enterococcus faecalis, both nosocomial pathogens frequently isolated from biofilm-associated infections. Despite frequent co-isolation, their interactions in biofilms have not been well-characterized. We report that in combination, these two species can give rise to augmented biofilms biomass that is dependent on the activation of E. faecalis aerobic respiration. In E. faecalis, respiration requires both exogenous heme to activate the cydAB-encoded heme-dependent cytochrome bd, and the availability of O₂. We determined that the ABC transporter encoded by cydDC contributes to heme import. In dual species biofilms, S. aureus provides the heme to activate E. faecalis respiration. S. aureus mutants deficient in heme biosynthesis were unable to augment biofilms whereas heme alone is sufficient to augment E. faecalis mono-species biofilms. Our results demonstrate that S. aureus-derived heme, likely in the form of released hemoproteins, promotes E. faecalis biofilm formation, and that E. faecalis gelatinase activity facilitates heme extraction from hemoproteins. This interspecies interaction and metabolic cross-feeding may explain the frequent co-occurrence of these microbes in biofilm-associated infections.

Genome-Scale Metabolic Modelling Approach to Understand the Metabolism of the Opportunistic Human Pathogen Staphylococcus epidermidis RP62A

Staphylococcus epidermidis is a common commensal of collagen-rich regions of the body, such as the skin, but also represents a threat to patients with medical implants (joints and heart), and to preterm babies. Far less studied than Staphylococcus aureus, the mechanisms behind this increasingly recognised pathogenicity are yet to be fully understood. Improving our knowledge of the metabolic processes that allow S. epidermidis to colonise different body sites is key to defining its pathogenic potential. Thus, we have constructed a fully curated, genome-scale metabolic model for S. epidermidis RP62A, and investigated its metabolic properties with a focus on substrate auxotrophies and its utilisation for energy and biomass production. Our results show that, although glucose is available in the medium, only a small portion of it enters the glycolytic pathways, whils most is utilised for the production of biofilm, storage and the structural components of biomass. Amino acids, proline, valine, alanine, glutamate and arginine, are preferred sources of energy and biomass production. In contrast to previous studies, we have shown that this strain has no real substrate auxotrophies, although removal of proline from the media has the highest impact on the model and the experimental growth characteristics. Further study is needed to determine the significance of proline, an abundant amino acid in collagen, in S. epidermidis colonisation.

Detection of Enterotoxigenic Potential of Staphylococcus aureus Isolates from Cheese Samples with Two Different Methods

The primary objective of our study was to detect the occurrence of enterotoxigenic Staphylococcus aureus in diverse types of cheese (cow's milk cheese and mixed milk cheese) samples from R.N. Macedonia. Cheese samples were analyzed for enumeration and isolation of the S. aureus strains according to ISO 6888-1. We detected the toxigenic potential of the strains by the use of the Enzyme Link Fluorescent Assay VIDAS system, and we confirmed the presence of the SEs (sea, seb, sec, sed, see) genes by multiplex PCR. The results showed that out of 270 samples of cheese, coagulase-positive staphylococci (CPS) were detected in 27 (10%), and coagulase-negative staphylococci in five samples (1.8%). Biochemically, all 27 CPS samples were confirmed to be Staphylococcus aureus. With VIDAS SET2 test we confirmed that 11 isolates are producers of one of the toxins limited by the test. With the conventional PCR we confirmed genes in only 7 isolates. Most common detected gene was seb n=3 (42.8%), followed by sea n=2 (28.6%), and sec n=2 (28.6%). Additionally, sed and see genes were not detected in any of the S. aureus isolates. Discrepancies between the two test methods for detection of enterotoxigenic potential are not uncommon. The presence of viable Staphylococcus aureus cells that have enterotoxin potency demonstrates the importance of appropriate hygiene practices in the diary process and also the maintenance of the products in order to obtain a safe final product for the consumers.

Evaluation of antimicrobial compounds to inhibit growth of select Gram-positive pathogenic or antimicrobial resistant bacteria in air-exposed silage

Spoiled silages can harbor pathogenic and antimicrobial-resistant microbes. The potential of some antimicrobial additives to inhibit certain pathogenic and antimicrobial-resistant bacteria in air-exposed silage was measured using pure and mixed bacterial cultures. With pure cultures, laurate and monolaurin (5 mg·mL−1) caused decreases (P < 0.05) of 4 to >7 log10 colony-forming units (CFU)·mL−1 in Listeria monocytogenes and Enterococcus faecalis compared to controls. Ten-fold higher amounts of these inhibitors were needed to equivalently decrease staphylococci. 2-Nitropropanol (1 mg·mL−1) decreased (P < 0.05) E. faecalis and L. monocytogenes 2.9–3.8 and 2.4–7.2 log10 CFU·mL−1 after 6 and 24 h incubations, respectively. In air-exposed whole-plant corn silage the inhibitors caused decreases, although not necessarily significant, of 0.7–2.2 log10 CFU·mL−1 in L. monocytogenes, staphylococci and culturable aerobes after 24 h incubation, with modest yet significant (P < 0.05) inhibition (<0.1–0.3 log10 CFU·mL−1) of yeasts and molds. Tests for carry-over effects against ruminal microbes revealed laurate, monolaurin, and 2-nitropropanol inhibited methanogenesis by >50% (P < 0.05) after 24 h incubation and inhibited L. monocytogenes and enterococci. The antimicrobial activities exhibited by these compounds may yield opportunities to optimize their use to rescue spoiled silages.

