There is an article (I think I have it at work) by Gay, et al that discusses,
I believe, seven cases of infants hospitalized with botulism.  The reason
that breastfeeding is implicated is that the majority of them are breastfed
babies.  There is a hypothesis that this occurs because of the lower pH of
the breastfed gut may make the infant more susceptible to colonization of the
spores.  The actual exposure is due to spores in the soil not breastfeeding.
 The article also explains that there are only a few areas in the country
that have high levels of the spores in the soil that cause botulism.  All of
these infants had been in these areas at some time, I think.  The bottom line
is that there is a very small risk factor and the reality is that the
benefits of breastfeeding far outweigh the risks.

A couple months ago I heard of a doctor in the medical center where I work
who insists that ABM be introduced by 4 months to protect the baby from
infant botulism (we live in one of the areas where the spores are prevalent).
 The only thing I could figure was that his hopes were to raise the pH in the
gut to reduce the baby's suseptibiltiy to the spores.

Denise Parker, BA, IBCLC (La Crescenta, CA)