Effect of chemostat turnover rate and select antibiotics on Salmonella Typhimurium in the presence of porcine gastrointestinal tract bacteria

The effect of select antibiotics on Salmonella Typhimurium DT104 persistence in a porcine cecal continuous flow culture was examined under two different washout rates. Porcine continuous flow cultures were conducted in the presence or absence of gram-positive antibiotic carbadox. Carbadox eliminated chemostat anaerobes culturable on Brucella agar under 24 h turnover conditions, allowing Salmonella Typhimurium to persist for 15 days. Decreasing the culture dilution rate from a 24 to 48 h turnover time enabled Salmonella Typhimurium to maintain higher population levels more reflective of the theoretical washout rate when grown with than without added carbadox. This observation suggests that at the slower growth rate the presence of carbadox was antagonistic to the indigenous competitive exclusion potential of the mixed microbial population.