TREPONEMA PALLIDUM

 

INTRODUCTION: T. pallidum is the causative agent of venereal syphilis in man. Typical organisms are slender spirals measuring about 0.2 μm in width especially in wet preparations, and 6-15 μm in length. The spiral coils are regularly spaced at a distance of 1 mm from one another. In dry preparations the width is about 0.13 μm. The two ends of the spirochaete are tapering. It is actively motile, exhibiting rotation round the long axis, backward and forward movements and flexion of the whole body.  During motion the primary spirals are maintained though secondary curves appear and disappear in succession. When dark field microscopy is not available, the organism can be detected in wet films of the exudate mixed with India ink.

STAINING: T. pallidum cannot be stained by simple aniline dyes or by Gram’s method. In films stained with Giemsa’s prolonged method for 24 hours the organisms appear as delicate pink threads. It can be stained by silver impregnation methods. Fontana’s method is useful for smears and Levaditi’s for tissue sections.

MULTIPLICATION: The spirochaetes multiply by transverse binary fission. Divided organisms may adhere to one another for sometime. The division time is 30 hours, while the division time of cultivable Reiter’s strain is about 10 hours. Treponema pallidum, carateum and pertenue have not been cultivated in artificial media, not even in chick embryo or tissue culture where they appear only to persist for a long time. In proper suspending fluids and in the presence of reducing substances, T. pallidum may remain motile for 3-6 days at 25⁰C. In whole blood or plasma stored at 4⁰C, organisms remain viable for atleast 24 hours, which is important in blood transfusion services.

RESISTANCE: Drying kills the spirochaetes rapidly as does the elevation of the temperature to 42⁰C for about 60 minutes. When stored at referigerator temperatures, the organism is killed in 1-3 days. Stored frozen at –70⁰C in 10 percent glycerol or in liquid nitrogen the organism remains viable for 10-15 years. Resistance to penicillin has not been demonstrated in syphilis.

RELATED;

1.  PENICILLIN 

2.  ANTIMICROBIAL DRUG RESISTANCE 

3.  GRAM NEGATIVE BACTERIA

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