Staphylococcus aureus in Substrates for Black Soldier Fly Larvae (Hermetia illucens) and Its Dynamics during Rearing

Black soldier fly larvae (BSFL; Hermetia illucens) are promising insects for the conversion of organic waste streams into valuable biomolecules. Such waste streams can contain foodborne pathogens. To assess this risk factor, this study evaluated the presence of Staphylococcus aureus in waste streams as a substrate ingredient for BSFL production as well as in the rearing process. First, the general microbiological quality and the occurrence of S. aureus were investigated for different waste streams. Staphylococcus aureus was abundantly present. Control of pH and water activity should avoid pathogens, which cannot grow in single-substrate ingredients, redeveloping when mixing streams for optimal substrate conditions for BSFL production. Next, it was investigated whether S. aureus present in the substrate was ingested and/or eradicated by BSFL. In inoculation trials, with S. aureus added to chicken feed as the substrate at 3 or 7 log CFU/g, the larvae showed a reducing effect on S. aureus. After 6 days, S. aureus counts were below the detection limit (2.0 log CFU/g) in all larvae samples and decreased in the substrate to <2.0 and <3.1 log CFU/g for inoculation levels of 3 and 7 log CFU/g, respectively. While this is promising, it is still recommended to monitor and control this pathogen in BSFL rearing. Intriguingly, screening of antimicrobial activity of dominant microorganisms associated with BSFL showed a clear activity of Trichosporon isolates against S. aureus. Future research should explore whether Trichosporon, which is frequently observed in BSFL, plays a role in controlling specific microorganisms, such as S. aureus. IMPORTANCE Given the increasing need for (more sustainable) methods to upcycle organic waste streams, the interest to rear insects, like black soldier fly larvae (BSFL), on such streams is increasing. This study reveals that S. aureus is abundantly present in such waste streams, which might be a point of attention for insect producers. At the same time, it reveals that when S. aureus was inoculated in chicken feed as the substrate, it was not detected in the larvae and was reduced in the substrate after 6 days. Future inoculation trials should investigate whether this reduction is substrate dependent or not. Toward the future, the role of the BSFL microbiota in controlling intestinal bacterial community homeostasis should be explored, because one of the dominant microorganisms associated with BSFL, Trichosporon spp., showed clear activity against S. aureus.

Lactic Acid Bacteria-Fermentable Cereal- and Pseudocereal-Based Beverages

Plant beverages are becoming more popular, and fermented cereal- or pseudocereal-based beverages are increasingly used as alternatives for fermented products made from cow milk. This review aimed to describe the basic components of cereal- or pseudocereal-based beverages and determine the feasibility of fermenting them with lactic acid bacteria (LAB) to obtain products with live and active LAB cells and increased dietary value. The technology used for obtaining cereal- or pseudocereal-based milk substitutes primarily involves the extraction of selected plant material, and the obtained beverages differ in their chemical composition and nutritional value (content of proteins, lipids, and carbohydrates, glycemic index, etc.) due to the chemical diversity of the cereal and pseudocereal raw materials and the operations used for their production. Beverages made from cereals or pseudocereals are an excellent matrix for the growth of LAB, and the lactic acid fermentation not only produces desirable changes in the flavor of fermented beverages and the biological availability of nutrients but also contributes to the formation of functional compounds (e.g., B vitamins).

In Silico and In Vitro Evaluation of the Antimicrobial Potential of Bacillus cereus Isolated from Apis dorsata Gut against Neisseria gonorrhoeae

Antimicrobial resistance is a major public health and development concern on a global scale. The increasing resistance of the pathogenic bacteria Neisseria gonorrhoeae to antibiotics necessitates efforts to identify potential alternative antibiotics from nature, including insects, which are already recognized as a source of natural antibiotics by the scientific community. This study aimed to determine the potential of components of gut-associated bacteria isolated from Apis dorsata, an Asian giant honeybee, as an antibacterial against N. gonorrhoeae by in vitro and in silico methods as an initial process in the stage of new drug discovery. The identified gut-associated bacteria of A. dorsata included Acinetobacter indicus and Bacillus cereus with 100% identity to referenced bacteria from GenBank. Cell-free culture supernatants (CFCS) of B. cereus had a very strong antibacterial activity against N. gonorrhoeae in an in vitro antibacterial testing. Meanwhile, molecular docking revealed that antimicrobial lipopeptides from B. cereus (surfactin, fengycin, and iturin A) had a comparable value of binding-free energy (BFE) with the target protein receptor for N. gonorrhoeae, namely penicillin-binding protein (PBP) 1 and PBP2 when compared with the ceftriaxone, cefixime, and doxycycline. The molecular dynamics simulation (MDS) study revealed that the surfactin remains stable at the active site of PBP2 despite the alteration of the H-bond and hydrophobic interactions. According to this finding, surfactin has the greatest antibacterial potential against PBP2 of N. gonorrhoeae.

Microbiota and nanoparticles: Description and interactions

The healthy human body is inhabited with a large number of bacteria, forming natural flora. It is even estimated that for a human body, its amount of DNA is less important that its bacterial genetic material. This flora plays major roles in the sickness and health of the human body and any change in its composition may lead to different diseases. Nanoparticles are widely used in numerous fields: cosmetics, food, industry, and as drug delivery carrier in the medical field. Being included in these various applications, nanoparticles may interact with the human body at various levels and with different mechanisms. These interactions differ depending on the nanoparticle nature, its structure, its concentration and manifest in different ways on the microbiota, leading to its destabilization, its restoring or showing no toxic effect. Nanoparticles may also be used as a vehicle to regulate the microbiota or to treat some of its diseases.

