Fundamentals of CARBA-R Assay
A serious hazard to public health is posed by the widespread presence of organisms that produce enzyme carbapenemase, such as Pseudomonas aeruginosa, Acinetobacter baumannii and Enterobacteriaceae. Since plasmids typically contain the genes that make carbapenemase, they facilitate the transfer of resistance genes to other bacteria easily. Through this mechanism, carbapenemase producing organisms has been linked to outbreaks of infectious antibiotic resistance in healthcare facilities. These strains of invasive infections have high rates of morbidity and mortality, which puts clinical patient care and public health at risk. Therefore, timely and precise identification of strains that produce carbapenemase is essential for effective antibiotic treatment and infection management.
In clinical laboratories, phenotypic techniques are frequently employed to identify carbapenemase resistance in Gram-negative bacteria. However, they have a lengthy turnaround time of 24 to 48 hours and have limits with regard to sensitivity and specificity.
Carba-R assay is one of the genotypic test intended to quickly identify and distinguish five carbapenemase genes (blaKPC, blaIMP, blaNDM, blaVIM, and blaOXA-48-like) from rectal swabs and pure colonies directly. With only two easy steps and less than a minute of hands-on time, this test can be operated in under an hour. The automated PCR approach of direct sample testing shortens turnaround times as compared to culture-based techniques.
The Carba-R assay is a multiplex qualitative assay that is accurate and dependable, making it ideal for quickly identifying carbapenemase producing organisms in patients upon admission to the emergency room. This makes it possible for medical professionals and infection control staff to act quickly and accurately to stop the spread of these antibiotic-resistant organisms inside of healthcare institutions. Despite a few limitations, it has an advantage in areas where the carbapenemase genes are very abundant.
References
1. Xi Jin et al. Multicenter Evaluation of Xpert Carba-R Assay for Detection and Identification of the Carbapenemase Genes in Rectal Swabs and Clinical Isolates. The Journal of Molecular Diagnostics 2021;23(1):111-119.
2. L.L. Baeza et al. Comparison of five methods for detection of carbapenemases in Enterobacterales with proposal of a new algorithm. Clinical Microbiology and Infection 2019;25:1286.e9- e15.
3. Smith M et al. Rapid and accurate detection of carbapenemase genes in Enterobacteriaceae with the Cepheid Xpert Carba-R assay. Journal of Medical Microbiology 2016; 65:951–953.
4. Hou-He Li, Zhi-Jian He, Li-Min Xie, Jin-Sheng Zhang, Tian-Ao Xie, Shu-Jin Fan, Xu-Guang Guo. Evaluation of Xpert Carba-R Assay for the Detection of Carbapenemase Genes in Gram-Negative Bacteria. BioMed Research International 2021.
5. Jin S, Lee JY, Park JY, Jeon MJ. Xpert Carba-R assay for detection of carbapenemase-producing organisms in patients admitted to emergency rooms. Medicine (Baltimore). 2020;99(50):e23410.
6. https://www.cepheid.com/content/dam/www-cepheid-com/documents/package-insert-files/Xpert-Carba-R-Rx-Only-US-IVD-ENGLISH-Package-Insert-301-2438-Rev-G.pdf
Dr Kinjal Patel
Medical Microbiologist with an aptitude for holistic wellness and serving community with so far acquired knowledge. A dedicated reader in pursuit of improving human lives by transforming laboratory medicine and sharing pearls of medicine. Her life's mantra is "do what you love or love what you do".
