Biomaterial culture conditions impacting the performance of a PAM fluorometry based aquatic phytotoxicity assay.

An aquatic phytotoxicity assay, based on the principles of pulse amplitude modulated (PAM) fluorometry has recently been developed and validated under laboratory conditions. Characteristics of the assay include the use of photosynthesising biomaterial, most frequently whole organism microalgae. The instrument employs light probing measurements to monitor chlorophyll fluorescence signals emitted by the biomaterial component. These characteristics could leave assay performance susceptible to interference by minor variations in biomaterial treatment and culture conditions prior to testing. This study investigates assay performance in response to variations in two microalgae culture parameters; short-term light history (24h) prior to testing and the sterility of long-term culture conditions. Light history of the four microalgal species tested significantly impacted their toxicity response, as measured with the assay. Light treatments of 5 micromol photons m(-2)s(-1) produced the highest photosystem II quantum yields (Phi(II)) whilst higher light intensities resulted in an inverse relationship between Phi(II) and the measured toxicity response (inhibition (%) of photochemistry). Of the two microalgal cultures tested, sterility of culture conditions significantly impacted the performance of the green freshwater algae, Chlorella vulgaris as assay biomaterial. On average 1 microg L(-1) diuron inhibited photochemistry 2.6% less in axenically cultured C. vulgaris compared with non-axenically maintained cultures. This investigation series contributes valuable quality assurance data towards microalgal based PAM fluorometry assays and emphasises the importance of such investigations if new biorecognition systems are to be accredited and/or routinely incorporated for biomonitoring purposes.

The selection of a model microalgal species as biomaterial for a novel aquatic phytotoxicity assay.

A phytotoxicity assay based on the ToxY-PAM dual-channel yield analyser has been developed and successfully incorporated into field assessments for the detection of phytotoxicants in water. As a means of further exploring the scope of the assay application and of selecting a model biomaterial to complement the instrument design, nine algal species were exposed to four chemical substances deemed of priority for water quality monitoring purposes (chlorpyrifos, copper, diuron and nonylphenol ethoxylate). Inter-species differences in sensitivity to the four toxicants varied by a factor of 1.9-100. Measurements of photosystem-II quantum yield using these nine single-celled microalgae as biomaterial corroborated previous studies which have shown that the ToxY-PAM dual-channel yield analyser is a highly sensitive method for the detection of PS-II impacting herbicides. Besides Phaeodactylum tricornutum, the previously applied biomaterial, three other species consistently performed well (Nitzschia closterium, Chlorella vulgaris and Dunaliella tertiolecta) and will be used in further test optimisation experiments. In addition to sensitivity, response time was evaluated and revealed a high degree of variation between species and toxicants. While most species displayed relatively weak and slow responses to copper, C. vulgaris demonstrated an IC10 of 51 microgL-1, with maximum response measured within 25 minutes and inhibition being accompanied by a large decrease in fluorescence yield. The potential for this C. vulgaris-based bioassay to be used for the detection of copper is discussed. There was no evidence that the standard ToxY-PAM protocol, using these unicellular algae species, could be used for the detection of chlorpyrifos or nonylphenol ethoxylate at environmentally relevant levels.

Unidentified trematode eggs in faeces of Australian aboriginal children.

In routine surveys for intestinal parasites among Aboriginal/Torres Strait Islander populations, eggs of unidentified trematode species have been found in the faeces of three children. In two of these, the eggs appeared to belong to a schistosome, or perhaps monogenean, species, and in the third, they were most likely from a monostome of dugongs. Although these probably represent cases of spurious parasitism, one or more may have been a true infection.

Evaluation of a new antihelminthic for trichuriasis, hookworm, and stronglyloidiasis.

Mebendazole was tested in a double-blind trial for its efficacy in the treatment and control of enteric helminths. One hundred and twenty-two children from a community near the Gulf of Carpentaria, and from a community in Cape York Peninsula in northern Queensland were divided into two equal groups to receive a course of either mebendazole or placebo after the identification of one or more intestinal helminths in a single pretreatment specimen of faeces. Between the tenth and twentieth days after a four-day course of treatment, three specimens of faeces were collected from each child. Mebendazole cured trichuriasis in 75% of cases, and over-all egg reduction rate was 96%. The drug also cured hookworm in 13 out of 15 cases and Strongyloides sterocoralis infestation in 14 out of 21 cases. Mebendazole was ineffective against Hymenolepis nana. No cases of Ascaris lumbricoides infestation were present. No side effects or adverse reactions to the drug were noted and patient acceptance was excellent. Mebendazole appears to be a safe drug for use in the treatment of human parasitic intestinal nematode infestations, and should be especially useful in the treatment and control of trichuriasis.

PIP: Mebendazole was tested in a double-blind trial for its efficacy in the treatment and control of enteric helminths. 122 children from a community near the Gulf of Carpentaria, and from a community in Cape York Peninsula in northern Queensland were divided into 2 equal groups to receive a course of either mebendazole or placebo after the identification of 1 or more intestinal helminths in a single pretreatment specimen of feces. Between days 10-20 following a 4-day course of treatment, 3 specimens of feces were collected from each child. Mebendazole cured trichuriasis in 75% of the cases, and the overall egg reduction rate was 96%. The drug also cured hookworm in 13 of 15 cases and Strongyloides sterocoralis infestation in 14 of 21 cases. Mebendazole was ineffective against Hymenolepsis nana. No cases of Ascaris lumbricoides infestation were present. No side effects or adverse reactions to the drug were noted and patient acceptance was excellent. Mebendazole appears to be a safe drug for use in the treatment of human parasitic intestinal nematode infestations and should be especially useful in the treatment and control of trichuriasis.