Implementation of Chromatic Super CAZ/AVI® medium for active surveillance of ceftazidime-avibactam resistance: preventing the loop from becoming a spiral
Gabriele Bianco, Matteo Boattini, Sara Comini, Alessio Leone, Alessandro Bondi, Teresa Zaccaria, Rossana Cavallo, Cristina Costa
Abstract
Abstract Acquired resistance towards ceftazidime-avibactam (CAZ-AVI) is increasingly reported. Several mechanisms can be involved, but mutations in the Ω-loop region of β-lactamases are the most described. Herein, we assessed the implementation of Chromatic Super CAZ/AVI ® medium in rectal swab surveillance cultures in a geographic area with endemic distribution of KPC-producing Klebsiella pneumoniae . Routine rectal swabs collected from the intensive care unit (ICU) and non-ICU patients were screened for carbapenemase-producing Enterobacterales (CPE), carbapenem-resistant Gram-negative organisms (CR-GN) and CAZ-AVI-resistant organisms by Chromatic CRE and Super CAZ/AVI ® media. Among the 1839 patients screened, 146 (7.9%) were found to be colonized by one or more CPE and/or CR-GN isolates during hospitalization. Overall, among colonized patients the most common bacteria encountered were KPC-producing Enterobacterales ( n = 60; 41.1%), carbapenem-resistant Pseudomonas aeruginosa ( n = 41; 28.1%) and carbapenem-resistant A. baumannii ( n = 34; 23.3%). Among patients colonized by KPC-producing Enterobacterales, thirty-five (58.3%) had CAZ-AVI-resistant strains. A 30.5% rate of faecal carriage of CAZ-AVI-resistant KPC-producing K. pneumoniae , substantially higher than that of susceptible isolates (2.8%), was observed in the COVID-19 ICU. Prevalence of faecal carriage of metallo-β-lactamase-producing organisms was low (0.5% and 0.2% for Enterobacterales and P. aeruginosa , respectively). Chromatic Super CAZ/AVI ® medium showed 100% sensitivity in detecting CPE or CR-GN isolates resistant to CAZ-AVI regardless of both MIC values and carbapenemase content. Specificity was 86.8%. The Chromatic Super CAZ/AVI ® medium might be implemented in rectal swab surveillance cultures for identification of patients carrying CAZ-AVI-resistant organisms to contain the spread of these difficult-to-treat pathogens.