Eucamp2

BfR-CA-14430 was pre-cultured on Columbia blood agar for 24 h at 42 °C under microaerobic atmosphere. Broth microdilution susceptibility testing was performed according to VET06 and M45-A [7 ]. 2–8 × 10⁵ CfU/ml were inoculated into cation-supplemented Mueller Hinton broth (TREK Diagnostic Systems, UK) supplemented with 5% fetal calf serum (PAN-Biotech, Germany), into the European standardized microtiter EUCAMP2 or EUVSEC plate formats (TREK Diagnostic Systems). Samples were incubated for 48 h at 37 °C under microaerobic conditions. Minimal inhibitory concentrations (MIC; [mg/l]) were semi-automatically analyzed using the Sensititre Vizion system and the SWIN-Software (TREK Diagnostic Systems). Epidemiological cut-off values for resistance determination were based on the European Committee on Antimicrobial Susceptibility Testing (EUCAST.org), if already defined for C. jejuni or, alternatively, for Salmonella (EUVSEC plate format).

C. jejuni and C. coli isolates were tested for antimicrobial susceptibility by microdilution method in cation-adjusted Mueller-Hinton broth with 5% lysed horse blood (TREK Diagnostic Systems Ltd. East Grinstead, United Kingdom) and minimal inhibitory concentration (MIC) panel (Sensititre, reference EUCAMP2, TREK diagnostic Systems Ltd.).
The susceptibility of Campylobacter isolates was determined following the standard M45-A2 for fastidious bacteria form the Clinical and Laboratory Standards Institute [15 ]. According to European Committee on Antimicrobial Susceptibility Testing (EUCAST) guidelines epidemiological cut-off values (ECOFFs) were set: nalidixic acid 16 µg/mL, ciprofloxacin 0.5 µg/mL, gentamycin 2 µg/mL, streptomycin 4 µg/mL, erythromycin 4 µg/mL and 8 µg/mL, tetracycline 1 µg/mL and 2 µg/mL for C. jejuni and C. coli, respectively [16 ]. An isolate was defined as multidrug-resistant (MDR) when resistance to three or more nonrelated antimicrobials was observed.

Phenotypic AST of C. jejuni isolates was performed using the microdilution method in cation-adjusted Mueller–Hinton broth with 5  % lysed horse blood, and minimum inhibitory concentrations (MICs) for erythromycin, ciprofloxacin, tetracycline, gentamicin, nalidixic acid and streptomycin (Sensititre, EUCAMP2; TREK Diagnostic Systems) were determined according to the European Committee on Antimicrobial Susceptibility Testing (EUCAST; version 12.0; www.eucast.org). Strain C. jejuni ATCC 33560 was used as a quality control, according to the manufacturer’s instructions.