Preston agar

A 25 g meat sample was mixed with 225 mL Bolton broth (Oxoid, Hampshire, UK and homogenized using a stomacher for 2 min, and then incubated at 37 °C for 4–6 h under microaerobic conditions (CampyGen, Oxoid, Hampshire, UK) and at 41.5 °C for 48 h. A loopful of the suspension was inoculated on a modified charcoal cefoperazone deoxycholate (mCCD; Oxoid, Hampshire, UK) agar and Preston agar (Oxoid, Hampshire, UK) and incubated at 41.5 °C for 48 h. To identify Campylobacter, the typical flat and moist grayish colonies, frequently with a metallic sheen, were observed on mCCD agar and the moist, gray, flat spreading colonies were observed on Preston agar [40 (link)]. The suspected colonies were streaked on a Columbia blood agar (CBA; Oxoid, Hampshire, UK) supplemented with 5% (v/v) sterile defibrinated sheep blood (Clinag, Bangkok, Thailand) and incubated under microaerobic conditions as described at 41.5 °C for 48 h. The pure cultures were then confirmed by morphology, motility, and oxidase tests [41 ,42 ], and multiplex PCR for genus and species confirmation followed the primers and condition in Denis’ study [43 (link),44 (link)]. For Campylobacter enumeration, the homogenate of 25 g and 225 mL of the diluent underwent ten-fold dilution, and 50 μL of the sample was dropped onto mCCD agar and incubated at 41.5 °C for 48 h under microaerobic conditions [42 ].