Bacteriological examination
Faecal examination was initiated within 2 h of collection. Salmonella was isolated
using the ISO 6579 Annex D method (ISO 6579:2002). Briefly, samples were
inoculated in buffered peptone water (BPW, Bio-Rad) in dilution 1:10 and incubated
aerobically for 16–20 h at 37 C. Of this solution, 0.1 mL was inoculated on a modified
semi-solid Rappaport Vassiliadis plate (MSRV, Bio-Rad) and incubated aerobically
at 42 C for 48 h. Growth halos were plated on a xylose lysine deoxycholate
agar plate (XLD, Bio-Rad) and a brilliant green agar plate (BGA, LabM) – the latter
supplemented with 20 lg/mL nalidixic acid – and then incubated aerobically for
21–27 h at 37 C. One Salmonella-suspected colony on these XLD plates (challenge
or vaccine strain) or on the BGA plates (only the challenge strain) was inoculated
in triple sugar iron agar (TSI, Bio-Rad) and lysine decarboxylase bouillon (Oxoid)
and incubated for 18–24 h at 37 C for final identification.