Thursday, October 31, 2013

Efficacy of azithromycin cream for prophylaxis of Lyme

I thought this was interesting. I had actually thought about this over the years, because of the shape of the bull's-eye rash. I assume that because Lyme spirochetes can live in the skin, that the rash is just the result of the spirochetes invading the skin and disseminating outward, which would create a circular shape.  (Bold emphasis below, added.). -Bob

Efficacy of an experimental azithromycin cream for prophylaxis of tick-transmitted Lyme disease spirochete infection in a murine model.

Joseph Piesman, Andrias Hojgaard, Amy J. Ullmann and Marc C. Dolan
Antimicrobial Agents and Chemotherapy, online ahead of print 28 October 2013.


As an alternative to oral prophylaxis for the prevention of tick transmission of Borrelia burgdorferi, we tested antibiotic cream prophylactic formulations in a murine model of spirochete infection. A 4% preparation of doxycycline cream afforded no protection, but a single application of 4% azithromycin cream was 100% protective when applied directly to the tick bite site at the time of tick removal.

Indeed, the azithromycin cream was 100% effective when applied up to 3 days after tick removal and protected 74% of mice exposed to tick bite when applied up to 2 weeks after tick removal. Azithromycin cream was also protective when applied at a site distal to the tick-bite-site, suggesting it was having a systemic effect in addition to a local transdermal effect. Mice that were protected from tick-transmitted infection did not seroconvert and did not infect larval ticks on xenodiagnosis.

Azithromycin cream formulations appear to hold promise for Lyme disease prophylaxis.

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