Effects of temperature on the bactericidal activities of ciprofloxacin and levofloxacin against Staphylococcus aureus and Staphylococcus epidermidis.

The bactericidal activities of the 4-quinolones ciprofloxacin and levofloxacin against Staphylococcus aureus and Staphylococcus epidermidis in nutrient broth were dramatically reduced when the temperature of incubation was decreased from 37 to 20 degrees C. For S. aureus the relative reduction in the activities was 86- and 46-fold with ciprofloxacin or levofloxacin, respectively. For S. epidermidis the corresponding reduction in activities was 82- and 19-fold, respectively. At infectious sites which are at lower-than-body temperature the reduced activity of 4-quinolones may contribute to clinical failure and/or the development of resistance. Levofloxacin was more bactericidal than ciprofloxacin against either of the staphylococci at every temperature tested. These results tend to suggest that levofloxacin may be preferable to ciprofloxacin for staphylococcal infections especially at skin and soft-tissue sites.