PCR-Based quantification of Borrelia burgdorferi organisms in canine tissues over a 500-Day postinfection period.

 J Clin Microbiol. 2000 Jun; 38,6, :2191-9. PCR-Based quantification of Borrelia burgdorferi
organisms in canine tissues over a 500-Day postinfection period. Straubinger RK. James A. 
Baker Institute for Animal Health, College of Veterinary Medicine, Cornell University, Ithaca, 
New York 14853, USA. rks4@cornell.edu
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 x 10, 6, organisms per 100 microgram 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, 10, 2, to 10, 4, organisms per 100 microgram 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




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