2170. Xpert Carba-R Assay on Flagged Blood Culture Samples: Clinical Utility in Intensive Care Unit Patients with Gram-Negative Bacteremia

Abstract

Abstract Background Rapid molecular diagnostics that predict carbapenem resistance (CR) 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). 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 a tertiary care Indian intensive care unit between January 2015 and November 2018. Results The study included 160 patients who had a median (Sequential Organ Failure Assessment) SOFA score of 16. A total of 164 GNB were isolated with 4 patients having polymicrobial bacteremia. Klebsiella pneumoniae and Escherichia coli were the predominant isolates (Figure 1). Carba-R was positive in 58/164 (35.36%) samples (Figure 2) and 73/161 isolates (45.34%) were CR (after excluding intrinsic CR organisms) on routine DST. The distribution of CR genes overall was: OXA-48 like (29/58–50%), followed by NDM (19/58–32.7%), followed by OXA-48 and NDM co-expression (9/58–15.51%) and in individual groups as in Figure 3. The sensitivity, specificity, positive likelihood ratio, negative likelihood ratio, positive predictive value (PPV) and negative predictive value (NPV) of Carba-R vs. routine DST were 90.74%, 93.15%, 13.25, 0.10, 83.58% and 96.31% for enterobacteriaceae (Figure 4). The median time to obtaining the Carba-R report was 30 hours 34 minutes vs. 74 hours and 20 minutes for carbapenem resistance on routine DST. Based on the Carba-R report, 9.72% of patients had escalation of antibiotics (e.g., colistin) to cover CR organisms and 27.08% had de-escalation from CR cover that had already been started. Conclusion Xpert Carba-R serves as a rapid diagnostic tool for CR Gram-negative bacteremia, particularly hospital-acquired enterobacteriaceae in intensive care units with a high CRE prevalence. It assists in initiating early appropriate therapy and early institution of infection control measures in these patients, as well as in de-escalation of colistin in patients without carbapenem resistance. We recommend that clinicians consider routinely utilizing this test in this setting. Disclosures All authors: No reported disclosures.