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This chart has three columns labeled components, interactions and mictotiter results. In row A the components are the red blood cells which do not interact with anything and show no reaction in a microtiter result. The lack of reaction is seen as a small red dot in the center of the well. In row B the components are viruses and red blood cells. The viruses and red blood cells clump together and this is seen in a microtiter result as redness throughout the well. This is called hemagglutination. In row C, the components are viruses, red blood cells and antibodies. The viruses and antibodies clump together but the red blood cells do not clump with anything. This is again seen as no reaction; this is called hemagglutination inhibition.
This chart shows the possible outcomes of a hemagglutination test. Row A: Erythrocytes do not bind together and will sink to the bottom of the well plate; this becomes visible as a red dot in the center of the well. Row B: Many viruses have hemagglutinins that causes agglutination of erythrocytes; the resulting hemagglutination forms a lattice structure that results in red color throughout the well. Row C: Virus-specific antibody, the viruses, and the erythrocytes are added to the well plate. The virus-specific antibodies inhibit agglutination, as can be seen as a red dot in the bottom of the well. (credit: modification of work by Centers for Disease Control and Prevention)
  • What is the outcome of a positive HIA test?

Nucleic acid amplification test

Nucleic acid amplification tests (NAAT) are used in molecular biology to detect unique nucleic acid sequences of viruses in patient samples. Polymerase chain reaction (PCR) is an NAAT used to detect the presence of viral DNA in a patient’s tissue or body fluid sample. PCR is a technique that amplifies (i.e., synthesizes many copies) of a viral DNA segment of interest. Using PCR, short nucleotide sequences called primers bind to specific sequences of viral DNA, enabling identification of the virus.

Reverse transcriptase-PCR (RT-PCR) is an NAAT used to detect the presence of RNA viruses. RT-PCR differs from PCR in that the enzyme reverse transcriptase (RT) is used to make a cDNA from the small amount of viral RNA in the specimen. The cDNA can then be amplified by PCR. Both PCR and RT-PCR are used to detect and confirm the presence of the viral nucleic acid in patient specimens.

Hpv scare

Michelle, a 21-year-old nursing student, came to the university clinic worried that she might have been exposed to a sexually transmitted disease (STD). Her sexual partner had recently developed several bumps on the base of his penis. He had put off going to the doctor, but Michelle suspects they are genital warts caused by HPV. She is especially concerned because she knows that HPV not only causes warts but is a prominent cause of cervical cancer. She and her partner always use condoms for contraception, but she is not confident that this precaution will protect her from HPV.

Michelle’s physician finds no physical signs of genital warts or any other STDs, but recommends that Michelle get a Pap smear along with an HPV test. The Pap smear will screen for abnormal cervical cells and the CPEs associated with HPV; the HPV test will test for the presence of the virus. If both tests are negative, Michelle can be more assured that she most likely has not become infected with HPV. However, her doctor suggests it might be wise for Michelle to get vaccinated against HPV to protect herself from possible future exposure.

  • Why does Michelle’s physician order two different tests instead of relying on one or the other?

Enzyme immunoassay

Enzyme immunoassays (EIAs) rely on the ability of antibodies to detect and attach to specific biomolecules called antigens. The detecting antibody attaches to the target antigen with a high degree of specificity in what might be a complex mixture of biomolecules. Also included in this type of assay is a colorless enzyme attached to the detecting antibody. The enzyme acts as a tag on the detecting antibody and can interact with a colorless substrate, leading to the production of a colored end product. EIAs often rely on layers of antibodies to capture and react with antigens, all of which are attached to a membrane filter (see [link] ). EIAs for viral antigens are often used as preliminary screening tests. If the results are positive, further confirmation will require tests with even greater sensitivity, such as a western blot or an NAAT . EIAs are discussed in more detail in EIAs and ELISAs .

The explanation of EIA is separated to show what occurs in a positive sample and what occurs in a negative sample. First patient sample is applied to a membrane filter. If the sample contains viruses they are trapped by the filter. Next, antibody with enzyme conjugate is added. Antibody will attach to antigen if present. Next is a wash step. If the virus is present the enzyme binds to the virus, otherwise the enzyme washes away. Finally substrate is added. If the antibody is present (because it is bound to the virus) the attached enzyme causes a color change. If no enzyme linked antibody is present, no color change occurs.
Similar to rapid, over-the-counter pregnancy tests, EIAs for viral antigens require a few drops of diluted patient serum or plasma applied to a membrane filter. The membrane filter has been previously modified and embedded with antibody to viral antigen and internal controls. Antibody conjugate is added to the filter, with the targeted antibody attached to the antigen (in the case of a positive test). Excess conjugate is washed off the filter. Substrate is added to activate the enzyme-mediated reaction to reveal the color change of a positive test. (credit: modification of work by “Cavitri”/Wikimedia Commons)
  • What typically indicates a positive EIA test?

Part 3

Along with the RT/PCR analysis, David’s saliva was also collected for viral cultivation. In general, no single diagnostic test is sufficient for antemortem diagnosis, since the results will depend on the sensitivity of the assay, the quantity of virions present at the time of testing, and the timing of the assay, since release of virions in the saliva can vary. As it turns out, the result was negative for viral cultivation from the saliva. This is not surprising to David’s doctor, because one negative result is not an absolute indication of the absence of infection. It may be that the number of virions in the saliva is low at the time of sampling. It is not unusual to repeat the test at intervals to enhance the chance of detecting higher virus loads.

