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PubMed2000

Microbicidal activity of MDI-P against Candida albicans, Staphylococcus aureus, Pseudomonas aeruginosa, and Legionella pneumophila.

BACKGROUND: MDI-P (Medical Discoveries, Inc-Pharmaceutical, Layton, Utah) is a clear, colorless liquid generated by electrolysis of preservative-free and endotoxin-free, nonpyrogenic, sterile, injection saline (0.9% NaCl, wt/vol). It contains numerous highly reactive chlorine and oxygen species, including HOCl(-1,) OCl-(1), Cl(-1), Cl(2), O(2-)(1), and O(3). This report presents data on the in vitro microbicidal activity of MDI-P against 4 clinically relevant microbial pathogens that are often difficult to eradicate. METHODS: MDI-P was generated from injection saline by using a patented electrolysis instrument. It was then tested for microbicidal activity at concentrations ranging from 0.01% to 50% against Staphylococcus aureus, Pseudomonas aeruginosa, Legionella pneumophila, and Candida albicans (10(5) to 10(9) colony-forming units/mL). The effect of serum (50% and 90%) and pH on MDI-P activity were also tested. The morphologic effects of MDI-P on microbial cells were studied by light microscopy of cells stained by Gram's method and by transmission electron microscopy. Morbidity, mortality, and the effect of MDI-P on tissues were studied by using a mouse model. RESULTS: The microbicidal activity of MDI-P occurred within the first minute of exposure for all the organisms tested. When 50% MDI-P was tested against cell titers of 10(5) or 10(7) colony-forming units/mL, all test organisms were killed within 1 minute; at lower MDI-P concentrations, C albicans was the most sensitive organism, and L pneumophila was the most resistant. Even with beginning cell titers of 10(9) colony-forming units/mL, killing by 50% MDI-P was >99.9% for all test strains. Furthermore, at the same beginning cell titer, killing of C albicans by MDI-P diluted to 50% with normal human serum rather than injection saline was only slightly reduced. No acute morbidity, mortality, or tissue damage was detected in mice that were intravenously given 17 mL/kg of undiluted MDI-P. CONCLUSIONS: MDI-P is a very fast-acting, broad-spectrum microbicidal material. The lack of evidence for acute morbidity, mortality, or tissue injury, ease of preparation, and low cost suggest that it may be useful for various sterilization and disinfection applications.

Animals↗
PubMed1986

Relationship of drinking water disinfectants to plasma cholesterol and thyroid hormone levels in experimental studies.

The effects of drinking water containing 2 or 15 ppm chlorine (pH 6.5 and 8.5), chlorine dioxide, and monochloramine on thyroid function and plasma cholesterol were studied because previous investigators have reported cardiovascular abnormalities in experimental animals exposed to chlorinated water. Plasma thyroxine (T4) levels, as compared to controls, were significantly decreased in pigeons fed a normal or high-cholesterol diet and drinking water containing these drinking water disinfectants at a concentration of 15 ppm (the exception was chlorine at pH 6.5) for 3 months. In most of the treatment groups, T4 levels were significantly lower following the exposure to drinking water containing the 2 ppm dose. Increases in plasma cholesterol were frequently observed in the groups with lower T4 levels. This association was most evident in pigeons fed the high-cholesterol diet and exposed to these disinfectants at a dose of 15 ppm. For example, after 3 months of exposure to deionized water or water containing 15 ppm monochloramine, plasma cholesterol was 1266 +/- 172 and 2049 +/- 212 mg/dl, respectively, a difference of 783 mg/dl. The factor(s) associated with the effect of these disinfectants on plasma T4 and cholesterol is not known. We suggest however that these effects are probably mediated by products formed when these disinfectants react with organic matter in the upper gastrointestinal tract.

Animals↗
PubMed1987

Organization and nucleotide sequence determination of a gene cluster involved in 3-chlorocatechol degradation.

Three critical enzymes catechol oxygenase II (chlorocatechol dioxygenase), muconate cycloisomerase II, and dienelactone hydrolase, are involved in the degradation of chlorocatechols, which are obligatory intermediates in the catabolism of chlorinated aromatic compounds. The organization and complete nucleotide sequence of the genes for these enzymes have been determined on a 4.2-kilobase-pair (kbp) Bgl II fragment cloned from the plasmid pAC27, based on the agreement of open reading frame lengths with apparent mobilities of polypeptides expressed in Escherichia coli maxicells, predicted N-terminal amino acid sequences with those of the purified proteins, and predicted total amino acid compositions with those of the purified proteins. The 4.2-kbp fragment contains the three genes and ribosome binding sites for those genes but no promoter. When placed downstream of the tac promoter in the broad-host-range plasmid pMMB22, this fragment directs the synthesis of all three enzymes in both E. coli and Pseudomonas putida only on induction with isopropyl beta-D-thiogalactopyranoside, suggesting that the gene cluster is regulated as a single unit under the control of a single promoter. Endogenous transcription initiation of the gene cluster on pAC27, however, occurs from a site present within a 386-bp Bgl II fragment upstream of the 4.2-kbp fragment, and sequences 5' to that site are similar to the sequences of other positively controlled Pseudomonas promoters occurring on the TOL and NAH plasmids.

