2.2. Preparation of chicken liver
Chicken liver samples were purchased from local supermarkets in Nottingham and Loughborough in the UK. Samples were kept at 4 °C and analysed before their expiry date as stated on the packaging. Each package contained 5–9 livers which were divided into two halves. Half of the liver was transferred into a stomacher bag (Seward Ltd., Worthing, UK) and 10 ml of Maximum Recovery Diluent CM733 (MRD; Oxoid; Basingstoke, UK) was added. The liver was gently massaged to re-suspend Campylobacter on the liver surface. To recover Campylobacter from internal tissues, the other half of liver was sterilised by dipping the liver into boiling water for 20–30 s (Whyte et al., 2006) and then tissue was excised with hot scalpel before being stomached with the addition of MRD (1:1 dilution ratio).