Interaction of air ions and bactericidal vapours to control micro-organisms.

AIMS: The aim of this study was to investigate the antibacterial activity of candles containing specific-antibacterial compounds, such as essential oils and their constituent compounds. The importance of the ionization products from the flame and the aerial concentration of the volatile compounds were investigated. METHODS AND RESULTS: Agar plates inoculated with Escherichia coli (DH5alpha) or Staphylococcus aureus (NCTC strain number 8532) were exposed in a large air-tight chamber to candle flames combined with the volatile bactericidal compounds beta-pinene and orange oil. A steady decline in E. coli numbers was observed over time because of the effect of a candle flame. This was significantly increased by the addition of volatile oils. The number of S. aureus colonies was not reduced by a plain candle, but significant reductions were caused following exposure to beta-pinene and orange oil candles. As aerial concentration of the volatiles was increased the viability of E. coli and S. aureus declined. Ionization products from the flame made a significant contribution to the observed effects, as intercepting the ions on a grounded grid over the agar plates allowed at least 20% more cells to survive. CONCLUSIONS: This study demonstrates the antibacterial properties of ionization products from a candle flame, and that this effect can be significantly increased by the addition of specific-antibacterial compounds, such as orange oil and beta-pinene. The role of both the ionization products from the candle flame and the concentration of volatile compounds released are important to the effect. SIGNIFICANCE AND IMPACT OF THE STUDY: The technique described here offers a new and novel technique for reducing the concentration of bacteria on surfaces.

The effect of corona discharge on Der p 1.

BACKGROUND: Reduction of house dust mite allergens in the domestic environment can play an important part in reducing sensitization and in the amelioration of symptoms in atopic individuals. Chemical and physical methods have been tried with varied levels of success. The present paper presents a novel electrostatic way of destroying Der p 1, the major mite allergen. OBJECTIVE: To assess the efficacy of negative Trichel, negative continuous glow, positive pulse and positive continuous glow corona in destroying Der p 1. To determine whether ozone has any effect on the integrity of Der p 1 in the experimental conditions present. METHODS: A simple point-to-plane apparatus was used to irradiate samples of Der p 1 for periods of 1, 15, 30, 45, 60, 120, 180, 240 and 300 min. Controls were exposed to the atmosphere with no corona products present for the equivalent time. The effect of the corona by-product ozone was investigated alone by exposing samples of Der p 1 to molecular ozone for 60 min. Der p 1 concentration was quantified by two-site monoclonal antibody ELISA. RESULTS: High current negative glow resulted in a 67.37% reduction in Der p 1 concentration after 300 min compared with a 50.5% reduction from a low current Trichel regime. High current positive glow corona gave a reduction of 25.22% while a low current positive pulse corona caused a 13.72% reduction after 300 min. All these reductions were statistically significant (P < 0.05) compared with unexposed controls. Negative corona always gave greater percentage reductions in Der p 1 concentration for each time exposure investigated. The pattern of percentage reduction follows an exponential rise to maximum relationship in respect to time. Samples of Der p 1 were not affected by exposure to molecular ozone. CONCLUSION: These data indicate corona products to be a powerful new method of destroying Der p 1 allergen that is not dependent on the presence of the oxidizing corona product ozone.

Long-range destruction of Der p 1 using experimental and commercially available ionizers.

BACKGROUND: To reduce the risk of sensitization and the elicitation of allergy symptoms, it is important to reduce the level of allergens in the home. It has previously been demonstrated that corona discharge, the process by which ionizers produce ions, can destroy the major house dust mite allergen Der p 1. OBJECTIVE: In this paper the denaturing efficacy of an experimental ionizer and two commercially available products are evaluated. METHODS: The first test was conducted in an electrically grounded chamber with samples of Der p 1 placed in various positions for 1, 2 and 3 weeks. The second test was conducted in situ in an unoccupied, furnished office room for 1 week. Der p 1 concentration was quantified by two-site monoclonal antibody enzyme-linked immunosorbent assay (ELISA). RESULTS: All ionizers in both tests caused significant reductions in allergen concentration (P < 0.05), reaching a maximum of 92% with the experimental ionizer in the chamber after 3 weeks. The percentage reductions observed in situ with the experimental and the larger commercial ionizer were similar, reaching a maximum of 32% at a distance of 4 m away from the experimental ionizer after 1 week of exposure. CONCLUSION: With a revised protocol for use, air ionizers may offer a simple, efficient and inexpensive way to reduce allergen levels in the domestic environment.

