Thermal inactivation kinetics of Shiga toxin-producing Escherichia coli in buffalo Mozzarella curd

The use of raw milk in the processing of buffalo Mozzarella cheese is permitted, but the heat treatment used for stretching the curd must ensure that the final product does not contain pathogens such as Shiga toxin-producing Escherichia coli (STEC) that may be present on buffalo dairy farms. This study carried out challenge tests at temperatures between 68 °C and 80 °C for 2 to 10 min to simulate curd temperatures during the stretching phase. Curd samples were inoculated with 2 STEC strains (serotypes O157 and O26), and their inactivation rates were assessed in the different challenge tests. The curd samples were digested with papain to ensure a homogeneous dispersion of bacteria. The STEC cells were counted after inoculation (range 7.1-8.7 log cfu/g) and after heat treatments using the most probable number (MPN) technique. A plot of log MPN/g versus time was created for each separate experiment. The log linear model with tail was used to provide a reasonable fit to observed data. Maximum inactivation rate (k(max), min(-1)), residual population (log MPN/g), decimal reduction time (min), and time for a 4D (4-log10) reduction (min) were estimated at each temperature tested. A 4D reduction of the O26 STEC strain was achieved when curd was heated at 68 °C for 2.6 to 6.3 min or at 80 °C for 2.1 to 2.3 min. Greater resistance was observed for the O157 strain at 68 °C because k(max) was 1.48 min(-1). The model estimates can support cheesemakers in defining appropriate process criteria needed to control possible STEC contamination in raw milk intended for the production of Mozzarella

Does animal origin and hide status affect microbial contamination in pig carcasses?

Contamination in pigs and pig carcasses by Listeria monocytogenes and Salmonella spp. in an industrial abattoir was co-related with animal origin and their hide status. Animals supplied by farms joining to an integrated quality control program or other pig fatteners were kept in lairage for the night and showered or were slaughtered within few hours. Prevalence in Salmonella was similar in animals supplied by farms joining or not the IQC program and Listeria monocytogenes was never detected in pigs at bleeding. The differences in the prevalence of Salmonella, which varied from 14 to 86% in different stocks of pigs, were related to suppliers and lairage time. The prevalence was much lower (11%) at time of carcass dressing and boning. Listeria monocytogenes contamination was very low in pigs at bleeding, but increased after slaughtering (13%) and much more after boning (68%). Any correlation was found between number of Enterobacteriaceae or TMC and prevalence of the pathogens

Effect of Non-thermal Atmospheric Plasma on Viability and Histamine-Producing Activity of Psychotrophic Bacteria in Mackerel Fillets

open5noNon-thermal atmospheric plasma (NTAP) has gained attention as a decontamination and shelf-life extension technology. In this study its effect on psychrotrophic histamine-producing bacteria (HPB) and histamine formation in fish stored at 0–5°C was evaluated. Mackerel filets were artificially inoculated with Morganella psychrotolerans and Photobacterium phosphoreum and exposed to NTAP to evaluate its effect on their viability and the histidine decarboxylase (HDC) activity in broth cultures and the accumulation of histamine in fish samples, stored on melting ice or at fridge temperature (5°C). NTAP treatment was made under wet conditions for 30 min, using a dielectric barrier discharge (DBD) reactor. The voltage output was characterized by a peak-to-peak value of 13.8 kV (fundamental frequency around 12.7 KHz). This treatment resulted in a significant reduction of the number of M. psychrotolerans and P. phosphoreum (≈3 log cfu/cm2) on skin samples that have been prewashed with surfactant (SDS) or SDS and lactic acid. A marked reduction of their histamine-producing potential was also observed in HDC broth incubated at either 20 or 5°C. Lower accumulation of histamine was observed in NTAP-treated mackerel filets that have been inoculated with M. psychrotolerans or P. phosphoreum and pre-washed with either normal saline or SDS solution (0.05% w/v) and stored at 5°C for 10 days. Mean histamine level in treated and control groups for the samples inoculated with either M. psychrotolerans or P. phosphoreum (≈5 log cfu/g) varied from 7 to 32 and from 49 to 66 μg/g, respectively. No synergistic effect of SDS was observed in the challenge test on meat samples. Any detectable amount of histamine was produced in the meat samples held at melting ice temperature (0–2°C) for 7 days. The effects of NTAP on the quality properties of mackerel’s filets were negligible, whereas its effect on the psychrotrophic HPB might be useful when time and environmental conditions are challenging for the cool-keeping capacity throughout the transport/storage period.openTrevisani M.; Cevoli C.; Ragni L.; Cecchini M.; Berardinelli A.Trevisani M.; Cevoli C.; Ragni L.; Cecchini M.; Berardinelli A

