> Imagine if terramycin was only used as a preventative and all active cases
were destroyed, as was recommended by most researchers. It seems to me that
terramycin would have retained its effectiveness far longer than it did
given the alternative scenario, where it was used to treat active
infections.

But with the misuse of extender patties, that did not happen.  Patties
applied across the operation would inevitably be put on some colonies with
active, yet subclinical infection (this is the norm).

Since the spores are not killed by antibiotics, there will always be active
cases of spores germinating in larval guts throughout the bee population.
If constant prophylactic treatment is used, the nonresistant bacteria will
be killed prior to reaching a level in the gut that they can create enough
of  the peptides to breach the gut epithelium, and cause pathogenicity.

So under the circumstances of constant treatment, the few *resistant*
strains could slowly build up, even if one never observed a larva dying,
since the bacteria could still be transmitted through the colony via larval
meconium (it does not require that Paenibacillus larvae actually kill the
larva to produce spores (Yue 2008).  Lindstrom (2008) observed that spores
could build up in colonies without any signs of disease.

Under the regime of constant treatment with an antibiotic then, one would
expect the few antibiotic resistant bacteria (which would likely be present,
given the 40 years of exposure to OTC prior to the use of extender patties),
to begin to thrive in the absence of competition from nonresistant forms,
and perhaps without inhibition from competetive endosymbiont gut bacteria
suppressed by the antibiotic.

After a relatively short selection process under the sort of constant
pressure induced by the year round extender patty regime, one would expect
the population of the many Paenibacillus strains to shift toward those
resistant to the antibiotic.

Randy Oliver

             ***********************************************
The BEE-L mailing list is powered by L-Soft's renowned
LISTSERV(R) list management software.  For more information, go to:
http://www.lsoft.com/LISTSERV-powered.html

Guidelines for posting to BEE-L can be found at:
http://honeybeeworld.com/bee-l/guidelines.htm