Spirochetes

• To which order do spirochetes belong?

  Spirochaetales
• What are the morphological characteristics of spirochetes?

  They are long, slender, helically curved, gram-negative bacilli
• What are the unusual morphologic features of spirochetes?

  • Axial fibrils/filaments: flagella-like organelles that wrap around the cell wall and facilitate motility.
  • Insertion discs: attach axial fibrils to the cell wall.
  • Protoplasmic cylinder: gyrates around the fibrils, causing corkscrew-like movement.
• What factors are used to differentiate genera within the spirochetes family?

  Number of axial fibrils, number of insertion disks, and biochemical/metabolic features
• What are the morphologic features of the genera Treponema, Borrelia, Leptospira, and Brachyspira?

  • Treponema: slender with tight coils
  • Borrelia: thicker with fewer and looser coils
  • Leptospira: resembles Borrelia but has hooked ends
  • Brachyspira: comma-shaped or helical with tapered ends and four flagella at each end
• How many axial filaments does Treponema have?

  6 to 10
• How many insertion disks does Borrelia have?

  2
• Why do Treponema species stain poorly with Gram staining?

  They have a unique cell wall structure that does not retain the stain well
• What microscopy methods are best for observing Treponema?

  Dark-field or phase-contrast microscopy
• What is Vincent’s disease?

  It is a destructive lesion of the gums
• What stain is used for specimens of patients with Vincent’s disease?

  Methylene Blue
• What are the pathogenic Treponema species and their associated diseases?

  • T. pallidum subsp. pallidum: Venereal syphilis
  • T. pallidum subsp. pertenue: Yaws
  • T. pallidum subsp. endemicum: Endemic nonvenereal syphilis
  • T. carateum: Pinta
• How is T. pallidum subsp. pallidum transmitted?

  Through sexual contact or congenital transmission
• What are the clinical manifestations of Yaws caused by T. pallidum subsp. pertenue?

  Skin papules, nodules, ulcers, and may progress to destructive lesions
• What is the primary lesion associated with Yaws?

  The mother yaw
• How is endemic nonvenereal syphilis transmitted?

  By mouth-to-mouth contact using utensils
• What are the clinical manifestations of endemic nonvenereal syphilis?

  Skin/mucous patches, papules, macules, ulcers, and scars
• What is Pinta caused by T. carateum?

  It causes skin papules and hyperkeratotic pigmented lesions
• What are the stages of syphilis caused by T. pallidum subsp. pallidum?

  1. Primary syphilis: Chancre at the site of inoculation
  2. Secondary syphilis: Widespread rash and generalized lymphadenopathy
  3. Early latent: Subclinical but detectable by serology
  4. Latent: Asymptomatic and noninfectious
  5. Tertiary syphilis: Tissue-destructive phase with various complications
• What is the characteristic feature of primary syphilis?

  The appearance of a chancre
• What occurs during secondary syphilis?

  Patients experience a widespread rash and generalized lymphadenopathy
• What is neurosyphilis?

  It is a complication of syphilis affecting the nervous system
• How is congenital syphilis transmitted?

  From the mother to the child at any stage of infection
• What is the procedure for specimen collection for Treponema detection?

  1. Clean the site with sterile gauze moistened with saline.
  2. Abrade the ulcer surface until blood is expressed.
  3. Blot the lesion and squeeze to express serous fluid.
  4. Touch a clean slide to the exudate and allow to dry.
  5. Transport in a dust-free container for staining.
• What is the purpose of dark-field examination in Treponema detection?

  To visualize motile spirochetes in genital lesions
• What is the magnification used for dark-field examination of Treponema?

  400x high-dry magnification
• What is the role of fluorescein-labeled antibody in Treponema detection?

  It is used for direct fluorescent antibody detection
• What are the serologic diagnostic methods for Treponema infections?

  1. Treponemal antibodies: produced against Treponema antigens.
  2. Nontreponemal antibodies: produced against mammalian cell components.
  3. Common tests: VDRL, RPR, EIAs, and agglutination tests.
• What is the significance of nontreponemal antibodies in syphilis diagnosis?

  They are always produced in syphilis but can also appear in other diseases
• What is the causative agent of Lyme disease?

  Borrelia burgdorferi
• How is Borrelia burgdorferi transmitted?

  By Ixodes ticks
• What is the characteristic skin lesion of Lyme disease?

  Erythema migrans
• What are the stages of Lyme disease caused by Borrelia burgdorferi?

  1. 1st Stage: Erythema migrans (red, ring-shaped lesion)
  2. 2nd Stage: Arthritis, neurologic disorders, and carditis
  3. 3rd Stage: Chronic arthritis or acrodermatitis chronica atrophicans
• What is the role of IgM antibodies in Lyme disease?

  They are produced continually months to years after initial infection
• How does Borrelia burgdorferi evade the human immune response?

  By varying its surface antigens
• What are the laboratory diagnosis methods for Borrelia burgdorferi?

  1. Direct detection: Warthin-Starry silver stain, PCR.
  2. Cultivation: Modified Kelly’s medium under microaerophilic conditions.
  3. Serodiagnosis: IgM and IgG responses against specific antigens.
• What is the best specimen for culture of Borrelia burgdorferi?

  The peripheral area of the erythema migrans ring lesion
• What is the significance of IgM response in Borrelia infections?

  It indicates an early immune response to the infection
• What is the role of antigenic variability in Borrelia recurrentis?

  It accounts for the cyclic fever patterns associated with the disease
• How is Borrelia recurrentis transmitted?

  By the louse Pediculus humanus subsp. humanus