YabJ from Staphylococcus aureus entraps chlorides within its pocket.

Chlorination is a potent disinfectant against various microorganisms, including bacteria and viruses, by inducing protein modifications and functional changes. Chlorine, in the form of sodium hypochlorite, stands out as the predominant sanitizer choice due to its cost-effectiveness and powerful antimicrobial properties. Upon exposure to chlorination, proteins undergo modifications, with amino acids experiencing alterations through the attachment of chloride or oxygen atoms. These modifications lead to shifts in protein function and the modulation of downstream signaling pathways, ultimately resulting in a bactericidal effect. However, certain survival proteins, such as chaperones or transcription factors, aid organisms in overcoming harsh chlorination conditions. The expression of YabJ, a highly conserved protein from Staphylococcus aureus, is regulated by a stress-activated sigma factor called sigma B (σB). This research revealed that S. aureus YabJ maintains its structural integrity even under intense chlorination conditions and harbors sodium hypochlorite molecules within its surface pocket. Notably, the pocket of S. aureus YabJ is primarily composed of amino acids less susceptible to chlorination-induced damage, rendering it resistant to such effects. This study elucidates how S. aureus YabJ evades the detrimental effects of chlorination and highlights its role in sequestering sodium hypochlorite within its structure. Consequently, this process enhances resilience and facilitates adaptation to challenging environmental conditions.

Effects of sodium hypochlorite and ethylenediaminetetraacetic acid on proliferation, osteogenic/odontogenic differentiation, and mechanosensitive gene expression of human dental pulp stem cells.

Sodium Hypochlorite (NaOCl) and Ethylene Diamine Tetraacetic Acid (EDTA) can change the biochemical and biophysical properties of dentin. However, the response of human dental pulp stem cells (hDPSCs) to NaOCl and EDTA-treated dentin remains unknown. This study was conducted to investigate the effect of NaOCl and EDTA on cell proliferation, osteogenic/odontogenic differentiation, and the response to mechanosensitive gene expression in hDPSCs. Dentin slices were treated with 5.25% NaOCl, 17% EDTA, and saline (0.9% NaCl) separately. The cell viability and osteogenic/odontogenic differentiation of hDPSCs were analyzed using scanning electron microscopy, cell counting assay, alkaline phosphatase (ALP) staining, and quantitative polymerase chain reaction (qPCR). Besides, the hardness was measured by a Vickers microhardness tester. The expression of mechanosensitive genes was detected by the qPCR assay. All the irrigant-treated dentin allowed cell attachment. The EDTA-treated dentin significantly boosted the ALP and osteogenic/odontogenic differentiation, followed by NaCl and NaOCl groups. Remarkably, these trends were similar to the expression of mechanosensitive genes but were different from the trends of hardness values. The effect of irrigant-treated dentin on regulating hDPSCs differentiation might correlate with mechanosensitive signals. Whereas, the hardness changes between groups might not produce significant roles in regulating osteogenic/odontogenic differentiation of stem cells on dentin surfaces.

Prevalence of the fimbrial operon mrkABCD, mrkA expression, biofilm formation and effect of biocides on biofilm formation in carbapenemase-producing Klebsiella pneumoniae isolates belonging or not belonging to high-risk clones.

