Submitted to: World Congress on Anaerobic Bacteria and Infections
Publication Type: Abstract Only
Publication Acceptance Date: April 27, 1996
Publication Date: N/A
This study was performed in order to study the survivability of Salmonella typhimurium (ST) in a mixed microbial ecosystem of native avian bacteria maintained in continuous-flow (CF) culture at a dilution rate of 0.416h**- 1 under strict anaerobic conditions. The CF culture was challenged with a novobiocin, nalidixic acid resistant strain of ST at concentrations from 10**1 to 10**6 CFU/ml. Samples were withdrawn from the CF culture at 0, 4, 8, 24, 36, and 48 hrs post challenge, then every 24 hrs. The CF culture sample was spread plated on Brilliant Green Agar Plates containing novobiocin and nalidixic acid in order to selectively enumerate ST population changes within the CF culture and monitor the culture until ST populations remained static or until ST could no longer be detected. When challenged with 10**1 and 10**2 CFU/ml ST, the CF culture cleared ST within 24 and 36 hrs, respectively. At ST challenges between 10**3 and 10**5 CFU/ml, ST was cleared at a rate corresponding to a slope of 13.5. When the CF culture was challenged with 10**6 CFU of ST, the concentration of ST in the CF culture decreased to levels below 50 CFU/ml after 5 vessel turnovers. However, the CF culture did not clear ST at the 10**6 challenge level (3 replicates) and ST populations increased and remained at concentrations of 10**2 to 10**3 CFU/ml of CF culture. Fermentation end products, pH, or cell concentrations within the CF culture did not change due to ST challenge. The data suggest that the physiology of ST can change over time in a mixed microbial ecosystem allowing it to survive in a hostile environment such as the gastrointestinal tract.