General Overview of Spirochaetales. Gram-negative spirochetes Spirochete from Greek for “coiled hair” Extremely thin and can be very long Tightly coiled helical cells with tapered ends Motile by Periplasmic flagella (axial fibrils or endoflegalla). Human pathogen. Treponema
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Staining by Giemsa and Fontana
Treponemescannot be cultivated in laboratory media and are maintained by subculture in susceptible animals.
A. Direct detection of spirochetes :
B. Culture : not used
C. Serology: non-specific and specific tests
- General screening test, can be adapted to automation.
- CANNOT be performed on CSF.
All positive nontreponemal test results should be confirmed with a specific treponemal test
- Causes Lyme disease, transmitted by the bite of Ixodid ticks (deer tick)
- Diagnosis– serological tests
- Very thin, delicate spirochetes with hooked ends
- 2 species are recognised:
L. interrogansinsilver stained smear, hooked ends resemble umbrella handles
- Examination of blood – 1st week only
- Urine– 2nd week of disease, should be examined immediately after voiding
- Serology– Abs appear by the end of 1st week & increase till 4th week of disease.
- Historically the “gold standard”
- Variable sensitivity (50%-80%)
- High specificity
- Use in legal investigations
- Not suitable for widespread screening
- NAATs amplify and detect organism-specific genomic or plasmid DNA or rRNA
- Significantly more sensitivity than other tests
- Direct fluorescent antibody (DFA)
- Detects intact bacteria with a fluorescent antibody
- Variety of specimen sites
- Enzyme immunoassay (EIA)
- Detects bacterial antigens with an enzyme-labeled antibody
- Nucleic acid hybridization (NA probe)
- Detects specific DNA or RNA sequences of C. trachomatis and N. gonorrhoeae
- Screening can reduce the incidence of PID by more than 50%.
- Most infections are asymptomatic.
- Screening decreases the prevalence of infection in the population and reduces the transmission of disease.