Comparative in vitro activity of telavancin (TD-6424), a rapidly bactericidal, concentration-dependent anti-infective with multiple mechanisms of action against Gram-positive bacteria

Objective: We compared the in vitro activity of telavancin with that of vancomycin, teicoplanin, linezolid, quinupristin/dalfopristin, moxifloxacin and ampicillin, penicillin or oxacillin as appropriate, by the NCCLS/EUCAST and BSAC methods. Methods: The organisms (n = 401) included in the study were patient isolates from St Thomas' Hospital and were selected to include representatives of the clinically important Gram-positive aerobic species. Susceptibility testing was performed by agar dilution methods on Mueller-Hinton agar according to the NCCLS/EUCAST guidelines, in comparison with Iso-Sensitest agar according to the BSAC guidelines. Results: Telavancin was active against all the Gram-positive species tested and nearly 90% of isolates included in the study had telavancin MICs less than or equal to 1 mg/L. Vancomycin-resistant enterococci and lactobacilli isolates with vancomycin MICs > 64 mg/L had telavancin MIC ranges of 0.5-8 and 2-16 mg/L, respectively. There was no evidence of cross-resistance with other comparator drugs. The results for telavancin for the two susceptibility testing methods were mostly either the same or within one doubling dilution. Conclusion: The susceptibility breakpoints for telavancin have yet to be established, but it would appear that telavancin has superior potency to the other tested glycopeptides, and on a weight-for-weight basis displays activity that is comparable to, or better than, that of the other agents tested.