<< Chapter < Page Chapter >> Page >

Learning objectives

  • Compare direct and indirect agglutination
  • Identify various uses of hemagglutination in the diagnosis of disease
  • Explain how blood types are determined
  • Explain the steps used to cross-match blood to be used in a transfusion

In addition to causing precipitation of soluble molecules and flocculation of molecules in suspension, antibodies can also clump together cells or particles (e.g., antigen-coated latex beads) in a process called agglutination ( [link] ). Agglutination can be used as an indicator of the presence of antibodies against bacteria or red blood cells. Agglutination assays are usually quick and easy to perform on a glass slide or microtiter plate ( [link] ). Microtiter plates have an array of wells to hold small volumes of reagents and to observe reactions (e.g., agglutination) either visually or using a specially designed spectrophotometer. The wells come in many different sizes for assays involving different volumes of reagents.

A plastic plate about the size of a hand with wells in a grid. The top is labeled 1-12 and the side is labeled A-H.
Microtiter plates are used for conducting numerous reactions simultaneously in an array of wells. (credit: modification of work by “Microrao”/Wikimedia)

Agglutination of bacteria and viruses

The use of agglutination tests to identify streptococcal bacteria was developed in the 1920s by Rebecca Lancefield working with her colleagues A.R. Dochez and Oswald Avery . Lancefield, Rebecca C., “The Antigenic Complex of Streptococcus haemoliticus . I. Demonstration of a Type-Specific Substance in Extracts of Streptococcus haemolyticus ,” The Journal of Experimental Medicine 47, no. 1 (1928): 91-103. She used antibodies to identify M protein , a virulence factor on streptococci that is necessary for the bacteria’s ability to cause strep throat. Production of antibodies against M protein is crucial in mounting a protective response against the bacteria.

Lancefield used antisera to show that different strains of the same species of streptococci express different versions of M protein, which explains why children can come down with strep throat repeatedly. Lancefield classified beta-hemolytic streptococci into many groups based on antigenic differences in group-specific polysaccharides located in the bacterial cell wall. The strains are called serovars because they are differentiated using antisera. Identifying the serovars present in a disease outbreak is important because some serovars may cause more severe disease than others.

The method developed by Lancefield is a direct agglutination assay , since the bacterial cells themselves agglutinate. A similar strategy is more commonly used today when identifying serovars of bacteria and viruses; however, to improve visualization of the agglutination, the antibodies may be attached to inert latex beads . This technique is called an indirect agglutination assay (or latex fixation assay ), because the agglutination of the beads is a marker for antibody binding to some other antigen ( [link] ). Indirect assays can be used to detect the presence of either antibodies or specific antigens.

Photo of 6 wells. Well 4 has blue spots. All the other wells have a clear blue color.
Antibodies against six different serovars of Group A strep were attached to latex beads. Each of the six antibody preparations was mixed with bacteria isolated from a patient. The tiny clumps seen in well 4 are indicative of agglutination, which is absent from all other wells. This indicates that the serovar associated with well 4 is present in the patient sample. (credit: modification of work by American Society for Microbiology)

Questions & Answers

what is fermentation example ?
Sonal Reply
is proceess in which an agent couses of an oganic substances breakdown into simpler substance,especially in aneorobic breakdown of suger into alcohol.
Okashat
is it better to study microbiology and then medicine it makes no difference to go directly to medicine?
Jessee Reply
Dray's mathdme cell wall konse color k hote he
Jinal Reply
what is dray's mathdme cell wall
Prabhat
I confused. please help me
Karen
just confused
Raj
l don't understand it please explain it for me.
Karen Reply
epitopes are present on the surface of
Rohit Reply
at the tip of variable region on the antibody...where antigen and antibody binding sites combine...
Fiza
The term that is used refer to moving microbes under a microscope are referred to as?
Lee Reply
Members of the genus Neisseria cause which of the folowing human diseases?
Farah Reply
genital infections
Kamaluddeen
gonorrhoea
sandip
gonorrhoea
Jessee
4. Which of the following specimens should not be refrigerated? a. Urine b. Urogenital swab
Zahraa Reply
urine
Muuse
urine
Agatha
Urine
Tean
urine
Yasser
Urine
Ebtehal
urine
anamika
urine
Puja
urine
Inemesit
urine
Samuel
Urine
Muhammad
Details about McConkey agar
Muhammad
urine
SK
urine
what is bacteria
anamika Reply
a member of large number of unicellular microorganism which have cell wall but lack of cell organelles an oranised nucleus including somewhat can cause disease
Sukhdeep
Bacteria are usually composed of one cell onl to that are neither plants nor animals, microscopic, that may cause diseases or may be beneficial(in gut)... it depends upon their weapons. Nearly all animal life is dependent on Bacteria for their survival
Fiza
thanks
anamika
what factor make bacteria colony large and how could we sterlise it in large scale
fatty
nutrient concentration temp gaseous conc ph ion or salt concentration mositure condition factors contribute to make large colony. by autoclaving we will sterilize bactetia
Sukhdeep
Colony is actually visible growth of Bacteria that is as a result of suitable environment for growth i.e optimal conditions for growth, temperature, moisture etc. there're many methods to get rid of bacteria. If We stop giving them optimal conditions for living Bacteria will die soon .
Fiza
what's the difference between an antigen and a pathogen?
Pathogens are organisms that cause disease in other organisms whereas Antigen is a part of a pathogen that triggers the immune response..
Rajat
so it is the antigen that dendritic cells present to the T cells and not the pathogen itself?
no no antigen are the west product or part of the pathogen. in such case bacteria it self fight with over immune response & in another case bacteria release antigens
vasava
& other antigen like pollan grain, dust particles etc.....
vasava
pathogen are microbes that can infect the body and causw illness....antigens are the part of pathogens that alert the body to an infection
Sukhdeep
antigen is a part of blood and pathogen is foreign particle which causes diseases
Yogyata
antigen could be non microorganism.... where as pathogen is mixroorganism
tadesse
Thanks
Karen
a pathogen is a disease causing organism while an antigen is a protein in the white blood cells which combats pathogens.
Jessee
what type of widal test
sobhit Reply
this test determine for typhoid in this test if H,O antigen are present that indicate the positive test bac. are salmonella typhy
vasava
what h.o denotes
Iqra
o: body of bacteria, h: flagellate
Explain Mould
Chinenye Reply
Explain mycoses and it's classification
Chinenye
why do we have hiccups?
Manisha Reply
shakey diaphragm
Curlisse
The antibody binding site is formed primarily by:
Asalla Reply
How many types of MICROORGANISMS do we have?
Hope Reply
Hello friends
Hope
microorganisms are divided into seven type Bacteria archaea protozoa algae fungi virus and multicellular animal parasites
Raj

Get the best Microbiology course in your pocket!





Source:  OpenStax, Microbiology. OpenStax CNX. Nov 01, 2016 Download for free at http://cnx.org/content/col12087/1.4
Google Play and the Google Play logo are trademarks of Google Inc.

Notification Switch

Would you like to follow the 'Microbiology' conversation and receive update notifications?

Ask