Augmenting effect of acetic acid for acidification on bactericidal activity of hypochlorite solution

AIMS: Bactericidal activity of chlorine solution is enhanced by weak acidification. We compared the effects of various acids on the bactericidal activity of hypochlorite solution to establish a method for safe and effective use of an acidic hypochlorite solution. METHODS AND RESULTS: The bactericidal activities of acidic hypochlorite solutions that had been adjusted to pH 5.0 with hydrochloric acid, acetic acid, citric acid, lactic acid, formic acid, phosphoric acid or sulphuric acid against Bacillus subtilis spores were compared. The acidic solutions prepared with hydrochloric acid and acetic acid showed the highest bactericidal activity, and all of the spores (5 x 106 cfu ml(-1)) were killed within 10 min. On the other hand, the solutions prepared with citric acid and lactic acid showed no bactericidal activity against any bacterial strains tested in this study despite the low pH. The amount of chlorine gas produced by the preparation using acetic acid was sixfold less than that produced from the preparation using hydrochloric acid. CONCLUSIONS: Acetic acid is the most suitable and safe acid for the preparation of an acidic hypochlorite solution. SIGNIFICANCE AND IMPACT OF THE STUDY: The results of this study provide useful information for establishing a method for safe and effective use of an acidic hypochlorite solution.     

Patulin and aflatoxin in brown rot lesion of apple fruits and their regulation

Aspergillus flavus, A. niger, Penicillium expansum and Rhizopus stolonifer were the most frequently isolated fungi from healthy apple fruits. Alternaria alternata was the most common organism of rotten apple fruits, followed by A. niger, A. flavus, P. expansum and R. stolonifer. The prevalent type of decay, brown rot lesion, is caused by R. stolonifer followed by A. flavus, A. niger, A. alternata and P. expansum. Sodium hypochlorite had good curative properties against fruit rots. The main natural mycotoxins produced in rotten apple were patulin and aflatoxins. The optimum temperature for patulin production by P. expansum was 15 °C after 15 days. Complete inhibition of patulin formation was attained using 0.2% lemon oil and > 90% inhibition using 0.05% lemon and 0.2% orange oils. Also significant inhibition (> 90%) of aflatoxin production was observed with 0.2% lemon oil. This revised version was published online in July 2006 with corrections to the Cover Date.     

Sodium hypochlorite perturbation of a graywater treatment system

A novel graywater treatment system consisting of an aerated batch reactor and biomass-retaining ultrafiltration unit was evaluated for treatment of shipboard wastes. The focus of this study was to determine the resilience of the biomass recycle reactor to perturbations of sodium hypochlorite, the major component of bleach. A bench-scale reactor was perturbed with 50, 190, and 1000 mg L⁻¹ sodium hypochlorite and monitored for changes in respiration, substrate utilization, viable plate counts, fatty acid methyl ester profiles, and Biolog-GN patterns. Following the addition of hypochlorite, respiration and substrate utilization were not detected, and viable biomass decreased. Recovery times following perturbations were longer with higher concentrations of sodium hypochlorite. Community composition (determined by fatty acid methyl ester analysis) changed during the recovery from hypochlorite perturbations. However, more significant differences in community composition were noted between different perturbations and were a function of time. Irrespective of initial community composition, the reactor communities recovered from hypochlorite perturbations. Biolog patterns showed no notable change in the overall metabolic capacity of the community. The biomass recycle reactor’s resistance to sodium hypochlorite perturbations contributes to its usefulness in treatment of shipboard wastes. Journal of Industrial Microbiology & Biotechnology (2000) 24, 191–197. Received 28 July 1999/ Accepted in revised form 03 December 1999     