Livestock-associated methicillin-resistant Staphylococcus aureus (LA-MRSA) prevalence in humans in close contact with animals and measures to reduce on-farm colonisation

Since the 1940s, Staphylococcus aureus has adapted to the use of different antimicrobials to treat infections. Although S. aureus can act as a commensal bacterium, some strains are facultative pathogens and acquiring them can be fatal. In particular, treating infections caused by S. aureus with acquired antimicrobial resistance is problematic, as their treatment is more difficult. Some of these S. aureus variants are methicillin-resistant S. aureus (MRSA) with prevalence across the globe in health-care facilities, community settings and on livestock farms. Apart from humans, MRSA can colonise other animal species, and because of this, resistance to new antimicrobials can appear and jump between species. Livestock and companion animals are particularly important in this regard considering the relatively high usage of antimicrobials in these species. There is a risk to humans who come into direct contact with animals acquiring MRSA but there is also the risk of animals acquiring MRSA from colonised humans. In this review, we summarise studies conducted worldwide to characterise the prevalence of MRSA in veterinarians, farmers and other personnel who come into close contact with animals. Finally, alternative treatment, preventive measures and on-farm strategies to reduce MRSA introduction to a farm and carriage within a herd are discussed.

Acetate Activates Lactobacillus Bacteriocin Synthesis by Controlling Quorum Sensing

Bacteriocins are useful for controlling the composition of microorganisms in fermented food. Bacteriocin synthesis is regulated by quorum sensing mediated by autoinducing peptides. In addition, short-chain fatty acids, especially acetic acid, reportedly regulate bacteriocin synthesis. Five histidine kinases that regulated the synthesis of bacteriocins were selected to verify their interactions with acetate. Acetate activated the kinase activity of PlnB, SppK, and HpK3 in vitro and increased the yield of their cognate bacteriocins plantaricin EF, sakacin A, and rhamnosin B in vivo. The antimicrobial activity against Staphylococcus aureus of the fermentation supernatants of Lactobacillus plantarum, Lactobacillus sakei, and Lactobacillus rhamnosus with addition of acetate increased to 298%, 198%, and 289%, respectively, compared with that in the absence of acetate. Our study elucidated the activation activity of acetate in bacteriocin synthesis, and it might provide a potential strategy to increase the production of bacteriocin produced by Lactobacillus. IMPORTANCE Bacteriocins produced by lactic acid bacteria (LAB) are particularly useful in food preservation and food safety. Bacteriocins might increase bacterial competitive advantage against the indigenous microbiota of the intestines; at the same time, bacteriocins could limit the growth of undesired microorganisms in yogurt and other dairy products. This study confirmed that three kinds of histidine kinases were activated by acetate and upregulated bacteriocin synthesis both in vitro and in vivo. The increasing yield of bacteriocins reduced the number of pathogens and increased the number of probiotics in milk. Bacteriocin synthesis activation by acetate may have a broad application in the preservation of dairy products and forage silage.

A Study on the Synbiotic Composition of Bifidobacterium bifidum and Fructans from Arctium lappa Roots and Helianthus tuberosus Tubers against Staphylococcus aureus

A number of mechanisms have been proposed explaining probiotics and prebiotics benefit human health, in particular, probiotics have a suppression effect on pathogen growth that can be enhanced with the introduction of prebiotics. In vitro models enhanced with computational biology can be useful for selecting a composition with prebiotics from new plant sources with the greatest synergism. Water extracts from burdock root and Jerusalem artichoke tubers were purified by ultrafiltration and activated charcoal and concentrated on a rotary evaporator. Fructans were precipitated with various concentrations of ethanol. Bifidobacterium bifidum 8 VKPM AC-2136 and Staphylococcus aureus ATCC 43300 strains were applied to estimate the synbiotic effect. The growth of bifidobacteria and staphylococci in monocultures and cocultures in broths with glucose, commercial prebiotics, as well as isolated fructans were studied. The minimum inhibitory concentrations (MICs) of lactic and acetic acids for the Staphylococcus strain were determined. A quantitative model joining the formation of organic acids by probiotics as antagonism factors and the MICs of pathogens (as the measure of their inhibition) was tested in cocultures and showed a high predictive value (R2 ≥ 0.86). The synbiotic factor obtained from the model was calculated based on the experimental data and obtained constants. Fructans precipitated with 20% ethanol and Bifidobacterium bifidum have the greater synergism against Staphylococcus.

Quantitative Microbiological Analysis of Artisanal Stretched Cheese Manufacture

To evaluate the behavior of the relevant microbial populations during stretched cheese production, quantitative microbiological analysis was performed during the critical steps of the preparation. The obtained data distributions proved statistically significant increases in all indicators, on average by 4.55 ± 0.64 log CFU/g of presumptive lactococci counts, 4.06 ± 0.61 of lactobacilli, 1.53 ± 0.57 log CFU/g of coliforms, 2.42 ± 0.67 log CFU/g of Escherichia coli, 1.53 ± 0.75 log CFU/g of yeasts and molds, and 0.99 ± 0.27 log CFU/g of presumptive Staphylococcus aureus, from the early stage of milk coagulation until curd ripening (0–24 h). The following steaming/stretching process caused reductions in viable counts with the most significant inactivation effect on coliform bacteria, including E. coli (−4.0 ± 1.0 log CFU/g). Total viable counts and yeasts and molds showed 2 and almost 3 log reduction (−2.2 ± 1.1 log CFU/g and −2.6 ± 0.9 log CFU/g), respectively. The lowest decreases in presumptive S. aureus counts were estimated at the level of −1.50 ± 0.64 log CFU/g. The counts of yeasts and molds showed the best indicatory function during the entire storage period of vacuum-packaged cheeses at 6 °C.

