Antimicrobial Susceptibility Among Bacterial Isolates from ICU and Non-ICU Settings and Different Age Groups: Results from the Tigecycline Evaluation and Surveillance Trial in North America

Abstract

As part of the tigecycline evaluation and Surveillance trial (T.E.S.T.), isolates were collected from centers in North America. In vitro activity was assessed for isolates collected in 2006 using CLSI guidelines and CLSI or FDA interpretive criteria. Data were analyzed according to intensive care unit (ICU) or non-ICU location and age group (18-64 years and ≥65 years).

Rates of mRSA in 2006 were higher among isolates from patients aged ≥65 years (52.0%) than younger patients (48.4%) and from non-iCU settings (48.0%) than from the ICU (45.3%). Rates of vancomycin-resistant E. faecium, multidrug-resistant Acine-tobacter spp. (resistant to levofloxacin and amikacin as well as the carbapenems and/or third generation cephalosporins), and eSbl-producing K. pneumoniae among isolates collected from the ICU were 70.7%, 5.8%, and 16.6%, respectively.

Tigecycline, linezolid and vancomycin were active against all isolates of S. aureus, including MRSA, from both settings and the two age groups. Among E. faecium, >95% of isolates were susceptible to linezolid, and tigecycline maintained MIC₉₀s of 0.06-0.12 mg/L. Against Acinetobacter spp., the most active antimicrobials were tigecycline and minocycline irrespective of age group or patient setting (MIC₉₀s 2 and 8 mg/L, respectively). percentage susceptibility of K. pneumoniae was >90% against tigecycline, imipenem, meropenem, cefepime and amikacin for isolates from both age groups and settings. Against eSbl-producing K. pneumoniae, imipenem (88.9%-96.4%) and tigecycline (85.1%-100%) demonstrated the highest rates of activity. Tigecycline demon-strated excellent activity against clinically relevant resistant organisms.

Keywords:

• Tigecycline
• antimicrobial resistance
• age groups
• intensive care unit
• bacterial infections