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Flocculation assays

A flocculation assay is similar to a precipitin reaction except that it involves insoluble antigens such as lipids. A flocculant is similar to a precipitin in that there is a visible lattice of antigen and antibody, but because lipids are insoluble in aqueous solution, they cannot precipitate. Instead of precipitation, flocculation (foaming) is observed in the test tube fluid.

Using flocculation to test for syphilis

Syphilis is a sexually transmitted infection that can cause severe, chronic disease in adults. In addition, it is readily passed from infected mothers to their newborns during pregnancy and childbirth, often resulting in stillbirth or serious long-term health problems for the infant. Unfortunately, syphilis can also be difficult to diagnose in expectant mothers, because it is often asymptomatic, especially in women. In addition, the causative agent, the bacterium Treponema pallidum , is both difficult to grow on conventional lab media and too small to see using routine microcopy. For these reasons, presumptive diagnoses of syphilis are generally confirmed indirectly in the laboratory using tests that detect antibodies to treponemal antigens.

In 1906, German scientist August von Wassermann (1866–1925) introduced the first test for syphilis that relied on detecting anti-treponemal antibodies in the patient’s blood. The antibodies detected in the Wassermann test were antiphospholipid antibodies that are nonspecific to T. pallidum . Their presence can assist in the diagnosis of syphilis, but because they are nonspecific, they can also lead to false-positive results in patients with other diseases and autoimmune conditions. The original Wasserman test has been modified over the years to minimize false-positives and is now known as the Venereal Disease Research Lab test, better known by its acronym, the VDRL test .

To perform the VDRL test, patient serum or cerebral spinal fluid is placed on a slide with a mixture of cardiolipin (an antigenic phospholipid found in the mitochondrial membrane of various pathogens), lecithin, and cholesterol. The lecithin and cholesterol stabilize the reaction and diminish false positives. Anti-treponemal antibodies from an infected patient’s serum will bind cardiolipin and form a flocculant. Although the VDRL test is more specific than the original Wassermann assay, false positives may still occur in patients with autoimmune diseases that cause extensive cell damage (e.g., systemic lupus erythematosus ).

Neutralization assay

To cause infection, viruses must bind to receptors on host cells. Antiviral antibodies can neutralize viral infections by coating the virions, blocking the binding ( [link] ). This activity neutralizes virions and can result in the formation of large antibody-virus complexes (which are readily removed by phagocytosis) or by antibody binding to the virus and blocking its binding to host cell receptors. This neutralization activity is the basis of neutralization assays , sensitive assays used for diagnoses of viral infections.

