Stefano Dumontet

Transformations of carbon and nitrogen during composting of animal manure and shredded paper

Abstract Composts produced from animal manures and shredded paper were characterized in terms of their carbon (C) and nitrogen (N) forms and C mineralization. Total, water-soluble, acid-hydrolyzable and non-hydrolyzable C and N contents were determined on composts sampled on days 0, 11, 18, 26, 33, 40 and 59 after composting was initiated. Water-soluble and acid-hydrolyzable C and N decreased during composting, whereas non-hydrolyzable C remained relatively constant, and non-hydrolyzable N greatly increased during composting. The water-soluble forms of N were characterized by a decrease of ammomium (NH4+-N) at the beginning of composting, followed by an increase of nitrate (NO3–-N) towards the end of composting. The mineralization of C in composted materials was generally higher at the beginning than at the end of composting, whereas no differences were observed for mineralization of C in non-hydrolyzable materials. The addition of N inhibited C mineralization in composts except in samples collected on days 40 and 59, while C mineralization was strongly stimulated by adding N to the non-hydrolyzable materials. The data suggest that the N forms in the non-hydrolyzable materials were chemically similar and not readily available to microbes, indicating that the C/N ratios often used to assess the biodegradability of organic matter and to develop compost formulations should be based on biologically available N and C and not on total N and C.

Effects of organic amendment and herbicide treatment on soil microbial biomass

Abstract The interactive effects of vermi-compost from sewage sludge and either the sulfonylurea herbicide, rimsulfuron, or the imidazolinone herbicide, imazethapyr, on some soil biochemical and microbiological properties were investigated. The herbicides were applied at field and 10-fold field rates. Both herbicides exerted a detrimental effect on soil microbial biomass and its biochemical properties. Even though the effect of both herbicides on soil microbial biomass was not detectable at the field rate, some significant influences on acid and alkaline phosphatase were observed. The higher rate of herbicide application impaired the observed microbial parameters to a greater degree. The detrimental effects seemed to be reduced by organic amendments. Among the studied microbial characteristics, the specific respiration quotient was particularly reliable and sensitive in determining the influence of herbicides on the soil microbial biomass. In this paper a new synthetic index, specific hydrolytic activity (qFDA), for assessing microbial activity in reply to xenobiotic treatments is proposed.

Prevalence and diversity of Aeromonas and Vibrio spp. in coastal waters of Southern Italy.

A survey was undertaken to examine sea water and sediment for the presence of Vibrio and Aeromonas spp. along approximately 900 km of coast in Southern Italy during early and late summer. A quantitative analysis was also done to evaluate the water fecal contamination at the stations examined. The results indicate that all the investigated areas were submitted to a wide spatial fluctuation of fecal contamination and that Vibrio and Aeromonas spp. were present in both high and low fecal-contaminated stations. Sixty two percent of the investigated samples were positive for Aeromonas spp., while 42% of samples were positive for Vibrio spp. It was interesting to note that 38% of the positive stations for both Aeromonas and Vibrio spp. showed a fecal coliform contamination of water at < 10(2) cells 100 ml(-1). Thus, these findings support the hypothesis that the bacterial indicators (such as fecal coliforms) do not always satisfactorily reflect the hygienic quality of water. The presence of Vibrionaceae on copepods was also investigated. Copepods were sampled at a station located inside the harbour of the city of Naples and were found contaminated by V. cholerae non-O1, V. alginolyticus, V. fluvialis and A. caviae. Furthermore, the antibiotic resistance patterns of isolated bacteria showed the presence of a number of resistant strains among the isolates. In order to discriminate the isolates on the basis of their biochemical profiles and/or antibiotic resistance patterns, cluster analysis was carried out which showed that no unique assay could fully discern these isolates. However, the best discrimination resulted from complete pattern profile based on both biochemical profiles and antibiotic resistance patterns.

The Importance of Pathogenic Organisms in Sewage and Sewage Sludge

ABSTRACT Deficient sanitation poses a serious threat to human and animal health, involving complex relationships between environments, animals, refuse, food, pathogens, parasites, and man. However, by sanitizing and stabilizing the organic matter of sewage sludge, agriculture can utilize it to maintain soil, water, and air quality. As ingredients in soil amendments, such bioresidues are a source of nutrients for plants. Stabilization and sanitation of sewage sludge safely couple its recycling and disposal. This coupling becomes increasingly important as economic and environmental constraints make strategies for waste disposal more difficult to apply. The occurrence of viruses, bacteria, yeasts, fungi, and zooparasites in sewage sludge is reviewed in this article, and consequential epidemiologic concerns that arise from sewage sludge recycling is also addressed.

