FIG 1.

Workflow diagram showing the detection of carbapenemase activity directly from clinical urine samples. (Republished from reference 44 with permission of the British Society for Antimicrobial Chemotherapy.) ¹, expected time for direct identification of bacteria and detection of carbapenemase susceptibility in urine samples by MALDI-TOF MS. ², expected time for identification of bacteria and detection of carbapenemase susceptibility in urine samples by routine microbiological processing. ³, according to the manufacturer, a score of <1.7 indicates unreliable identification, a score of between 1.7 and 2.0 indicates genus identification, and a score of ≥2.0 indicates species identification. ⁴, carbapenemase activity was detected directly in urine samples and was measured by MALDI-TOF MS and automated spectrum interpretation. LogRQ values below 0.2 represent negative strains, values above 0.4 indicate carbapenemase activity, and values between 0.2 and 0.4 represent an ambiguous hydrolysis pattern. ⁵, invalid samples were those in which the amount of pellet obtained was not sufficient to carry out direct identification of bacteria and the carbapenem resistance assay. ⁶, urine samples were considered positive with ≥10⁴ CFU/ml of one microorganism, whereas samples with two or more microorganisms were considered contaminated. ⁷, Gram-negative bacilli in positive urine samples were characterized by PCR and further sequencing of carbapenemase genes.