Microbial community dynamics of a blue-veined raw milk cheese from the UK

A commercial blue-veined cheese made from unpasteurized milk was examined by conventional culturing and PCR Density Gradient Gel Electrophoresis analysis of the bacterial community 16S rRNA genes using three primer sets V3, V4V5, V6V8. Genomic DNA for amplification was extracted directly from raw milk, starter culture, cheese at different stages of production, fully ripened cheese and from the cultured cells grown on various media. The outer rind was sampled separately from the inner white core and blue veins. A diverse microbiota containing Lactococcus lactis subsp. lactis, Lactobacillus plantarum, Lactobacillus curvatus, Staphylococcus gallinarum, Staphylococcus devriesei, Microbacterium sp., Sphingobacterium sp., Mycetocola sp., Brevundimonas sp., Enterococcus faecalis, Proteus sp. and Kocuria sp. was detected in the raw milk using culturing methods, but only Lactococcus lactis subsp. lactis, Lactobacillus plantarum and Enterococcus faecalis survived into the final cheese and were detected both in the core and the rind. Using PCR Density Gradient Gel Electrophoresis analysis of the cheese process samples, Staphylococcus equorum and Enterococcus durans were found in the rind of pre-piercing samples but not in the core and veins; after piercing, these species were found in all parts of the cheese but survived only in the rind when the cheese was fully ripened. Brevibacterium sp., Halomonas sp., Acinetobacter sp., Alkalibacterium sp. and Corynebacterium casei were identified only by PCR Density Gradient Gel Electrophoresis and not cultured from the samples. Brevibacterium sp. was initially identified in the cheese post piercing (core and veins), Halomonas sp. was found in the matured cheese (rind), Acinetobacter sp., Alkalibacterium sp. and Corynebacterium casei were also in the pre-piercing samples (rind) and then found through the subsequent process stages. The work suggests that in this raw milk cheese, there is a limited community from the milk surviving into the final cheese, with salt addition and handling contributing to the final cheese consortium

Acid production, growth kinetics and aroma profiles of Lactobacillus flora from Stilton cheese

The effect of Lactobacillus plantarum isolates from Stilton cheese on aroma profiles of milk fermentation was examined. Representative Lb. plantarum isolates were cultured alone and in combination with acid-producing and non-acid producing Lactococcus lactis NCIMB 9918 in UHT milk at 30 & 18oC for 48 h & 12 weeks, respectively in presence and absence of salt, simulating cheese production and ripening. During long-term ripening, Lb. plantarum grew faster when co-cultured with non-acid producing Lc. lactis in the presence of salt. One isolate of Lb. plantarum produced the highest concentration of alcohols, organic acids and acetoin. Co-culture of Lb. plantarum with acid-producing Lc. lactis enhanced acid and alcohol production, whereas co-inoculation with non-acid producing Lc. lactis increased acetoin synthesis. Lb. plantarum is an incidental organism in cheese and its presence is unpredictable. Occurrence of different genotypes of Lb. plantarum could contribute to batch to batch variation in the cheese aroma characteristics

Isolation and characterization of Campylobacter bacteriophages from retail poultry

The ability of phages to survive processing is an important aspect of their potential use in the biocontrol of Campylobacter in poultry production. To this end, we have developed a procedure to recover Campylobacter bacteriophages from chilled and frozen retail poultry and have validated the sensitivity of the method by using a characterized Campylobacter phage (i.e., NCTC 12674). By using this method, we have shown that Campylobacter phages can survive on retail chicken under commercial storage conditions. Retail chicken portions purchased in the United Kingdom were screened for the presence of endogenous Campylobacter phages. Thirty-four Campylobacter bacteriophages were isolated from 300 chilled retail chicken portions, but none could be recovered from 150 frozen chicken portions. The phage isolates were characterized according to their lytic profiles, morphology, and genome size. The free-range products were significantly more likely to harbor phages (P < 0.001 by single-factor analysis of variance) than were standard or economy products. This study demonstrates that Campylobacter bacteriophages, along with their hosts, can survive commercial poultry processing procedures and that the phages exhibited a wide range of recovery rates from chicken skin stored at 4°C

Multidrug resistant, extended spectrum β-lactamase (ESBL)-producing Escherichia coli isolated from a dairy farm