Isolation, and Virulence Profiles, of Aeromonas hydrophila Implicated in an outbreak of Food Poisoning in Sweden

A case of food poisoning outbreak involving Aeromonas hydrophila is reported in this study. A group of 27 people consumed a typical Swedish food “landgång” which is a type of smörgåsbord containing shrimps with mayonnaise, liver paté, ham, sausage, and legume salad which was purchased from a food store. Twenty‐two of the 27 persons became ill within 20‐34 hr of consumption of the food and reported the symptoms ranging from severe acute diarrhea, abdominal pain, headache, fever and vomiting. One person also fainted. The symptoms lasted for a couple of days. Of the remaining 5 healthy persons who consumed the left‐over food the next day, 2 became ill with similar symptoms. The bacteriological examination of left‐over food samples resulted in the isolation of A. hydrophila from shrimps with mayonnaise, smoked sausage, liver paté and boiled ham. The total number of A. hydrophila in these foods were log 106 to log >107 organisms per gram of food sample. A. hydrophila was however, not isolated from legume/mayonnaise salad samples. All the food samples tested showed low numbers of other expected food contaminating organisms such as coliforms at 37 C and 44 C, fecal streptococci, Staphylococcus aureus, fungi and yeast etc., while Bacillus cereus, Clostridium perfringens and Salmonella spp. were not detected in the food samples. Investigations of the virulence profiles of the A. hydrophila isolates showed their capacity to produce β‐hemolysin, cytotoxins, cytotonic toxins, enterotoxins, and adhesion to and invasion of human intestinal (Henle 407) cells in culture.

Ecological relationship between Aeromonas and Vibrio spp. and planktonic copepods in the coastal marine environment in Southern Italy

The colonisation of planktonic copepod integument by bacteria belonging to the family of Vibrionaceae is a well described phenomenon. In this study, besides reporting on the occurrence of Vibrionaceae and other enteropathogens, we further report on the bacterial attachment to the Estuarine copepod Acartia margalefi in a faecal polluted coastal lagoon near Naples, Southern Italy. In addition, we also performed a laboratory experiment to study the ability of 7 bacterial strains (Vibrio cholerae non-Ol, V. mimicus, V. parahaemolyticus, V. alginolyticus, Aeromonas hydrophila, Escherichia coli and Pseudomonas sp.) to colonise the copepod integument. For this laboratory study, 4 different species of copepods, namely Temora stylifera, A. clausi, Centropages typicus and Paracalanus parvus sampled from the Gulf of Naples (Southern Italy) were used. Scanning electron microscope (SEM) studies on the copepods sampled from the lagoon indicated that the bacterial attachment on the integument of Acartia margalefi was mainly on the ventro-lateral body region of the host and in the joints of the thoracic segments, as well as on the swimming and feeding appendages. This infestation, made by rod-like bacteria, was absent in winter but reached peak values of 70% frequency in June. The laboratory studies showed that while V. cholerae non-O1 and A. hydrophila attached on live and dead copepods, respectively, the V. parahaemolyticus, V. alginolyticus, V. mimicus, E. coli and Pseudomonas sp. failed to colonise either live or dead copepods. Thus, this study provides further valuable information about the ecological relationship between different microorganisms (pathogens) and copepods in the coastal marine environment in Southern Italy.

Toxic effects of four sulphonylureas herbicides on soil microbial biomass

The effect of four triazinyl-sulfonylurea herbicides (cinosulfuron, prosulfuron, thifensulfuron methyl, triasulfuron) on soil microbial biomass, soil respiration, metabolic activity, metabolic quotient, and some enzymatic activities (acid and alkaline phosphatase, β-glucosidase, arylsulphatase, and fluorescein diacetate hydrolysis) were monitored under controlled conditions over 30 days. The herbicides were applied at the normal field dose (FD) and at ten-fold (10 FD) the field dose, in order to mimic a long term toxic effect. The measured soil microbial parameters showed that the FD had slight effects on soil microflora, while at 10 FD the tested herbicides exerted a stronger detrimental effect on soil microbial biomass and its biochemical activities.

