Effects of triclosan on growth viability and fatty acid synthesis of the oyster protozoan parasitePerkinsus marinus

Abstract

Perkinsus marinus, a protozoan parasite of the Eastern oyster Crassostrea virginica, has severely impacted oyster populations from the Mid-Atlantic region to the Gulf of Mexico coast of North America for more than 30 yr. Although a chemotherapeutic treatment to reduce or eliminate P. marinus from infected oysters would be useful for research and hatchery operations, an effective and practical drug treatment does not currently exist. In this study, the antimicrobial drug triclosan 5-chloro-2-(2, 4 dichlorophenoxy) phenol, a specific inhibitor of Fab1 (enoyl-acyl-carrier-protein reductase), an enzyme in the Type II class of fatty acid synthetases, was tested for its effects on viability, proliferation and fatty acid synthesis of in vitro-cultured P. marinus meronts. Treatment of P. marinus meront cell cultures with concentrations of ≥2 µM triclosan at 28°C (a temperature favorable for parasite proliferation) for up to 6 d stopped proliferation of the parasite. Treatment at ≥5 µM at 28°C greatly reduced the viability and fatty acid synthesis of meront cells. Oyster hemocytes treated with ≥20 µM triclosan exhibited no significant (p < 0.05) reduction in viability relative to controls for up to 24 h at 13°C. P. marinus meronts exposed to ≥2 µM triclosan for 24 h at 13°C exhibited significantly (p < 0.05) lower viability relative to controls. Exposure of P. marinus meronts to triclosan concentrations of ≥20 µM resulted in > 50% mortality of P. marinus cells after 24 h. These results suggest that triclosan may be effective in treating P. marinus-infected oysters. KEY WORDS: Triclosan · Dermo disease · Perkinsus marinus · Eastern oyster · Fatty acid synthesis Resale or republication not permitted without written consent of the publisherDis Aquat Org 67: [217][218][219][220][221][222][223][224] 2005 To be practical for use in controlling Perkinsus marinus infection, a drug therapy needs to have several important features: (1) high specific action against the parasite; (2) low toxicity to the host; (3) application through direct addition to water in holding containers; (4) low/no toxicity to humans; (5) low cost and ready availability. Several studies evaluating potential chemotherapeutic agents for treatment of Dermo disease have been published, but the protocols so far developed to successfully treat P. marinus infection in oysters fail to meet several of these criteria (Ray 1966a,b, Calvo & Burreson 1994, Faisal et al. 1999, Delaney et al. 2003.Parasitic protozoans must either acquire lipids from their host or synthesize lipids de novo to produce the new cell membrane necessary for cell replication. Inhibiting the ability to synthesize new membrane prevents the parasite from increasing in surface area, thereby halting cell proliferation and disease progression.The antimicrobial drug triclosan, 5-chloro-2-(2, 4 dichlorophenoxy) phenol, has been used in a wide array of consumer products such as soaps, toothpastes and household plastics for the last 30 yr. Triclosan inhibits fatty acid synthesis and stops the...

The Alveolate Perkinsus marinus: Biological Insights from EST Gene Discovery

“…Indeed, it has been shown that Perkinsus proliferation is inhibited by Triclosan and cerulenin, which has been interpreted as evidence for the presence of a plastidic FAS II pathway [24,25]. However, when considering the effect of Triclosan as indicative of the relevance of the apicoplast FASII biosynthesis, results should be interpreted with caution, since in Plasmodium , the antimalarial activity of Triclosan is not targeted to FabI [90].…”

Co-transcribed Genes for Long Chain Polyunsaturated Fatty Acid Biosynthesis in the Protozoon Perkinsus marinus Include a Plant-like FAE1 3-Ketoacyl Coenzyme A Synthase

“…In the case of P. marinus, it may be possible to use K3 anilide herbicides to control their infection of oysters, as the toxicity of compounds such as flufenacet, although severe toward terrestrial and aquatic plants, shows much reduced (several orders of magnitude) toxicity to non-photosynthetic organisms including the eastern oyster (see www.epa.gov/opprd001/ factsheets/flufenacet.pdf). An analogous approach to controlling P. marinus has recently been proposed using the type II fatty acid synthase inhibitor triclosan (31). Alternatively, the knowledge that flufenacet disrupts the P. marinus FAE elongase, and by implication the synthesis of ARA, may serve as the basis for chemical design and synthesis of more specific inhibitors.…”

Current Advances in Detection and Treatment of Babesiosis

“…Parasitic protozoa must either acquire lipids from their host or synthesize lipids de novo to produce the new cell membrane during cell replication. Inhibiting the ability to synthesize new membrane prevents the parasite from increasing in surface area, thereby halting cell proliferation and disease progression [134]. Triclosan has demonstrated an inhibitory effect on the growth of Plasmodium falciparum, Toxoplasma gondii, Theileria parva, Trypanosoma brucei and Perkinsus marinus in in vitro studies, and in in vivo studies with P. berghei in a mouse model [134-138].…”