BACKGROUND: The role of mrkA adhesin expression, biofilm production, biofilm viability and biocides in the biofilm of carbapenemase-producing Klebsiella pneumoniae isolates was investigated. METHODS: Seventeen isolates representing different sequence types and carbapenemases were investigated. mrkA expression was determined by real-time reverse transcription polymerase chain reaction. Biofilm production (25°C and 37°C, with and without humidity) was determined by the crystal violet assay. The effect of isopropanol, povidone-iodine, sodium hypochlorite, chlorhexidine digluconate, benzalkonium chloride, ethanol and triclosan on biofilm was determined. The effect of povidone-iodine on biofilm biomass and thickness was also determined by confocal laser scanning microscopy. RESULTS: mrkA expression ranged from 28.2 to 1.3 [high or intermediate level; 64% of high-risk (HR) clones] and from 21.5 to 1.3 (50% of non-HR clones). At 25°C, biofilm formation was observed in 41% of isolates (absence of humidity) and 35% of isolates (presence of humidity), whereas at 37°C, biofilm formation was observed in 76% of isolates with and without humidity. At 25°C, biofilm producers were more frequently observed in HR clones (45% with humidity and 55% without humidity) than non-HR clones (17% with and without humidity). Biofilm viability from day 21 was higher at 25°C than 37°C. The greatest decrease in biofilm formation was observed with povidone-iodine (29% decrease), which also decreased biofilm thickness. CONCLUSIONS: Biofilm formation in carbapenemase-producing K. pneumoniae is related to mrkA expression. Biofilm formation is affected by temperature (37°C>25°C), whereas humidity has little effect. Biofilm viability is affected by temperature (25°C>37°C). At 25°C, HR clones are more frequently biofilm producers than non-HR clones. Povidone-iodine can decrease biofilm production and biofilm thickness.

Exposure to Sodium Hypochlorite or Cigarette Smoke Induces Lung Injury and Mechanical Impairment in Wistar Rats.

Pulmonary irritants, such as cigarette smoke (CS) and sodium hypochlorite (NaClO), are associated to pulmonary diseases in cleaning workers. We examined whether their association affects lung mechanics and inflammation in Wistar rats. Exposure to these irritants alone induced alterations in the lung mechanics, inflammation, and remodeling. The CS increased airway cell infiltration, acid mucus production, MMP-12 expression, and alveolar enlargement. NaClO increased the number of eosinophils and macrophages in the bronchoalveolar lavage fluid, with cells expressing IL-13, MMP-12, MMP-9, TIMP-1, and iNOS in addition to increased IL-1ß and TNF-α levels. Co-exposure to both irritants increased epithelial and smooth muscle cell area, acid mucus production, and IL-13 expression in the airways, while it reduced the lung inflammation. In conclusion, the co-exposure of CS with NaClO reduced the pulmonary inflammation, but increased the acidity of mucus, which may protect lungs from more injury. A cross-resistance in people exposed to multiple lung irritants should also be considered.

Calcium hypochlorite on mouse embryonic fibroblast cells (NIH3T3) in vitro cytotoxicity and genotoxicity: MTT and comet assay.

Antimicrobial irrigation solutions are widely used under clinical settings. Their effect on dental tissue is a subject of recent research, which aims for a safer irrigant for clinical use. In this regard, here our goal was to evaluate the cytotoxicity and the genotoxicity of calcium hypochlorite (Ca(OCl)2) solution, along with NaOCl, on Mouse embryonic fibroblast cells (NIH3T3). First, Cells were treated either with NaOCl or Ca(OCl)2 in a time- and dose-dependent manner for cytotoxicity by 3-(4,5-dimethylthiazolyl-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay, then cell viability was calculated according to cell proliferation plots. Secondly, genotoxicity was assessed by Comet assay. Data were statistically analyzed by Tukey's test (P < .05). NaOCl and Ca(OCl)2 had similar effects on cellular viability at 3 and 6 h treatments. Cell viability of Ca(OCl)2 at concentrations of 0.0125%, 0.025%, 0.05%, or 0.125% was significantly lower than that of NaOCl at 24 h treatment (P < .05).Comparing Ca(OCl)2 and NaOCl treatments at all time points and concentrations, the damaged cell number of Ca(OCl)2 was almost fourfold higher than that of NaOCl. In conclusion, both, NaOCl and Ca(OCl)2 solutions were cytotoxic and genotoxic to NIH3T3, however, Ca(OCl)2 had a significantly higher damaged cell percentage than NaOCl at all time points and concentrations investigated.

Effect of EDTA, sodium, and calcium hypochlorite on the inorganic component of root canal dentin: A SEM analysis.

