monensin and Gram-Positive-Bacterial-Infections

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.. 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). SDS-PAGE and transmission electron microscopy (TEM) were used to determine protein expression and visualize extracellular morphology changes.. Monensin-non-exposed isolates did not display monensin adaptation during in vitro monensin exposure. In contrast, in vivo monensin-exposed isolates displayed monensin adaptation enabling growth at 32× MIC. Upon consecutive subculturing, monensin MICs returned to baseline, or one dilution above, for the monensin-adapted strains. SDS-PAGE identified overexpression of a 14 kDa protein (C. perfringens) and a 20.5 kDa protein (E. faecium and E. faecalis) in the monensin-adapted isolates. TEM demonstrated that in vitro monensin-adapted strains had a significantly thicker cell wall or glycocalyx compared with in vivo monensin-exposed or subcultured isolates.. In vivo monensin-exposed isolates of C. perfringens, E. faecium and E. faecalis have the ability to grow in the presence of high monensin concentrations in vitro. This is associated with an increased thickening of the cell wall or glycocalyx that is reversible upon serial passage, suggesting a phenotypically expressed, but not genetically stable, trait.

Topics: Animals; Anti-Bacterial Agents; Bacterial Proteins; Cattle; Cattle Diseases; Cell Wall; Clostridium perfringens; Electrophoresis, Polyacrylamide Gel; Enterococcus faecalis; Enterococcus faecium; Food Safety; Glycocalyx; Gram-Positive Bacterial Infections; Microbial Sensitivity Tests; Microscopy, Electron, Transmission; Monensin

Streptococcosis is a major disease of several fish species in Australia, Japan and South Africa. The minimum inhibitory concentration of some ionophores (lasalocid, monensin, narasin and salinomycin) was determined in vitro for an Enterococcus-like species pathogenic for rainbow trout (Oncorhynchus mykiss) in Australia. Forty isolates of the fish pathogen were tested, together with control strains of Staphylococcus aureus ATCC 29213, Enterococcus faecalis ATCC 29212 and Streptococcus bovis ATCC 9809. The minimum inhibitory concentrations (MIC) of erythromycin, the drug of choice for controlling streptococcosis, ranged between 0.1 and 0.8 microgram/ml whereas the MIC values for the ionophores ranged between 0.2 and 1.5 micrograms/ml. Of the ionophores tested, narasin was the most inhibitory (0.2-0.4 microgram/ml), while monensin was the least inhibitory (0.4-1.5 micrograms/ml). Salinomycin was marginally more inhibitory (0.4-0.8 microgram/ml) than lasalocid (0.8 microgram/ml).

Topics: Animals; Anti-Bacterial Agents; Enterococcus; Erythromycin; Fish Diseases; Gram-Positive Bacterial Infections; Ionophores; Lasalocid; Microbial Sensitivity Tests; Monensin; Oncorhynchus mykiss; Pyrans