Fungal diversity of "solom" a Ghanaian traditional beverage of millet (Pennisetum glaucum)

The association of cereals with fungi cannot be disregarded as their manifestation in our foods poses serious health risks. The aim of this study was to investigate the mycofloral (fungal) and chemical (pH) qualities of the "solom" (beverage of millet) available for consumption from their respective sales points in Ho. "Solom" a cereal beverage of millet was sampled from ten (10) different locations in the Ho Municipality of Ghana and evaluated for their pH, fungal counts, and species diversity. Mycological analyses were done on Oxytetracycline Glucose Yeast Extract (OGYE) and Dichloran Rose Bengal Chloramphenicol (DRBC) media from three (3) points per location using serial dilution. A total of fourteen (14) fungal species belonging to eight (8) genera were isolated on both media; Aspergillus (A. niger, A. flavus, A. fumigatus, A. parasiticus, A. alutaceaus, A. terreus), Rhizopus (R. stolonifer), Mucor (M. racemosus), Fusarium (F. oxysporum), Penicillium (P. digitatum, P. verucosum), Cladosporium (C. cladosporoides), Curvularia (C. lunata), and Rhodotorula sp. were recorded. Fungal counts on both media ranged between 1.68 ± 0.8 and 4.11 ± 0.9 log10 CFU/ml. There were statistically significant (p < .05) differences observed in the samples from different locations. The values of pH recorded were in the range of 3.03 ± 0.09-4.03 ± 0.23 and showed no significant differences (p > .05) among them. All samples were found to be in the acceptable range of values prescribed by the International Commission for Microbiological Specification of Foods (ICMSF, 1998). Good Manufacturing Practices (GMP) and Good Hygiene Practices (GHP) should be employed to enhance food safety.

Improvement of Bacterial Vaginosis by Oral Lactobacillus Supplement: A Randomized, Double-Blinded Trial

Bacterial vaginosis (BV) is the most common vaginal infection globally, with a high recurrent rate after antibiotic treatment. Probiotics consumption is known to improve BV with different efficacy among species or strains. After in vitro selection of Lactobacillus strains with growth inhibition and preventing adhesion to HeLa cervical epithelial cells, a randomized and double-blinded trial of two Lactobacillus formula, namely, VGA-1 and VGA-2, in BV patients with Nugent scores of 4–10 was conducted. Among 37 subjects who completed the trial, we observed significantly decreased Nugent scores in both VGA-1 (n = 18) and VGA-2 (n = 19) consumption groups. VGA-1 consumption significantly improved vaginal discharge odor/color and itching at both 2-week and 4-week-consumption, but those only observed after a 4-week-consumption in the VGA-2 group. We also observed a tendency to reduce recurrent rates among enrolled participants after VGA-1 or VGA-2 consumption. The improvement effect of VGA-1/VGA-2 was associated with the significant reduction of interleukin-6 expression after 4-week-consumption and the restoration of normal vaginal microflora by quantitative polymerase chain reaction analysis. In conclusion, VGA-1 or VGA-2 displayed beneficial effects in BV patients, but the VGA-1 formula showed a better efficacy, potentially used for BV intervention.

Effect of Lactic Acid Bacteria Addition on the Microbiological Safety of Pasta-Filata Types of Cheeses

In this work, the effects of different combinations of lactic acid bacteria (LAB) on the growth of coagulase-positive staphylococci (CPS) and Escherichia coli were evaluated during ripening of 23 curd cheeses, and their subsequent behavior during the manufacture and storage of pasta-filata cheeses was characterized. Three groups of cheeses were prepared in total: first, control cheeses from raw milk without LAB addition; further pasteurized milk cheeses with LAB, CPS and E. coli intentional inoculation; and finally, raw milk cheeses with LAB added. The aim was to compare the effect of LAB from starter culture, and also in combination with native LAB, and to evaluate the LAB effect as a group, and further to suggest the culture with the best inhibitory potential. Based on the results, counts of CPS increased over 24 h in control curd cheese by 1.76 ± 0.56 log CFU/g. On the other hand, in raw milk cheeses with the addition of starter culture, the increase in CPS counts by 0.76 ± 0.87 log CFU/g was noticed. Counts of E. coli increased during the first 24 h of curd manufacture by 3.56 ± 0.41 log CFU/g in cheeses without LAB addition. Contrary to this, using of LAB cultures resulted in an increase in E. coli counts by only 1.40 ± 1.07 log CFU/g. After steaming at 63.6 ± 1.9°C for 7.2 ± 2.1 min (temperature of heated acidified curd was 54.9 ± 1.7°C), CPS decreased by 0.58 ± 1.12 log CFU/g, and E. coli decreased by 1.23 ± 0.97 log CFU/g in all cheeses, regardless of LAB addition. Finally, during storage of cheeses at 6 ± 0.5°C for 28 days, the levels of E. coli in control cheeses and in raw milk LAB-enriched cheeses reached levels of 2.07 ± 2.28 log CFU/g and 1.20 ± 0.85 log CFU/g, respectively. In addition, the counts of CPS at the end of storage met the criteria of EU Commission Regulation (EC) No. 1441/2007 (2007) (less than 4 log CFU/g) in all manufactured cheeses with added LAB culture, while in the control raw milk cheeses, a level of 3.80 ± 1.22 log CFU/g was observed. Regarding the culture used, the best microbiological inhibitory effect in 28-day-old cheeses was reached by the combination of Fresco culture with Lacticaseibacillus rhamnosus GG, and the best sensory properties were judged to be those for cheeses manufactured with Culture A. A moderate negative effect of storage on overall sensory acceptance was noted, according to the final evaluation of overall acceptability of pasta-filata cheeses. The most satisfactory overall acceptability after 28 days of storage at 6°C was reached for cheese with the addition of culture A.