Escherichia coli strains were isolated from a single dairy farm as a sentinel organism for the persistence of antibiotic resistance genes in the farm environment. Selective microbiological media were used to isolate 126 E. coli isolates from slurry and faeces samples from different farm areas. Antibiotic resistance profiling for 17 antibiotics (seven antibiotic classes), showed 57.9% of the isolates were resistant to between 3 and 15 antibiotics. The highest frequency of resistance was to ampicillin (56.3%), and the lowest to imipenem (1.6%), which appeared to be an unstable phenotype and was subsequently lost. Extended spectrum beta-lactamase resistance (ESBL) was detected in 53 isolates and blaCTX-M, blaTEM and blaOXA genes were detected by PCR in twelve, four and two strains, respectively. Phenotypically most isolates showing resistance to cephalosporins were AmpC rather than ESBL, a number of isolates having both activities. Phenotypic resistance patterns suggested co-acquisition of some resistance genes within subsets of the isolates. Genotyping using ERIC PCR demonstrated these were not clonal, and therefore co-resistance may be associated with mobile genetic elements. These data show a snapshot of diverse resistance genes present in the E. coli population reservoir, including resistance to historically used antibiotics as well as cephalosporins in contemporary use

Draft genome sequence of the bacteriophage vB_Eco_slurp01.

Bacteriophage vB_Eco_slurp01 was isolated from porcine feces using Escherichia coli MG1655 as a host. With a genome size of 348 kb, vB_Eco_slurp01 is one of the largest bacteriophages isolated to date

Influence du sevrage et de l’addition de levures vivantes sur la population bactérienne fécale chez le porcelet

Influence of weaning and live yeast on faecal bacteria populations in pigsThe current studies describe how the diversity of faecal bacteria is affected by weaning and incorporation of live yeast into the post-weaning diet of pigs. Pigs were weaned at 28 days of age onto an experimental weaner diet with or without Saccharomyces cerevisiae boulardii CNCM I-1079 (4 x 106 CFU/g in feed, plus an extra dose of 3 x 109 CFU delivered through oral drenching). A longitudinal analysis was performed, collecting faecal samples of the same individual pigs pre-weaning and at + 4 and + 11 days post-weaning. Culture-based and next generation sequencing (16S rDNA) approaches were used to describe the diversity and composition of the faecal bacterial community. We observed that a different and characteristic bacterial diversity depicts the faecal bacteria microbiota of individual pigs at weaning and after both 4 and 11 days post-weaning. In addition, our results show a difference in bacterial diversity and community structure between pigs fed live yeast versus control and that this difference may be attributable to changes in the composition of low abundance taxa. The specific changes on microbiota induced by adding live yeast to pig diets will then be investigated

Anthropogenic environmental drivers of antimicrobial resistance in wildlife

The isolation of antimicrobial resistant bacteria (ARB) from wildlife living adjacent to humans has led to the suggestion that such antimicrobial resistance (AMR) is anthropogenically driven by exposure to antimicrobials and ARB. However, ARB have also been detected in wildlife living in areas without interaction with humans. Here, we investigated patterns of resistance in Escherichia coli isolated from 408 wild bird and mammal faecal samples. AMR and multi-drug resistance (MDR) prevalence in wildlife samples differed significantly between a Sewage Treatment Plant (STP; wastes of antibiotic-treated humans) and a Farm site (antibiotic-treated livestock wastes) and Central site (no sources of wastes containing anthropogenic AMR or antimicrobials), but patterns of resistance also varied significantly over time and between mammals and birds. Over 30% of AMR isolates were resistant to colistin, a last-resort antibiotic, but resistance was not due to the mcr-1 gene. ESBL and AmpC activity were common in isolates from mammals. Wildlife were, therefore, harbouring resistance of clinical relevance. AMR E. coli, including MDR, were found in diverse wildlife species, and the patterns and prevalence of resistance were not consistently associated with site and therefore different exposure risks. We conclude that AMR in commensal bacteria of wildlife is not driven simply by anthropogenic factors, and, in practical terms, this may limit the utility of wildlife as sentinels of spatial variation in the transmission of environmental AMR

Antimicrobial resistance in dairy slurry tanks: A critical point for measurement and control

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