Amino Acid Sequence↗
PubMed1998

Crystal structures of reaction intermediates of L-2-haloacid dehalogenase and implications for the reaction mechanism.

Crystal structures of L-2-haloacid dehalogenase from Pseudomonas sp. YL complexed with monochloroacetate, L-2-chlorobutyrate, L-2-chloro-3-methylbutyrate, or L-2-chloro-4-methylvalerate were determined at 1.83-, 2.0-, 2.2-, and 2.2-A resolutions, respectively, using the complex crystals prepared with the S175A mutant, which are isomorphous with those of the wild-type enzyme. These structures exhibit unique structural features that correspond to those of the reaction intermediates. In each case, the nucleophile Asp-10 is esterified with the dechlorinated moiety of the substrate. The substrate moieties in all but the monochloroacetate intermediate have a D-configuration at the C2 atom. The overall polypeptide fold of each of the intermediates is similar to that of the wild-type enzyme. However, it is clear that the Asp-10-Ser-20 region moves to the active site in all of the intermediates, and the Tyr-91-Asp-102 and Leu-117-Arg-135 regions make conformational changes in all but the monochloroacetate intermediates. Ser-118 is located near the carboxyl group of the substrate moiety; this residue probably serves as a binding residue for the substrate carboxyl group. The hydrophobic pocket, which is primarily composed of the Tyr-12, Gln-42, Leu-45, Phe-60, Lys-151, Asn-177, and Trp-179 side chains, exists around the alkyl group of the substrate moiety. This pocket may play an important role in stabilizing the alkyl group of the substrate moiety through hydrophobic interactions, and may also play a role in determining the stereospecificity of the enzyme. Moreover, a water molecule, which is absent in the substrate-free enzyme, is present in the vicinities of the carboxyl carbon of Asp-10 and the side chains of Asp-180, Asn-177, and Ala-175 in each intermediate. This water molecule may hydrolyze the ester intermediate and its substrate. These findings crystallographically demonstrate that the enzyme reaction proceeds through the formation of an ester intermediate with the enzyme's nucleophile Asp-10.

Binding Sites↗
PubMed2000

Identification of a serine hydrolase as a key determinant in the microbial degradation of polychlorinated biphenyls.

The ability of 2-hydroxy-6-oxo-6-phenylhexa-2,4-dienoate (HOPDA) hydrolase (BphD) of Burkholderia cepacia LB400 to hydrolyze polychlorinated biphenyl (PCB) metabolites was assessed by determining its specificity for monochlorinated HOPDAs. The relative specificities of BphD for HOPDAs bearing chlorine substituents on the phenyl moiety were 0.28, 0.38, and 1.1 for 8-Cl, 9-Cl, and 10-Cl HOPDA, respectively, versus HOPDA (100 mm phosphate, pH 7.5, 25 degrees C). In contrast, HOPDAs bearing chlorine substituents on the dienoate moiety were poor substrates for BphD, which hydrolyzed 3-Cl, 4-Cl, and 5-Cl HOPDA at relative maximal rates of 2.1 x 10(-3), 1.4 x 10(-4), and 0.36, respectively, versus HOPDA. The enzymatic transformation of 3-, 5-, 8-, 9-, and 10-Cl HOPDAs yielded stoichiometric quantities of the corresponding benzoate, indicating that BphD catalyzes the hydrolysis of these HOPDAs in the same manner as unchlorinated HOPDA. HOPDAs also underwent a nonenzymatic transformation to products that included acetophenone. In the case of 4-Cl HOPDA, this transformation proceeded via the formation of 4-OH HOPDA (t(12) = 2.8 h; 100 mm phosphate, pH 7.5, 25 degrees C). 3-Cl HOPDA (t(12) = 504 h) was almost 3 times more stable than 4-OH HOPDA. Finally, 3-Cl, 4-Cl and 4-OH HOPDAs competitively inhibited the BphD-catalyzed hydrolysis of HOPDA (K(ic) values of 0.57 +/- 0. 04, 3.6 +/- 0.2, and 0.95 +/- 0.04 microm, respectively). These results explain the accumulation of HOPDAs and chloroacetophenones in the microbial degradation of certain PCB congeners. More significantly, they indicate that in the degradation of PCB mixtures, BphD would be inhibited, thereby slowing the mineralization of all congeners. BphD is thus a key determinant in the aerobic microbial degradation of PCBs.