This study evaluated the influence of canal irrigation protocols with 5.25% calcium hypochlorite [Ca(OCl)2 ], 5.25% sodium hypochlorite (NaOCl) and 17% EDTA solution on the inorganic component of root canal dentin. Sixty roots were randomly divided into six groups (n = 10): Saline solution (SS) (control); Saline solution (SSE) +17% EDTA; CH - 5.25% Ca(OCl)2 ; CHE - 5.25% Ca(OCl)2 + 17% EDTA; SH - 5.25% NaOCl; SHE - 5.25% NaOCl +17% EDTA. After canal irrigation, the specimens were longitudinally split and analyzed by scanning electron microscopy (SEM). Dentinal tubules were observed in transverse (middle and apical thirds) direction. The images were classified in scores, according to smear layer removal and peritubular dentin alteration, and data were analyzed by Kruskal-Wallis's test, followed by Dunn's test (α = 0.05). In the middle third, all groups with EDTA presented better removal of the smear layer with higher peritubular dentin alteration (p < .05). In the apical third, this happened only in SHE (p < .05). Ca(OCl)2 and NaOCl exhibit similar performance to remove smear layer and alteration of the inorganic component in the middle third. In the apical third, NaOCl associated with EDTA showed better performance in smear layer removal.

Diffusion of antimicrobials in multispecies biofilms evaluated in a new biofilm model.

AIM: To describe the application of a newly-developed in vitro model in which the diffusion of antimicrobials in oral biofilms can be studied. METHODOLOGY: In a flow chamber consisting of three parallel feeding channels connected with each other by eight perpendicular side channels, multispecies biofilms were grown from saliva of a single donor for 48 h. The dimensions of the side channels were 100 µm × 100 µm × 5130 µm (H × W × L). When one or more side channels were filled with biofilm, the biofilms were stained with fluorescent stains. Then, one side-channel biofilm was selected and treated with phosphate buffered saline, 2% sodium hypochlorite (NaOCl), 17% ethylenediaminetetra-acetic acid (EDTA) or modified salt solution (MSS). Diffusion of the irrigants was observed by acquiring fluorescence images at 10× objective every 15 s for 30 min. RESULTS: It was possible to culture biofilms in the narrow (100 µm) channels. The biofilms varied in phenotype. In this model, no diffusion of NaOCl into the biofilms was seen after its application. Seventeen-percentage EDTA only diffused into the biofilm up to 200 µm in 30 min. MSS did diffuse in the biofilm over a distance of 450 µm within 2 min after a single application. CONCLUSIONS: This new model enables the investigation of the diffusion of antimicrobials in biofilms. Other applications to improve our understanding of the characteristics of biofilms are now possible.

Polydiacetylene sensor interaction with food sanitizers and surfactants.

Polydiacetylene (PDA) vesicles are of interest as biosensors, particularly for pathogenic bacteria. As part of a food monitoring system, interaction with food sanitizers/surfactants was investigated. PDA vesicles were prepared by inkjet-printing, photopolymerized and characterized by dynamic light scattering (DLS) and UV/Vis spectroscopy. The optical response of PDA vesicles at various concentrations verses a fixed sanitizer/surfactant concentration was determined using a two variable factorial design. Sanitizer/surfactant response at various concentrations over time was also measured. Results indicated that only Vigilquat and TritonX-100 interacted with PDA vesicles giving visible colour change out of 8 sanitizers/surfactants tested. PDA vesicle concentration, sanitizer/surfactant concentration, and time all had a significant (P<0.0001) effect on colour change. As they are highly sensitive to the presence of Vigilquat and TritonX-100, PDA sensors could be used to detect chemical residues as well as for detection of various contaminants in the food industry.

Altered susceptibility to the bactericidal effect of photocatalytic oxidation by TiO2 is related to colistin resistance development in Acinetobacter baumannii.

