Determining Thermal Inactivation of Escherichia coli O157:H7 in Fresh Compost by Simulating Early Phases of the Composting Process ▿

A three-strain mixture of Escherichia coli O157:H7 was inoculated into fresh dairy compost (ca. 107 CFU/g) with 40 or 50% moisture and was placed in an environmental chamber (ca. 70% humidity) that was programmed to ramp from room temperature to selected composting temperatures in 2 and 5 days to simulate the early composting phase. The surviving E. coli O157:H7 population was analyzed by direct plating and enrichment. Optimal and suboptimal compost mixes, with carbon/nitrogen (C/N) ratios of 25:1 and 16:1, respectively, were compared in this study. In the optimal compost mix, E. coli O157:H7 survived for 72, 48, and 24 h in compost with 40% moisture and for 72, 24, and 24 h with 50% moisture at 50, 55, and 60°C, respectively, following 2 days of come-up time (rate of heating up). However, in the suboptimal compost mix, the pathogen survived for 288, 72, and 48 h in compost with 40% moisture and for 240, 72, 24 h in compost with 50% moisture at the same temperatures, respectively. Pathogen survival was longer, with 5 days of come-up time compared with 2 days of come-up. Overall, E. coli O157:H7 was inactivated faster in the compost with 50% moisture than in the compost with 40% at 55 and 60°C. Both moisture and come-up time were significant factors affecting Weibull model parameters. Our results suggest that slow come-up time at the beginning of composting can extend pathogen survival during composting. Additionally, both the C/N ratio and the initial moisture level in the compost mix affect the rate of pathogen inactivation as well

New evidence of the involvement of Lichtheimia corymbifera in farmer's lung disease.

International audienceFarmer's lung disease (FLD) is a form of hypersensitivity pneumonitis resulting from recurrent exposure to moldy plant materials. We investigated and compared the initial response of respiratory epithelium after exposure to extracts of Sacharopolyspora rectivirgula, Lichtheimia corymbifera (formerly Absidia corymbifera), Eurotium amstelodami and Wallemia sebi. The two criteria for selection of these species were their high prevalence in the hay handled by FLD patients and the presence of high levels of specific precipitins to these molds in FLD patients' sera. Hydrosoluble extracts were prepared from spores and hyphae grown in culture under optimal conditions for each of the four species. Confluent A549 cells were inoculated with one of the four calibrated soluble extracts. Two mediators, one inflammatory (Interleukin (IL)-8) and one allergic (IL-13), were quantified using real-time PCR and ELISA assay, after four exposure periods (30 min, 2 h, 4 h and 8 h). S. rectivirgula and L. corymbifera extracts were the only ones which induced a marked upregulation of IL-8, as shown by both real-time PCR and ELISA assay 8 h after the initial contact. This study adds to the growing body of evidence that L. corymbifera should be recognized as an etiologic agent of FLD along with S. rectivirgula