Bacterial Proteins↗
PubMed2006

Transcriptional activation of dehalorespiration. Identification of redox-active cysteines regulating dimerization and DNA binding.

Desulfitobacterium dehalogenans can use chlorinated aromatics including polychlorinated biphenyls as electron acceptors in a process called dehalorespiration. Expression of the cpr gene cluster involved in this process is regulated by CprK, which is a member of the CRP/FNR (cAMP-binding protein/fumarate nitrate reduction regulatory protein) family of helix-turn-helix transcriptional regulators. High affinity interaction of the chlorinated aromatic compound with the effector domain of CprK triggers binding of CprK to an upstream target DNA sequence, which leads to transcriptional activation of the cpr gene cluster. When incubated with oxygen or diamide, CprK undergoes inactivation; subsequent treatment with dithiothreitol restores activity. Using mass spectrometry, this study identifies two classes of redox-active thiol groups that form disulfide bonds upon oxidation. Under oxidative conditions, Cys105, which is conserved in FNR and most other CprK homologs, forms an intramolecular disulfide bond with Cys111, whereas an intermolecular disulfide bond is formed between Cys11 and Cys200. SDS-PAGE and site-directed mutagenesis experiments indicate that the Cys11/Cys200 disulfide bond links two CprK subunits in an inactive dimer. Isothermal calorimetry and intrinsic fluorescence quenching studies show that oxidation does not change the affinity of CprK for the effector. Therefore, reversible redox inactivation is manifested at the level of DNA binding. Our studies reveal a strategy for limiting expression of a redox-sensitive pathway by using a thiol-based redox switch in the transcription factor.

Amino Acid Sequence↗
PubMed2001

Capability of mucoid Pseudomonas aeruginosa to survive in chlorinated water.

Mucoid strains of Pseudomonas aeruginosa are characterized by an overproduction of the extracellular polysaccharide alginate. When suspended into chlorinated swimming-pool water or drinking water samples, mucoid bacteria revealed enhanced survival compared with isogenic nonmucoid cells. Removal of slime from mucoid bacteria abolished chlorine resistance, addition of purified alginate to washed bacteria again enhanced survival. Thus, alginate-containing slime confers protection on P. aeruginosa against chlorine and may contribute to survival of these bacteria in chlorinated water systems.

Chlorine Compounds↗
PubMed2001

A case report of false negative Legionella test results in a chlorinated public hot water distribution system due to the lack of sodium thiosulfate in sampling bottles.

We examined samples from the showers and the central water distribution system of a public building with an indoor swimming pool. The pool was used for school and recreational activities and as a sports therapy facility for patients with coronary heart disease. The building's hot water system was contaminated with Legionella pneumophila. Due to the building's intricate piping system, several attempts to completely eliminate legionellae by thermal and chemical disinfection had failed, so an external sanitation company was charged with the installation of a continuous chlorination device in order to keep Legionella concentrations low. The laboratory which was contracted by the sanitation company to monitor bacteria levels after installation of the chlorination device used sampling bottles without sodium thiosulfate and repeatedly reported an absence of Legionella. However, up to 69,000 colony forming particles (CFP) of Legionella pneumophila (Lp) per litre and up to 171 CFP/ml of heterotrophic bacteria could be detected when parallel samples were collected in bottles containing sodium thiosulfate at standard concentrations. Laboratories, epidemiologists, public health officials and technical staff who may be in charge of delivering, preparing or using sterile sampling devices for the collection of environmental samples to be tested for legionellae should be aware that cultures can return false negative results if the sampling containers used to collect chlorinated drinking water or chlorinated pool water samples do not contain a neutralizing agent to instantly inactivate residual halogen biocides. False negative results may lead to a false sense of security regarding the safety of water systems or the success of disinfection measures, and may thus endanger public health or even hinder the epidemiological clarification of outbreaks.

Chelating Agents↗
PubMedDate not supplied

Are high-dose toxic exposures always associated with reactive airways dysfunction syndrome (RADS)?

