Carnobacterium maltaromaticum as bioprotective culture against spoilage bacteria in ground meat and cooked ham.

This study assessed the bioprotective effect of Carnobacterium maltaromaticum (CM) against Pseudomonas fluorescens (PF) and Brochothrix thermosphacta (BT) in ground beef and sliced cooked ham stored in high- and low-oxygen-modified atmospheres (66/4/30% O2/N2/CO2 and 70/30% N2/CO2, respectively). Both meat products were inoculated with CM, PF, and BT individually or in combination and stored for 7 days (3 days at 4 °C + 4 days at 8 °C) for ground beef and 28 days (10 days at 4 °C + 18 days at 8 °C) for sliced cooked ham. Each food matrix was assigned to 6 treatments: NC (no bacterial inoculation, representing the indigenous bacteria of meat), CM, BT, PF, CM + BT, and CM + PF. Bacterial growth, pH, instrumental color, and headspace gas composition were assessed during storage. CM counts remained stable from inoculation and throughout the shelf-life. CM reduced the population of inoculated and indigenous spoilage bacteria, including BT, PF, and enterobacteria, and showed a negligible impact on the physicochemical quality parameters of the products. Furthermore, upon simulating the shelf-life of ground beef and cooked ham, a remarkable extension could be observed with CM. Therefore, CM could be exploited as a biopreservative in meat products to enhance quality and shelf-life.

Gut Microbiota Associated with Clostridioides difficile Carriage in Three Clinical Groups (Inflammatory Bowel Disease, C. difficile Infection and Healthcare Workers) in Hospital Field.

Clostridioides difficile is an anaerobic spore-forming Gram-positive bacterium. C. difficile carriage and 16S rDNA profiling were studied in three clinical groups at three different sampling times: inflammatory bowel disease (IBD) patients, C. difficile infection (CDI) patients and healthcare workers (HCWs). Diversity analysis was realized in the three clinical groups, the positive and negative C. difficile carriage groups and the three analysis periods. Concerning the three clinical groups, ß-diversity tests showed significant differences between them, especially between the HCW group and IBD group and between IBD patients and CDI patients. The Simpson index (evenness) showed a significant difference between two clinical groups (HCWs and IBD). Several genera were significantly different in the IBD patient group (Sutterella, Agathobacter) and in the CDI patient group (Enterococcus, Clostridioides). Concerning the positive and negative C. difficile carriage groups, ß-diversity tests showed significant differences. Shannon, Simpson and InvSimpson indexes showed significant differences between the two groups. Several genera had significantly different relative prevalences in the negative group (Agathobacter, Sutterella, Anaerostipes, Oscillospira) and the positive group (Enterococcus, Enterobacteriaceae_ge and Enterobacterales_ge). A microbiota footprint was detected in C. difficile-positive carriers. More experiments are needed to test this microbiota footprint to see its impact on C. difficile infection.

Impact of environmental conditions and gut microbiota on the in vitro germination and growth of Clostridioides difficile.

Clostridioides difficile is a spore-forming anaerobic Gram-positive bacterium responsible for a broad spectrum of intestinal symptoms and healthcare-associated diarrhoea. The hypothesis of this work was that different in vitro conditions, notably pH and human faecal microbiota composition, impact the germination and/or the growth of C. difficile. This study aimed to correlate growth kinetics of the bacterium with these two physiochemical parameters by using a static in vitro model. To better understand the initial gut colonisation, several growth curve assays were carried out to monitor the behaviour of the spores and vegetative forms of C. difficile strain 078 under different conditions mimicking the gut environment. When the faeces were added, no spore germination or growth was observed, but C. difficile spores germinated in vitro when the pH was maintained between 6.6 and 6.9 for four different faeces donors. The evolution of microbiota studied by 16S rDNA profiling showed high proportions of Enterobacteriaceae and E. coli/Shigella when C. difficile grew, regardless of the inoculated faeces. This model helped us to understand that the germination and growth of C. difficile are strongly pH dependent, and further research is needed to evaluate the potential impact of the gut microbiota composition on C. difficile.

Effect of five decontamination methods on face masks and filtering facepiece respirators contaminated with Staphylococcus aureus and Pseudomonas aeruginosa.