Multidrug-resistant Acinetobacter baumannii is a well-documented pathogen associated with hospital-acquired infections. In addition to multidrug resistance, A. baumannii can also become resistant to colistin, the antibiotic treatment of last resort, by the loss of the lipopolysaccharide from its outer membrane. Here, we demonstrate that the development of colistin resistance also increases the resistance of A. baumannii to titanium dioxide (TiO2) photocatalysis. Both colistin-sensitive A. baumannii (CSAB) and colistin-resistant A. baumannii (CRAB) were inactivated by TiO2 when irradiated by ultraviolet A (UV-A). The resistance of CRAB to TiO2 photocatalysis was 1.5 times higher than that of CSAB, as determined by either culture assay or quantification of leaked proteins after photocatalysis (p < 0.05). The results of two-dimensional gel electrophoresis led to the speculation that the high resistance of CRAB may be associated with a lack of sensitive targets and oxidative enzymes. This hypothesis was confirmed by antimicrobial assays with 25 mM hydrogen peroxide (H2O2) and 1.07 mM sodium hypochlorite (NaClO). CRAB was significantly more resistant to H2O2 and NaClO treatment than CSAB (p < 0.01), consistent with the results of the TiO2 inactivation experiment. Therefore, the antibiotic resistance profiles of bacterial strains should be considered before the use of strains as indicators to represent sanitary quality after TiO2 photocatalysis.

Differential proteomics to explore the inhibitory effects of acidic, slightly acidic electrolysed water and sodium hypochlorite solution on Vibrio parahaemolyticus.

Slightly acidic electrolysed water (SlAEW) and acidic electrolysed water (AEW) have been demonstrated to effectively inactivate food-borne pathogens. However, the underlying mechanism of inactivation remains unknown. Therefore, in this study, a differential proteomic platform was used to investigate the bactericidal mechanism of SlAEW, AEW, and sodium hypochlorite (NaOCl) solutions against Vibrio parahaemolyticus. The upregulated proteins after SlAEW, AEW, and NaOCl treatments were identified as outer membrane proteins K and U. The downregulated proteins after the SlAEW, AEW, and NaOCl treatments were identified as adenylate kinase, phosphoglycerate kinase, glyceraldehyde-3-phosphate dehydrogenase (GAPDH), and enolase, all of which are responsible for energy metabolism. Protein synthesis-associated proteins were downregulated and identified as elongation factor Tu and GAPDH. The inhibitory effects of SlAEW and AEW solutions against V. parahaemolyticus may be attributed to the changes in cell membrane permeability, protein synthesis activity, and adenosine triphosphate (ATP) biosynthesis pathways such as glycolysis and ATP replenishment.

Effect of chemical interaction on the bonding strengths of self-etching adhesives to deproteinised dentine.

OBJECTIVES: The present study examined (1) the chemical interaction between three self-etching adhesives and sodium hypochlorite (NaOCl)-deproteinised dentine, and (2) the influence of NaOCl treatment on bond strength of self-etching adhesives with/without adhesive functional monomers to dentine. METHODS: Caries-free dentine disks (control) and those treated with 5.25% NaOCl for 60s were prepared. Xeno V (no functional monomers), G-Bond (containing 4-MET) or S3 Bond (containing 10-MDP) were applied to the NaOCl-treated dentine and either left without further treatment, or rinsed with 100% ethanol or distilled water. Attenuated total reflection (ATR) spectroscopy and field-emission scanning electron microscopy (FE-SEM) were used to evaluate the affinity of functional monomers with deproteinised dentine. Chemical interaction between the functional monomers and deproteinised dentine was evaluated using thin-film X-ray diffraction (TF-XRD). Microtensile bond strength (MTBS) was used to evaluate the mechanical property of the adhesives, either immediately or after thermo-cycling (5-55°C) for 10,000 cycles. RESULTS: According to the ATR and FE-SEM results, G-Bond and S3 Bond showed stronger affinity to deproteinised dentine than Xeno V even after rinsing with water. TF-XRD showed that chemical interaction between S3 Bond and deproteinised dentine occurred by formation of 10-MDP-Ca salt. Both deproteinisation and thermo-cycling adversely affected the MTBS of Xeno V (P<0.05) but deproteinisation had no significant influence on S3 Bond. CONCLUSIONS: When bonding to NaOCl-treated dentine, self-etch adhesives containing functional monomers (10-MDP) can maintain immediate and aged bond strengths after 10,000 thermal cycles.

