5 mg/L); ceftiofur, XNL (R > 2 mg/L); chloramphenicol, CHL (R > 16 mg/L); Selleckchem STI571 ciprofloxacin, CIP (R > 0.064 mg/L); colistin COL (R > 2 mg/L); florfenicol, FFN (R > 16 mg/L); gentamicin, GEN (R > 2 mg/L); nalidixic acid, NAL (R > 16 mg/L); neomycin, NEO (R > 4 mg/L); spectinomycin, SPT (R ≥ 64 mg/L); streptomycin, STR (R > 16 mg/L); sulphamethoxazole, SMX (R ≥ 256 mg/L); tetracycline, TET
(R > 8 mg/L); and trimethoprim, TMP (R > 2 mg/L). Epidemiological cut-off values were interpreted according to current EUCAST (http://www.eucast.org) and European Food Safety Authority (EFSA) recommendations. Exceptions were made for interpretation of AMC, SMX, and SPT, where Clinical and Laboratory CH5183284 ic50 Standards Institute (CLSI) guidelines and clinical breakpoints were used [11–13]. Due to the absence of some epidemiological cut-off values in the EUCAST system and clinical breakpoints from CLSI, exceptions were made for the interpretation of APR MIC values which were interpreted according to research results from DTU. Quality control using E. coli ATCC 25922 was conducted according to CLSI [12, 13]. Phage typing Phage typing Ro 61-8048 clinical trial was performed at the National Microbiology Laboratory, Public Health Agency of Canada, Winnipeg, MB, Canada using the Enteritidis phage typing scheme provided
by the Health Protection Agency, Colindale, London, UK. This phage-typing scheme is composed of 17 Salmonella serovar Enteritidis specific phages. Isolates with lytic patterns that did not match standard Phosphoribosylglycinamide formyltransferase phage lytic profiles were assigned an atypical phage type [14]. Pulsed-field gel electrophoresis PFGE was performed at DTU-Food using XbaI and BnlI macrorestriction enzymes (Fermentas, Glen Burnie, Maryland, United States) according to the CDC PulseNet protocol [15]. The patterns were compared to the PulseNet USA database and named following the standardized PulseNet USA pattern naming scheme [16]. The electrophoresis was performed with a CHEF DR III System (Bio-Rad Laboratories, Hercules, CA, USA) using 1% SeaKem Gold agarose
in 0.5× Tris-borate-EDTA. Running conditions consisted of increasing pulse times of 2.2 – 63.8 s for 20 h at 6 V/cm on a 120 deg. angle in 14°C TBE buffer. Multiple-locus variable-number tandem repeat analysis MLVA was performed at the Centers for Disease Control and Prevention (CDC) in the United States of America by following the standardized PulseNet USA protocol for Salmonella serovar Enteritidis (Laboratory standard operating procedure for PulseNet MLVA of Salmonellas serovar Enteritis – Beckman Coulter 8000 platform. Accessed at: http://www.pulsenetinternational.org and Laboratory standard operating procedure for analysis of MLVA data of Salmonella serovar Enteritidis in BioNumerics – Beckman Coulter 8000 data. Accessed at: http://www.pulsenetinternational.org) Analysis of the composite data set Analysis of PFGE data was performed at CDC. Comparisons were performed using Bionumerics software version 5.