Probiotic characteristics of Lactobacillus strains isolated from cheese and their antibacterial properties against gastrointestinal tract pathogens

In the present study, four Lactobacillus strains from the cheese were analyzed for its probiotic potential against enteropathogenic bacteria. The probiotic properties of the selected strains were also analyzed and the selected bacterial strains showed high tolerance in bile salts and organic acid. The strain L. plantarum LP049 showed maximum survival rate (92 ± 4.2% and 93.3 ± 2%) after 3 h of treatment at 0.25% (w/v) bile salts and 0.25% (w/v) organic acid concentrations. The ability of the Lactobacillus strains to adhere to human epithelial cells (HT-29 cell lines) was evaluated and L. plantarum LP049 showed maximum adhesion property (19.2 ± 1.1%) than other tested strains. The Lactobacillus strains produced lactic acid at various concentrations. Compared with other strains, maximum level of lactic acid (3.1 g/L), hydrogen peroxide (4.31 mM) and bacteriocin (31 AU/mg) was detected in LB049. The inhibitory activity of culture supernatant against various bacterial pathogens was observed. The zone of inhibition ranged between 6 ± 2 mm and 23 ± 2 mm. The cell free extract showed activity against, Escherichia coli (ATCC 10536), Salmonella enteritidis (ATCC 13076), Shigella flexneri (ATCC 29903), and Enterococcus faecium (ATCC 8459). Consequently, L. plantarum LP049 may be considered as a potential candidate for the production of novel bioactive metabolites for therapeutic and bio-protective applications.

Dietary administration of probiotic Lactobacillus rhamnosus modulates the neurological toxicities of perfluorobutanesulfonate in zebrafish

Perfluorobutanesulfonate (PFBS), an aquatic pollutant of emerging concern, is found to disturb the neural signaling along gut-brain axis, whereas probiotic additives have been applied to improve neuroendocrine function of teleosts. Both PFBS and probiotics can commonly target nervous system. However, whether and how probiotic bacteria can modulate the neurotoxicities of PFBS remain not explored. It is thus necessary to elucidate the probiotic modulation of PFBS neurotoxicity, which can provide implications to the application of probiotic bacteria in aquaculture industry. In the present study, adult zebrafish were exposed to 0, 10 and 100 μg/L PFBS with or without dietary administration of probiotic Lactobacillus rhamnosus. Interaction between PFBS and probiotic along gut-brain axis was examined, covering three dominant pathways (i.e., neurotransmission, immune response and hypothalamic-pituitary-adrenal (HPA) axis). The results showed that, compared to the single effects, PFBS and probiotic coexposure significantly altered the acetylcholinesterase activity and neurotransmitter profiles in gut and brain of zebrafish, with mild effects on neuronal integrity. Neurotransmitters closely correlated reciprocally in intestines, which, however, was distinct from the correlation profile in brains. In addition, PFBS and probiotic were combined to impact brain health through absorption of bacterial lipopolysaccharides and production of inflammatory cytokines. Relative to neurotransmission and immune signaling, HPA axis was not involved in the neurotoxicological interaction between PFBS and probiotic. Furthermore, it needs to point out that interactive modes between PFBS and probiotic varied a lot, depending on exposure concentrations, sex and toxic indices. Overall, the present study provided the first evidence that probiotic supplement could dynamically modulate the neurotoxicities of PFBS in teleost.

The effect of protective cultures on Staphylococcus aureus growth and enterotoxin production

Staphylococcus aureus is the causative agent of staphylococcal food poisoning and is a common contaminant in milk. Despite efforts to control S. aureus, recalls and outbreaks continue to occur, highlighting the need for additional interventions. This study determined the potential for protective cultures (PC) that are commercially available to producers to control S. aureus growth in raw milk and attenuate virulence by impeding staphylococcal enterotoxin (SE) production in raw milk and laboratory medium. Cultures of Hafnia alvei and Lactococcus lactis effectively inhibited S. aureus growth in raw milk to counts ~5 log CFU/mL lower than control when cocultured following a cheesemaking time and temperature profile; two cultures of Lactobacillus plantarum inhibited growth to ~1.5 log CFU/mL less than control. Cocultures of S. aureus with Lc. lactis, H. alvei and Lb. plantarum in raw milk reduced SE levels by 24.9%, 62.4%, and 76%, respectively. Lc. lactis also decreased SE production in raw milk in the absence of PC-mediated growth inhibition. Significant reductions in SE production in the absence of pathogen growth inhibition were also achieved in laboratory medium. Together, these results demonstrate the potential for PCs to inhibit S. aureus growth and impede SE production in the absence of growth inhibition.

Antimicrobial Activity of a Phage Mixture and a Lactic Acid Bacterium against Staphylococcus aureus from Bovine Mastitis

The antimicrobial activity of a phage mixture and a lactic acid bacterium against Staphylococcus aureus isolates from bovine origin was investigated in vitro with regard to possible applications in the therapy of udder inflammation (mastitis) caused by bacterial infections. The S. aureus isolates used for inoculation derived from quarter foremilk samples of mastitis cases. For the examination of the antimicrobial activity, the reduction of the S. aureus germ density was determined [log10 cfu/mL]. The phage mixture consisted of the three obligatory lytic and S. aureus-specific phages STA1.ST29, EB1.ST11 and EB1.ST27 (1:1:1). The selected Lactobacillus plantarum strain with proven antimicrobial properties and the phage mixture were tested against S. aureus in milk, both alone and in combination. The application of the lactic acid bacterium showed only a low reduction ability for a 24 h incubation period. The bacteriophage mixture as well as its combination with the lactic acid bacterium showed high antimicrobial activity against S. aureus for a 24 h incubation period at 37 °C, with only the phage mixture showing significance.

