Multicenter Performance Assessment of Carba NP Test.

Area of Science:

• Microbiology
• Clinical Diagnostics
• Antimicrobial Resistance

Background:

• Carbapenemase-producing Gram-negative bacilli pose a significant threat to public health.
• Accurate and rapid detection of carbapenemase production is essential for effective infection control and treatment.
• The Carba NP test is a phenotypic method for detecting carbapenemase activity.

Purpose of the Study:

• To evaluate the reproducibility and performance of the Carba NP test across multiple testing laboratories.
• To assess the consistency of the Carba NP test when performed using standardized Clinical and Laboratory Standards Institute (CLSI) procedures.

Main Methods:

• Eighty Gram-negative bacilli isolates, including Enterobacteriaceae and nonfermenting Gram-negative bacilli, were used.
• Seven laboratories performed the Carba NP test following CLSI guidelines in a blinded manner.
• Site-versus-site comparisons were conducted to assess assay consistency.

Main Results:

• The Carba NP test demonstrated a high level of consistency across the seven participating laboratories.
• Only 3 out of 21 site comparisons showed a difference in sensitivity (P < 0.05).
• Known limitations regarding blaOXA-48-like and blaOXA carbapenemases in Acinetobacter baumannii were observed.

Conclusions:

• The Carba NP test, when implemented with standardized CLSI methodology, provides reproducible results for carbapenemase detection.
• The assay is a reliable tool for identifying carbapenemase-producing Gram-negative bacilli in a multi-laboratory setting.