spirochetes

• medically important spirochetes

  • axial periplasmic flagella propel the cell in a corkscrew like manner
  • borrelia burgdorferi --> lyme disease
  • treponema pallidum --> syphilis
• • tickborne infection spread through the bite of blacklegged tick (or deer tick), Ixodes scapularis or Ixodes pacificus
  • most humans are infected through the bite of immature ticks called nymphs
  • nymphs are tiny (< 2 mm and difficult to see)
  • adult ticks can also transmit Lyme disease bacteria, but they are larger and are more likely to be discovered
• development stages of the deer tick

  • feeding period > 36 - 48 hrs is needed for transmission to occur
• lyme disease

  • Erythemia migrans (EM) rash:
  • ~80% of infected persons
  • begins at the site of a tick bite after a delay of ~7 days and expands gradually
  • may feel warm to the touch but not itchy or painful, sometimes clears as it enlarges, resulting in a target or "bull's-eye" appearance
  • may appear on any area of the body
  • disseminated disease (wks to several months after tick bite)
  • neurologic, cardiac complications
  • join pain/arthritis
• lyme disease prevention and treatment

  • diagnosis
  • clinical (erythema migrans)
  • serology (IgM and/or IgG antibodies)
  • prevention
  • avoid tick-infested areas, especially during summer months
  • use insect repellant (ie, DEET)
  • perform daily tick checks
  • remove ticks as soon as found
  • treatment
  • doxycycline (drug of choice)
• treponema pallidum

  • causes syphilis
  • transmission: sexual (3rd most common STD)
  • laboratory diagnosis
  • nontreponemal tests --> used for screening
  • detect biomarkers released from damaged cells from the infection
  • titers correlate w/ disease activity --> allows monitoring of response to therapy
  • not specific for syphilis (false positives) but rapid and inexpensive
  • examples: venereal disease research laboratory (VDRL) test and rapid plasma reagin (RPR) test
• treponema pallidum

  • laboratory diagnosis (cont.)
  • treponemal test
  • detect anti-treponemal test antibodies
  • will always be positive in pts w/in hx of syphilis
  • pts typically get both tests to distinguish btwn treated and untreated diseases
• syphilis laboratory testing

  • treatment: penicillin (drug of choice)