Sanitisation of fresh-cut celery and radicchio by gas plasma treatments in water medium

open7noNome progetto: STARTEC: “Decision Support Tools to ensure safe, tasty and nutritious Advanced Ready-to-eat foods for healthy and vulnerable Consumers”.The antimicrobial efficacy of dielectric barrier discharge atmospheric gas plasma (DBD) was tested against Listeria monocytogenes and shigatoxin-producing Escherichia coli serogroups O157 and O26. Challenge tests were carried out with samples of cut celery and radicchio leaves inoculated with a mix of five strains of L. monocytogenes or the two strains of E. coli immersed in deionised water. The treatment efficacy was also assessed considering only the contaminated deionised water. For deionised inoculated water alone, a treatment time-dependent strong effect was observed and a pathogens reduction higher than 6LogCFU/mL was obtained after 40min of treatment. With the vegetables presence in the liquid medium, the efficacy appeared reduced and related to the treatment time, microorganism, substrate and storage duration (reduction up to 2.5 and 3.7LogCFU/cm2 for L. monocytogenes and E. coli, respectively). No significant changes were observed on celery visual attributes, soluble solids content and textural parameters. A significant decrease of the chroma colour parameter during storage was noted in treated radicchio samples respect to control ones.openBerardinelli, Annachiara; Pasquali, Frederique; Cevoli, Chiara; Trevisani, Marcello; Ragni, Luigi; Mancusi, Rocco; Manfreda, GerardoBerardinelli, Annachiara; Pasquali, Frederique; Cevoli, Chiara; Trevisani, Marcello; Ragni, Luigi; Mancusi, Rocco; Manfreda, Gerard

Does animal origin and hide status affect microbial contamination in pig carcasses?

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Fecal carriage of Escherichia coli O157:H7 and carcass contamination in cattle at slaughter in northern Italy

Feedlot cattle slaughtered at a large abattoir in northern Italy during 2002 were examined for intestinal carriage and carcass contamination with Escherichia coli O157:H7. Carcass samples were taken following the excision method described in the Decision 471/2001/EC, and fecal material was taken from the colon of the calves after evisceration. Bacteria were isolated and identified according to the MFLP-80 and MFLP-90 procedures (Food Directorate’s Health Canada’s). Eighty-eight non-sorbitol-fermenting E. coli O157:H7 isolates were obtained from 12 of the 45 calves examined. In particular, E. coli O157:H7 isolates were found in 11 (24%) fecal and five (11%) carcass samples. PCR analysis showed that all 11 fecal samples and five carcass samples carried eae-γ1-positive E. coli O157:H7 isolates. In addition, genes encoding Shigatoxins were detected in O157:H7 isolates from nine and two of those 11 fecal and five carcasses, respectively. A representative group of 32 E. coli O157:H7 isolates was analyzed by phage typing and DNA macrorestriction fragment analysis (PFGE). Five phage types (PT8, PT32v, PT32, PT54, and PT not typable) and seven (I–VII) distinct restriction patterns of similarity > 85% were detected. Up to three different O157:H7 strains in an individual fecal sample and up to four from the same animal could be isolated. These findings provide evidence of the epidemiological importance of subtyping more than one isolate from the same sample. Phage typing together with PFGE proved to be very useful tools to detect cross-contamination among carcasses and should therefore be included in HACCP programs at abattoirs. The results showed that the same PFGE-phage type E. coli O157:H7 profile was detected in the fecal and carcass samples from an animal, and also in two more carcasses corresponding to two animals slaughtered the same day. [Int Microbiol 2007; 10(2):109-116

Whole genome sequencing based typing and characterisation of Shiga-toxin producing Escherichia coli strains belonging to O157 and O26 serotypes and isolated in dairy farms

