209. Clinical Cure Rates in Patients Treated with Azithromycin (AZ) for Community Acquired Respiratory Tract Infections (CARTI) Caused by Azithromycin-Susceptible (AZ-S) and Azithromycin-Resistant (AZ-R) Streptococcus pneumoniae (SPN): Analysis of Randomized Comparative Clinical Trial Data
Session: Poster Abstract Session: Antimicrobial Resistance: Clinical Studies
Friday, October 21, 2011
Room: Poster Hall B1
Background: CARTI including community-acquired pneumonia (CAP), acute bacterial exacerbations of chronic bronchitis (ABECB), acute bacterial sinusitis (ABS) and acute otitis media (AOM) are commonly caused by SPN and empirically treated with macrolides such as AZ. The purpose of this study was to determine clinical cure rates in patients with a CARTI caused by AZ-S and AZ-R SPN in randomized comparative trials (RCT) for AZ.

Methods: 1127 patients with a CARTI (402 AOM, 309 CAP, 255 ABECB, and 161 ABS) received AZ in 16 Phase 3 RCT (1993-2007) to assess the clinical efficacy of AZ. 31.8% (358/1127) patients with CARTI had a positive culture for AZ-S or AZ-R SPN and were assessed for cure/failure.  AZ susceptibility was assessed using CLSI methods. Low-level AZ resistance (LLAR) was defined as AZ MIC 2-8µg/ml, high-level AZ resistance (HLAR) was defined as AZ MIC ≥16µg/ml. Chi-square analysis was used to assess differences in clinical cure based upon AZ-S or AZ-R SPN.

Results: 27.4% (98/358) patients with CARTI had infection caused by AZ-R SPN. 40.8% (40/98) of AZ-R SPN were LLAR, while 59.2% (58/98) were HLAR.  Clinical cure rates were: 87% (310/358) for all SPN CARTI patients, 90% (234/260) for AZ-S patients,   78% (76/98) for CARTI patients with AZ-R SPN (p=0.002, compared to AZ-S SPN), 78% (31/40) for CARTI patients with LLAR SPN (p=0.022) and 78% (45/58) for CARTI patients with HLAR SPN (p=0.009).

Conclusion: Overall clinical cure rate in patients with CARTI infected with SPN and treated with AZ was 87%. Cure rates were higher in patients infected with AZ-S SPN (90%) compared to AZ-R SPN (78%; p=0.002). No difference in cure occurred in patients infected with LLAR SPN (78%) versus HLAR SPN (78%).

Subject Category: A. Antimicrobial agents and Resistance

George G. Zhanel, PhD1, Kevin Wolter, MD2, Cristina-Dana Calciu, MD3, Patricia Hogan, PhD2, Karl Weiss, MD4 and Donald Low, MD5, (1)University of Manitoba, Winnipeg, MB, Canada, (2)Pfizer Inc, New York, NY, (3)Pfizer Inc, Kirkland, QC, Canada, (4)Hop. Maisonneuve-Rosemont, Montreal, QC, Canada, (5)Mount Sinai Hospital, Toronto, ON, Canada


G. G. Zhanel, Pfizer Inc: Research Contractor, Research support

K. Wolter, Pfizer Inc: Employee, Salary

C. D. Calciu, Pfizer Inc: Employee, Salary

P. Hogan, Pfizer Inc: Employee, Salary

K. Weiss, Pfizer Inc: Research Contractor, Research support

D. Low, Pfizer Inc: Research Contractor, Research support

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.