Questions & Answers

what are eukaryotes
Kakande Reply
eukaryotes simply refers to a cell who does not have a definite nucleus.
Franca
Eukaryotic cell has a true nucleus
arfa
what is right answer ?
krishna
I can remember now truly that eukaryotes have true nucleus.I was referring to procaryotes.
Franca
Eukaryotes have got true nuclues
Ede
they have a nucleus, larger than prokaryotes
Alanna
The eukaryotes cell are found in advance organisms.
Franca
Eukaryotes are multicellular organism which has a membrane bounded structure mostly found in animals and some plant cells
KINGSFORD
bacteria growth curve
sani Reply
No bacteria's don't grow curvey. Curve is a shape for a bacteria not growth
KINGSFORD
What is the difference between eukaryotes and prokaryotes?
KINGSFORD Reply
What's a multicellular organism?
KINGSFORD
multicellular organisms is an organism composed of many cells which are to varying degree integrated and independent.
Ruth
Boiling of milk to kill germs is called?
Kasigwa
pasteurization
Aiyedun
pasteurization
Katta
kadha
Katta
pasteurization
Gomathi
what is microscopic
monish
Pasteurization
Hosy
what are Flora
Hosy
you mean like the normal flora?
Tenucharity
pasteurization has to do with killing of the harmful microbes present for safe consumption. Eg. pasteurized yoghurt beside the bacteria that are supposed to be present, there may be harmful ones that have been killed
Tenucharity
Can someone explain flora
KINGSFORD
what is cell?
Anita Reply
the cell is the functional and structural unit of the body
Ruth
yes ur right
Kasigwa
who add me
Wali
hy
Katta
hy
Shivangi
basic structural, functional, and biological unit of all known living organisms. A cell is the smallest unit of life.
Haru
hi
Ruth
hi
Haru
coming Oct 2 I have a exam on microbiology
Haru
okay all the best
Ruth
hi
sachin
hi
Ruth
plz bro send question of microbiology
umesh
structural and functional unit of the life
monish
this is not the correct answer
Alanna Reply
why
Hayat
why not
Zaajid
what is the correct answer?
vannessa
where is question
Zaajid
ask you question
Zaajid
What are mitochondria
Hayat
what is mitochondria
Hayat
who is the father of microbiology
T-
not
Hayat
Antonie Van Luweenhoek
Ravikumar
Mitochondria is the powerhouse of the Cell. And is the cell organelle which helps cell in generation of energy by Cellular Respiration
Ravikumar
Mitochondria are threadlike structuresbounded by double membrane,and serves as the power house of the cell
Felicity
can I get notes on introduction to microbiology just started I have no idea please
rita
Mitochondria is a membrane bounded structure, it's sausage in shape and has inner and outer membrane. The inner membrane is folded at the surface called cristae which project to form matrix. They function as the power house for the cell.
KINGSFORD
Rita are you a medilab student?
KINGSFORD
the father of microbiology is Luis pasture
Able
Erythromycin--------(+++) Cefuroxine ------------(++++) Chloramphenicol --(++) Vancomycin ---------(++++) please what does the above result means. under urine culture and sensitivity?
Kwame
francesco redi was the first to challenge spontaneous generation not pasteur
Alanna
Rita are you a medilab student? no please am a public health student
rita
kwame Evans this result ll mean that the bacterial in the urine can be remedy / killed by this antibacterial (cefuroxime and the rest are antibiotics
rita
Rita Appiah thanks.
Kwame
contact backstage
Emmanuel
what is a vacual
Star Reply
What is microbiology
Nji Reply
it is the study of microscopic organisms and basically their relation to the environment
Tenucharity
what is elements
Erneet Reply
an Element is a substance that can not be further decomposed by ordinary chemical means.
vannessa
can i get notes of biochemistry
Sneha Reply
yep why not
Abdullah
what is microbiology?
Gayanjali Reply
what is malaria
Gayanjali
bios- life/living things micro- small things that cannot be seen with the naked eye In other words the study of living things that cannot be seen with the naked eye but with the help of a microscope
Coltuneac
logos- science
Coltuneac
it is 10 to the power minus 6 biology which studies life forms on those scales including metabolism , physiology, nutrition requirements
barun
what are prokarytes
NDIMUKIKA Reply
A prokaryotic is a unicellular organanism that lacks a membrane bound nucleus ,mitochondria or other any membrane bound organelle. .......
Maryam
in prokaryotic nucleus is not developed and cell organelles are absent
Harshad
how is one who is feeling blockage in the chest with mucus be diagnosed
Essy Reply
be talking sepitol every morning
Ikenna
is that all?
Ven.phumie
What is prions
Sangeeta Reply
Prions are microscopic organism which have no nucleic acid, no nuclear bounded membrane and affect the brain of animals like sheep's and human such a CJD and Kuru
KINGSFORD
is tuberculosis a viral infection?
hildar Reply
No. It is a Bacterial Infection.
Orooj
what are zn staining
Evelyn Reply
full meaning zeil neelson staining
kezia
By using zn stain we diagnose / examine acid fast bacilli .
Deepak

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Source:  OpenStax, Microbiology. OpenStax CNX. Nov 01, 2016 Download for free at http://cnx.org/content/col12087/1.4
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