The effect of the temperature changes of EDTA and MTAD on the removal of the smear layer: a scanning electron microscopy study.

The purpose of this study was to determine the effectiveness of EDTA and MTAD at different temperatures as a final irrigant to remove the smear layer after the use of 5.25% NaOCl. Seventy-eight human mandibular premolars with single straight canal were prepared by a crown-down technique using rotary 0.06 taper nickel-titanium files. Final irrigation was performed with EDTA and MTAD at different temperatures. The removal of the smear layer in the coronal, middle and apical level of each canal was examined under scanning electron microscope. No difference was found between the EDTA and MTAD at 4°C, 25°C, and 37°C temperatures regardless of the canal level (coronal, middle and apical) (P = 0.286). In EDTA-25, EDTA-37, MTAD-25, and MTAD-37 groups, the difference among the coronal, middle, and apical levels were statistically no significant (P > 0.05). Our findings showed that EDTA and MTAD at 25°C and 37°C are more effective than EDTA and MTAD at 4°C even in the apical level.

S-bacillithiolation protects conserved and essential proteins against hypochlorite stress in firmicutes bacteria.

AIMS: Protein S-bacillithiolations are mixed disulfides between protein thiols and the bacillithiol (BSH) redox buffer that occur in response to NaOCl in Bacillus subtilis. We used BSH-specific immunoblots, shotgun liquid chromatography (LC)-tandem mass spectrometry (MS/MS) analysis and redox proteomics to characterize the S-bacillithiolomes of B. subtilis, B. megaterium, B. pumilus, B. amyloliquefaciens, and Staphylococcus carnosus and also measured the BSH/oxidized bacillithiol disulfide (BSSB) redox ratio after NaOCl stress. RESULTS: In total, 54 proteins with characteristic S-bacillithiolation (SSB) sites were identified, including 29 unique proteins and eight proteins conserved in two or more of these bacteria. The methionine synthase MetE is the most abundant S-bacillithiolated protein in Bacillus species after NaOCl exposure. Further, S-bacillithiolated proteins include the translation elongation factor EF-Tu and aminoacyl-tRNA synthetases (ThrS), the DnaK and GrpE chaperones, the two-Cys peroxiredoxin YkuU, the ferredoxin-NADP(+) oxidoreductase YumC, the inorganic pyrophosphatase PpaC, the inosine-5'-monophosphate dehydrogenase GuaB, proteins involved in thiamine biosynthesis (ThiG and ThiM), queuosine biosynthesis (QueF), biosynthesis of aromatic amino acids (AroA and AroE), serine (SerA), branched-chain amino acids (YwaA), and homocysteine (LuxS and MetI). The thioredoxin-like proteins, YphP and YtxJ, are S-bacillithiolated at their active sites, suggesting a function in the de-bacillithiolation process. S-bacillithiolation is accompanied by a two-fold increase in the BSSB level and a decrease in the BSH/BSSB redox ratio in B. subtilis. INNOVATION: Many essential and conserved proteins, including the dominant MetE, were identified in the S-bacillithiolome of different Bacillus species and S. carnosus using shotgun-LC-MS/MS analyses. CONCLUSION: S-bacillithiolation is a widespread redox control mechanism among Firmicutes bacteria that protects conserved metabolic enzymes and essential proteins against overoxidation.

PEGylated single-walled carbon nanotubes activate neutrophils to increase production of hypochlorous acid, the oxidant capable of degrading nanotubes.