In the present study, the genetic relationships as well as the virulome and resistome of newly sequenced O26 and O157 Shiga-toxin producing E. coli (STEC) isolates, collected from dairy farms in Italy, were investigated in comparison to publicly available genomes collected worldwide. The whole genome of Italian isolates was sequenced on Illumina MiSeq Platform. Reads quality control, de novo draft genome assembly, species confirmation and the 7-loci Multi-Locus Sequence Type assignment were performed using INNUca pipeline. Reference-based SNPs calling was performed on O157 and O26 genomes, separately, mapping contigs to high-quality finished genomes. Virulence and antimicrobial resistance determinants were detected in silico using the tool ABRicate. Phylogenetic reconstructions revealed that genomes clustered mainly based on their 7-loci MLST type. The virulome of tested genomes included 190 determinants. O157 genomes carried chu genes associated to heme mediated iron uptake, whereas O26 genomes harboured genes ybt associated to siderophore mediated iron uptake. Resistome analysis showed the presence of tet(34) on all but one O157 genomes and on only one O26 genomes. Only 4 genomes carried genes associated to multiresistance. In the present study, the genes chu and ybt were identified as potential biomarker for the differentiation of O157 and O26 serotypes

The role of pulmonary vascular endothelium in chronic obstructive pulmonary disease (COPD): Does endothelium play a role in the onset and progression of COPD?

Chronic obstructive pulmonary disease (COPD) is an inflammatory lung pathology characterized by persistent airflow limitation and is the third leading cause of death globally. COPD pathophysiology includes both environmental and host risk factors and the presence of comorbidities contributes to its harmful outcome. Cardiovascular disease (CVD) is closely related to COPD and their coexistence is associated with worse outcomes than either condition alone. COPD impairs the cardiovascular system favoring mostly endothelial dysfunction that is a significant COPD prognostic factor at different stages of the disease. The mechanisms promoting endothelial dysfunction in the systemic and/or pulmonary circulation of COPD patients are different and include systemic inflammation, alteration of adhesion and pro-inflammatory molecules, oxidative stress, cellular senescence, and apoptosis. Nevertheless, the role of endothelium in the onset and progression of COPD and CVD is not yet fully understood. Hence, the purpose of this narrative review is to analyze the literature and provide evidence supporting the importance of endothelial dysfunction in COPD

Limiti di carica microbica ed accettabilità delle carni avicole fresche

The minimum number of bacteria, which correlate to end of shelf-life, should be defined by producers in order to establish microbiological standards at the end of productive process or at specifie defect action points, taking into account the possible temperature conditions the various products will probably meet. This would allow the quality assurance of all lots of products until the end of declared shelf life. Entire chicken, sliced chicken breast, skewers of chicken with pepper, ripened chicken leg and cordon bleu samples were stored at temperature condition from -0.2° to 5.9°C for 9-11 days. Then they were analysed for microbiological traits and, on the basis of sensorial characteristics, were classified as acceptable, marginally acceptable or not acceptable. It was defined the maximum number of Pseudomonas spp., total coliforms or total plate count at which unacceptable products were not found and significance of these discriminatory limits was evaluated. Per stabilire la durata commerciale delle diverse preparazioni di carni avicole i produttori dovrebbero conoscere quali sono le concentrazioni minime di batteri alteranti correlabili alla comparsa di alterazioni e quali sono, quindi, gli standard microbiologici in fase di produzione od in specifici punti critici di controllo (defect action point) che permettano di assicurare, in condizioni programmate di temperatura, la qualità di un lotto di produzione fine al termine indicato in etichetta. Campioni di diversi lotti di busti di pollo, petti di pollo a fette, spiedini con peperone, fusotti ripieni e cordon bleu sono stati sottoposti a regimi di temperatura tra -0,2° e 5,9°C per 9-11 giorni. Al termine di questo periodo sono stati fatti controlli microbiologici e sulla base delle caratteristiche organolettiche sono stati classificati accettabili, marginali o inaccettabili. È stato quindi individuato il limite più alto di Pseudomonas spp., coliformi totali o carica mesofila totale al di sotto del quale non fossero riscontrabili unità inaccettabili ed è stata valutata la significatività di questo limite discriminante