You are here

Water - Rapid Legionella Confirmations

rapid legionella testing

ALcontrol Laboratories have introduced a new method for rapid confirmation of Legionella bacteria. This technology reduces the time of confirmations from days to minutes, removing presumptive results and the uncertainty associated with them.

Key benefits of rapid confirmations for Legionella are:

rapid legionella testing

This technique has been widely used in routine clinical microbiology for over 15 years. Using this technique in Legionella testing is ground-breaking in environmental microbiology and Legionella control. The traditional technique for confirming the identification of a presumptive Legionella colony involves further culture and incubation of the colony which can take two to four days. This new rapid technique allows the colony to be confirmed within minutes. The benefit to you is that you will no longer receive a presumptive result, we will always provide you with a confirmed positive result upon which you can act.

 

rapid legionella testing

 

These rapid confirmation results are achieved by use of a technique called Matrix Assisted Laser Desorption Ionisation Time of Flight Mass Spectrometry (MALDI-TOF MS). MALDI-TOF MS identifies the unique molecular fingerprint of an organism by measuring highly abundant ribosomal proteins that are found in all microorganisms. The characteristic patterns of these highly abundant proteins are used to reliably and accurately identify a particular microorganism by matching the respective pattern with an extensive open database to determine the identity of the microorganism down to the species level. The database contains more than 4,600 species of bacteria, yeasts and fungi, including 38 species of Legionella.

Background

A technology developed in the late 80s, MALDI-TOF did not have widespread usage until the early 2000s due to the lack of a suitably sized instrument and of established standard operating procedures. Ever since then there has been increasing use in the clinical environment, where its speed and reliability have provided a much needed tool for the rapid identification of bacteria in patients in a field where faster results mean saved lives. In 2013, Clark et al. defined it as a “paradigm-shifting, rapid, and robust method for accurate microbial identification”. 

MALDI-TOF is a type of “soft” (or “mild”) mass spectrometry. The sample is placed onto a target plate and covered with a matrix before being bombarded by a laser beam. The laser’s energy is absorbed by the matrix and then released gently. This allows the proteins present in the sample to pass into gaseous form (desorption) and become charged (ionization) without being broken down into their building blocks, as they would be in traditional mass spectrometry methods.

The ionized molecules generated through this process are then fired through a tube with a detector at the end. Because the tube is under high vacuum the only variable that will influence the time these molecules take to reach the detector is mass. This allows the instrument to create a spectrum depicting the mass and numbers of each of the molecules that are put through the process and that fit the mass range specified. For species level identification the protein size range detected is generally between 2 and 20 kDa (kilodaltons). This range is dominated by ribosomal proteins, which are found to be very stable, ionize well, provide reproducible spectra and are only minimally influenced by microbial growth conditions unlike many cell-wall associated proteins, which can vary in levels of expression under different culture conditions.

 

The table above summaries the scores obtained for 660 ‘wild’ type colonies tested on the instrument for Drinking water (DW)and Process water (PW) matrices from direct, heat and acid treated plates. Scores above 2.0 are reported as a species, results between 1.7 and 1.99 are reported as Legionella spp.

The spectra obtained through this process are then processed by software similar to the ones used by police forces around the world for fingerprint identification and compared to a database of known spectra, resulting in an ID in less than five minutes.

The database currently contains almost 6,000 species and is continuously being improved and enlarged.

ALcontrol Laboratories is a pioneering UK Food and Waters commercial laboratory offering this technique for advanced, rapid Legionella confirmation. After extensive internal validation work and stringent UKAS assessment against ISO17025, MALDI-TOF confirmation is now UKAS accredited - Click here for the UKAS Schedule of Accreditation


MALDI-TOF confirmation is equivalent to our traditional method for accuracy and reliability but gives an improved service to our customers allowing them to obtain confirmed results at least 2 days earlier than with the traditional confirmation, removing the presumptive stage.

In summary

This technique brings the reliability and speed of mass spectrometry to microbiology, shortening or eliminating the presumptive stage for many test types, removing the problems associated with lengthy culture stages and biochemical tests and allowing your results to be faster, more accurate and more reliable – providing you with the confidence to act quickly.

Stop presuming... start acting! Find out how by contacting us at:

Email: experts@alcontrol.com | Tel: 08450 738808