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

4.4.7 Progression of disease post-infection with PA14 ∆PAPI-1∆PAPI-2
An investigation into ∆PAPI-1∆PAPI-2 infected mice was conducted to verify the
mice were succumbing to P. aeruginosa infection. To achieve this the mice were
monitored over a 96 hour period, mice were culled at set timepoints during the
experiment to monitor CFU numbers within the nasopharynx, lungs and blood, as
well as monitoring the immune response via histopathology and leukocyte counts.
All the mice in the experiment had to be culled at 72 hours, previous data generated
during this project suggested to expect 70% to be culled at this timepoint.
The CFU recovered from the nasopharynx, lungs and blood significantly (P >0.05)
increased from 18 hours to 72 hours as shown in Figure 4-17. The numbers found
within the nasopharynx and the lungs were not significantly dissimilar (P >0.05) to
the numbers found within mice infected with wild-type PA14 and ∆PAPI-1 at 18
hours post-infection. This suggests that these numbers represent a critical mass
resulting in severe morbidity. The symptom scores also correlated with an increase
in bacterial load within the tissues and blood (Figure 4-18).
log CFU/mg
6
4
2
0
0 24 48 72
Hours post infection
115
Nasopharynx
Lungs
Blood
Figure 4-17 shows the CFU numbers recovered from the nasopharynx, lung and blood at 18,
48 and 72 hours post-infection with ∆PAPI-1∆PAPI-2 at 2x10 6 CFU/50µl; n=10 for 18 and 72
hours post-infection and n=3 for 48 hours post-infection. Each symbol represents the mean log
CFU/mg for nasopharynx and lungs and the mean log CFU/ml of blood. The 18 hour timepoint
data was generated over two independent experiments and the 48 and 72 hour data was
generated over a single experiment. The error bar represents the standard error of the mean.