HETEROGENEITY OF BORRELIA-BURGDORFERI IN THE SKIN

The reliability of various in vitro techniques to identify Borrelia bu rgdorferi infection is still unsatisfactory. Using a high-power resolu tion videomicroscope and staining with the borrelia genus-specific mon oclonal flagellar antibody H9724, we identified borrelial structures i n skin biopsies of erythema chronicum migrans (from which borrelia lat er was cultured), of acrodermatitis chronica atrophicans, and of morph ea. In addition to typical borreliae, we noted stained structures of v arying shapes identical to borreliae found in a ''borrelia-injected sk in'' model; identical to agar-embedded borreliae; and identical to cul tured borreliae following exposure to hyperimmune sera and/or antibiot ics. We conclude that the H9724-reactive structures represent various forms of B. burgdorferi rather than staining artifacts. These ''atypic al'' forms of B. burgdorferi may represent in vivo morphologic variant s of this bacterium.