Laboratory Diagnosis Direct Detection

Treponemes can be detected in material taken from skin lesions by dark-field examination or fluorescent anti? body staining and microscopic examination. Material for, microscopic examination is collected from suspidou$ lesions by first cleansing the area around the lesion witf

Table 48-2 fyidemiology and Spectrum of Disease of the Treponemes Pathogenic for Humans i

Table 48-2 fyidemiology and Spectrum of Disease of the Treponemes Pathogenic for Humans

Agent

Transmission

Geographic Location

Disease

Clinical Manifestations*

Age Group

7!paMmsubsp. pallidum

Sexual contact or congenital (mother to fetus)

Worldwide

Venereal syphifisf

Refer to text above, this page

All ages

T. pallidum subsp. perienue

Traumatized skin comes in contact with an infected lesion

Humid, warm climates: Africa, South and Central America, Pacific Islands

Yaws

Skin—papules,1 nodules, ulcers

Children

T, pallidum aibsp. endemicum

NUTto mouth by utensils

Arid, warm climates: North Africa, Southeast Asia, Middle East

Endemic nonvenereal syphilis

Skin/mucous patches, papules, macules, ulcers, scars*

Children

T.caiateum

Traumatized skin comes in contact with an infected lesion

Semiarid, warm climates: Central and South America, Mexico

Pinta

Skin papules, macules

All ages but primarily children and adolescents

  • AS diseases have a relapsing clinical course and prominent cutaneous manifestations.12 t|f untreated, organisms can dssemiiate to other parts of the body such as bone.
  • AS diseases have a relapsing clinical course and prominent cutaneous manifestations.12 t|f untreated, organisms can dssemiiate to other parts of the body such as bone.
Figure 48-2 Appearance of Treponema pallidum in dark-field preparation.

p a terile gauze pad moistened in saline. The surface of ;div ulcer is then abraded until some blood is expressed. After blotting the lesion until there is no further bleed, the area is squeezed until serous fluid is expressed. ■The surface of a clean glass slide is touched to the exudate, allowed to air-dry, and transported in a dustfree container for fluorescent antibody staining. A T. pallidum fluorescein-labeled antibody is commercially available for staining (Viro Stat, Pordand, Maine). For dark-field examination, the expressed fluid is aspirated »sing a sterile pipette, dropped onto a clean glass slide, and coverslipped. The slide containing material for dark-;ld examination must be transported to the laboratory Immediately. Because positive lesions may be teeming with viable spirochetes that are highly infectious, all supplies and patient specimens must be handled with extreme caution and carefully discarded as required for contaminated materials. Gloves should always be worn.

Material for dark-field examination is examined i&mediately under 400x high-dry magnification for the presence of motile spirochetes. Treponemes are long (8 to 10 |«n, slightly larger than a red blood cell) and consist of 8 to 14 tighdy coded, even spirals {Figure 48-2). Once «en, characteristic forms should be verified by examination under oil immersion magnification (lOOOx). Although the dark-field examination depends gready on technical expertise and the numbers of organisms in the fesion, it can be highly specific when performed on genital lesion's.

Direct detection of T. pallidum in clinical material, such as serous exudate, has been accomplished using polymerase chain reaction (PCR) technology but is not presently widely available. Optimal clinical specimens for

PCR analysis have not been clearly delineated. However, PCR appears useful in the diagnosis of congenital syphilis.

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