In Vitro Activity of Ceftazidime-Avibactam (CAZ-AVI) against Urinary Tract Infection (UTI) and Intra-Abdominal Infection (IAI) Pathogens from Latin America: Results of the INFORM Surveillance Initiative

Background: Increasing resistance in Gram-negative pathogens has been reported worldwide, seriously limiting treatment options in some regions. Avibactam is a novel non-β-lactam β-lactamase inhibitor that restores the in vitro activity of ceftazidime against Enterobacteriaceae that produce class A (including KPC), class C, and some class D β-lactamases. In this study we evaluated the in vitro activity of ceftazidime-avibactam (CAZ-AVI) against Enterobacteriaceae collected from UTI and IAI sources across Latin America. 

Methods: Isolates for this analysis were collected from 2012 – 2014 from six countries in Latin America.  All isolates came from either a UTI or IAI source and were collected centrally for confirmatory identification and antimicrobial susceptibility testing.  MICs were determined by broth microdilution according to CLSI guidelines for testing and interpretations.  The percent susceptible (%S) was assessed using the FDA breakpoint of ≤8 mg/ml for CAZ-AVI with AVI tested at a constant concentration of 4 mg/ml.

Results: The CAZ-AVI activities against each organism group within each of the six countries is shown below.   

Organism

Argentina

Brazil

Chile

Colombia

Mexico

Venezuela

n

%S/MIC90

n

%S/MIC90

n

%S/MIC90

n

%S/MIC90

n

%S/MIC90

n

%S/MIC90

All Enterobacteriaceae

499

99.2/0.5

513

99.8/1

590

100/1

377

100/0.5

494

99.8/0.25

430

100/0.25

Escherichia coli

232

100/0.25

218

100/0.25

267

100/0.25

151

100/0.25

202

100/0.25

177

100/0.25

Klebsiella spp.

123

99.2/1

156

99.4/2

177

100/2

111

100/0.5

148

100/0.25

129

100/0.5

Conclusion: Based on MIC₉₀s and % susceptibility CAZ-AVI demonstrated potent in vitro activity against all Enterobacteriaceae encountered from UTI and IAI specimens obtained from several countries in Latin America over the three years studied. This activity included the most prominent species E. coli and Klebsiella spp. Currently these data demonstrate that CAZ-AVI has potent activity against all targeted species. However, this level of potency could change if these organisms acquire other potent b-lactamases (e.g. MBLs).