Antibacterial Activity of Synthetic Fire Ant Venom: The Solenopsins and Isosolenopsins

Background. We determined the in vitro activity of 9 synthetic fire ant venom alkaloids (+/-)-solenopsin A, (2R, 6R)-solenopsin A, (2S, 6S)-solenopsin B, (+/-)-isosolenopsin A, (2S, 6R)-isosolenopsin A,(2R, 6S)-isosolenopsin A, (+/-)-isosolenopsin 13, (2S, 6R)-isosolenopsin 13, and (2R, 6S)-isosolenopsin B against 6 species of bacteria (Streptococcus pneumoniae, Staphylococcus aureus, Enterococcus faecalis, Escherichia coli, Stenotrophomonas maltophilia, and Pseudomonas aeruginosa). Methods: The minimum inhibitory concentration and minimum bacteriocidal concentration were determined in accordance with the Clinical Laboratory Standards Institute guidelines. Time kill studies Used American Type Culture Collection bacterial isolates tested at 5 times the minimum inhibitory concentration. Results: None of the venom alkaloids inhibited E. coli or P. aeruginosa, whereas all the alkaloids inhibited S. pneumoniae. Only 4 alkaloids inhibited S. pneumoniae, S. aureus, and S. maltophilia Time-kill kinetics indicates that all 4 active alkaloids had bactericidal activity. Conclusions: Specific isomers of synthetic fire ant venom alkaloids have antibacterial activity against human pathogens.