​rivm.​nl Bacterial cultures and serotyping The detection of Salmonella spp. was performed based on the ISO 6579:2002 method. In brief, 25 g of clinical specimen (10 g in the case of minced meat in accordance with the EC regulation 2073/2005 – Microbiological Criteria for Foodstuffs) were added to 225 ml of buffered peptone water in a Stomacher® bag, sealed

and placed in a Stomacher® blender for 3 min. The blended sample was incubated for 18 h at 37°C and a 0.1 ml aliquot of sample was inoculated into 10 ml Rappaport-Vassiliadis medium with Soya (RVS) and into 10 ml Muller-Kauffmann tetrathionate/novobiocin (MKTTn) selleck chemicals llc broth; these cultures were see more incubated for 24 h at 41.5°C and 37°C, respectively. Each culture was inoculated into xylose lysine deoxycholate agar (XLD) and brilliant green agar (BGA) and incubated at 37°C for 24 h. One colony was selected from each XLD and BGA plate

and spread onto nutrient agar for incubation at 37°C for 24 h. The resulting colonies were subject to biochemical analysis and serotyping. Salmonella spp. was characterised into different serovars on the basis of their surface (LPS, O-antigens) and flagellar antigens (Evofosfamide concentration H-antigens) as defined by the Kauffman-White Scheme [10, 44] and based on the Global Salm-Surv laboratory protocol of the World Health Organisation (Global Salm-Surv, Serotyping of Salmonella enterica O and H antigen, Level 3 Training Course, WHO, 6th edition, Jan. 2004). To extract DNA for use in the molecular detection assay, bacteria were cultured on the XLD agar and one colony was selected

and grown on nutrient agar. A colony was then selected and incubated in 5 ml nutrient broth, 1 ml of which was transferred into a 1.5 ml tube for centrifugation for 10 min at 18,000 rcf. The supernatant was discarded and the cell pellet was kept at -80°C until DNA extraction. Bacterial genomic DNA preparation Bacterial genomic DNA was extracted from the cell Casein kinase 1 pellets using QIAGEN DNeasy Blood and Tissue Kit (Hilden, Germany) according to the manufacturer’s instructions. The purified DNA was eluted in 100 μl of AE buffer and the concentration was determined by measuring the optical density at 260 nm using a NanoDrop UV spectrophotometer (NanoDrop Technologies, USA). The extracted DNA was kept at -30°C until further use. Internal amplification control An artificial 129 nt oligonucleotide fragment was designed as an IAC to be amplified by the same primers as the invA target. The IAC is a completely synthetic and unique oligonucleotide, designed to avoid sequence homology with any entries in the GenBank database, tested using the BLAST (Basic Local Alignment Search Tool) software [45].