Bottling plant workers were evaluated for respiratory symptoms following an accidental exposure to a chlorine dioxide aerosol. Six exposed employees underwent medical and occupational histories, skin testing to common allergens, spirometry before and after use of bronchodilators, and methacholine challenge. The reported exposure to chlorine dioxide ranged from 30 min to 12 hr. Physical examinations were all normal. Four workers had positive prick skin tests to common aeroallergens. None of the workers demonstrated significant changes in forced expiratory volume in 1 sec following use of bronchodilators, and none experienced methacholine hyperresponsiveness. These cases suggest that the occurrence of reactive airways dysfunction syndrome is unpredictable and may not always occur in heavily exposed individuals.

Adult↗
PubMed2004

Thyroid function of newborns and exposure to chlorine dioxide by-products.

In this study, the authors compared thyroid function of newborns from 11 municipalities where drinking water was disinfected by chlorine dioxide (ClO2) with that of newborns from 15 municipalities using chlorine disinfection. They estimated the mean neonatal blood thyroid stimulating hormone (TSH) levels and proportion of congenital hypothyroidism cases using the results of the Quebec neonatal screening for congenital hypothyroidism for 32,978 newborns over the period 1993-1999. There was no significant increase in the TSH level and no excess of congenital hypothyroidism when all newborns exposed to ClO2 were considered. However, for newborns with low birth weight, mean TSH level was significantly higher among those exposed to ClO2 than for those in the reference group.

Child, Preschool↗
PubMedDate not supplied

Chlorine dioxide water disinfection: a prospective epidemiology study.

An epidemiologic study of 198 persons exposed for 3 months to drinking water disinfected with chlorine dioxide was conducted in a rural village. A control population of 118 nonexposed persons was also studied. Pre-exposure hematologic and serum chemical parameters were compared with test results after 115 days of exposure. Statistical analysis (ANOVA) of the data failed to identify any significant exposure-related effects. This study suggests that future evaluations of chlorine dioxide disinfection should be directed toward populations with potentially increased sensitivity to hemolytic agents.

Adolescent↗
PubMedDate not supplied

Effect of chlorine dioxide water disinfection on hematologic and serum parameters of renal dialysis patients.

A study of the blood chemistry parameters of 20 renal dialysis patients was undertaken when a local water district introduced chlorine dioxide (CIO2) as a disinfectant at the filtration plant headworks for 12 months without informing the renal dialysis clinic in the area of this potentially adverse change. Due to data limitations, including changes in clinical laboratories and lack of pre-exposure data for some patients, the analysis was focused on 17 patients for whom data was produced by the same clinical laboratory, for 3 months of pre-exposure and 1 month of exposure. Least-squares means of each parameter by CIO2 levels of 0.0 and 1.0 mg/L at the treatment plant were adjusted for age, sex, and creatinine. Water purification at the clinic included passing the water through granular activated carbon, filtration by 5-mu filters, and the use of reverse osmosis. Chlorination products measured at the clinic after this purification and prior to preparation of the dialysate consisted only of chlorite at the 0.02-0.08 mg/L level. No evidence of CIO2-induced anemia was found, nor were any other biologically significant responses observed. Study limitations include several potentially important hematologic parameters which were not measured, the small sample size, and three clinical laboratory changes.

Blood↗
PubMedDate not supplied

Symptoms and health status in individuals with multiple chemical sensitivities syndrome from four reported sensitizing exposures and a general population comparison group.

Self-reported information about health and mental health status and history on (a) three diverse samples of individuals who reported multiple chemical sensitivities syndrome (n = 60) and (b) one sample of the general population (n = 60) was collected by telephone interview. Subjects from the general population were selected randomly from the telephone directory and were matched for age, gender, and socioeconomic status with index subjects. Data on an additional 10 subjects with multiple chemical sensitivities syndrome were also available for comparison on many of the variables of interest. The four diverse groups of patients with multiple chemical sensitivities syndrome had very similar general and specific indices of illness and sensitivity to chemicals. Members of the general population reported mild sensitivity to chemicals, and even those with more sensitivity differed from the multiple chemical sensitivities syndrome groups with respect to number and types of symptoms reported, duration and frequency of response, and associated features. Multiple chemical sensitivities syndrome was associated consistently with only one psychiatric variable, elevated negative affect scores, which were correlated significantly with the presence of illness. Patients with multiple chemical sensitivities syndrome from the diverse samples had very similar characteristic features, despite whether they had or had not received treatment by clinical ecologists.

Adult↗
PubMed2005

Effectiveness of antimicrobial food packaging materials.

