Dee Lusby asked:

> What is meant by kills most strains of B. larvae?
> Here strains being plural and noted as such and not
> singular. What are different strains of B. larvae?

In plain English, bacteria like B. larvae have very rapid reproduction rates
when given even a half decent medium in which to grow.  Anything that does
not kill 100% of the spores and "live" bacteria (and nothing short of gamma
beam or electron beam irradiation will kill them all) will certainly result in a
"surviving strain" developing.  The "survivor strain" survives due to some small
difference between it and the strain(s) that were killed.

    If your gamma ray generator is on the fritz, ethylene oxide gas will
    also kill 100% of them, but what self-respecting modern beekeeper
    would neglect regular maintenance on his gamma ray gear?   :)

The old saying of Marines "that which does not kill me makes me stronger",
applies well to bacteria.  (Any conclusion one draws from this about the position
of Marines on the evolutionary ladder is merely a dead give-away that you were
[or should have been] a Naval officer.)

So, "strains" are differentiated and described as "strains" merely because they
react differently to the same tests (attempts to kill them).  They are clearly the
same type of bacteria (B. larvae), and not something else, but the ugly little
suckers are too small to see anything more than gross physical anatomy.
(And they are very gross!)  As I recall, they run from 2 to 5 microns long by
about 0.5 micron wide. The spores average about 0.5 micron by 1 micron.

So, if I found AFB in one of my hives, and you found AFB in one of yours,
and we each sent samples in to the Beltsville or Tucson Bee Labs, I would
bet some serious money that they would be different "strains".  I'm not sure
anyone knows how many strains of AFB are out there, but I have read studies
that examined 20, 40, or more strains at one time, all collected from single
countries without any trouble.

It is interesting to note that one needs about 100 spores of B. larvae
to get a culture growing in a petri dish, but a single scale (the remains
of dead honeybee larva) contains roughly 2.5 billion spores.  It follows
that before AFB kills a single bee larva, the population in this single
larva grows from some number in the hundreds to several billion.  Since
AFB kills bee larva while they are still larva, this population growth
happens over a period of mere days.  The rapid population growth from
a small subset of spores ingested by the single bee could result in a
different B. larvae "strain" developing simply from the random draw of
spores fed to the first bee "victim".

The regular and unthinking use of antibiotics as a "preventative" by
beekeepers who were not properly instructed has certainly resulted in
an unknown, but clearly large number of "resistant strains" of AFB.

The term "resistant" implies a lack of sensitivity to drugs, based upon the
much smaller size of "inhibition zones" on nutrient plates.  In other words,
one cultures the spores on a growth media, and once it has gotten a good
start, one applies a fixed amount of an antibiotic at the center of the petri dish,
and then simply measures the size of the "killed area"  (the "inhibition zone").

To make matters more complex, the mere fact that different doses of the same
drugs have different "inhibition zones" when tested implies that even different
doses of the same hard to mix, and impossible to consistently administer drugs
can create different "survivor strains" of the targeted bacterium.

Bottom line, every time anyone uses any form of antibiotic on bacteria, they are
very likely, if not certain, to be creating yet another "strain" of the targeted bacterium
in the process.  This is happening all the time, and to be honest, we are running out
of antibiotics that will have any effect at all on the nasty mug-you-and-take-your-wallet
strains of stuff that are running around in hospitals, infecting and killing people who
came into the emergency room with simple cuts that needed stitches.

It is like a bad science-fiction novel.  We can't kill them, and everything we try
simply changes them into something that is even harder to kill.  Michael Crichton's
"The Andromeda Strain" is an example of a bad science-fiction novel with exactly this plot.
The movie stank too.

        jim