Microbiological and physicochemical changes during ripening in Bulgarian white brined cheese made from raw cow milk

The main microbiological hazards of raw milk cheese are associated with Listeria monocytogenes, Escherichia coli and Staphylococcus aureus. Due to its high nutritional value, cheese is an excellent medium for the growth of these pathogens. This study was aimed to observe microbial dynamics of Bulgarian white brined cheese during cheese production and ripening. Microbiological analysis included determination of Staphylococcus aureus, Listeria spp. and Escherichia coli counts. Some physicochemical parameters, such as total titratable acidity, sodium chloride content, water activity and pH were also examined. Results revealed statistically significant increase in bacterial counts after cheesemaking steps and decrease at the end of the ripening period. Listeria monocytogenes was not detected in any of the cheese samples. Raw milk cheese was of unsatisfactory quality that emphasises the need for applying and maintaining good hygiene practices along the food chain to prevent microbial contamination and growth

Characterization and comparison of metaproteomes in traditional and commercial dajiang, a fermented soybean paste in northeast China

Dajiang is a popular Chinese fermented soybean condiment. Here, a comparative metaproteomic analysis of traditional and commercial dajiang was performed during fermentation. A total of 4250 and 1421 peptide sequences were obtained from 3493 and 1987 proteins in traditional and commercial dajiang, respectively. 4299 differentially expressed microbial proteins show a high metabolic heterogeneity between the two types of dajiang. The KEGG annotation indicated that there were some pathways related to human diseases, which suggest that some microbes in traditional dajiang fermentation may have greater food safety hazards. In combination with qualitative metabolomic analysis, we further traced metabolic intermediates and key enzymes in several main fermentation pathways of dajiang to be mainly affiliated with Penicillium, Tetracoccus and Bacillus in traditional samples, as well as Aspergilus in commercial samples. These results could provide information for the selection of strains that are more suitable to produce high quality dajiang and other fermented products.

Probiotics for the treatment of women with bacterial vaginosis: A systematic review and meta-analysis of randomized clinical trials

This systematic review and meta-analysis systematically evaluated the efficacy of probiotic monotherapy and combination therapy for bacterial vaginosis (BV). Published randomized controlled trials were searched in the Cochrane Library, PubMed, EMBASE, OVID Database and ClinicalTrials.gov from the inception dates to 12 July 2019. The literature was screened and evaluated according to the inclusion criteria, and the data were analysed by a random effect model. A chi-square test was used to test heterogeneity between trials. This study included 13 randomized controlled trials (RCTs), which included 1258 patients, and the cure rate of BV was analysed. Three RCTs compared probiotics with a placebo (control) [risk ratios (RR) = 4.39, 95% CI (2.05, 9.41), P = 0.0001]. Two RCTs compared probiotics with antibiotics (control) [RR = 1.03, 95% CI (0.38, 2.81), P = 0.95]. Nine of 13 RCTs compared the combination of probiotics and antibiotics with antibiotics alone [RR = 1.28, 95% CI (1.05, 1.56), P = 0.02]. Despite the high heterogeneity of the pooled analysis, neither the subgroup analysis results nor the sensitivity analysis results were statistically significant. Probiotics may have a positive effect on the treatment of BV, but there is a lack of strong evidence.

Nitroso-hemoglobin Increased the Color Stability and Inhibited the Pathogenic Bacteria in a Minced Beef Model: A Combined Low-field NMR Study

This study mainly investigated the improvement effect of nitroso-hemoglobin (NO-Hb) and four lactic acid bacteria (LAB) (Streptococcus thermophiles, Lactobacillus bulgaricus, Lactobacillus casei, and Montessori enterococcus) on the color and microbiological qualities of raw beef. Three strains of Escherichia coli, Staphylococcus, Salmonella, and Pseudomonas were used as pathogenic bacteria. The results showed that both NO-Hb and LAB could enhance the color stability and scavenged the spoilage bacteria in a minced beef model. But the improvement effect of NO-Hb was more significant than LAB. This suggested that NO-Hb, as a novel ingredient, could be used as a promising substitute for nitrite in meat products to improve the color and safety of meat products. In addition, low field (LF)-NMR method has been established to be practicable to identify changes in the relaxation times of water and fat caused by different type of bacteria and the storage periods. The number of relaxation components in minced beef was affected by bacteria and increase of the storage period.

Maternal Dietary Protein Intake Influences Milk and Offspring Gut Microbial Diversity in a Rat (Rattus norvegicus) Model

Historically, investigators have assumed microorganisms identified in mother’s milk to be contaminants, but recent data suggest that milk microbiota may contribute to beneficial maternal effects. Microorganisms that colonize the gastrointestinal tracts of newborn mammals are derived, at least in part, from the maternal microbial population. Milk-derived microbiota is an important source of this microbial inocula and we hypothesized that the maternal diet contributes to variation in this microbial community. To evaluate the relationship between a mother’s diet and milk microbiome, we fed female rats a low- or high-protein diet and mated all individuals. Milk and cecal contents were collected from dams at peak lactation (14-day post-partum), and the bacterial composition of each community was assessed by 16S rRNA gene amplicon sequencing. Our findings revealed higher dietary protein intake decreased fecal microbial diversity but increased milk microbial and pup cecum diversity. Further, the higher dietary protein intake resulted in a greater abundance of potentially health-promoting bacteria, such as Lactobacillus spp. These data suggest that dietary protein levels contribute to significant shifts in the composition of maternal milk microbiota and that the functional consequences of these changes in microbial inocula might be biologically important and should be further explored.

