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Journal of Clinical Microbiology, June 2000, p. 2191-2199, Vol. 38, No. 6
James A. Baker Institute for Animal Health,
College of Veterinary Medicine, Cornell University, Ithaca, New
York 14853
Received 19 October 1999/Returned for modification 27 February
2000/Accepted 25 March 2000
Borrelia burgdorferi infection in beagle dogs was
studied quantitatively with skin punch biopsy samples and blood samples collected at 4- and 2-week intervals, respectively, over a 500-day period. Thereafter, 25 tissue samples of each dog were collected for
further analysis. Starting at day 120 after tick challenge, 12 dogs
were treated with antibiotics (azithromycin, ceftriaxone, or
doxycycline) for 30 consecutive days. Four dogs received no antibiotic
therapy. Quantification of B. burgdorferi DNA was done with
an ABI Prism 7700 Sequence Detection System with oligonucleotide primers and a fluorescence-labeled probe designed to specifically amplify a fragment of the ospA gene of B. burgdorferi strain N40. All 16 dogs became infected with B. burgdorferi after tick challenge. In skin biopsy samples,
spirochete numbers peaked at day 60 postinfection (<1.5 × 106 organisms per 100 µg of extracted DNA), at the same
time when clinical signs of arthritis developed in 11 of 16 dogs, and
decreased to almost undetectable levels during the following 6 months.
The number of B. burgdorferi organisms detected in skin
biopsy samples was inversely correlated with the antibody levels
measured by enzyme-linked immunosorbent assay. Antibiotic treatment
reduced the amount of detectable spirochete DNA in skin tissue by a
factor of 1,000 or more. At the end of the experiment, B. burgdorferi DNA was detectable at low levels (102 to
104 organisms per 100 µg of extracted DNA) in multiple
tissue samples regardless of treatment. However, more tissue samples of
untreated dogs than of antibiotic-treated dogs were positive, and
tissue samples of untreated dogs also were positive by culture. Only 1.6% of 576 blood samples of all dogs were positive for B. burgdorferi by PCR.
0095-1137/00/$04.00+0
Copyright © 2000, American Society for Microbiology. All rights reserved.
PCR-Based Quantification of Borrelia
burgdorferi Organisms in Canine Tissues over a 500-Day
Postinfection Period
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Mailing address: James A. Baker Institute for Animal
Health, College of Veterinary Medicine, Cornell University, Hungerford Hill Rd., Ithaca, NY, 14853. Phone: (607) 256-5672. Fax: (607) 256-5608. E-mail: rks4{at}cornell.edu.
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