Comparative effect of salinomycin and monensin on Streptococcus bovis strain ATCC 9809

The effect of salinomycin (2.5 mg/l) on the in vitro growth of Streptococcus bovis strain ATCC 9809, on its catabolism of glucose and on its anabolism of lactic acid was compared with that of monensin (5.0 mg/l). In control cultures containing no ionophore, glucose consumption and lactic acid production were completed concomitantly with maximal growth which was reached after 2 h of incubation at 37 degrees C. No further growth of S. bovis was observed within 2 h after the addition of one or the other ionophore to exponentially growing cultures. Glucose consumption and lactic acid production continued for 6 h after the addition of monensin and for 8 h after the addition of salinomycin. As observed in cultures without ionophore, glucose was totally consumed and lactic acid was stoichiometrically produced in cultures grown in the presence of one or the other ionophore. Thus, salinomycin and monensin inhibited bacterial growth but not fermentation of glucose by S. bovis.