Disinfection characteristics of waterborne pathogenic protozoaGiardia lamblia

Giardia lamblia is a parasitic protozoa which is transmitted in the form of a cyst through untreated water and also treated drinking water. Since its presence in water has led to frequent outbreaks of giardiasis and death in many countries, the removal and disinfection of this protozoan cyst from the water supply are of great concern for public health. This study examined the disinfection characteristics ofG. lamblia cysts isolated from a Korean patient with giardiasis. When using sodium hypochlorite includdig 5 or 10 ppm chlorine, the killing rate was initially rapid however, the disinfection slowed down and a Blog reduction could not be achieved even after 2 h. The disinfection effectiveness was also reduced at a lower temperature, thereby implying that the risk of a giardiasis outbreak will be higher in the winter season. A CT (concentration time) curve was constructed based on the results with sodium hypochlorite for use in designing and predicting disinfection performance. The organic chlorination disinfectant SDIC (sodium dichloroisocyanurate) produced a lower pH and a much higher residual effect than sodium hypochlorote. The disinfection of cysts by SDIC continued steadily throughout 2 h of contact, although the initial killing rate was lower than that with sodium hypochlorite.     

What do we measure with luminol-, lucigenin- and penicillin-amplified chemiluminescence? 1. Investigations with hydrogen peroxide and sodium hypochlorite

Evidence is provided that the amplifiers luminol and lucigenin react with different reactive oxygen species (ROS), depending on the ROS-generating system used. H₂O₂ is used to produce calibration curves for luminol- and lucigenin-amplified chemiluminescence. With this chemiluminescence generator we characterized the specificity and sensitivity of luminol- and lucigenin-amplified chemiluminescence and also studied penicillin G, a known enhancer of luminol-amplified chemiluminescence. The combination of luminol and lucigenin in reciprocally changing concentrations is effective in an additive manner, but the weak amplifier penicillin increases luminol-amplified chemiluminescence distinctly more than in an additive manner in different combinations. Lucigenin-amplified chemiluminescence is increased by penicillin at about 1% of the optimum concentration of penicillin; increasing concentrations of penicillin are less and less effective. On the other hand, low lucigenin concentrations enhance penicillin-amplified chemiluminescence at optimum penicillin concentrations more than in an additive manner. Fe²⁺ does not alter luminol-, lucigenin- or penicillin-amplified chemiluminescence. Co²⁺ increases luminol-amplified chemiluminescence by a factor of 100. Lucigenin- and penicillin-amplified chemiluminescence are minimally enhanced by Co²⁺. Cu²⁺ enhances luminol-amplified chemiluminescence with increasing concentrations by a factor of 1000. Lucigenin-amplified chemiluminescence increases also by the factor of 1000, but the concentration–reaction curve is not as steep. NaOCl enhances H₂O₂/Fe²⁺-driven luminol-amplified chemiluminescence in a concentration-dependent manner by a factor of 10⁴ (in the highest concentration of 10 mmol/L) and lucigenin amplified chemiluminescence only by a factor of about 25. Catalase (CAT) abolishes luminol-, lucigenin- and penicillin-amplified chemiluminescence completely, whereas superoxide dismutase (SOD) has no effect on luminol- or penicillin-amplified chemiluminescence, but enhances lucigenin-amplified chemiluminescence five-fold increasingly with increasing SOD activity. © 1998 John Wiley & Sons, Ltd.     

A ratiometric fluorescent probe for rapid and specific detection of hypochlorite

Hypochlorite (ClO⁻), as a kind of essential reactive oxygen species, plays a crucial role in vitro and in vivo. Here, a ratiometric fluorescent probe ( TPAM ) was designed and constructed for sensing ClO⁻ based on substituted triphenylamine and malononitrile, which exhibited obvious colour transfer from orange to colourless under daylight accompanied by noticeable fluorescence change from red to green in response to ClO⁻. TPAM could effectively monitor ClO⁻ with the merits of fast response, excellent selectivity, high sensitivity and a low detection limit of 0.1014 μM. ¹H NMR, mass spectra and theoretical calculations proved that ClO⁻ caused the oxidation of the carbon–carbon double bond in TPAM , resulting in compound 1 and marked changes in colour and fluorescence. In addition, TPAM was utilized for imaging ClO⁻ in living cells successfully with good photostability and biocompatibility.     

