Evaluation of the French novel disc diffusion-based algorithm for the phenotypic screening of carbapenemase-producing Enterobacterales

Rapidly spreading Enterobacterales with OXA-48-like carbapenemases

Enterobacterales (mostly Klebsiella pneumoniae, Escherichia coli) with OXA-48-like carbapenemases (e.g., OXA-48, -181, -232, -244) are undermining the global efficiency of carbapenem therapy. In the Middle East, North Africa, and some European countries, OXA-48-like carbapenemases are the most common types of carbapenemases among Enterobacterales. Currently, OXA-48 is endemic in the Middle East, North Africa, Spain, France, and Belgium; OXA-181 is endemic in Sub-Saharan Africa and the Indian Subcontinent, while OXA-232 has been increasing in the Indian Subcontinent. European countries (e.g., Germany, Denmark, Switzerland, France) are experiencing community outbreaks with E. coli ST38 that produce OXA-244, and these strains have been introduced into Norwegian, Polish, and Czech hospitals. The global ascendancy of OXA-48-like genes is due to the combination of carbapenemases with horizontal spread through promiscuous plasmids (e.g., IncL, IncX3, ColE2) and vertical spread with certain high-risk multidrug-resistant clones (e.g., K. pneumoniae ST14, ST15, ST147, ST307; E. coli ST38, ST410). This is a powerful "gene survival strategy" that has assisted with the survival of OXA-48-like genes in different environments including the community setting. The laboratory diagnosis is complex; therefore, bacteria with "difficult to detect" variants (e.g., OXA-244, OXA-484) are likely underreported and are spreading silently "beneath the radar" in hospital and community settings. K. pneumoniae and E. coli with OXA-48-like carbapenemases are forces to be reckoned with.

Evaluation of the Reveal® AST (SPECIFIC) for Antimicrobial Susceptibility Testing from Positive Blood Culture Spiked with Carbapenem-Resistant Isolates

As bloodstream infections and associated septic shock are common causes of mortality in hospitals, rapid antibiotic susceptibility testing (AST) performed directly on positive blood cultures is needed to implement an efficient therapy in clinical settings. We evaluated the Reveal® rapid AST system on a collection of 197 fully characterized carbapenem-resistant Enterobacterales, including 177 carbapenemase producers (CPE) spiked in blood culture bottles. The clinical categorization based on the Minimal Inhibitory Concentration (MIC) determination of eighteen antimicrobial molecules was compared to the clinical categorization based on the disk diffusion assay as a reference. The Reveal AST system provided results within a mean time to result of 5 h. Overall, the categorical agreement (CA) between the two techniques was 94.1%. The rates of very major errors (VMEs), major errors (MEs) and minor errors (mEs) were 3.8%, 3.7% and 5.6%, respectively. Imipenem was the antimicrobial with the lowest CA rate (78.7%), with rates of 15% VMEs and 10.7% MEs, but the performances were better when considering only the non-CPE category (CA of 89%). On this resistant collection of Enterobacterales with numerous acquired β-lactamases, the Specific Reveal assay proved to be useful for a rapid determination of AST compatible with a quick adaptation of the patient's antimicrobial treatment.