257. Activity Profile of Anti-Pseudomonal Agents in Areas with Elevated Beta-lactam Resistant P. aeruginosa in the US; Results from CAPITAL Surveillance
Session: Poster Abstract Session: Antimicrobial Susceptibility and Resistance
Friday, October 21, 2011
Room: Poster Hall B1
Background: Treatment of P. aeruginosa infections is difficult due to the degree of resistance to available agents, including cephalosporins and carbapenems.  When considering the use of beta-lactams against P. aeruginosa, it is important to understand that resistance can vary by site and region, and that activity among beta-lactams can vary depending on potency and the prevailing mechanisms of resistance.  As part of the CAPITAL surveillance program, areas with a high degree of resistance to beta-lactams were identified, and the activity of anti-pseudomonal agents against isolates from these areas was evaluated.

Methods: 8,837 clinical isolates of P. aeruginosa were collected from 277 distributed US sites as part of CAPITAL surveillance (Carbapenem Antimicrobial Pseudomonas Isolate Testing At regional Locations) in 2009-2010.  Isolates were tested centrally for susceptibility by broth microdilution (CLSI M7); results were interpreted per current CLSI criteria (excluding doripenem where FDA criteria were applied).

Results: Among sites, 14.4% (40/277) had ceftazidime and imipenem resistance exceeding 20%.  This degree of beta-lactam resistance was most common among sites from the East South Central (38%), Pacific (27%), West South Central (21%), and Mountain (18%) regions.  The susceptibility/MIC90 [mg/mL] of isolates from these sites (N=1,269) was 95%/2 for colistin, 82%/64 for tobramycin, 74%/16 for meropenem, 71%/16 for doripenem, 67%/64 for ceftazidime, 67%/32 for imipenem, and 63%/64 for piperacillin-tazobactam.  Variations in potency among carbapenems was apparent by the percentage of isolates with MICs of <2, <4, <8, and <16 mg/mL, respectively (doripenem: 71%, 79%, 90%, 95%; meropenem: 68%, 74%, 83%, 92%; imipenem: 62%, 67%, 74%, 89%). 

Conclusion: The degree of beta-lactam resistance among P. aeruginosa varies across sites in the US, and >20% resistance to imipenem and ceftazidime is more prevalent among sites in certain regions relative to others.  In vitro potency among anti-pseudomonal agents varied among isolates from regions with a high degree of beta-lactam resistance, with colistin maintaining potent activity and, among the carbapenems, more isolates were susceptible to doripenem and meropenem than imipenem.

Subject Category: A. Antimicrobial agents and Resistance

Chris Pillar1, Jennifer Deane1, A. Simon Lynch, PhD2, R.K. Flamm, PhD2, Todd A. Davies2, Janet Peterson, PhD3, Clyde Thornsberry1 and Dan Sahm1, (1)Eurofins, Global Infectious Disease Services, Chantilly, VA, (2)Johnson & Johnson Pharmaceutical Research and Development, LLC, Raritan, NJ, (3)Ortho-McNeil Janssen Scientific Affairs, LLC, Raritan, NJ


C. Pillar, None

J. Deane, None

A. S. Lynch, Johnson & Johnson Pharmaceutical Research and Development, LLC: Employee and Shareholder, Salary

R. K. Flamm, Johnson & Johnson Pharmaceutical Research and Development, LLC: Employee and Shareholder, Salary

T. A. Davies, Johnson & Johnson Pharmaceutical Research and Development, LLC: Employee and Shareholder, Salary

J. Peterson, Ortho-McNeil Janssen Scientific Affairs, LLC: Employee and Shareholder, Salary

C. Thornsberry, None

D. Sahm, None

Findings in the abstracts are embargoed until 12:01 a.m. EST Thursday, Oct. 20 with the exception of research findings presented at IDSA press conferences.