Perspectives for the use of carbon nanotubes in biomedical applications depend largely on their ability to degrade in the body into products that can be easily cleared out. Carboxylated single-walled carbon nanotubes (c-SWCNTs) were shown to be degraded by oxidants generated by peroxidases in the presence of hydrogen peroxide. In the present study we demonstrated that conjugation of poly(ethylene glycol) (PEG) to c-SWCNTs does not interfere with their degradation by peroxidase/H(2)O(2) system or by hypochlorite. Comparison of different heme-containing proteins for their ability to degrade PEG-SWCNTs has led us to conclude that the myeloperoxidase (MPO) product hypochlorous acid (HOCl) is the major oxidant that may be responsible for biodegradation of PEG-SWCNTs in vivo. MPO is secreted mainly by neutrophils upon activation. We hypothesize that SWCNTs may enhance neutrophil activation and therefore stimulate their own biodegradation due to MPO-generated HOCl. PEG-SWCNTs at concentrations similar to those commonly used in in vivo studies were found to activate isolated human neutrophils to produce HOCl. Both PEG-SWCNTs and c-SWCNTs enhanced HOCl generation from isolated neutrophils upon serum-opsonized zymosan stimulation. Both types of nanotubes were also found to activate neutrophils in whole blood samples. Intraperitoneal injection of a low dose of PEG-SWCNTs into mice induced an increase in percentage of circulating neutrophils and activation of neutrophils and macrophages in the peritoneal cavity, suggesting the evolution of an inflammatory response. Activated neutrophils can produce high local concentrations of HOCl, thereby creating the conditions favorable for degradation of the nanotubes.

Peroxide-sensing transcriptional regulators in bacteria.

The ability to maintain intracellular concentrations of toxic reactive oxygen species (ROS) within safe limits is essential for all aerobic life forms. In bacteria, as well as other organisms, ROS are produced during the normal course of aerobic metabolism, necessitating the constitutive expression of ROS scavenging systems. However, bacteria can also experience transient high-level exposure to ROS derived either from external sources, such as the host defense response, or as a secondary effect of other seemingly unrelated environmental stresses. Consequently, transcriptional regulators have evolved to sense the levels of ROS and coordinate the appropriate oxidative stress response. Three well-studied examples of these are the peroxide responsive regulators OxyR, PerR, and OhrR. OxyR and PerR are sensors of primarily H(2)O(2), while OhrR senses organic peroxide (ROOH) and sodium hypochlorite (NaOCl). OxyR and OhrR sense oxidants by means of the reversible oxidation of specific cysteine residues. In contrast, PerR senses H(2)O(2) via the Fe-catalyzed oxidation of histidine residues. These transcription regulators also influence complex biological phenomena, such as biofilm formation, the evasion of host immune responses, and antibiotic resistance via the direct regulation of specific proteins.

Effect of disinfectant solutions on gutta-percha and resilon cones.

The aim of this study was to evaluate the effects of the 5.25% sodium hypochlorite (NaOCl), 2% chlorhexidine (CHX), and MTAD solutions on the surface of gutta-percha and Resilon cones by using atomic force microscopy (AFM). Accessory cones were washed and dried. The cones were randomly divided into six groups: gutta-percha immersed in NaOCl, CHX, and MTAD, and Resilon immersed in NaOCl, CHX, and MTAD. AFM images of the same area were made in different periods of time. JPK™ Image Processing Software was used to evaluate the images. The parameters used to evaluate the changes were RMS and line profiles. No statistically significant change was observed in the RMS values. The line profiles detected changes only for gutta-percha surfaces after immersion in NaOCl and MTAD solutions. In conclusion, 5.25% NaOCl and MTAD are associated with local changes in surface roughness of gutta-percha cones. No change was observed when 2% CHX was used. The use of all tested solutions did not produce any changes on Resilon surface.

Investigation of bacterial resistance to the immune system response: cepacian depolymerisation by reactive oxygen species.

Reactive oxygen species (ROS) are part of the weapons used by the immune system to kill and degrade infecting microorganisms. Bacteria can produce macromolecules, such as polysaccharides, that are able to scavenge ROS. Species belonging to the Burkholderia cepacia complex are involved in serious lung infection in cystic fibrosis patients and produce a characteristic polysaccharide, cepacian. The interaction between ROS and bacterial polysaccharides was first investigated by killing experiments, where bacteria cells were incubated with sodium hypochlorite (NaClO) with and without prior incubation with cepacian. The results showed that the polysaccharide had a protective effect towards bacterial cells. Cepacian was then treated with different concentrations of NaClO and the course of reactions was followed by means of capillary viscometry. The degradation products were characterised by size-exclusion chromatography, NMR and mass spectrometry. The results showed that hypochlorite depolymerised cepacian, removed side chains and O-acetyl groups, but did not cleave the glycosidic bond between glucuronic acid and rhamnose. The structure of some oligomers produced by NaClO oxidation is reported.

