The South Australian Safe Drinking Water Act: summary of the first year of operation.

The Safe Drinking Water Act 2011 was introduced in South Australia to provide clear direction to drinking water providers on how to achieve water safety. The Act requires drinking water providers to register with SA Health and develop a risk management plan (RMP) for their water supply that includes operational and verification monitoring plans and an incident notification and communication protocol. During the first year of operation, 212 drinking water providers registered under the Act, including one major water utility and a range of small to medium sized providers in regional and remote areas of the State. Information was captured on water source(s) used and water treatment. Rainwater was the most frequently reported drinking water source (66%), followed by bore water (13%), on-supply or carting of mains water (13%), mixed source (rainwater with bore water backup) (6%) and surface water (3%). The majority of providers (91%) treated the water supply, 87% used disinfection. During the first year of operation, 16 water quality incidents were formally reported to SA Health. These included both microbial and chemical incidents. Case studies presented highlight how the RMPs are assisting drinking water providers to identify incidents of potential health concern and implement corrective actions.

Cytotoxicity screening for the cyanobacterial toxin cylindrospermopsin.

The cell lines C3A, HepG2, NCI-87, HCT-8, HuTu-80, Caco-2, and Vero were screened for sensitivity to the cyanobacterial toxin cylindrospermopsin (CYN), with the aim of determining the most sensitive cells to be used in cytotoxicity tests. Cell lines were chosen to be representative of the organs targeted by the toxin; liver, kidney, intestine, and were expected to have different metabolic activities and uptake capabilities. Over the range of cell lines tested, IC(50) determinations at 24 h (MTT assay) ranged fourfold, from 1.5 muM for hepatocyte-derived cell lines (C3A IC(50) = 1.5 +/- 0.54; HepG2 IC(50) = 1.5 +/- 0.87) to 6.5 +/- 3.3 micro the colon-derived Caco-2 cell line. The cell-line sensitivity seemed to decrease in cell lines derived from progressively more distal regions of the gastrointestinal tract: gastric > duodenal > ileal > colonic. The greater sensitivity of the hepatic cell lines to CYN was also apparent in 7-d exposure studies, with low toxin concentrations exerting cytotoxic effects that were not seen in other cell lines. Short-term exposure of C3A cells to CYN (1-6 h) was shown to induce cytotoxicity at 24 h despite a washout and recovery incubation, demonstrating the protracted and apparently irreversible nature of CYN's toxic effects.

An examination of the antibiotic effects of cylindrospermopsin on common gram-positive and gram-negative bacteria and the protozoan Naegleria lovaniensis.

The importance of the toxin cylindrospermopsin to the function and fitness of the cyanobacteria that produce it remains a matter of conjecture. Given that the structure of cylindrospermopsin has commonalities with other antibacterial protein synthesis inhibitors, such as streptomycin, authors tested the possibility that the toxin might act as an antibacterial compound that can kill competing microbes. Escherichia coli, Bacillus subtilis, Staphylococcus aureus, and Pseudomonas aeruginosa were tested by the minimal inhibitory concentration method and significant antibacterial activity was only observed at a cylindrospermopsin concentration of 300 microg mL(-1) after exposure for 5 days. No effect on log phase growth of E. coli was observed for this same toxin concentration. Protein synthesis was inhibited by cylindrospermopsin in E. coli 70S extracts, reduced by 25% compared with controls when treated with 41.5 microg mL(-1) of the toxin; however, a much greater reduction of 97% was observed for chloramphenicol in the same experiment. Naegleria lovaniensis, a phagotrophic protozoan, was more susceptible to cylindrospermopsin, with a decrease in the number of N. lovaniensis plaques after 24-h treatment with 5-50 microg mL(-1) of toxin and an LC(50) of approximately 60 microg mL(-1). Given these results, cylindrospermopsin is clearly not antibacterial at concentrations found in environmental waters, nor will it adversely affect N. lovaniensis at these concentrations. For organisms that are able to ingest cylindrospermopsin-producing cells, the response of N. lovaniensis to the toxin suggests that only a few ingested cells would be enough to kill predatory organisms with similar susceptibility.

Cylindrospermopsin-induced protein synthesis inhibition and its dissociation from acute toxicity in mouse hepatocytes.

The toxicology of the cyanobacterial alkaloid cylindrospermopsin (CYN), a potent inhibitor of protein synthesis, appears complex and is not well understood. In exposed mice the liver is the main target for the toxic effects of CYN. In this study primary mouse hepatocyte cultures were used to investigate the mechanisms involved in CYN toxicity. The results show that 1-5 microM CYN caused significant concentration-dependent cytotoxicity (52%-82% cell death) at 18 h. Protein synthesis inhibition was a sensitive, early indicator of cellular responses to CYN. Following removal of the toxin, the inhibition of protein synthesis could not be reversed, showing behavior similar to that of the irreversible inhibitor emetine. In contrast to the LDH leakage, protein synthesis was maximally inhibited by 0.5 microM CYN. No protein synthesis occurred over 4-18 h at or above this concentration. Inhibition of cytochrome P450 (CYP450) activity with 50 microM proadifen or 50 microM ketoconazole diminished the toxicity of CYN but not the effects on protein synthesis. These findings imply a dissociation of the two events and implicate the involvement of CYP450-derived metabolites in the toxicity process, but not in the impairment of protein synthesis. Thus, the total abolition of protein synthesis may exaggerate the metabolite effects but cannot be considered a primary cause of cell death in hepatocytes over an acute time frame. In cell types deficient in CYP450 enzymes, protein synthesis inhibition may play a more crucial role in the development of cytotoxicity.