Characterization of antimicrobial activity of three Lactobacillus plantarum strains isolated from Chinese traditional dairy food

Many Lactobacillus plantarum strains can secrete some antimicrobial substances and be added to food as antimicrobial agents and preservatives. In this study, three L. plantarum strains (P1, S11, and M7) with strong antimicrobial activity against three pathogenic bacteria were isolated from Xinjiang traditional dairy products. Five common organic acids produced by fermentation of strains play a key role in inhibiting three pathogenic bacteria. At the same pH, the antimicrobial activity of the fermentation broth against Escherichia coli and Salmonella is stronger than that of the organic acid alone. Thus, three kinds of antimicrobial agents (P1-1, M7-1, and S11-1) mixed with five common organic acids were produced. Moreover, the antimicrobial activity against Salmonella ASI.1174 of the antimicrobial agents was about 30% higher than that of the fermentation broth. In addition, organic acid antimicrobial agents combined in different proportions can inhibit different pathogenic bacteria. According to this result, it is a potential approach to develop novel antimicrobial agents used in food preservation by mixing different organic acids.

Rectal and Vaginal Eradication of Streptococcus agalactiae (GBS) in Pregnant Women by Using Lactobacillus salivarius CECT 9145, A Target-specific Probiotic Strain

Streptococcus agalactiae (Group B Streptococci, GBS) can cause severe neonatal sepsis. The recto-vaginal GBS screening of pregnant women and intrapartum antibiotic prophylaxis (IAP) to positive ones is one of the main preventive options. However, such a strategy has some limitations and there is a need for alternative approaches. Initially, the vaginal microbiota of 30 non-pregnant and 24 pregnant women, including the assessment of GBS colonization, was studied. Among the Lactobacillus isolates, 10 Lactobacillus salivarius strains were selected for further characterization. In vitro characterization revealed that L. salivarius CECT 9145 was the best candidate for GBS eradication. Its efficacy to eradicate GBS from the intestinal and vaginal tracts of pregnant women was evaluated in a pilot trial involving 57 healthy pregnant women. All the volunteers in the probiotic group (n = 25) were GBS-positive and consumed ~9 log10 cfu of L. salivarius CECT 9145 daily from week 26 to week 38. At the end of the trial (week 38), 72% and 68% of the women in this group were GBS-negative in the rectal and vaginal samples, respectively. L. salivarius CECT 9145 seems to be an efficient method to reduce the number of GBS-positive women during pregnancy, decreasing the number of women receiving IAP during delivery.

Invitro synergistic activity of lactic acid bacteria against multi-drug resistant staphylococci

Background

Multi-drug resistance in microorganisms is a serious problem at national as well as at a global level. Many researches have suggested alternatives to antibiotics with minimal or no major side effects. LAB is one of the most human-friendly probiotic strains known to mankind from times immemorial. With the objective to deal with progressing antibiotic resistance among microorganisms, the present work demonstrates the inhibitory activity of LAB consortium against MDR clinical isolates.

Methods

Total of nine hospital isolates of staphylococci were obtained and distinguished as S.aureus and coagulase-negative Staphylococcus (CoNS) based on their ability to ferment mannitol and form clumping with citrated plasma. All the test organisms were tested for antibiotic sensitivity with HiMedia (India) Octadisc Combi 92. Sets of L .plantarum, L .acidophilus and L.casei var. rhamnosus were prepared and tested against a standard culture of S.aureus NCIM 2129 by agar well diffusion method. To identify the primary source of substances responsible for inhibitory action, whole broth, cell-free supernatant, and cell lysate was prepared from the above-mentioned set. These were tested for their inhibitory action initially against standard S.aureus NCIM 2127, followed by clinical isolates.

Results

The antibiotic sensitivity profile revealed that all clinical isolates were multi-drug resistant. The maximum inhibitory potential was seen in a combination of the three LAB in the ratio 1:1:1. Highest antagonistic activity was observed with whole broth and cell lysate of LAB consortium. In liquid broth assay, the cell lysate of LAB consortium astoundingly exhibited up to 85% inhibition of multi-drug resistant Staphylococcus isolates.

Conclusions

Our results suggest antagonistic role of LAB metabolites against methicillin resistant staphylococci.

Behavior of Foodborne Pathogens Listeria monocytogenes and Staphylococcus aureus in Mixed-Species Biofilms Exposed to Biocides

