Lactococcus lactis strains from raw ewe’s milk samples from the PDO Ossau-Iraty cheese area: levels, genotypic and technological diversity

International audienc

Safety and Quality Aspects of Smear Ripened Cheeses

International audienceDiarrhoeic diseases at world scale are the 5th most important cause of death, mainly due to lack of sanitation and unsafe drinking water. They can also originate from food, generating most of food-borne outbreaks. Eggs and egg products are the most common foodstuff category implied in food-borne outbreaks in EU, while cheese plays a limited role (2.3 % of strong evidence outbreaks in 2010) mainly due to staphylococcal toxins. Because of their physico-chemical traits, smear cheeses can offer favorable conditions to the development of Listeria monocytogenes. The bacterium is most often detected in soft and semi-soft cheeses made from pasteurised vs raw milk. Natural combination of various microorganisms and their metabolites in milk and cheese could act as multiple hurdles. Antilisterial activity is exhibited by some actinomycetes isolated from smear cheese but is less effective than that of microbial consortia. Microbial interactions, in which actinomycetes may play an important role, could be a key point in explaining antilisterial activity, but mechanisms are not fully understood. Quality of smear cheese can be affected by blowing defects due to gas-producing bacteria like coliform and butyric acid bacteria. Pigmented strains of Gram negative bacteria, e.g. Pseudomonas fluorescens are associated with fluorescent spots and off-flavours. How microbial balance affects spoilage activity has to be investigated

Microbiological composition of raw milk from selected farms in the Camembert region of Normandy.

International audienceRaw milk from 27 farms was sampled over 6 months for listerias, salmonellas, Yersinia enterocolitica and campylobacters. Total bacterial counts and somatic cell counts were measured. Lactococci, lactobacilli, dextran-producing leuconostocs, Brevibacterium linens, yeasts and moulds, Staphylococcus aureus and other Micrococcaceae, Pseudomonas, coliforms, Escherichia coli, enterococci, Clostridium perfringens and spores of anaerobic lactate-fermenting bacteria were also counted. Pseudomonas (2000 cfu ml-1), lactococci (760 cfu ml-1) and Micrococcaceae (720 cfu ml-1) were the most numerous groups. Lactic acid bacteria were detected in all samples. Coliforms were present in most samples, but 84% of samples had counts < 100 cfu ml-1. Staphylococcus aureus was detected in 62% of milks, the average count was 410 cfu ml-1. About 80% of supplies had < or = 10 E. coli cfu ml-1 and all samples had < or = 1 Cl. perfringens cfu ml-1. Two of the tested milks were positive for salmonellas (2.9%), four were positive for Listeria monocytogenes (5.8%), 25 for Yersinia enterocolitica (36%) and one for campylobacters (1.4%)

Monitoring the microbiology of high quality milk by monthly sampling over 2 years.

International audienceThe concentrations of seven types of microorganism in the milk produced by farms using high quality milking procedures were monitored monthly. The most commonly encountered bacterium was Pseudomonas, whose concentration varied greatly between samples, but lactococci, lactobacilli and yeasts were also present at more stable concentrations. Staphylococcus aureus and beta-glucuronidase-positive Escherichia coli were occasionally detected. Listeria monocytogenes was found in the samples from only one farm, while Yersinia enterocolitica was never detected. There were seasonal variations in the concentrations of lactobacilli and yeasts over the 2 years monitored. The changes in certain bacteria (Lactococcus, Lactobacillus) on any given farm were very similar from one year to the next. The microbiological characteristics of the milk from the farms examined seemed to be fairly constant. The profiles of some bacteria used for cheesemaking were relatively stable over time. It thus seems that the milk provided by different producers could be typed

Utilité nutritionnelle et fonctionnelle de la biodiversité des ferments fromagers

International audienc

Phage community involvement in fermented beverages: an open door to technological advances?

International audienc

A PCR-based method for identification of lactobacilli at the genus level.

International audienceWe developed a polymerase chain reaction (PCR)-based method for the identification of lactobacilli at the genus level. One specific primer, LbLMA1-rev, was designed by analysing similarities between the nucleotide sequence of the spacer between the 16S and 23S rRNA genes in a number of Lactobacillus strains. Amplification with LbLMA1-rev and R16-1, a universal primer, generated a PCR product for 23 Lactobacillus species. Electrophoresis did not reveal any discrete bands when Escherichia coli, Lactococcus lactis, Leuconostoc mesenteroides, Streptococcus thermophilus, Carnobacterium pissicola, Pediococcus pentosaceus, Bifidobacterium bifidum, Weissella confusa, Enterococcus hirae, Staphylococcus aureus or Listeria monocytogenes DNA were used as template

Smear Ripened Cheeses

International audienceCheeses are produced at local and industrial scales generating over 1,000 varieties of cheese in Europe. Most cheeses have a complex successional microbial flora through milk fermentation, curd maturation and storage, to cheese maturation. Microorganisms are introduced with raw materials, by deliberate inoculation and from the environment. Microorganisms are responsible for most of the changes which produce cheese, give it its organoleptic properties and contribute to its preservation, but they may include pathogens, of which Listeria monocytogenes is the most common. The activity of aminotransferase, enzymatic degradation of L-methionine and the subsequent formation of volatile sulphur compounds leads to the development of the typical flavour in smear cheese. The characteristic features of cheese evolve from complex interaction of the metabolic activities of the smear cheese flora. So it is essential to define and identify surface microflora to enable the selection of strains that generate the colour, aroma and organoleptic qualities of specific cheeses, and to screen for anti-listerial activity

Identification of anti-Salmonella bacterial strains by a high-throughput screening method

International audienc