Latex agglutination tests

Figure 5.6. Percentage of samples from Mycobacterium tuberculosis (TB) patients and healthy controls exhibiting different degrees of agglutination when tested using the conventional slide prooedure or the US-enhanced latex agglutination test. (Reproduced with permission of Elsevier, Ref [76].)...

Clostridium difficile can be cultured from the stool, and toxins A and B can be assessed by different techniques (116). The most accurate method is still a cytotoxin tissue culture assay. This detects the cytopathic effect of cytotoxin B, which can be neutralized by Clostridium sordellii antitoxin, but it takes 24 8 hours to show a result. Alternative tests that produce faster results have been developed. A latex agglutination test lacks sensitivity and specificity, and does not distinguish toxigenic from non-toxigenic strains. An enzyme immunoassay for toxin A may be an acceptable alternative to the cell cytotoxin assay and the results are rapidly available. A dot immunobinding assay has not yet been extensively studied (164). 

Igarashi, H., Fujikawa, H., Shingaki, M., and Bergdoll, M. S. 1986. Latex agglutination test for staphylococcal toxic shock syndrome toxin. J. Clin. Microbiol. 23 509-512. 

Latex agglutination immunoassays are easily formatted into simple kits which can provide yes/no and semiquantitative estimates of antigen (or antibody) in a sample. The first such assay was developed in 1957 for rheumatoid factor (15) and assays are on the market for the deterrnination of many species of bacteria, fungi. Mycoplasma, parasites, ckettsia, and vimses, as well as for the deterrnination of autoimmune disease, hormones (qv), dmgs (see Pharmaceuticals), and blood proteins (16). Latex agglutination is also the basis of many home pregnancy tests. 

If CSF Gram stain and/or culture is negative, rapid diagnostic tests (such as latex agglutination) may be useful these tests are positive even if bacteria are dead. 

Quash, G., Roch, A.M., Niveleau, A., Grange, J., Keolouangkhot, T., and Huppert, J. (1978) The preparation of latex particles with covalently bound polyamines, IgG and measles agglutinins and their use in visual agglutination tests./. Immunol. Meth. 22, 165-174. 

Immunological methods Methods such as gel-agglutination tests were introduced many years ago (according to Outcherlony) however they are not sufficiently sensitive. Reversed passive latex agglutination kits (SET-RPLA and TST-RPLA) are presently applied for enterotoxin detection and are more sensitive than gel diffusion (Wieneke, 1988). The ELISA technique is also very popular - toxins are detected via VIDAS STAPH ENTEROTOXIN SET and indirect double sandwich ELISA (Meyrand et al., 1998). 

Polystyrene latex particles, 0.2 p, in diameter, have recently been used as immunochemical markers for sceuining electron microscopyS. (SEM). But applications of such a reagent are limited because the lydrophobic surface of the polystyrene particles makes them stick nonspeciflcally to many surfaces and molecules. The same disadvantage applies to agglutination tests. Furthermore, reliance on weak adsorption forces to hold the antibodies on the particles is not always satisfactoryifi and chemical bonding of antibodies to polystyrene particles is virtually... 

Thus, Bhaskar et al. developed a novel US-enhanced latex agglomeration test for the detection of serum antibodies against Mycobacterium tuberculosis. The use of US enabled the detection of low levels of antibodies in serum by increasing the sensitivity of the test. The rate of particle-particle collisions under an oscillator frequency of 100 kHz was raised to such an extent that the sensitivity for samples diluted up to 20 times exhibited agglutination, which was visible to the naked eye [76]. Figure 5.6 clearly shows the advantage in using US for this purpose. 

Park CE, Szabo R (1986) Evaluation of the reversed passive latex agglutination (RPLA) test kits for detection of staphylococcal enterotoxins A, B, C, and D in foods. Can J Microbiol 32 723-727... 

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