Antimicrobial additives have been used successfully for many years as direct food additives. The literature provides evidence that some of these additives may be effective as indirect food additives incorporated into food packaging materials. Antimicrobial food packaging is directed toward the reduction of surface contamination of processed, prepared foods such as sliced meats and Frankfurter sausages (hot dogs). The use of such packaging materials is not meant to be a substitute for good sanitation practices, but it should enhance the safety of food as an additional hurdle for the growth of pathogenic and/or spoilage microorganisms. Studies have focused on establishing methods for coating low-density polyethylene film or barrier films with methyl cellulose as a carrier for nisin. These films have significantly reduced the presence of Listeria monocytogenes in solutions and in vacuum packaged hot dogs. Other research has focused on the use of chitosan to inhibit L. monocytogenes and chlorine dioxide sachets for the reduction of Salmonella on modified atmosphere-packaged fresh chicken breasts. Overall, antimicrobial packaging shows promise as an effective method for the inhibition of certain bacteria in foods, but barriers to their commercial implementation continue to exist.

Animals↗
PubMed2006

Studies on the coupling product between oxidation products derived from pentachlorophenol and cyclodextrins.

The coupling products (CPs), which were formed via the peroxosulfate catalyzed oxidation of pentachlorophenol (PCP) with iron(III)-tetrakis(sulfonatophenyl)porphyrin (Fe(III)-TPPS) in the presence of hydroxypropyl-beta -cyclodextrin (HP-beta -CD) or HP-gamma -CD, were separated by ultrafiltration from the reaction mixture. When the percentages of chlorine species in the reaction mixture were calculated from the concentrations of organic chlorine in the reaction mixture and CPs, 10-25% of chlorine species in the reaction mixture was organic chlorine that was incorporated into CDs. Analyses of the CPs by pyrolysis-GC/MS (Py-GC/MS) and 13C NMR showed that the PCP-derived products were covalently incorporated into the CDs. To evaluate the acute toxicity of the CPs, a Microtox test was examined. Toxicities of the CPs were reduced slightly, compared to the controls (PCP alone and PCP + reaction blanks). In the reaction blanks, mesaconic acid (MA) moieties were detected as a result of the oxidation of CDs in the absence of PCP. Thus, factors in the toxicities, detected in the CPs, can be attributed to the oxidation products derived from CDs, such as MA, as well as the PCP-derived products incorporated into the CDs.

Catalysis↗
PubMed1999

Microbial dechlorination of 2,4,6-trichlorophenol in anaerobic sewage sludge.

The dechlorination of 2,4,6-trichlorophenol (TCP) in municipal sewage sludge with a chlorophenol (CP)-adapted consortium was investigated. Results show that dechlorination rates differed according to the source of the sludge samples used in the batch experiments. No significant differences in 2,4,6-TCP dechlorination were observed following treatment with inoculum at densities ranging from 10% to 50% (V/V), but a significant delay was noted at 5% (V/V) density. Overall, results show that the higher the 2,4,6-TCP concentration, the slower the dechlorination rate. The addition of acetate, lactate, pyruvate, vitamin B12 or manganese dioxide did not results in a significant change in 2,4,6-TCP dechlorination. Data collected from a bioreactor experiment revealed that pH 7.0 and a total solid concentration of 10 g/L were optimal for dechlorination. Dechlorination rates decreased significantly at higher agitation speeds. 2,4,6-TCP dechlorination was enhanced under methanogenic conditions, but it was inhibited under denitrifying and sulfate-reducing conditions.

Anaerobiosis↗
PubMed2003

Reductive dechlorination of TCE by zero valent bimetals.

Six zero valent bimetal combinations were tested for trichloroethene (TCE) dechlorination. Palladium, nickel, and copper were coated at 500 mg kg(-1) or less onto zero valent iron, producing Pd/Fe, Ni/Fe, and Cu/Fe bimetals, and zinc, producing Pd/Zn, Ni/Zn, and Cu/Zn bimetals. The order of reactivity of the six bimetals and two metals based on surface area normalized pseudo first order rate constants was observed to be: Pd/Fe > Pd/Zn > Ni/Fe > Cu/Fe > Ni/Zn > Cu/Zn > Fe > Zn. Thus, in general, 1) iron metal and bimetals exhibit faster reaction rates than the corresponding zinc reductants, 2) bimetals exhibit faster reaction rates than pure metals, and 3) metal coating enhance reactivity in the order of Pd > Ni > Cu. Chlorinated intermediate products were observed in small amounts for Fe only. In all cases, the chloride balance, calculated from TCE and chloride concentrations, ranged from 90 to 111%. The results are discussed in terms of the effects of bimetal combinations on catalytic dechlorination, prevention of nonreactive film and metal corrosion.

Chlorine Compounds↗