To compare polymerase chain reaction (PCR) amplification of borrelial DNA and culture isolation of spirochaetes for the diagnosis of
Lyme borreliosis by direct detection of Borrelia burgdorferi sensu lato in patients with erythema migrans and acrodermatitis chronica atrophicans lesions.
Skin biopsy specimens from erythema migrans and acrodermatitis chronica atrophicans lesions were subdivided and tested by PCR amplification assay and culture using two artificial growth media, Barbour-Stoenner-Kelly II (BSK II) and modified Kelly-Pettenkofer (MKP). Five classes of lesions were studied: typical erythema migrans, spontaneously resolved erythema migrans, atypical/partially treated erythema migrans, typical acrodermatitis chronica atrophicans, and atypical/partially treated acrodermatitis chronica atrophicans.
For both erythema migrans and acrodermatitis chronica atrophicans lesions, the most sensitive detection method was MKP culture. PCR was less sensitive than MKP culture, but more sensitive than BSK II culture. Results for 758 typical erythema migrans specimens showed positivity rates of 36% for MKP, 25% for PCR, and 24% for BSK II. Differences were statistically significant. The overall positivity rate for all three methods combined was 54%, but few specimens (6%) were positive by all three methods. Examination of multiple erythema migrans lesions from the same patient increased the diagnostic yield. These findings, and similar results for acrodermatitis chronica atrophicans lesions, suggest that the distribution of spirochaetes in skin biopsies is not homogeneous.
Although possessing the potential to provide a rapid diagnosis, PCR is not more sensitive than culture for the direct detection of borrelia. Spirochaetes appear to be unevenly distributed throughout biopsy specimens, suggesting that diagnosis of
Lyme borreliosis by direct detection of the causative agent in skin lesions in vulnerable to sample bias.