Evidence for genomic rearrangements mediated by human endogenous retroviruses during primate evolution.

Human endogenous retroviruses (HERVs), which are remnants of past retroviral infections of the germline cells of our ancestors, make up as much as 8% of the human genome and may even outnumber genes. Most HERVs seem to have entered the genome between 10 and 50 million years ago, and they comprise over 200 distinct groups and subgroups. Although repeated sequence elements such as HERVs have the potential to lead to chromosomal rearrangement through homologous recombination between distant loci, evidence for the generality of this process is lacking. To gain insight into the expansion of these elements in the genome during the course of primate evolution, we have identified 23 new members of the HERV-K (HML-2) group, which is thought to contain the most recently active members. Here we show, by phylogenetic and sequence analysis, that at least 16% of these elements have undergone apparent rearrangements that may have resulted in large-scale deletions, duplications and chromosome reshuffling during the evolution of the human genome.

Enhanced efficiency of electrostatically charged insecticide aerosols.

The bioefficacy of a standard domestic aerosol insecticide has been compared with that of a similar spray in which the droplets were electrostatically charged. The aerosol was charged without the need for an external power supply, by enhancing natural charge separation processes that occur during atomisation. The charge-to-mass ratio achieved was 1.1 x 10(-4) C kg-1, compared with 2.2 x 10(-5) C kg-1 for the standard aerosol. Efficiency was assessed for insects in free flight. A direct space-spray application method was used to study the bioefficacy of these aerosols on houseflies, Musca domestica, and an indirect space-spray method on houseflies and mosquitoes, Culex quinquefasciatus. Two levels of concentration of active ingredients were compared. At low concentrations of 1.57 g kg-1 of bioallethrin and 0.29 g kg-1 of bioresmethrin, the charged aerosol achieved a significant reduction in KDT50 (time at which 50% of the flies were knocked down), compared with the standard aerosol. In the direct spray application to houseflies, the KDT50 was reduced by 50%, while in the indirect spray the KDT50 was reduced by 40%. In the indirect spray of mosquitoes, the KDT50 was reduced by 22%. With higher active ingredient concentrations of 2.09 g kg-1 for bioallethrin and 0.39 g kg-1 for bioresmethrin, the charged aerosol also demonstrated faster knockdown than the standard, but the improvement was less marked. In the direct spray application to houseflies, the KDT50 was reduced by 21% compared with the standard aerosol, while in the indirect spray the KDT50 was reduced by 16%. In the indirect spray of mosquitoes, the KDT50 was reduced by 24%. The percentage mortality after 24 h was also increased with the charged aerosol. Charge carried by the droplets results in increased interception of the insecticide, as the droplets are attracted to the insects in flight and space charge effects within the aerosol could cause improved dispersion in the test chamber.

Electrostatic charge characteristics of Der p1 allergen-carrying particles and the house dust mite dermatophagoides pteronyssinus.