Effectiveness of microbial indexes in discriminating interactive effects of tillage and crop rotations in a Vertic ustorthens

Abstract. Conservation tillage is a soil management practice able to reduce erosion, increase organic matter content and improve physical, chemical and biological soil properties. Conservation tillage reduces the incorporation of crop residues into the soil profile and minimises the exposure of humified organic matter to biotic and abiotic degradative processes. In this article the effect of conventional (ploughing at 40-cm depth coupled with harrowing at 20-cm depth) and reduced tillage (harrowing at 20-cm depth) and two rotations (vetch-oat/wheat and fallow/wheat) on biochemical and microbial properties of a Vertic Ustorthens, located in a semi-arid region of southern Italy, has been investigated. Tillage had a more pronounced effect on soil properties studied here than did rotations. By comparison to conventional tillage (CT), the reduced tillage (RT) resulted in improved soil C and microbial biomass content. Even though some of the selected enzymes showed seasonal variability and, when averaged across the sampling period, were not always able to discriminate among treatments, their sum showed a strong correlation with soil organic C and soil microbial biomass C (MBC), for all these parameters increased in RT plots.

Toxigenic Clostridium difficile PCR Ribotypes from Wastewater Treatment Plants in Southern Switzerland

ABSTRACT The occurrence of Clostridium difficile in nine wastewater treatment plants in the Ticino Canton (southern Switzerland) was investigated. The samples were collected from raw sewage influents and from treated effluents. Forty-seven out of 55 characterized C. difficile strains belonged to 13 different reference PCR ribotypes (009, 010, 014, 015, 039, 052, 053, 066, 070, 078, 101, 106, and 117), whereas 8 strains did not match any of those available in our libraries. The most frequently isolated ribotype (40%) was 078, isolated from six wastewater treatment plants, whereas ribotype 066, a toxigenic emerging ribotype isolated from patients admitted to hospitals in Europe and Switzerland, was isolated from the outgoing effluent of one plant. The majority of the isolates (85%) were toxigenic. Forty-nine percent of them produced toxin A, toxin B, and the binary toxin (toxigenic profile A+ B+ CDT+), whereas 51% showed the profile A+ B+ CDT−. Interestingly, eight ribotypes (010, 014, 015, 039, 066, 078, 101, and 106) were among the riboprofiles isolated from symptomatic patients admitted to the hospitals of the Ticino Canton in 2010. Despite the limitation of sampling, this study highlights that toxigenic ribotypes of C. difficile involved in human infections may occur in both incoming and outgoing biological wastewater treatment plants. Such a finding raises concern about the possible contamination of water bodies that receive wastewater treatment plant effluents and about the safe reuse of treated wastewater.

Extractable Soil Lipids and Microbial Activity as Affected by Bt and Non Bt Maize Grown on a Silty Clay Loam Soil

Pyrolysis‐gas (Py‐GC) chromatography was used to characterize extractable lipids from Bt and non‐Bt maize shoots and soils collected at time of harvesting. Py‐GC‐MS (mass spectrometry) showed that the concentrations of total alkenes identified in non‐Bt shoots and soils were 47.9 and 21.3% higher than in Bt maize shoots and soils, respectively. N‐alkanes identified were of similar orders of magnitude in Bt and non‐Bt maize shoots, but were 28.6% higher in Bt than in non‐Bt soils. Bt maize shoots contained 29.7% more n‐fatty acids than non‐Bt maize shoots, whereas the concentrations of n‐fatty acids in Bt soils were twice as high as those in non‐Bt soils. Concentrations of unsaturated fatty acids in Bt maize shoots were 22.1% higher than those in non‐Bt maize shoots, while concentrations of unsaturated fatty acids were 22.5% higher in non‐Bt than in Bt soils. The cumulative CO2–C evolved from soils under Bt and non‐Bt crops was 30.5% lower under Bt as compared to non‐Bt crops, whereas when maize shoots were added to Bt and non‐Bt soils, the decrease in CO2–C evolved were 16.5 and 23.6%, respectively. Our data showed that the cultivation of Bt maize significantly increased the saturated to unsaturated lipid ratios in soils which appeared to negatively affect microbial activity.