Prevalence and concentration of Verotoxigenic Escherichia coli O157:H7 in adult sheep at slaughter from Italy

A 1-year study on the animal-level prevalence and concentration of Escherichia coli O157 in adult sheep at slaughter was performed, to collect qualitative and quantitative information on the diffusion of the pathogen in adult sheep from Italy. A total 533 samples were collected, with a similar distribution in the four seasons. For prevalence estimates, a simple random sampling technique was used. An immuno-magnetic separation technique was used for sample screening, with enumeration of the pathogen in positive samples, along with molecular and serological identification of isolates. An overall prevalence of 7.1% (38/ 533, 95% CI 4.9-9.3%) was observed for fully virulent E. coli O157. A wide interval of VTEC O157 per gram was observed (< 100 to 6 x 10(5) CFU g(-1)), with 28.9% (11/38) of positive samples > or = 1 x 10(3) CFU g(-1), set as the threshold for those animals defined 'active shedders' for the purpose of the study. Eight per cent (3/38) of animals shed > 1 x 10(4) g(-1) VTEC O157, which represents > 96% of the total VTEC O157 bacteria cultured from all animals tested. The prevalence estimate of active shedders was therefore 2.1% (95% CI 0.9-3.3%). Most (34/38, 89.5%) of the positive animals were found in summer (July-September). Prevalence and concentrations of virulent VTEC O157 obtained in this study contribute to the demonstration that adult sheep represent a relevant source of environmental contamination from virulent VTEC O157, as well as a source of VTEC O157 contamination for food of ovine origin (meat and dairy products), especially during warm months.

EXTRAPOLATION METHOD FOR MAXIMAL AND 24-H AVERAGE LTE TDD EXPOSURE ESTIMATION

The Long-Term Evolution (LTE) system represents the evolution of the Universal Mobile Telecommunication System technology. This technology introduces two duplex modes: Frequency Division Duplex and Time Division Duplex (TDD). Despite having experienced a limited expansion in the European countries since the debut of the LTE technology, a renewed commercial interest for LTE TDD technology has recently been shown. Therefore, the development of extrapolation procedures optimised for TDD systems becomes crucial, especially for the regulatory authorities. This article presents an extrapolation method aimed to assess the exposure to LTE TDD sources, based on the detection of the Cell-Specific Reference Signal power level. The method introduces a βTDD parameter intended to quantify the fraction of the LTE TDD frame duration reserved for downlink transmission. The method has been validated by experimental measurements performed on signals generated by both a vector signal generator and a test Base Transceiver Station installed at Linkem S.p.A facility in Rome.