Antimicrobial Susceptibility of Bloodstream Isolates of Staphylococcus aureus: Global Results from the Tigecycline Evaluation and Surveillance Trial, 2004-2008

Problem statement: The Tigecycline Evaluation and Surveillance Trial (TEST) commenced in 2004 to monitor the activity of tigecycline, a new glycylcycline and numerous comparators against major hospital-and community-associated pathogens. In this report we examine the efficacy of tigecycline and comparators against isolates of Staphylococcus aureus collected from blood. Approach: Almost 4000 blood-derived isolates of Staphylococcus aureus were collected from participating centers globally between 2004-2008. Results: All isolates were susceptible to tigecycline (MIC₉₀ 0.25 mg L^-1) and linezolid (MIC₉₀ 4 mg L^-1); 99.9% of isolates were susceptible to vancomycin (MIC₉₀ 1 mg L^-1). Tigecycline and linezolid activity were unaffected by resistance to methicillin, ICU vs non-ICU isolate collection or the age of patients from which the isolates were collected. Although 95.3% of MSSA were levofloxacin susceptible, only 14.4% of MRSA isolates were susceptible to levofloxacin in this study. Conclusion: Tigecycline is shown here to be active against S. aureus isolates collected from blood and is unaffected by methicillin resistance. However, tigecycline is not as yet approved for the treatment of bacteremic infections.