Medical Fun Facts Podcast

MFF0061: Latex agglutination

It’s Monday 1 May 2017. It’s my birthday. Feel free to leave me a happy birthday message in the comments of the show notes!

Tonight, I’m going to describe latex agglutination assays and how they’re used. Latex agglutination assays can be used to detect antigens and antibodies and the specimen substrates include stool, sputum, urine, blood and cerebrospinal fluid.

Apart from clinical specimens, the most common application for latex agglutination assays is in bacteriology using suspensions of bacteria in sterile saline. Latex agglutination is a common way to get a quick and reasonably accurate way to identify a bacterium or to confirm a characteristic of a bacterium.

Common examples include grouping β-hæmolytic streptococci into groups A, B, C, D, F and G. Grouping these streptococci is important because identifying the bacterium gives specialist microbiologists a better appreciation of the pathogenic potential of the bacterium and the potential clinical path for the affected patient. Group A BHS are arguably the most important to identify correctly because some types of GAS are associated with necrotising fasciitis which journalists have a predilection for calling the flesh-eating bacterium. Although they never use the word bacterium preferring to confuse bacteria with insects for reasons that escape me. I think all journalists should be taught science and specifically biology in school and whatever tertiary education they undertake. It’s remarkable that journalists and their editors seem to enjoy sharing mistakes and inaccuracies rather than striving for truth and accuracy and dare I say integrity in reporting. I’m sick of reading about bacteria described as viruses and outbreaks being referred to as pandemics. You’d think they never went to school.

Another important quick and dirty latex agglutination assay used on the bench is for identifying Staphylococcus aureus from other staphylococci and these assays can also give a clue to the Staph. aureus being MRSA or not.

As far as clinical diagnosis is concerned, latex agglutination was a well-used assay to detect Rotavirus in faeces to diagnose Rotavirus gastroenteritis. In 1986, I took a year out of medical school to do a bachelor of medical science. I spent the year up to my elbows in infantile faeces looking for Rotavirus. I used electron microscopy, latex agglutination and enzyme immunoassay.

In episode 56 I mentioned the use of bacterial antigen detection or BAD tests used on cerebrospinal fluid to diagnose acute bacterial meningitis. I suggest you go to the show notes for that episode and you can find the link and read a paper my registrar at the time and I published on BAD tests or you can just go to the show notes for this episode and find the link. These days, we prefer to use PCR for detecting bacterial and viral pathogens in CSF.

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