Effects of hypochlorite on cultured respiratory epithelial cells

Neutrophils and eosinophils are involved in the pathogenesis of many respiratory diseases. The enzymes myeloperoxidase and eosinophil peroxidase catalyze the reaction of H₂O₂ with Cl to produce the reactive oxygen species HOCl.

Normal human bronchial epithelial (NHBE) cells were exposed to 0.18–0.90 mM HOCl for 48 h, and studied with immunohistochemical, metabolic and morphological studies.

The ability of the cells to attach to each other and/or to the matrix was altered. Immunohistochemical studies showed a decreased amount of desmosomes and focal adhesion sites, although the morphology of the cells was not affected. The ability of the mitochondria to oxidize glucose was reduced. HOCl-exposed cells had an increased production of NO, probably by an increased activity of cNOS, due to increased intracellular Ca²⁺. The antioxidant N-acetylcysteine inhibited both the NO production and the effects of HOCl on glucose oxidation. The cNOS-inhibitor N-propyl-L-arginine inhibited HOCl-induced NO production. X-ray microanalysis showed an increase in the intracellular Na⁺/K⁺ ratio, which indicates cell damage.

In conclusion, exposure to HOCl results in cell detachment and metabolic alterations in normal human bronchial epithelial cells. Oxygen radicals could in part mediate the effects. Oxygen radicals could hence contribute to the observed epithelial damage in respiratory diseases.     

Intra-specific hybridization: generator of genetic diversification and heterosis in Andrographis paniculata Nees. A bridge from extinction to survival

Andrographis paniculata (AP) has been stated as a low-diverse, endangered and red-listed plant species. Self-pollinated mating system, being an introduced species and experiencing a bottleneck as well as over exploitation cause such a consequence. Inter and intra-specific hybridizations have been suggested as essential techniques for generating genetic diversity. To test the effect of intra-specific hybridization on diversification and heterosis of AP, seven accessions were outcrossed manually in all 21 possible combinations. Three types of markers including morphological, phytochemical and RAPD markers were employed to evaluate the mentioned hypothesis. The results revealed that hybridization acted as a powerful engine for diversification of AP as it caused heterotic expression of the studied traits, simultaneously. Initially, it seems that additive and non-additive gene effects both can be considered as the genetic basis of heterosis in AP for the investigated traits. Agronomic and morphological traits were differentiated from each other, while positive heterosis was recorded mainly for agronomic traits but not for the morphological traits. Intra-specific hybridization increased the genetic diversity in AP population. Nevertheless, a part of this variation could also be attributed to the negative heterosis. The current exploration demonstrated the first ever conducted manual intra-specific hybridization among AP accessions in a mass scale. However, the 17 RAPD primers produced a monomorph pattern, but perhaps increasing the number of markers can feature a new genetic profile in this plant.     

Wide variation in effectiveness of laboratory disinfectants against bacteriophages

Aims: The purpose of this study was to identify an effective disinfectant for the inactivation of the bacteriophages (phages) being used in our laboratory, as published studies on phage inactivation are far from unanimous in their conclusions. Methods and Results: The phages studied were three closely related strains of Myoviridae and three strains of Siphoviridae. Three disinfectants which are used commonly in microbiology laboratories were evaluated: Virkon (1%), ethanol (75%) and sodium hypochlorite (2500 ppm available chlorine). The most effective of these was Virkon, which inactivated all six phages rapidly. Ethanol was effective against the Myoviridae but had little effect on the Siphoviridae. Sodium hypochlorite was the least effective of the disinfectants evaluated. Conclusions: The findings of this study demonstrate a wide diversity in the effectiveness of disinfectants tested for inactivation of phages. Significance and Impact of the Study: Of the disinfectants tested Virkon is the most suitable choice for those unable to carry out disinfection validation studies, or where a broad spectrum disinfectant against phages is required. All of the phages in this study showed resilience to inactivation by sodium hypochlorite, and therefore this disinfectant is an unwise choice for use against phage without first assessing its effectiveness.