  • Should David’s doctor modify his course of treatment based on these test results?

Jump to the next Clinical Focus box. Go back to the previous Clinical Focus box.

Key concepts and summary

  • Viral cultivation requires the presence of some form of host cell (whole organism, embryo, or cell culture).
  • Viruses can be isolated from samples by filtration.
  • Viral filtrate is a rich source of released virions.
  • Bacteriophages are detected by presence of clear plaques on bacterial lawn.
  • Animal and plant viruses are detected by cytopathic effects , molecular techniques (PCR, RT-PCR), enzyme immunoassays, and serological assays (hemagglutination assay, hemagglutination inhibition assay).

Fill in the blank

Viruses can be diagnosed and observed using a(n) _____________ microscope.

Electron

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Cell abnormalities resulting from a viral infection are called ____________ _____________.

cytopathic effects

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Short answer

Briefly explain the various methods of culturing viruses.

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Questions & Answers

microbial genetics mcqs
kajal Reply
hi
Shafiq
hii
Happy
how are you
Shafiq
please send me whattsapp contact
Shafiq
what is the importance of learning microbiology in nursing?
Grace Reply
привет
__
it's about child-care?
__
the way of common children disease? hmm 🤔🤔
__
how do you mean child care?
Grace
Was ist die Wichtigkeit beim Lernen von Mikrtobiologie in der Pflege? Es ist notwendig dass die Schwestern allgemein und auch die Kinderschwestern eine Ausbildung in der Mikrobiologie erfahren. Sie sind in ihrem Beruf gefo
__
you need to know the truth about diseases. the microbes are have immunity to some pharmacy.
__
is base pairing rule states that adenine pair with thymine cytosine pair with guannie what will be the complementry strand to acggt
KooL Reply
tgcca
Tanaya
hi
Shafiq
yes
Swetha
introduction to microbiology
Shweta Reply
Study the life of microorganisms present in the environment their survivals etc..
ayesha
Microscopic organisms, commonly known as microorganisms or microbes, are found all around us and even inside our bodies. The category 'Microbes' includes a massive range of organisms including bacteria, fungi, viruses, algae, archaea and protozoa.
Amre
fermented foods likely benefited ancestors to preserve foods and make other foods like milk, cheese, and bread using microbes.
Zinnia Reply
the evidence that I would support the statement regarding ancient people ideas that disease was transmitted by things they could not see is by the discoveries under a microscope. Many microbiologists have discovered certain diseases caused by microbes.
Zinnia
plz give the information about glyoxylate cycle
kamini Reply
what type of information?
Sapiens
I need medical microbiology mcqs books for Mbbs
Kisota
for pakistani mbbs or other?
Sapiens
what is microbial soup?
Osborn Reply
😃😂funny question isn't it?!!! sorry for inconvenience 😊
ayesha
most bacterial pathogens that cause disease in humans are classified in terms if their preferable ph as
Beesan Reply
what is micro
Kabul Reply
extremely small in size
Swetha
almost invisible to the naked eye
Peter
thanks
Sadiq
uwc
Peter
invisible sized objects
Sivasri
invisible sized object or specimens.which is used to see in only the microscope that specimens or objective called the micro
Sivasri
small organism that can be seen by use of Microbes
Manyang
why do you need to study microorganisms
Sala
what is microbiology?
Green Reply
microbiology is a branch of biology .it deals with the study of microorganisms life cycle , uses, disadvantages,and it impact in any other fields .which is used to view in microscope .
Sivasri
Microbiology is the study of microorganisms, those being unicellular, multicellular, or acellular. Microbiology encompasses numerous sub-disciplines including virology, bacteriology, protistology, mycology, immunology and parasitology. 
Raj
In short , it is the study of micro organisms and types , characteristics.
Kaviya
can you explain the structure of rna in detail
Dhanalakshmi Reply
RNA is of many types....like mRNA,tRNA,rRNA,snRNA,guideRNA..etc .
Swetha
but generally RNA is single stranded
Swetha
It contains adenine guanine cytosine , instead of thymine it contains uracil.
Swetha
ribonucleic acid present in RNA.. where as in DNA it is deoxyribonucleic acid...and ribonucleotide is present in RNA
Swetha
RNA is a blue print of DNA. it has the information from DNA....and we can predict the base panirs in DNA if we have the RNA....copy of that DNA
Swetha
can either have positive or negative polarity
Ernestine
Diatoms need..... With the help of which they can construct their beautiful cell wall
Prathmesh Reply
Microbial growth curve shows a.... Curve.
Shambhuraj Reply
diminishing curve
Oluwapamilerin
It represents the decreasing growth of an organism.
Swetha
what is meant by reverse isolation in tuberculosis treatment?
Swetha Reply
why do we study microbiology
HABIBA Reply
Microbiology is the way of gaining knowledge about those organisms which are surround us but we can't see them with our naked eye,such organisms called microorganisms..We can see them only under microscope.
ayesha
from our birth to death microorganisms are with us in the environment as well as on our body which are called Microflora.
ayesha
Microfloras are non pathogenic
ayesha

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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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