5 The role of quorum-sensing in the virulence of Pseudomonas ...

A challenge dose of 2x10 5 CFU/50µl was attempted with PA14 and the results are
shown in Figure 4-5. CFU numbers in the nasopharynx and lungs were detected up
to 48 hours post-infection.
log CFU/mg
4
3
2
1
0
1
2
Days post-infection
100
7
Nasopharynx
Lungs
Figure 4-5 shows the CFU numbers recovered from the nasopharynx and lungs at 1, 2 and 7
days post-infection for Pseudomonas aeruginosa PA14 at 2x10 5 CFU/50µl ; n=5 mice for each
timepoint. Each symbol the mean log CFU/mg and the error bar represents the standard error
of the mean.
In summary, a pilot experiment with PAO1 at a challenge dose of 2x10 4 CFU/50µl
allowed recovery of bacteria 7 days post-infection. Subsequent repeat experiments
did not achieve this initial success. Similar experiments were attempted with PA14
and ∆PAPI-1∆PAPI-2. The chronic infection model was shown not to be robust and
the subsequent experiments focussed solely on the acute respiratory model of
infection.
4.3 Preliminary studies of acute respiratory infection model
The acute respiratory model used during this project is modified from Shaver et al.
(2004). To develop a murine acute respiratory model, preliminary experiments were
conducted using P. aeruginosa PAO1. The pilot studies involved determining the
dose and the organs to recover for further analysis. The mice were symptom scored
and the organs were recovered at 18 hours post-infection. The challenge dose was
2x10 6 CFU/50µl. The results of the pilot experiment are shown in Figure 4-6. The