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G . B R A N D I , M . S I S T I A N D G . A M A G L I A N I . 2000. Using three sampler devices (SAS, AndersenSix-Stages and All Glass Impinger), the environmental impact of bacterial and fungal aerosols generated by municipal wastewater treatment plants operating with different methods of sludge oxygenation were evaluated. The highest microbial concentrations were recovered above the tanks (2247 cfu m À3 ) and in downwind positions (1425 cfu m À3 ), where a linear correlation (P < 0Á05) was found between the quantity of sewage treated and the entities of microbial aerosol dispersion. Moreover, an exponential increase (P < 0Á05) in the bacteria recovered from the air occurred at increasing times of treatment. However, after long-term plant operation, high bacterial and fungal concentrations were found in almost all of the sites around the plant. Coliforms, enterococci, Escherichia coli and staphylococci were almost always recovered in downwind positions. Considerable fractions (20±40%) of sampled bacteria were able to penetrate the ®nal stages of the Andersen apparatus and thus, are likely to be able to penetrate the lungs. The plant operating with a ®ne bubble diffused air system instead was found to generate rather low concentrations of bacteria and fungi; moreover, staphylococci and indicator micro-organisms were almost absent. Finally, salmonellae, Shigella, Pseudomonas aeruginosa and Aeromonas spp. were not detected in either of the plants. The results indicate a remarkable dispersion of airborne bacteria and fungi from tanks in which oxygen is supplied via a mechanical agitation of sludge, and suggest the need to convert them to diffused aeration systems which pose a lesser hazard for human health.

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Aims:  A rapid and sensitive method for Listeria monocytogenes direct detection from milk was developed. It is based on a magnetic capture hybridization procedure for selective DNA purification, followed by PCR identification. A comparison with two similar commercial systems from Dynal (Dynabeads) was carried out. Methods and Results:  The technique used previously developed nanoparticles modified with a 21‐mer oligonucleotide. This sequence, sharing homology with all the L. monocytogenes strains, was selected on hlyA gene and located outside the desired specific PCR site to avoid cross‐contaminations. Capture probe properties, in term of spacer length and purification, were determined to obtain the highest hybridization efficiency. Its specificity was tested in hybridization experiments with nontarget bacterial species. Any inhibitory effect of the nanoparticles on PCR was also examined. The amplification performed with the purified DNA could reliably identify a 10 CFU ml−1 contamination rate. Conclusions:  The optimized purification method showed a high specificity and sensitivity, with a detection level one log more sensitive than PCR carried out with nucleic acids obtained using commercial nanoparticles. Significance and Impact of the Study:  The method, avoiding pre‐enrichment, provides a rapid alternative to conventional microbiological detection methods. Furthermore, it is suitable for automation and can be proposed for the screening of a large number of samples.

Many vegetables of the Cruciferae family have been found to possess antimicrobial properties against several microorganisms of clinical importance. In this study, we reported the antibacterial effect of Brassica oleracea juice on several food-borne pathogens. The juice was found to be effective in inhibiting the growth of Salmonella Enteritidis, verotoxigenic Escherichia coli O157:H7, E. coli HB producing thermolabile toxin, nontoxigenic E. coli, and Listeria monocytogenes, but not Enterococcus faecalis. All cauliflower cultivars tested suppressed bacterial growth in a dose-dependent manner after 5 h of treatments, and the reduction in the number of viable cells ranged from 1 log with a 10% juice concentration to more than 3 log with a 20% juice concentration. The foodborne bacteria tested were also markedly reduced by isothiocyanates, natural components abundant in the genus Brassica, indicating that glucosinolate-derived isothiocyanates can play a major role in the antimicrobial activity of cauliflower. The antimicrobial effect of juice was reduced in presence of cysteine, suggesting that one mechanism of action of the juice involves blocking bacterial sulfhydryl groups.

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