Direct Lateral Flow Detection of Carbapenemase-producing Acinetobacter baumannii From Screening Samples Using the RESIST ACINETO Lateral Flow Assay: A Proof-of-Concept Study.

OBJECTIVES

To evaluate the lateral flow assay (LFA) RESIST ACINETO targeting the Acinetobacter baumannii-associated carbapenemases, applied directly to screening swabs and compare this culture-independent approach with conventional culture-based diagnostics during a suspected outbreak.

METHODS

We analysed 106 screening swabs from 35 patients. Routine diagnostics included culture, species identification, antimicrobial susceptibility testing and carbapenemase detection from isolates, while the LFA was applied directly to eSwab transport medium without prior culture. Samples positive by both methods were classified as true-positives. Discordant results were resolved by enrichment culture. A confirmation set of 24 swabs from nine known CRAB carriers was analysed to assess sensitivity, and the analytical detection limit was determined using serial dilutions of a blaOXA-23-carrying A. baumannii reference strain.

RESULTS

Routine diagnostics detected CRAB in six samples from two patients. Direct LFA identified these samples and yielded positive results in five additional samples from three patients. Enrichment culture confirmed three of the five discordant samples as CRAB positive, resulting in nine true positive samples. The LFA achieved 100% sensitivity (9/9) and 97.9% specificity (95/97). One false-positive result was caused by an NDM-producing Klebsiella pneumoniae, while one remained unexplained. LFA results were available at least 24 hours earlier than routine diagnostics. In the confirmation set, the direct LFA was positive in all 24 swabs from nine CRAB carriers. The analytical limit of detection was 107 CFU/mL.

CONCLUSIONS

Direct LFA application enabled the rapid, culture-independent detection of carbapenemase-producing A. baumannii and provided results earlier than culture. As an adjunct to conventional screening, it may support earlier infection-control decisions.