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When viruses infect cells, they often cause damage ( cytopathic effects ) that may include lysis of the host cells. Cytopathic effects can be visualized by growing host cells in a petri dish, covering the cells with a thin layer of agar, and then adding virus (see Isolation, Culture, and Identification of Viruses ). The virus will diffuse very slowly through the agar. A virus will enter a host cell, proliferate (causing cell damage), be released from the dead host cell, and then move to neighboring cells. As more and more cells die, plaques of dead cells will form ( [link] ).

During the course of a viral infection, the patient will mount an antibody response to the virus, and we can quantify those antibodies using a plaque reduction assay . To perform the assay, a serial dilution is carried out on a serum sample. Each dilution is then mixed with a standardized amount of the suspect virus. Any virus-specific antibodies in the serum will neutralize some of the virus. The suspensions are then added to host cells in culture to allow any nonneutralized virus to infect the cells and form plaques after several days. The titer is defined as the reciprocal of the highest dilution showing a 50% reduction in plaques. Titer is always expressed as a whole number. For example, if a 1/64 dilution was the highest dilution to show 50% plaque reduction, then the titer is 64.

The presence of antibodies in the patient’s serum does not tell us whether the patient is currently infected or was infected in the past. Current infections can be identified by waiting two weeks and testing another serum sample. A four-fold increase in neutralizing titer in this second sample indicates a new infection.

A photograph of wells showing a smooth purple background with white spots.
In a neutralization assay, antibodies in patient serum neutralize viruses added to the wells, preventing the formation of plaques. In the assay pictured, the wells with numerous plaques (white patches) contain a low concentration of antibodies. The wells with relatively few plaques have a high concentration of antibodies. (credit: modification of work by Centers for Disease Control and Prevention)
  • In a neutralization assay, if a patient’s serum has high numbers of antiviral antibodies, would you expect to see more or fewer plaques?

Immunoelectrophoresis

When a patient has elevated protein levels in the blood or is losing protein in the urine, a clinician will often order a polyacrylamide gel electrophoresis ( PAGE ) assay (see Visualizing and Characterizing DNA, RNA, and Protein ). This assay compares the relative abundance of the various types of serum proteins. Abnormal protein electrophoresis patterns can be further studied using immunoelectrophoresis (IEP) . The IEP begins by running a PAGE. Antisera against selected serum proteins are added to troughs running parallel to the electrophoresis track, forming precipitin arcs similar to those seen in an Ouchterlony assay ( [link] ). This allows the identification of abnormal immunoglobulin proteins in the sample.

IEP is particularly useful in the diagnosis of multiple myeloma , a cancer of antibody-secreting cells. Patients with multiple myeloma cannot produce healthy antibodies; instead they produce abnormal antibodies that are monoclonal proteins (M proteins). Thus, patients with multiple myeloma will present with elevated serum protein levels that show a distinct band in the gamma globulin region of a protein electrophoresis gel and a sharp spike (in M protein) on the densitometer scan rather than the normal broad smear ( [link] ). When antibodies against the various types of antibody heavy and light chains are used to form precipitin arcs, the M protein will cause distinctly skewed arcs against one class of heavy chain and one class of light chain as seen in [link] .

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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