In vitro viability test for the eggs of Echinococcus granulosus: a rapid method.

In this study an attempt was made to develop an efficient, rapid, simple, and reproducible method for the in vitro viability test of Echinococcus granulosus eggs. The eggs were obtained from an experimentally infected dog and kept at 4°C until use. To prepare the dead or damaged eggs, the eggs were heated in hot water (69-72°C for 10 min), preserved in 70% ethyl alcohol (16 days) or exposed to direct sunlight (18 h). Sodium hypochlorite (0.5-0.7%) was used for the hatching process, and the hatched oncospheres were stained with 0.1% eosin for the viability test. With 0.5% sodium hypochlorite, the hatching rates for viable eggs and eggs killed or damaged by heat (69°C), 70% ethyl alcohol, and direct sunlight were 96%, 97.5%, 91.5%, and 94.6% respectively and there was no significant difference between the hatching rate for viable and dead or damaged eggs (p > 0.05). After staining with 0.1% eosin, the rates of the viable oncospheres hatched from viable eggs and the eggs killed or damaged by heat (69°C), 70% ethyl alcohol, and direct sunlight were 97.5% 3.6%, 7%, and 10.5%, respectively. The difference between the rates of viable oncospheres hatched from viable and dead or damaged eggs was extremely significant (P < 0.0001). With 0.7% sodium hypochlorite, the hatching rates for viable and dead eggs (killed by 72°C for 10 min) were 99.1% and 99.9%, respectively. In this condition, the rate of viable oncospheres was an average of 98.5% for viable eggs and 0.0% for dead ones. The results of this study showed that hatching of eggs by 0.7% sodium hypochlorite and staining of hatched oncospheres by 0.1% eosin are practical methods for the differentiation of viable and nonviable (dead) eggs of Echinococcus granulosus.

Degradation models and ecotoxicity in marine waters of two antifouling compounds: sodium hypochlorite and an alkylamine surfactant.

Industrial wastes have a substantial impact on coastal environments. Therefore, to evaluate the impact of cooling water discharges from coastal power plants, we studied the kinetics of the degradative processes and the ecotoxicity of two antifouling products: (1) a classic antifouling product; sodium hypochlorite (NaClO) and (2) an alternative one; aliphatic amines (commercial under the registered trade mark Mexel432). To assess the persistence of both compounds the decay of sodium hypochlorite and the primary biodegradation rate of Mexel432 were determined in natural seawater at 20 degrees C. The results indicated a more rapid decay of NaClO than Mexel432. The degradation behavior of both chemicals was described following a logistic model, which permitted calculating kinetic parameters such as t(50) or t(90). The t(50) was 1h and 2d for NaClO and Mexel432, respectively. To evaluate the potential risks of the aforementioned treatments to marine organisms, the acute toxicity of both antifouling products was studied on the microalgae Isochrysis galbana and Dunaliella salina, and on the invertebrate Brachionus plicatilis, using growth inhibition and death tests as toxic response, respectively. For I. galbana, the 96-h EC(50) values were 2.91+/-0.15mg/L of NaClO and 4.55+/-0.11mg/L of Mexel432. D. salina showed values of 96-h EC(50) of 1.73+/-0.16mg/L of NaClO and 7.21+/-0.1mg/L of Mexel432. Brachionus plicatilis showed a 24-h LC(50) of 1.23+/-0.1mg/L of NaClO and 3.62+/-0.37mg/L of Mexel432. Acute toxicity was highly dependent on the chemical and species tested. NaClO presented more toxic effects than Mexel432, also B. plicatilis was the most sensitive species in both cases. The lowest NOECs obtained, 0.25mg/L for NaClO and 2.12mg/L for Mexel432, were similar to the theoretical residual concentrations of these biocides in cooling water discharges. Therefore, these discharges can cause undesirable negative effects upon the aquatic organisms present.