Control of the house dust mite allergen has received considerable attention owing to its importance in some allergic diseases. One aspect of dust mites and their allergen-carrying faecal particles that has not been reported on, which may have allergen control applications, is the electrostatic charge they carry in the natural environment. To promote tribo-electric charging, household dust containing dust mite allergen and live house dust mites are separately agitated while in contact with either polypropylene, nylon or earthed metal. The charged dust and mites are subsequently subjected to electrostatic separation and collection. Results for concentrations of the house dust mite allergen, Der p1, indicate that, when subjected to nylon, Der p1 carrier particles appear to be predominantly positively charged. Similarly, when subjected to polypropylene, Der p1 carrier particles also appear to be positively charged. Reduction of excess free charge by agitation against earthed metal does not appear to affect the observed charging characteristics, indicating that the positive charge may be bound or inherent in the Der p1 carrier particles. In contrast, house dust mites exposed to nylon appear to be generally charging negative, whereas mites exposed to polypropylene appear to be charging positive. The observed electrostatic characteristics of the mites and Der p1 carrying particles will be useful in the future development of electrostatic allergen control methods.

Dust anchoring characteristics of electret fibres with respect to Der p 1 allergen carrying particles.

The avoidance of house dust mite allergens is a major area of interest and essentially requires a significant removal of these allergens from the immediately respirable air. Electrostatic attraction and anchoring of particulate matter using electret polymers is commonly used for air filtration purposes. This effect is investigated for its possible use in domestic allergen avoidance. Polypropylene electret, heat-treated electret and non-electret, and wool and nylon fibre samples were soiled with house dust known to contain Der p 1 allergen. These samples were vacuumed at three air face velocities. The proportions of released and anchored dust were calculated. Released dust was collected and analysed for Der p 1 concentration and compared to stock dust values. Results showed that compared to uncharged fibres at least 95% more dust remained anchored in the electret fibres. Also, overall Der p 1 release was reduced by more than 49%. Der p 1 allergen concentrations in the collected dust were relatively constant for all the fibres tested, indicating no selective attraction or repulsion of Der p 1 allergen carrying particles in the experimental dust. The consistently high dust anchoring ability of the electret fibres could be used in many domestic products that are known to harbour particulate allergens, to reduce their release and inhalation.

Multiple-infected diagnostic specimens from foot and mouth disease endemic regions.

The current routine diagnostic procedures for foot and mouth disease (FMD) virus antigen detection combine the use of an indirect sandwich enzyme-linked immunosorbent assay (ELISA) with virus isolation and amplification on cell culture. Several field samples recently received by the World Reference Laboratory for Foot and Mouth Disease which were initially diagnosed as containing a single virus type have subsequently been found to contain an additional virus type. Examples are given of the results of ELISAs performed on certain Saudia Arabian samples; these examples illustrate the problem which such multiple-infected samples present for laboratory diagnosis.

Electrostatic emulsification of domestic and personal care products.

Synopsis A technique is described for producing high quality emulsions in a controllable and reproducible way. The dispersed liquid phase is atomized electrostatically, thus enabling particle size to be well below 10mum for wax solutions while at the same time maintaining a very narrow particle size distribution. The energy saving over conventional emulsification methods is considerable, amounting to up to 85% for one typical domestic care product. Emulsification is achieved in a one-step process in a machine which essentially has no moving parts and requires no auxiliary air supply. In addition to the ability to create high quality emulsions, electrostatic atomization of the dispersed phase itself introduces a new and useful parameter, electrical conductivity, enabling greater flexibility in terms of ensuring emulsion stability. Even in conventional emulsifier systems, electrically charging the dispersed phase may have important implications which have not to date been fully appreciated.

Lincomycin-clindamycin-associated psuedomembranous colitis.

Five cases of lincomycin-clindamycin-associated acute pseudomembranous colitis, demonstrating a spectrum of clinical, histological and radiological severity, were encountered over a five-months period. All patients presented with watery diarrhoea without the passage of macroscopic blood or pus. Two patients were seriously ill with fulminant colitis, but responded rapidly to corticosteroids given parenterally and supportive therapy. The diagnosis of acute colitis should be considered in all patients developing diarrhoea during or up to three weeks after beginning therapy with lincomycin or clindamycin and can be confirmed by sigmoidoscopic examination. Withdrawal of the antibiotic and symptomatic treatment is appropriate for mild cases of colitis, but our experience suggests that corticosteroid therapy is safe and effective in severe cases. Indiscriminate use of these antibiotics should be avoided.