Time-kill determination of the bactericidal activity of telavancin and vancomycin against clinical methicillin-resistant Staphylococcus aureus isolates from cancer patients

The bactericidal activity of vancomycin and telavancin was compared against 4 clinical methicillin-resistant Staphylococcus aureus isolates recently recovered from cancer patients, using minimum bactericidal concentration (MBC):MIC ratios and time-kill studies. All 4 isolates were susceptible to both agents based on individual MIC values. The 2 methodologies for assessing bactericidal activity produced variable results. Telavancin appeared to have somewhat better bactericidal activity than vancomycin based on narrower MBC:MIC ratios. However, based on the results of the time-kill studies, neither agent demonstrated reliable bactericidal activity (defined as a ≥3 log₁₀ reduction of the starting inoculum at the end of 24 hours) against these organisms. These findings might be of some therapeutic importance in certain clinical settings and/or specific patient populations (such as febrile neutropenic patients) in whom potent bactericidal activity is either desired or preferred.