Draft genome sequences of four Yersinia enterocolitica strains, isolated from wild ungulate carcasses

This study describes the draft genome sequences of four Yersinia enterocolitica strains, originally isolated from ungulate carcasses. These isolates were typed biochemically and two were determined to be highly virulent (biotype 1B). The draft genome sequences had a mean size of 4.77 Mb and a mean G+C content of 47.1%

Molecular characterization of Pseudomonas fluorescens isolates involved in the Italian "blue mozzarella" event.

Between June and September 2010, widespread Italian consumer reports of unusual blue spoilage on fresh dairy products were publicized, resulting in the so-called blue mozzarella event. An inordinately high number of samples from mozzarella and whey cheese products of Italian and German production subsequently tested positive for Pseudomonas fluorescens. The aim of this study was to verify whether a selected P. fluorescens strain was responsible for this apparently unusual event. Molecular characterization of 181 isolated P. fluorescens strains was conducted using a newly optimized pulsed-field gel electrophoresis protocol. Although a high number of pulsotypes was found (132), only four pulsotypes were associated with more than one production plant, and only one German isolate had the same pulsotype as was detected in two Italian plants. This is the only evidence of possible cross-contamination among cheeses from the two countries. The overall results did not support the spread of contamination from German to Italian plants or the presence of one environmental strain that spread in both countries

Arcobacter spp. in raw milk from vending machines in Piedmont and occurrence of virulence genes in isolates

Arcobacter spp. has been recognized as an emerging foodborne pathogen and a hazard to human health. In the dairy chain, it has been isolated from different sources, nevertheless data on Arcobacter occurrence in raw milk provided by vending machines are few. This study aimed to identify potentially pathogenic Arcobacter spp. in raw milk intended for human consumption sold through vending machines located in Piedmont. In an 8-month period, 37 raw milk samples were collected from 24 dairy farms: 12 (32,4%) were collected directly in farm from bulk tank milk and 25 (67,6%) from vending machines. Eight (21,6%) out of the 37 milk samples and 7 (29,2%) out of the 24 dairy farms were positive for Arcobacter spp. by culture examination. Four (16%) out of the 25 samples from vending machines and 4 (33,3%) out of the 12 samples from bulk tank milk were positive. All 8 isolates were identified as A. butzleri both by MALDI-TOF MS and multiplex end-point PCR. According to the detection of virulence genes, a total of four Patho-types were highlighted: 5 isolates in P-type 1 and only one isolate for each of the P-types 2-3-4. A. butzleri isolates carrying encoding virulence factors genes were isolated from raw milk intended for human consumption: these findings strengthen the compulsory consumption after boiling as required by current legislation and suggest the need of enlarging the analytical investigations to other microorganisms not yet included in the food safety criteria

Insight Into the Distribution of Staphylococci and Their Enterotoxins in Cheeses Under Natural Conditions

Staphylococcal food poisoning outbreaks are a major cause of food-borne illness in the European Union and their notification has been mandatory since 2005. Criteria for the enumeration of coagulase-positive Staphylococci (CPS) and the detection of staphylococcal enterotoxins (SEs) in cheese have been set down in Commission Regulation EC 2073/2005. Currently, few information are available about the distribution of SEs in naturally contaminated cheeses, including raw-milk and artisanal dairy products. The aim of this study was therefore to investigate at both the CPS enumeration and the succession of the enterotoxigenic Staphylococcus aureus and produced enterotoxins levels on the rind and the core of a raw-milk semi-hard cheese, produced on farm. The study has been conducted in three steps: (I) seven wheels at different time of ripening where tested for the presence of SEs. (II) from each wheel, four portions were subsequently sampled from four different areas (peripheral rind, central rind, peripheral core and central core). (III) two cheese wheels, characterized by the highest and lowest CPS numbers and SEs quantification, based on the second step of the study, were further analyzed. A significant difference has been observed in the distribution of CPS and SEs in the four areas sampled, irrespectively of the batch and the time of ripening. The results of this study provided a set of previously unknown information on the influence of natural conditions on the distribution of CPS and SEs thereof in the cheese matrix, filling a gap in the understanding of SEs biosynthesis process

Genome-Wide Profiling of Enterotoxigenic Staphylococcus aureus Strains Used for the Production of Naturally Contaminated Cheeses

peer-reviewedStaphylococcus aureus is a major human pathogen and an important cause of livestock infections. More than 20 staphylococcal enterotoxins with emetic activity can be produced by specific strains responsible for staphylococcal food poisoning, one of the most common food-borne diseases. Whole genome sequencing provides a comprehensive view of the genome structure and gene content that have largely been applied in outbreak investigations and genomic comparisons. In this study, six enterotoxigenic S. aureus strains were characterised using a combination of molecular, phenotypical and computational methods. The genomes were analysed for the presence of virulence factors (VFs), where we identified 110 genes and classified them into five categories: adherence (n = 31), exoenzymes (n = 28), genes involved in host immune system evasion (n = 7); iron uptake regulatory system (n = 8); secretion machinery factors and toxins’ genes (n = 36), and 39 genes coding for transcriptional regulators related to staphylococcal VFs. Each group of VFs revealed correlations among the six enterotoxigenic strains, and further analysis revealed their accessory genomic content, including mobile genetic elements. The plasmids pLUH02 and pSK67 were detected in the strain ProNaCC1 and ProNaCC7, respectively, carrying out the genes sed, ser, and selj. The genes carried out by prophages were detected in the strain ProNaCC2 (see), ProNaCC4, and ProNaCC7 (both positive for sea). The strain ProNaCC5 resulted positive for the genes seg, sei, sem, sen, seo grouped in an exotoxin gene cluster, and the strain ProNaCC6 resulted positive for seh, a transposon-associated gene. The six strains were used for the production of naturally contaminated cheeses which were tested with the European Screening Method for staphylococcal enterotoxins. The results obtained from the analysis of toxins produced in cheese, combined with the genomic features represent a portrait of the strains that can be used for the production of staphylococcal enterotoxin-positive cheese as reference material