Cross-strain immunity
Brenda Rashleigh

On Friday we discussed immunity to pathenogenic bacterial strains,
and we weren't sure how much cross-immunity there was between 
strains that were and were not resistance to antibiotics.  I spoke
with Dr. Ed Smith at the UT hospital.  He said that whether you
develop immunity to a bacterial strain or not depends on the
type of bacteria and your immune system.  In some cases, such as
Strep. pneumoniae, you can build up resistance to a strain, but there
are 88 similar strains out there, so in essence you can get sick again.

There is No DIFFERENCE in immunity to antibiotic resistant and non
resistant strains.  The antibodies produced by the immune response
recognize surface structures and differences in contained plasmids
will not cause any difference in the immune response.  So if you
can develop immunity to a particular bacterial strain, you
will be immune to the antibiotic resistant version of that strain.

Also a note on the modeling:  On friday we discussed a model with
a susceptible population (S) and two types of infected populations,
I1 and I2, where I2 was infected with an ABx resistant strain.  Although
we didn't draw them in, I think there may need to be an arrow from
bot I1 to box I2, representing mutation of the strain to the ABx
resistant form.  This would be a function of the population size of I1,
and the level of antibiotic use.  We may also need an arrow from box I2 to I1,
representing the competitive advantage of the I1 strain (because of the
cost associated with the resistant strain).  This would be a
function of the pop. size I2 and antibiotic ise (as Abx use increases,
transfer from box I2 to Box I1 decreases).  The transfer rate from
box S to box both I1 and box I2 should be the same, because both
strains have the same modes of transmission. Does that sound reasonable?