Introduction. In the context of the global pandemic due to SARS-CoV-2, procurement of personal protective equipment during the crisis was problematic. The idea of reusing and decontaminating personal surgical masks in facilities was explored in order to avoid the accumulation of waste and overcome the lack of equipment. Hypothesis. Our hypothesis is that this work will show the decontamination methods assessed are effective for bacteria, such as Staphylococcus aureus and Pseudomonas aeruginosa . Aim. We aim to provide information about the effects of five decontamination procedures (UV treatment, dry heat, vaporized H2O2, ethanol treatment and blue methylene treatment) on S. aureus and P. aeruginosa . These bacteria are the main secondary bacterial pathogens responsible for lung infections in the hospital environment. Methodology. The surgical masks and the filtering facepiece respirators were inoculated with two bacterial strains ( S. aureus ATCC 29213 and P. aeruginosa S0599) and submitted to five decontamination treatments: vaporized H2O2 (VHP), UV irradiation, dry heat treatment, ethanol bath treatment and blue methylene treatment. Direct and indirect microbiology assessments were performed on three positive controls, five treated masks and one negative control. Results. The five decontaminations showed significant (P<0.05) but different degrees of reductions of S. aureus and P. aeruginosa . VHP, dry heat treatment and ethanol treatment adequately reduced the initial contamination. The 4 min UV treatment allowed only a reduction to five orders of magnitude for face mask respirators. The methylene blue treatment induced a reduction to two orders of magnitude. Conclusions. The three methods that showed a log10 reduction factor of 6 were the dry heat method, VHP and ethanol bath treatment. These methods are effective and their establishment in the medical field are easy but require economic investment.

Potential resident bacterial microbiota in udder tissues of culled cows sampled in abattoir.

While mammary gland tissues (MGTs) are difficult to sample without risks for cow's health or milk production, milk analysis are used in routine to assess dairy cow udder's health. This study aimed to identify, quantify, compare the milk and MGTs microbiota of macroscopically healthy dairy bovine mammary glands (MG) in order to evaluate their degree of similarity. We harvested 13 couples of milk and MGTs samples, originated from the same quarter at culling. 16S rDNA Amplicon Sequencing was performed, showing Corynebacterium as the main bacterial genus in both types of samples but generally found in the milk in higher proportions than in tissues. Species evenness was higher in MGTs while species richness was higher in milk samples. Beta diversity was significantly different between both matrices suggesting the presence of a resident microbiota in MGTs of dairy cows at time of culling partially reflected by the milk microbiota from the same quarter.

A toddler SHIME® model to study microbiota of young children.

The 'first 1000 days of life' determine the gut microbiota composition and can have long-term health consequences. In this study, the simulator of the human intestinal microbial ecosystem (SHIME®) model, which represents the main functional sections of the digestive tract, was chosen to study the microbiota of young children. The aim of this study was to reproduce the digestive process of toddlers and their specific colonic environment. The ascending, transverse and descending colons of SHIME® model were inoculated with feces from three donors aged between 1 and 2 years-old, in three separate runs. For each run, samples from colon vessels were collected at days 14, 21 and 28 after microbiota stabilization period. Short chain fatty acid concentrations determined by HPLC showed that microbiota obtained in SHIME® model shared characteristics between adults and infants. In addition, microbial diversity and bacterial populations determined by 16S rRNA amplicon sequencing were specific to each colon vessel. In conclusion, the SHIME® model developed in this study seemed well adapted to evaluate prebiotic and probiotic impact on the specific microbiota of toddlers, or medicine and endocrine disruptor metabolism. Moreover, this study is the first to highlight some biofilm development in in vitro gastrointestinal modelling systems.

Effect of Bifidobacterium crudilactis and 3'-sialyllactose on the toddler microbiota using the SHIME® model.

The important changes in diet during the first years of life strongly modulate the intestinal microbiota of young children. Among in vitro digestive models, the simulator of human intestinal microbial ecosystem (SHIME®) model, seems particularly adapted to study the effects of prebiotics and/or probiotics on the dynamic microbiota of toddlers. The main purpose of this study was to investigate different formulations with prebiotic (3'-sialyllactose: 3'SL) and probiotic (Bifidobacterium crudilactis FR/62/b/3) effects on young child microbiota using the SHIME® model. The ascending (AC), transverse (TC) and descending (DC) colons of the SHIME® model were inoculated with feces from 3 donors aged between 1 and 2 years, in three separate vessels. After two weeks of microbiota stabilization, four treatments of one week (prebiotic, probiotic, synbiotic and cell-free spent media from the synbiotic) were administered. In all the colon vessels, the short chain fatty acid analyses, determined using high-performance liquid chromatography highlighted a ratio acetate/propionate/butyrate proportion of 5:19:6, situated between infant and adult normal values. As already observed in other validated studies focusing on the SHIME® model, the 16S rDNA sequencing highlighted a low richness and diversity in the AC, while the microbial communities in the TC and the DC remained similar to each other. Although some bacteria involved in biofilm development have been identified (Stenotrophomonas, Megasphera and Enterobacter), specific bacterial populations, proper to each colon were developed. Some bacteria associated to the upper intestinal tract, such as Lactobacillus and Veillonella genera, seemed to grow easily in the AC. The quantitative polymerase chain reaction (qPCR) targeting the hsp60 gene confirmed the ability of bifidobacteria to survive in this toddler model. In addition, the synbiotic treatment tended to a bifidogenic effect (P < 0.1). On the other hand, the feces of the donors and the content of the three colon vessels were filtered and placed in contact with Escherichia coli O157:H7 ATCC 43890 to evaluate the modulation of virulence gene expression using reverse transcription PCR. Finally, filtered supernatants from donor feces significantly up-regulated the expression of the luxS gene of E. coli O157:H7 (P = 0.013). In conclusion, despite the presence of biofilms, the toddler SHIME® model used in his study shared characteristics found both in adults and infants. Although additional investigations should be performed, combining 3'SL and B. crudilactis FR/62/b/3 could lead to a beneficial effect on infant microbiota by favoring bifidobacterial presence. Finally, the filtrated supernatant from young child feces could be able to modulate the quorum sensing mechanism for E. coli O157:H7.

