Stability of particle flocs upon addition of natural organic matter under quiescent conditions.

In this research, the influence of two natural organic polymers (polysaccharide and humic acid) on the stability of colloidal aggregates was examined. The primary objective of this research was to determine whether addition of organic matter to floc suspensions results in the fragmentation or stabilization of aggregates. A second objective was to determine how the size of aggregates and the composition of organic matter influence the floc breakup or stabilization process. It was found that the stability of aggregates depended on the type of organic material present as well as floc size. For example, humic acid increased the stability of aggregates more effectively than polysaccharides of larger size. It was also found that the addition of humic acid or polysaccharide generally decreased the rate of coagulation of small aggregates but had less influence on large aggregates. In no case did the addition of polysaccharide or humic acid result in the fragmentation of particle aggregates. The existence of strong interparticle forces within flocs prevented aggregate breakup upon adsorption of natural organic polymers. The results presented here provide important new information regarding the influence of NOM on the behavior of particles in aquatic systems.

Needs for care from a demand led community psychiatric service: a study of patients with major mental illness.

UNLABELLED: OBJECTIVE--To measure needs for care of patients aged 18-65 years with major mental illness. DESIGN: Identification of everyone in one area seen by a health professional within the previous five years because of a psychotic disorder. Interview of a one in three sample of patients and their main carers with the cardinal needs schedule. SETTING--Hamilton, a socially deprived district of Scotland. SUBJECTS--71 subjects were interviewed from the original sample of 263 patients. MAIN OUTCOME MEASURES--"Cardinal problems" in seven clinical and eight social areas of functioning; these are defined as problems requiring action. "Needs"-cardinal problems for which suitable interventions exist but have not been tried recently. RESULTS--High levels of morbidity were found. 30 interviewed patients (42%; 95% confidence interval 31% to 54%) had one or more clinical needs. 35 (49%; 38% to 61%) had one or more social needs. Skills to deal with all but seven needs in the sample were available at the time of investigation. Patients not being seen by the community mental health team were similar in severity and levels of need to those who were on the community team's caseload. Care was unequivocally and severely inadequate for four patients. Shortcomings in service delivery usually arose from failure to monitor some patients at home. Problems were not due to shortage of acute psychiatric beds nor the absence of an elaborate assertive community care team. CONCLUSIONS--Systematic assessment of needs with research instruments can give valuable insights into the successes and failures of community care of people with major mental illness. Most needs could be dealt with in these patients but in our area (and probably most other parts of the United Kingdom) this would entail diversion of resources from people with less severe disorders.

Inhibition of Aspergillus flavus and Selected Gram-positive Bacteria by Chelation of Essential Metal Cations by Polyphosphates.

A simple well-plate technique was utilized to determine the effect of various metals on the growth of microorganisms in media containing different polyphosphates. Aspergillus flavus and four gram-positive bacteria were completely inhibited by media containing 1% of various alkaline polyphosphates, whereas four gram-negative bacteria were not. Significant differences were observed between the type of polyphosphate added, the type of metal added, and the species of gram-positive bacterium inhibited. The addition of Mg2+ stimulated growth of A. flavus and Bacillus cereus in the presence of tetrasodium pyrophosphate, whereas Mn2+ permitted growth of A. flavus and Staphylococcus aureus in the presence of sodium hexametaphosphate. Iron supplementation allowed the growth of S. aureus and Listeria monocytogenes on media containing 1 % tetrasodium pyrophosphate. A method for determining the amount of calcium and magnesium in water was modified to detect free Mg2+ by replacing EDTA with phosphate. The addition of free Mg2+, but not Mg2+ chelated by tetrasodium pyrophosphate, permitted the growth of B. cereus on a medium containing tetrasodium pyrophosphate. It is speculated that polyphosphates specifically inhibited A. flavus and gram-positive bacteria by removing essential metals from cation-binding sites located within their cell walls.

Effects of growth temperature and strictly anaerobic recovery on the survival of Listeria monocytogenes during pasteurization.

Listeria monocytogenes F5069 was suspended in either Trypticase soy broth-0.6% yeast extract (TSBYE) or sterile, whole milk and heated at 62.8 degrees C in sealed thermal death time tubes. Severely heat-injured cells were recovered in TSBYE within sealed thermal death time tubes because of the formation of reduced conditions in the depths of the TSBYE. Also, the use of strictly anaerobic Hungate techniques significantly increased recovery in TSBYE containing 1.5% agar compared with aerobically incubated controls. The exogenous addition of catalase, but not superoxide dismutase, slightly increased the recovery of heat-injured cells in TSBYE containing 1.5% agar incubated aerobically. Growth of cells at 43 degrees C caused a greater increase in heat resistance as compared with cells heat shocked at 43 degrees C or cells grown at lower temperatures. Growth of L. monocytogenes at 43 degrees C and enumeration by the use of strictly anaerobic Hungate techniques resulted in D62.8 degrees C values that were at least sixfold greater than those previously obtained by using cells grown at 37 degrees C and aerobic plating. Results indicate that, under the conditions of the present study, high levels of L. monocytogenes would survive the minimum low-temperature, long-time treatment required by the U.S. Food and Drug Administration for pasteurizing milk. The possible survival of low levels of L. monocytogenes during high-temperature, short-time pasteurization and enumeration of injured cells by recovery on selective media under strictly anaerobic conditions are discussed.

