Reversible monensin adaptation in Enterococcus faecium, Enterococcus faecalis and Clostridium perfringens of cattle origin: potential impact on human food safety.

Objectives: To determine the stability/reversibility and mechanism of monensin adaptation in monensin-treated cattle isolates compared with reference bacterial isolates, exposed in vitro to high monensin concentrations.

Methods: We evaluated the potential for cattle-origin strains of Clostridium perfringens, Enterococcus faecium and Enterococcus faecalis exposed to monensin in vivo (in vivo monensin-exposed isolates) to maintain or achieve the ability to grow in the presence of high monensin concentrations (in vitro monensin-adapted isolates). Twenty-one consecutive subcultures of the in vitro monensin-adapted strains were performed, and monensin MICs were determined for the 3rd, 7th, 14th and 21st subcultures (subcultured isolates).

Effects of orally administered spinosad (Comfortis) in dogs on adult and immature stages of the cat flea (Ctenocephalides felis).

The efficacy of spinosad against adult fleas (Ctenocephalides felis) on dogs was evaluated in three controlled, blinded studies. One study was conducted to determine speed of kill on experimentally infested dogs. Two additional studies were designed to assess the efficacy of spinosad in preventing environmental contamination with flea eggs (USA study and EU study).