Corrigendum: Cell-Free Spent Media Obtained From Bifidobacterium bifidum and Bifidobacterium crudilactis Grown in Media Supplemented with 3'-Sialyllactose Modulate Virulence Gene Expression in Escherichia coli O157:H7 and Salmonella Typhimurium.

[This corrects the article DOI: 10.3389/fmicb.2016.01460.].

Cell-Free Spent Media Obtained from Bifidobacterium bifidum and Bifidobacterium crudilactis Grown in Media Supplemented with 3'-Sialyllactose Modulate Virulence Gene Expression in Escherichia coli O157:H7 and Salmonella Typhimurium.

Complex oligosaccharides from human milk (HMO) possess an antimicrobial activity and can promote the growth of bifidobacteria such as Bifidobacterium bifidum and Bifidobacterium longum subsp. infantis. In addition, fermentation of carbohydrates by bifidobacteria can result in the production of metabolites presenting an antivirulence effect on several pathogenic bacteria. Whey is rich in complex bovine milk oligosaccharides (BMO) structurally similar to HMO and B. crudilactis, a species of bovine origin, is able to metabolize some of those complex carbohydrates. This study focused on the ability of B. bifidum and B. crudilactis to grow in a culture medium supplemented in 3'-sialyllactose (3'SL) as the main source of carbon, a major BMO encountered in cow milk. Next, the effects of cell-free spent media (CFSM) were tested against virulence expression of Escherichia coli O157:H7 and Salmonella enterica serovar Typhimurium. Both strains were able to grow in presence of 3'SL, but B. crudilactis showed the best growth (7.92 ± 0.3 log cfu/ml) compared to B. bifidum (6.84 ± 0.9 log cfu/ml). Then, CFSM were tested for their effects on virulence gene expression by ler and hilA promoter activity of luminescent mutants of E. coli and S. Typhimurium, respectively, and on wild type strains of E. coli O157:H7 and S. Typhimurium using RT-qPCR. All CFSM resulted in significant under expression of the ler and hilA genes for the luminescent mutants and ler (ratios of -15.4 and -8.1 respectively) and qseA (ratios of -2.1 and -3.1) for the wild type strain of E. coli O157:H7. The 3'SL, a major BMO, combined with some bifidobacteria strains of bovine or human origin could therefore be an interesting synbiotic to maintain or restore the intestinal health of young children. These effects observed in vitro will be further investigated regarding the overall phenotype of pathogenic agents and the exact nature of the active molecules.

In vitro screening of mare's milk antimicrobial effect and antiproliverative activity.

The aims of this study were to examine the effect of mare's milk on virulence gene expression of Salmonella Typhimurium and observe its potential activity on proliferation of adenocarcinoma Caco-2 cells. Different supernatants of mare's milk, raw or heat-treated at 65°C for 15 s or 30 min, were studied. The changes in hilA gene expression of Salmonella Typhimurium in presence of mare's milk supernatants were assessed using a reporter luminescent strain. A significant decrease in hilA gene expression was observed with all tested supernatants. Virulence gene expression was then assessed using qPCR on a wild-type strain of Salmonella Typhimurium. A significant decrease of hilA and ssrB2 gene expression was observed with raw milk supernatants but not with heat-treated supernatants. The same supernatants were administered to Caco-2 cells to measure their proliferation rate. A significant reduction of proliferative effect was observed only with raw milk supernatants. This study reports that raw mare's milk was able to modulate virulence gene expression of Salmonella Typhimurium and exerts antiproliferative effects on Caco-2 cells. These results may offer new approaches for promoting gastrointestinal health.