Spirochetes Flashcards
Spirochete cell shape
elongated gram negative helix with thin cell wall, endoflagella and an outer membrane
What is the causative agent of syphilis
Treponema pallidum
How do you visualize syphilis bacteria
dark field microscopy with a darkfield condenser on an ordinary microscope or fluorescent antibody stains on a fluorescent microscope
How do you differentiate primary Herpes simplex ulcers and syphilis primary lesions
Herpes ulcers are painful while syphilis lesions are not
Three categories of diagnostic tests for syphilis
direct visualization tests, non-specific antibody tests (non-treponemial screening test, detect Abs against tissue damage antigens), and confirmatory specific antibody tests
2 common assays for a non-specific antibody test for syphilis
Rapid Plasma Reagin and Venereal Disease Research Lab tests
Why must the physician collect and read the darkfield exam for syphilis right away?
They must observe living organism from a moist lesion to see the characteristic corkscrew motion
Describe the technique for darkfield prep
Do not wash lesion, gently adrade a primary lesion or area with the heaviest rash for secondary syphilis while applying gental pressure to exude fluid, if needed add pure warm saline to float coverslip and observe at 400X
Describe the non-specific antibody test for syphilis
A synthetic reagin (lipoidal material relased in damaged tissues) is used to detect IgM and IgG antibodies in a patients serum, antigen antibody complexes form a visible precipitate, results reported as titer
What titer level for a non-specific syphilis antibody test is considered reactive
1:2 or higher
Do non-specific or specific syphilis antibody titers change after treatment
non-specific antibody titers change to reflect severity of disease while specific antibody titers do not change and persist for life
What can cause a false positive for a non-specific syphilis antibody test for less than 6 months
acute infections/conditions: hepatitis, mono, viral pneumonia, chicken pox, pregnancy, and some immunizations
What can cause a false positive non-specific syphilis antibody test for more than 6 months
autoimmune or connective tissue diseases: lupus, Ig abnormalities, malignancy, narcotic addiction, and aging
What is VDRL used to detect
neurosyphilis antibody in CSF
Name and describe the most popular specific syphilis antibody test
Fluorescent treponemia antibody test/FTA-ABS: killed Treponema pallidum put on a glass slide with serum of patient, fluorescent-tagged antibody to human Ig added then slide is rinsed, presence of flourescence is a positive result
What is different about specific syphilis antibody testing for early or congenital syphilis
IgM only FTA test used because IgM indicates more recent infection
Describe primary syphilis
incubation for 10-90 days then painless indurated palpule that progresses to chancre with regional lyphadenopathy
Why is darkfield the preferred diagnostic test for primary syphilis
It will be positive before the presence of antibodies and the patient can get the results immediately
Describe secondary syphilis
disease is silent after primary lesion for 2-10 weeks then secondary lesions appear on trunk, palms, soles, and face that can progress to warty erosions called painless condyloma lata
3 possible outcomes of untreated secondary syphilis
about equal chance of 1.becoming spontaneously cured, 2.progressing to non-infections tertiary stage after many years where the body harbors organisms ant delayed hypersensativity may cause tissue damage, and 3.entering latent stage with positive serology and infections capacity but no symptoms
Commplications of tertiary syphilis
Monocytic infiltrates and tissue damage cause gummatous lesions that cause anneurysms, valve incompetence, pressure necrosis, and rupture in the aorta; bacteria may also infect CNS causing meningovascular syphilis with decrease memory, psychosis, and shuffling gait
When is a fetus susceptible to syphilis infection from the mother
After 4 months gestation
What body structures are affected by congenital syphilis
eyes, meninges, bones, and skin; can develop anemia, jaundice and thrombocytopenia
What is the treatment for congenital syphilis
Usually penicillin and doxycycline
Nonvenereal treponemal diseases
Bejel, Yaws and Pinta, caused by Treponema pallidum sub-species, same diagnostic techniques and treatment as syphilis
How is Leptospira interrogans transmitted from animals to people and how is it killed
Bacteria are in water (survive for weeks) and food contaminated by animal urine and can enter the body through the skin; acid, drying and soap kill it
Who is at risk for leptospirosis and how can the disease be prevented
sewer workers, miners, farmers, veterinarians, meat packers, and athletes/children that swim together in natureal bodies of water are at risk; animal immunizations, rodent control, draining water, hygiene, and avoiding contact with dirty water can prevent
Clinical course of Leptospirosis
incubation of 7-13 days, flu-like phase for 1 week caused by the bacteremic phase, second stage with aches rash and further complications for 3 weeks
Diagnosis of Leptospirosis
culture from blood and CSF during bacteremic phase, culture urine during second phase (imediately before urine acidity kills bacteria), or rise in antibody from acute to convalescent sera
Treatment of Leptospirosis and why it is a challenge
tetracycline and penicillin must be given by 4th day of bacteremic phase which is difficult because definitive lab diagnosis takes to long with slowly culturing bacteria
cell structure of Borrelia recurrentis
irregular gram negative spiral that has microaerophilic metabolism
How are endemic and epidemic Borrelia recurrentis spread
Endemic form rodent reservoir by ticks and epidemic form spread from person to person my body louse in overcrowding, poverty and war
How does Borrelia recurrentis cause relapsing fever
Antibodies end symptoms but organism can develop a new antigenic coat and symptoms resume, incubation is about 7 days, usually 2-4 relapses each less severe than the last
Diagnosis of relapsing fever
Geisma or Wright stain of blood smears, culture in specialty labs
Treatment for Borrelia recurrentis
erythromycin and tetracycline with short regimen
Jarisch-Herxheimer reaction
B. recurrentis and syphilis so susceptible to antibiotics that in massive infections, the rapid and widespread cell death causes a backlash of TNF and Il that can be fatal if unanticipated
cell structure of Borrelia burgdorferi
Large irregular spiral that has toxic lipopolysaccharide and stain with silver and immunofluorescent dyes
What is the causative bacteria of Lyme disease and how is it spread
Borrelia burgdorferi is spread by prolonged bite from Ixodes ticks that fed on infected white-footed mice when they were larva
Describe stage 1 Lyme disease
primary lesion at bite site with slowly expanding red ring ring called erythema chronicum migrans rash and constitutional symptoms like fever and muscle/joint aches
Describe secondary Lyme disease
dissemination of bacteria, neurological and heart symptoms
Describe tertiary Lyme disease
fluctuating intermittent arthritis and mild neurological symptoms or encephalitis
Lab diagnosis of Lyme disease
ELISA: negative is significant if positive do a western blot BUT only PCR of joint fluid or fresh tissue or growth is confirmatory, culture or stains of tissue biopsy are not useful
Treatment for Lyme disease
doxycyclin, amoxicillin and erythromycin are effective in early disease and prophylaxis for multiple prolonged Ixodes tick bites (careful of overuse because not all bites transmit disease), antibiotics less affective in late disease and repeat therapy may be needed
