For today’s post, we are once again going to take a bit of a step back from the news and examine some of the fundamentals of Legionella bacteria and Legionnaires’ disease. With that in mind, today’s post will be doing a review of the basics regarding how testing for Legionella is done.
Traditionally, Legionella is found by a culture on a buffered charcoal yeast extract agar. One very common procedure for detecting Legionella in water is to concentrate the bacteria before inoculating it onto a charcoal yeast extract agar along with some agents like polymixin, GVPC, vancomycin, glycine, and cyclohexamide in order to suppress any other flora that may be in the sample. Some laboratories will instead use an acid or heat treatment in order to suppress the other flora along with the other microbes.
From there, the labs will allow incubation for a period of up to 10 days. Once this period is complete, suspect colonies can be confirmed if the Legionella is able to grow on the buffered charcoal yeast extract agar containing the cysteine, but not on the agar without the cysteine added. In order to determine the exact species and/or serogroup, immunological techniques are often used.
On a more practical level, individuals may encounter testing at hospitals through Legionella urinary antigen tests which can allow for the initial detection when it is suspected that the patient may have Legionella pneumonia. One major advantage of the urinary test is that the results can be found in several hours opposed to several days which would be necessary for testing with a culture. The major disadvantage, however, is that the urine antigen test can only detect the Legionella pneumophila serogroup 1 (LP1) so can not detect any non-LP1 strain or any other Legionella species, a problem which ultimately impairs public health investigations of a Legionnaires’ disease outbreak.
This page has covered a few examples of this before however new techniques for rapidly detecting Legionella in water are increasingly established and being used. These new detection techniques include ideas regarding the use of polymerase chain reaction and rapid immunological assays, both of which should provide much faster results.
While this is clearly not an exhaustive review of all the methods and details of testing for Legionella bacteria, it is this post’s hope that you will at least take away some information that will overall make you a more informed individual when it comes to Legionella and Legionnaires’ disease.
Jules Zacher is an attorney in Philadelphia who has tried Legionnaires’ disease cases across the U.S. Please visit LegionnaireLawyer.com again for updates.