Toxigenicity of enniatins from Western Australian Fusarium species to brine shrimp (Artemia franciscana)

The high prevalence (14 of 24 isolates) of enniatin-producing isolates from Western Australian Fusarium species isolated from pasture legumes associated with sheep feed refusal and rat deaths, and the high toxicity of their crude extracts to brine shrimp (Artemia franciscana) from a previous study warranted further investigation of this class of mycotoxin. Crude extracts from Fusarium acuminatum, Fusarium avenaceum, Fusarium tricinctum and Fusarium sambucinum, along with enniatins A, A1, B and B1 purified from a Western Australian strain of F. acuminatum using semi-preparative HPLC, were bioassayed using brine shrimp. All Fusarium isolates produced both enniatins B and B1, except for F. tricinctum WAC 8019, and 11 of the 17 isolates produced enniatin A1. Overall, all of the F. avenaceum isolates produced high amounts of enniatins, in particular enniatin B. One isolate of F. acuminatum (WAC 5715) and of F. tricinctum (WAC 11486) also produced high amounts of both enniatins B and B1. Only F. acuminatum WAC 5715 produced enniatin A among the tested isolates. All four purified enniatins A, A1, B, B1, individually and in combination, caused brine shrimp toxicity after 6 h of exposure, implicating that this emerging class of mycotoxin as a cause of the acute toxicity to brine shrimp observed. The mixture of all four enniatins was the most toxic to brine shrimp compared to purified individual enniatins, where the relative toxicity order was B > B1 > A1 > A. Enniatin B was the individual most toxic enniatin with some bioactivity at 5 μg/mL and almost 100% brine shrimp death at 50 μg/mL after 24 h of exposure. This study is the first report to confirm the acute toxicity of enniatins A, A1, B and B1 to brine shrimp, and also highlights the need for further investigation of the potential toxicity of these cyclic hexadepsipeptides to animals and humans.