Chloramphenicol is primarily bacteriostatic. It inhibits bacterial protein
synthesis. It has a broad spectrum of activity against gram-positive and
gram-negative cocci and bacilli (very interesting to me is its activity
against anaerobes.)

Chloramphenicol is used in the treatment of typhoid fever caused by
Salmonella typhi infection in some places. In Canada it is approved for
human use as a last resort drug in the treatment of life-threatening,
severe bacterial infections where no other treatment is available.
Perhaps the Chinese use it to try and limit the spread of Salmonella typhi
by bees that use water contaminated by nightsoil or sewage. It would be
surprising to me, however, if using Chloramphenicol, as they appear to do,
would have any benefit to those who consume the honey. The usual dose in
human adults is 12.5 mg per kg body weight every six hours. At the levels
available in the contaminated honey, the dose is not likely therapeutic or
prophylactic. I don't think it will control S. typhoid in the honey,
either, if that's their intention.

The broad spectrum activity of Chloramphenicol may control most bacteria
that potentially infect honey bees. Perhaps the Chinese have found
Chloramphenicol works where the rest fail on bacterial diseases of honey
bees. Another speculative reason, I think, for using Chloramphenicol would
be some sort disease prophylaxis aimed at Clostridium spp., (anearobic gram
positive, spore forming rods that can cause spectacular sudden death,
necrotizing and ulcerating diseases!). I have no idea if it would work on
actively growing Clostridium cultures or not. Certainly spores will not be
harmed.

I don't test for sensitivity of bacterial isolates to Chloramphenicol or
Florfenicol (a related antibiotic). None of my clients have ever asked. It
would be very interesting to see how it measures up.

Perhaps Chloramphenicol is used on the plants the bees forage. Erwinia
amylovora is a species of bacteria that causes fire blight in pome fruits
(pears, etc.). In the past Streptomycin was used. Whenever antibiotics are
overused (especially at low or uncontrolled doses when spraying trees),
bacterial resistance develops, as has happened with Streptomycin. So
someone thought, let's try Chloramphenicol to control fire blight?
Lastly, if Chloramphenicol is used in fresh water fish ponds (fish ponds
are very common in China), are the bees exposed when using the ponds for
their watering needs?

Richard Goetze

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