Topic:

Infectious disease surveillance

Abstract No.:

ISE.372

Title:

An Asian surveillance program studying the in vitro activity of Tigecycline (TIG) and common therapeutic agents against methicillin-resistant Staphylococcus aureus and vancomycin-resistant Enterococcus species from 2004-2011

Author(s):

S. Bouchillon¹, B. Johnson¹, M. Renteria¹, R. Badal¹, D. Hoban¹, M. Dowzicky²; ¹International Health Management Associates, Inc., , Schaumburg, IL/US, ²Pfizer Inc., Collegeville, PA/US

Abstract:

Background: The T.E.S.T. program determined the in vitro activity against methicillin-resistant S. aureus and vancomycin-resistant Enterococcus spp. of TIG and 10 antimicrobials commonly prescribed for serious gram-positive infections: amoxicillin-clavulanic acid (AUG), piperacillin-tazobactam (PT), levofloxacin (LVX), ceftriaxone (CAX), linezolid (LZD), minocycline (MIN), vancomycin (VAN), ampicillin (AMP), penicillin (PEN), and meropenem (MER). Study strains were collected from 113 laboratories in 10 countries in Asia throughout 2004-2011.
Methods: A total of 2,304 clinical isolates, E. faecalis (510) and E. faecium (346), and S. aureus (1448), was identified to the species level at each participating site and confirmed by a central laboratory. Minimum Inhibitory Concentrations (MICs) were determined by the local laboratory using broth microdilution panels. Antimicrobial resistance was interpreted according to CLSI breakpoints with TIG susceptible breakpoints defined as <0.5 mcg/ml for S. aureus and <0.25 mcg/ml for enterococci.
Results: 9.1% (78/856) of enterococci were resistant to vancomycin (VRE), and 51.7% (748/1448) of S. aureus were resistant to cefoxitin (MRSA). All but 1 of the VRE were E. faecium. Among the vancomycin resistant E. faecium (VREF), % resistant rates to other study drugs were LVX 100, PEN 97.4, AMP 100, MIN 15.6, and LZD 0. Percent resistant rates for MRSA were PEN 100, AMP 100, AUG 100, LVX 89.6, PT 100 CAX 100, IMP 100, MIN 15.4, LZD 0, and VAN 0. TIG inhibited 100% of the enterococci and 97.6% of all MRSA. Modal TIG MICs for VRE/nonVRE were 0.06/0.12, respectively, and 0.12/0.25 for MSSA/MRSA, respectively.
Conclusion: TIG retained potent activity against methicillin-resistant S. aureus and vancomycin-resistant enterococci, inhibiting >97% of all strains tested at their defined breakpoints of 0.5 and 0.25 mcg/ml, respectively.  There has been a significant decline in %Sus for LVX and all the beta-lactams against all S. aureus since 2004 (p<0.05).  MIN has shown significant decrease in %Sus against both MRSA and VRE isolates (p<0.05); however, there has been no cross-resistance seen between MIN and TIG or concomitant decline in TIG % Sus (p=0.436).