Xpert Carba-R Assay on Flagged Blood Culture Samples: Clinical Utility in Intensive Care Unit Patients with Bacteremia Caused by Enterobacteriaceae

Surendran Rajendran; Ram Gopalakrishnan; Anil Tarigopula; D Suresh Kumar; P Senthur Nambi; Nandini Sethuraman; Chitra Chandran; Nagarajan Ramakrishnan; V Ramasubramanian

doi:10.5005/jp-journals-10071-24533

Xpert Carba-R Assay on Flagged Blood Culture Samples: Clinical Utility in Intensive Care Unit Patients with Bacteremia Caused by Enterobacteriaceae

Indian J Crit Care Med. 2023 Sep;27(9):655-662. doi: 10.5005/jp-journals-10071-24533.

Authors

Surendran Rajendran¹, Ram Gopalakrishnan¹, Anil Tarigopula², D Suresh Kumar¹, P Senthur Nambi¹, Nandini Sethuraman³, Chitra Chandran⁴, Nagarajan Ramakrishnan⁵, V Ramasubramanian¹

Affiliations

¹ Department of Infectious Diseases, Apollo Hospitals, Chennai, Tamil Nadu, India.
² Department of Molecular Laboratory Services, Apollo Hospitals, Chennai, Tamil Nadu, India.
³ Department of Microbiology, Apollo Hospitals, Chennai, Tamil Nadu, India.
⁴ Department of Molecular Diagnostics, Apollo Hospitals, Chennai, Tamil Nadu, India.
⁵ Department of Critical Care Medicine, Apollo Hospitals, Chennai, Tamil Nadu, India.

Abstract

Introduction and background: Rapid molecular diagnostics to predict carbapenem resistance well before the availability of routine drug sensitivity testing (DST) can serve as an antimicrobial stewardship tool in the context of high rates of Carbapenem-resistant Enterobacteriaceae (CRE).

Materials and methods: A retrospective observational study of patients more than 18 years of age on whom Xpert Carba-R (FDA approved for rectal swab specimen) was done on gram-negative bacteria (GNB) flagged blood culture samples, in an Indian intensive care unit between January 2015 and November 2018. We analyzed the performance of Xpert Carba-R in comparison with routine DST.

Results: A total of 164 GNBs were isolated from 160 patients. Klebsiella pneumoniae and Escherichia coli were the predominant isolates. Carba-R was positive in 35.36% of samples and 45.34% were carbapenem-resistant (CR) on routine DST. The distribution of the CR gene was: Oxacillinase (OXA) (50%), NDM (32.7%) followed by OXA and NDM co-expression (15.51%). The sensitivity, specificity, positive likelihood ratio, negative likelihood ratio, positive predictive value, and negative predictive value of Carba-R were 90.74, 93.15, 13.25, 0.10, 83.58 and 96.31% for Enterobacteriaceae. The median time to obtain the Carba-R report was 30 hours 34 minutes vs 74 hours and 20 minutes for routine DST. Based on the Carba-R report, 9.72% of patients had escalation and 27.08% had de-escalation of antibiotics.

Conclusion: Xpert Carba-R serves as a rapid diagnostic tool for predicting carbapenem resistance in intensive care unit patients with bacteremia caused by Enterobacteriaceae.

How to cite this article: Rajendran S, Gopalakrishnan R, Tarigopula A, Kumar DS, Nambi PS, Sethuraman N, et al. Xpert Carba-R Assay on Flagged Blood Culture Samples: Clinical Utility in Intensive Care Unit Patients with Bacteremia Caused by Enterobacteriaceae. Indian J Crit Care Med 2023;27(9):655-662.

Keywords: Antimicrobial stewardship; Carbapenem-resistant enterobacteriaceae; Carbapenemase detection; Gram-negative resistance; Novel diagnostics for antimicrobial resistance; Rapid molecular diagnostics; Xpert Carba-R assay.