COMPARISON OF DARK-FIELD MICROSCOPY, CULTURE, AND POLYMERASE CHAIN-REACTION (PCR) FOR DETECTION OF BORRELIA-BURGDORFERI IN FIELD-COLLECTED IXODES-RICINUS TICKS

In a study based on 100 field-collected female Ixodes (I.) ricinus tic ks from the surroundings of Giessen, dark-field microscopy (DFM), cult ure, and PCR were compared as procedures for detecting Lyme borreliosi s spirochetes in ticks. By DFM, 16 ticks were found to be infected wit h spirochetes. From the midgut of 18 ticks (including 14 microscopical ly positive specimens), spirochetes were cultured in BSK II medium and in BSK II medium. supplemented with either co-trimoxazole (500 mu g/m l) or 5-fluorouracil and kanamycin (200 mu g/ml and 8 mu g/ml). Using these selective media, the isolation rate was increased by 50% compare d to BSK II medium without additives. Midgut homogenates of 22 ticks ( including 13 ticks positive by culture and 12 microscopically positive ticks) were found to contain Borrelia (B.) burgdorferi-specific DNA b y PCR using a primer set based on sequences of the flagellin gene of B . burgdorferi.