Comparison of clinical outcomes of patients with serial negative surveillance cultures according to a subsequent PCR test for carbapenemase-producing Enterobacterales.

OBJECTIVES: The aims of this study were to evaluate the impact of the result of a subsequent polymerase chain reaction (PCR) test for carbapenemase after serial negative surveillance cultures on positive culture conversion in patients with three consecutive negative surveillance cultures for carbapenemase-producing Enterobacterales (CPE), and to identify risk factors for conversion.

METHODS: We performed a retrospective study of patients with positive CPE cultures on CHROMagar KPC medium in a tertiary hospital in Korea from October 2018 to December 2022. A PCR test for the most common carbapenemases in Korea, blaKPC , blaNDM, blaIMP, blaVIM, blaGES, and blaOXA-48 was performed after three consecutive negative rectal swab cultures. We compared the clinical characteristics and outcomes of patients according to whether the follow-up PCR was positive (CNPP) or negative (CNPN).

RESULTS: Of 1075 patients with positive CPE cultures, 150 (14.0%) yielded three consecutive negative rectal swab cultures. Of these, 50 (33.3%) were CNPP, and 100 (66.7%) were CNPN. Risk factors associated with a positive PCR result on multivariate analysis were age, central venous catheter, and Escherichia coli infection. CNPP patients were more likely to have positive culture conversion for CPE than CNPN patients (39/44 [88.6%] vs. 21/50 [42.0%], P<0.001). In multivariate analysis, a positive PCR result after surveillance cultures, diabetes mellitus, central venous catheter, and Klebsiella pneumoniae were independent risk factors for culture conversion.

CONCLUSIONS: CNPP patients have higher rates of culture conversion than CNPN patients, and a follow-up PCR test after serial negative surveillance cultures is useful in deciding whether or not to discontinue contact precautions.