Isolation, characterization, and experimental infection of Streptococcus gallolyticus subspecies pasteurianus from...

Streptococcus gallolyticus (SG) is a Gram-positive cocci found as commensal gut flora in animals and humans. SG has emerged as a cause of disease in young poults between 1 and 3 wk of age. SG is associated with septicemia resulting in acute mortality with no premonitory signs in turkeys. Three SG isolates were obtained from clinical field cases of acute septicemia of commercial turkeys and used in three independent experiments. In Experiment 1, embryos were inoculated 25 d of embryogenesis with varying concentrations of SG1, SG2, or SG3. In Experiment 2, day of hatch, poults were inoculated with varying concentrations using different routes of administration of SG1, SG2, or SG3. In Experiment 3, day of hatch, poults were inoculated with only isolate SG1 using different paths. Poults were randomly selected for necropsy on d 8 and d 15 and sampled to collect spleen, heart, and liver for SG on d 21, the remaining poults were necropsied and cultured. Samples were plated on Columbia nalidixic acid and colistin agar (CNA) (40°C, 18-24 h). Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) confirmed suspect colonies. Data were analyzed using the chi-square test of independence, testing all possible combinations to determine significance (P < 0.05). Weight data were subjected to ANOVA using JMP with significance (P < 0.05). No differences were found in BW or BWG on d 0, 8, 15, or 22. Splenomegaly, focal heart necrosis, and pericarditis were observed in all groups in experiments 1 through 3. In Experiment 3, only airsacculitis was observed in a negative control in separate isolation (P > 0.05). On d 21 of Experiment 3, increased (P < 0.05) recovery of SG from spleens were observed in co-housed negative controls, as well as poults challenged by oral gavage (P > 0.05 for d 7 and d 14). These results confirm numerous previous studies indicating that SG subsp. pasteurianus is a primary infectious microorganism that causes septicemia in young poults.