Syphilis

Spirochetes are long, slender, motile, flexible, undulating, gram-negative bacilli that have a characteristic helical shape. Depending on the species, they can be facultative anaerobic. Some spp can be grown in laboratory culture (either cell-free culture or tissue culture), whereas others cannot. Some spp are free-living, and some are part of the normal flora of humans & animals. Thy are important human pathogens are:T. pallidum (syphilis), Borrelia (causes Lyme disease, & relapsing fever), and Leptospira (causes leptospirosis).
Treponema Pallidum
Syphilis is a sexually transmitted disease (STD) caused by T. pallidum. Starting with a small lesion (chancre), several progressive stages of the disease can span a period of 30 years or more. The causative organism of syphilis is extremely fastidious and fragile. It cannot be cultured routinely in the laboratory, and is sensitive to disinfectants, heat, and drying. T. pallidum is so thin that it cannot be observed by light microscopy, but requires immunofluorescent or dark-field techniques. It is produce hyaluronidase that disrupts ground substance, and facilitates dissemination of the organism.
Pathogenesis &