Quantification of Intestinal Bacteria

For bacterial quantification within the gastrointestinal tract feces was taken over time p.i. and luminal samples were derived from stomach, duodenum, ileum and colon at necropsy (day 14 p.i.) and dissolved in sterile PBS. For determination of C. jejuni loads, serial dilutions were cultured on Columbia-Agar supplemented with 5% sheep blood and Karmali-Agar (both Oxoid, Wesel, Germany) for two days at 37 °C under microaerobic conditions using CampyGen gas packs (Oxoid). For quantification of E. coli, serial dilutions were cultured on Columbia-Agar supplemented with 5% sheep blood and Mac Conkey Agar (both Oxoid) in aerobic atmosphere for two days at 37 °C.
Translocation of commensal intestinal bacteria to extra-intestinal compartments was quantitatively assessed in respective organ homogenates under aerobic, microaerobic and obligate anaerobic conditions as described earlier [24 (link)–26 (link)].
The respective weights of fecal or tissue samples were determined by the difference of the sample weights before and after asservation. The detection limit of viable pathogens was ≈100 CFU per g.