Lightmix modular carbapenemase panel

MDR was defined as resistance to at least one agent in three or more antimicrobial categories for each organism, according to current standard definitions [23] (link). Non-MDR was considered when resistance to fewer than three active antimicrobial categories was observed. According to this classification, the antimicrobial categories used to define MDR in Enterobacteriales were: aminoglycosides, anti-MRSA cephalosporins, antipseudomonal penicillins + β-lactamase inhibitors, carbapenems, 1st and 2nd generation cephalosporins, 3rd and 4th generation cephalosporins, cephamycins, fluoroquionolones, folate pathway inhibitors (trimethoprim-sulphamethoxazole), glycylcyclines (tigecycline), monobactams, penicillins + β-lactamase inhibitors, phenicols (chloramphenicol), phosphonic acids, polymyxins and tetracyclines [19] .
Routine identification and susceptibility testing of causative microorganisms was performed using automated systems (the Vitek-2® [BioMérieux] for blood cultures, and the MicroScan® WalkAway [Beckman-Coulter] for other sample types). Results were interpreted according to the European Committee on Antimicrobial Susceptibility Testing (EUCAST) standards in force at the time of culture. Carbapenemases were identified by multiplex PCR assay, using the LightMix® Modular Carbapenemase panel (Roche Diagnostics).

MDR was defined as resistance to at least one agent in three or more antimicrobial categories for each organism, in accordance with current standard definitions 24 (link) . MRSA was always considered as MDR.
Routine identification and susceptibility testing of causative microorganisms were performed using automated systems (Vitek-2® [BioMérieux] for blood cultures, and the MicroScan® WalkAway [Beckman-Coulter] for other types of samples) and interpreted according to standards defined by the European Committee on Antimicrobial Susceptibility Testing (EUCAST). Isolates with intermediate antimicrobial susceptibility were considered as resistant. For gram-negative bacilli, ESBLs, plasmid-mediated AmpC β-lactamases and carbapenemases were investigated. ESBL and plasmidmediated AmpC β-lactamase production was confirmed by the double disc approximation test. Synergy was determined between a disc of amoxicillin-clavulanic acid (20μg/10μg) and a 30μg disc of cefotaxime, ceftazidime and cefepime.
Carbapenemases were identified by multiplex PCR assay, using the LightMix® Modular Carbapenemase panel (Roche Diagnostics). For S. aureus, production of PBP2a was confirmed phenotypically by the cefoxitin disk diffusion test (30μg disc).