In nature and man-made environments, microorganisms reside in mixed-species biofilms, in which the growth and metabolism of an organism are different from these behaviors in single-species biofilms. Pathogenic microorganisms may be protected against adverse treatments in mixed-species biofilms, leading to health risk for humans. Here, we developed two mixed five-species biofilms that included one or the other of the foodborne pathogens Listeria monocytogenes and Staphylococcus aureus The five species, including the pathogen, were isolated from a single food-processing environmental sample, thus mimicking the environmental community. In mature mixed five-species biofilms on stainless steel, the two pathogens remained at a constant level of ∼105 CFU/cm2 The mixed five-species biofilms as well as the pathogens in monospecies biofilms were exposed to biocides to determine any pathogen-protective effect of the mixed biofilm. Both pathogens and their associate microbial communities were reduced by peracetic acid treatments. S. aureus decreased by 4.6 log cycles in monospecies biofilms, but the pathogen was protected in the five-species biofilm and decreased by only 1.1 log cycles. Sessile cells of L. monocytogenes were affected to the same extent when in a monobiofilm or as a member of the mixed-species biofilm, decreasing by 3 log cycles when exposed to 0.0375% peracetic acid. When the pathogen was exchanged in each associated microbial community, S. aureus was eradicated, while there was no significant effect of the biocide on L. monocytogenes or the mixed community. This indicates that particular members or associations in the community offered the protective effect. Further studies are needed to clarify the mechanisms of biocide protection and to identify the species playing the protective role in microbial communities of biofilms.IMPORTANCE This study demonstrates that foodborne pathogens can be established in mixed-species biofilms and that this can protect them from biocide action. The protection is not due to specific characteristics of the pathogen, here S. aureus and L. monocytogenes, but likely caused by specific members or associations in the mixed-species biofilm. Biocide treatment and resistance are a challenge for many industries, and biocide efficacy should be tested on microorganisms growing in biofilms, preferably mixed systems, mimicking the application environment.

Use of a water-based probiotic to treat common gut pathogens

This work reports the anti-pathogenic effect of a commercially available water-based probiotic suspension, Symprove™, against three commonly encountered infectious organisms; Escherichia coli, methicillin-resistant Staphylococcus aureus (MRSA) and Shigella sonnei. An isothermal calorimetric assay was used to the monitor growth of the species individually and in binary combinations, while colony plate counting was used to enumerate viable cell numbers. It was observed that all pathogenic species were faster growing than the probiotic bacteria in Symprove™ after inoculation into growth medium yet in all instances bacterial enumeration at the end of the experiments revealed a significant reduction in the pathogen population compared with the controls. A control population between 10⁸ and 10⁹ CFU/ml was obtained for E. coli and S. sonnei whilst approximately 10⁶ CFU/ml was obtained for MRSA. Upon co-incubation for 48 h, no viable counts were obtained for E. coli; a 4-log reduction was obtained for S. sonnei whilst MRSA numbers were down to less than 10 cells/ml. The results show that Symprove™ has antipathogenic activity against E. coli, S. sonnei and MRSA.

Dialogue between Staphylococcus aureus SA15 and Lactococcus garvieae strains experiencing oxidative stress

Background

Staphylococcus aureus is an important foodborne pathogen. Lactococcus garvieae is a lactic acid bacterium found in dairy products; some of its strains are able to inhibit S. aureus growth by producing H₂O₂. Three strains of L. garvieae from different origins were tested for their ability to inhibit S. aureus SA15 growth. Two conditions were tested, one in which H₂O₂ was produced (high aeration) and another one in which it was not detected (low aeration). Several S. aureus genes related to stress, H₂O₂-response and virulence were examined in order to compare their level of expression depending on the inoculated L. garvieae strain. Simultaneous L. garvieae H₂O₂ metabolism gene expression was followed.

Results

The results showed that under high aeration condition, L. garvieae strains producing H₂O₂ (N201 and CL-1183) inhibited S. aureus SA15 growth and impaired its ability to deal with hydrogen peroxide by repressing H₂O₂-degrading genes. L. garvieae strains induced overexpression of S. aureus stress-response genes while cell division genes and virulence genes were repressed. A catalase treatment partially or completely restored the SA15 growth. In addition, the H₂O₂ non-producing L. garvieae strain (Lg2) did not cause any growth inhibition. The SA15 stress-response genes were down-regulated and cell division genes expression was not affected. Under low aeration condition, while none of the strains tested exhibited H₂O₂-production, the 3 L. garvieae strains inhibited S. aureus SA15 growth, but to a lesser extent than under high aeration condition.

Conclusion

Taken together, these results suggest a L. garvieae strain-specific anti-staphylococcal mechanism and an H₂O₂ involvement in at least two of the tested L. garvieae strains.

Electronic supplementary material

The online version of this article (10.1186/s12866-018-1340-3) contains supplementary material, which is available to authorized users.

A Critical Appraisal of Probiotics for Mastitis Control

The urge to reduce antimicrobials use in dairy farming has prompted a search for alternative solutions. As infections of the mammary gland is a major reason for antibiotic administration to dairy ruminants, mammary probiotics have recently been presented as a possible alternative for the treatment of mastitis. To assess the validity of this proposal, we performed a general appraisal of the knowledge related to probiotics for mammary health by examining their potential modes of action and assessing the compatibility of these mechanisms with the immunobiology of mammary gland infections. Then we analyzed the literature published on the subject, taking into account the preliminary in vitro experiments and the in vivo trials. Preliminary experiments aimed essentially at exploring in vitro the capacity of putative probiotics, mainly lactic acid bacteria (LABs), to interfere with mastitis-associated bacteria or to interact with mammary epithelial cells. A few studies used LABs selected on the basis of bacteriocin production or the capacity to adhere to epithelial cells to perform in vivo experiments. Intramammary infusion of LABs showed that LABs are pro-inflammatory for the mammary gland, inducing an intense influx of neutrophils into milk during lactation and at drying-off. Yet, their capacity to cure mastitis remains to be established. A few preliminary studies tackle the possibility of using probiotics to interfere with the teat apex microbiota or to prevent the colonization of the teat canal by pathogenic bacteria. From the analysis of the published literature, it appears that currently there is no sound scientific foundation for the use of probiotics to prevent or treat mastitis. We conclude that the prospects for oral probiotics are not promising for ruminants, those for intramammary probiotics should be considered with caution, but that teat apex probiotics deserve further research.