Performed 16/06/2015 – 30/06/2015. A mouse competition experiment competing the ancestral ICC169 strain with the ancestral ICC180, N3, and W5 strains.
As before: 15 mL overnight cultures of ICC169 (3x), ICC180, N3 and W5 were spun down and resuspended in 1.5 mL sterile PBS (resulting in 10x concentrated cultures), and cultures were mixed in a 1:1 ratio as follows: ICC169 with ICC180, ICC169 with N3, and ICC169 with W5. 200 uL of the mixtures were orally gavaged to groups of 6 C57BL/6 mice. For the ICC169/N3 group, the animals received 10 ug/mL nalidixic acid in their drinking water for 1-day prior.
Mice received fresh drugs on Mondays, Wednesdays, and Fridays, and were imaged using an IVIS Kinetic (Caliper LifeScience) machine on Mondays and Fridays. Stools were taken and plated daily to measure relative ratios of the strains shed. At day 6 post-infection, mice were housed in a fresh cage for 1-day. At day 7, mice were re-housed and the 1-day old ‘contaminated’ cages were used to house naive animals (groups of 6) in order to follow natural transmission of the strains. These animals similarly received antibiotic (in the case of the ICC169/N3 group) in the drinking water and were monitored the same as the original animals.