Inhibition of Growth and Aflatoxin Production of Aspergilli in Medium Containing Phosphates.

Mycelial growth and mycotoxin production of Aspergillus flavus and A. parasiticus were studied in Sabouraud dextrose agar containing pure or blended pyro-, poly- or meta-phosphates during 9 d of incubation at 30°C. Pure tetrasodium pyrophosphate (TSPP) and sodium polyphosphate, glassy (SPG, formerly hexametaphosphate), as well as a commercial phosphate blend and three combinations all containing various proportions of sodium acid pyrophosphate (SAPP), TSPP and SPG were tested. Inhibition of growth of aspergilli was observed in media containing 2.0% TSPP and 1.0 and 2.0% SPG and 2.0% of the commercial phosphate blend. Lower concentrations of single or blended phosphates allowed only limited, atypical mycelial growth. Sporulation was totally inhibited by 2.0% concentrations of single or blended phosphates, and so was production of aflatoxins B1 and G1. TSPP or SPG at 1.0% reduced (P<0.05) aflatoxin production from parts per million (controls) to parts per billion.

Inhibition of Mold Growth and Mycotoxin Production in High-Moisture Corn Treated with Phosphates.

Mold growth and mycotoxin production were studied in high-moisture (20%) corn treated with tetrasodium pyrophosphate (TSPP); acid and alkaline sodium polyphosphate, glassy (SPG), also known as sodium hexametaphosphate; sodium tripolyphosphate (STPP); and tricalcium phosphate. Six mold cultures belonging to the genera Aspergillus , Fusarium , and Penicillium were tested in corn varieties highly resistant or highly susceptible to mold infection in the field, and in a mixture of five other varieties of corn. The acidic SPG, as well as TSPP and STPP totally prevented or reduced mold growth when added in powder form to corn at 1.0% or 2.0% (w/w), regardless of corn variety and high moisture content. Phosphates afforded protection in whole and damaged kernels. Similar results were obtained with 2.0% acidic SPG and TSPP when added in spray form. Whenever mold growth occurred, treatment of corn with 1.0% or 2.0% (w/w) TSPP and acidic or alkaline SPG inhibited (P<0.01) aflatoxin production by aspergilli.

Survival of Clostridium perfringens and Aerobic Bacteria in Ground Beef Patties during Microwave and Conventional Cookery 1.

Conventional oven cookery was more effective than microwave oven cookery for reducing numbers of aerobic microorganisms and Clostridium perfringens in ground beef patties when the meat was heated to approximately the same internal temperatures of 65-71°C for rare or 77-93°C for well done. Reductions in numbers of C. perfringens during microwave cookery of patties inoculated with 105 vegetative cells/g ranged from 0.75 to 1.48/g (log values); for conventional cookery, these reduction values ranged from 3.51 to 8.06/g (log values). Recovery of heat-stressed cells of C. perfringens was equally efficient in Trypton-Sulfite-Cycloserine agar and Sulfite-Polymyxin-Sulfadiazine agar.

Use of dogs as an assay for Clostridium perfringens enterotoxin.

Three techniques for using the dog as an assay organism for Clostridium perfringens enterotoxin are described. These are believed to be more convenient than ligated ileal-loop procedures.

Oxidation-reduction potential and growth of Clostridium perfringens and Pseudomonas fluorescens.

A new apparatus was developed for measuring changes in E(h), pH, and cell numbers. With this apparatus, the relationships of these parameters were studied at initial E(h) levels of 200 and 40 mv (pH 7.0), by using Clostridium perfringens and Pseudomonas fluorescens. One of the strains of C. perfringens grew more luxuriantly at the higher E(h), in the presence of small quantities of oxygen, than at the lower one in the absence of oxygen. P. fluorescens could grow at a relatively low E(h) (40 mv, pH 7.0) in pure culture but not in the presence of C. perfringens under the same conditions.

Fatty acids from vegetative cells and spores of Bacillus stearothermophilus.

In spores of Bacillus stearothermophilus produced at 45 and 55 C, branched-chain fatty acids predominated in the former and straight-chain acids in the latter.

Response of white mice to cells and culture constituents of Clostridium perfringens.

Broth cultures of Clostridium perfringens (ATCC 10543) were fractionated by ammonium sulfate precipitation and Sephadex G-150 chromatography. Components isolated, as well as some enzymes present in the culture, were assayed for toxicity by feeding to white mice. Early work indicated that when a meat-fat-starch slurry, infected with C. perfringens, was fed to mice, the intestinal passage time was reduced. By using large numbers of mice as test animals and analyzing the data statistically, we found that C. perfringens and several fractions from the culture supernatant significantly affected the mice. A toxic material present in the supernatant was not identifiable as phospholipase C. Phospholipase C and physphorylcholine affected the intestinal passage time of the mice only when large amounts were given. The enzyme, neuraminidase, and another unidentified compound present in the supernatant affected the passage time when very small amounts were fed to mice.

Detection of botulinal toxins by immunodiffusion.

A procedure employing concentration with Sephadex and analysis by gel diffusion (Ouchterlony) was used to detect the toxins of Clostridium botulinum in foods. Botulinal toxins with toxic levels of 370 to 557 mouse LD(50) per milliliter were detected in the food samples. Test results were verified by use of the mouse protection test. Approximately 24 hr were required to complete the entire procedure.