Survival of Escherichia coli O157:H7 during the manufacture and ripening of Cacioricotta goat cheese.
The aim of this study was to assess the growth and survival of Escherichia coli O157:H7 during the manufacturing and ripening of Cacioricotta goat cheese. Goat milk was artificially contaminated with E. coli O157:H7 and the bacterial load was monitored from production up to 90 days of ripening. Goat milk was inoculated with 102 cfu ml-1 of E. coli O157:H7 and the bacterial count of the curd at time zero was 2.31 log10 cfu g-1. During the first day of ripening, the bacterial load has increased to 5.73 log10 cfu g-1 to more than 6.20 log10 cfu g-1 during the first week. The bacterial load remained constant up to 28 days and then slightly decreased until the end of ripening, with values of aw and pH of 0.88 and 5.41 respectively. The results of this study highlighted that E. coli O157:H7 is able to survive the manufacturing process and they suggest that the 90-day period of ripening alone is insufficient to remove E. coli O157:H7 in contaminated Cacioricotta goat cheese. Moreover, these results support the assumption that the presence of a low contamination of milk with E. coli O157:H7 could represent a potential source of infection and a threat to consumers.
Real‐time loop‐mediated isothermal amplification assays combined with ethidium monoazide bromide and bentonite coated activated carbon for rapid and sensitive detection of viableEscherichia coliO157:H7 from milk without enrichment
A real‐time loop‐mediated isothermal amplification (Rti‐LAMP) DNA assay was developed for rapid and sensitive detection of viable Escherichia coli O157:H7 in milk by combining with ethidium monoazide bromide (EMA) and bentonite coated activated carbon (BCAC) treatment without enrichment. The assay involved inoculating 25 mL portions of milk with various numbers of E. coli O157:H7. Then each of milk sample was adsorbed with 4 g BCAC to remove DNA amplification inhibitor. The recovered purified bacteria sample was further treated with EMA for discrimination viable from dead cells in Rti‐LAMP assay. The detection limit of viable E. coli O157:H7 was 10 CFU/mL in milk by the BCAC‐EMA‐Rti‐LAMP, and the entire assay could be completed in 5 hr. Twenty‐five raw milk samples were detected by the BCAC‐EMA‐Rti‐LAMP assay, using three methods as controls including E. coli O157:H7 plate culture, BCAC‐Rti‐LAMP, and Rti‐LAMP combined with enrichment at 37°C (E‐Rti‐LAMP). The results showed that the BCAC‐EMA‐Rti‐LAMP had similar accuracy and sensitivity as that of plate culture, as they both detected one sample of viable E. coli O157:H7 positive from 25 fresh raw milk samples. These data strongly suggested that the BCAC‐EMA‐Rti‐LAMP could rapidly and sensitively detect viable E. coli O157:H7 in milk without enrichment. PRACTICAL APPLICATIONS: Escherichia coli O157:H7 is one of the foodborne pathogens in milk, which has low dose of infection and high pathogenicity. In milk, components such as Ca²⁺, proteinase, fats, and milk proteins may block DNA and shield it from access by polymerase. This study was targeting VT2 and Z3276 genes for rapid and sensitive detection of viable E. coli O157:H7 in milk. BCAC was used to remove DNA amplification inhibitor and improve the detection sensitivity. EMA was used to discriminate viable from dead cells. The assay will be a potential tool in the rapidity, sensitivity, and specificity for detection of E. coli O157:H7 in milk without enrichment.
Adrenocorticotropin insensitivity syndromes.
I. Introduction II. Familial Glucocorticoid Deficiency A. Clinical presentation B. Investigation C. Treatment D. Pathogenesis III. Triple A Syndrome A. Clinical features B. Treatment C. Pathogenesis D. Mapping of triple A syndrome gene E. Candidate genes IV. Acquired ACTH Resistance V. Conclusions