PMEU applications for water hygiene analyses have been published in "Rakennustarkastuspäivät 2010"

Novel PMEU water hygiene analyses, intended in the quantitative control of total coliforms, E.coli and enterococci, have been published in "Rakennustarkastuspäivät 2010" Conference, Kuopio, Finland at the end of March. This annual event is dedicated to professionals of building regulations and related administration and collected over 200 participants to the beutiful capital of Savo region, in the middle of Saimaa lake district.

SAMPLION Ltd. was exhibiting PMEU Spectrion and its water hygiene applications, now qualified by VTT, alongside Suomen Jätevesi Ltd. which is the major supplier of small-scale waste water purification systems in Finland.

The picture above demonstrates the combination of selective growth medium and MUG-based UV fluorescence confirmation of E.coli. Among the three PMEU syringes, only the one on the left, containing a culture of E.coli, indicates this fluorescence. This PMEU method is now approved by VTT, Technical Research Centre of Finland (VTT-S-01705-10) and it also follows the guidelines of international standardization (SFS-EN ISO 9308-3) to fulfill the needs of rapid, quantitative control of hygiene indicator bacteria.

Detection Time as the Variable in Quantitative Microbe Analyses

There are several methods to quantify the count of microbes. Historically the very first of them (if microscopy is excluded) was the use of dilutions series in nutrient broths. This methods was later developed to MPN (Most Probable Number) Method, which was the standard until the rise of Colony Count methods. Colony counts give accurate numbers but suffer of the poorer recovery of the microbial cells, compared to the broth methods. It is also unavailable for certain, difficult types of samples.

"Third Generation" of quantitative mb analyses was established some 30 years ago. They are based on analytical methods which give the results much faster than the traditional methods by measuring some chemical or physical features of the samples which are in a relationship with the count (or activity) of microbes of the original samples.

The increase of the nutrient broth turbidity, caused by the growth of microorganisms, is maybe the most common "3rd Generation" method used today. It is an optical method which gives levels of either total growth or specified microbes (in latter case, selective broths with confirmation tests are applied). An inversed corretation between microbial load and detection time (= the moment of the testing period when turbidity begins to rise) can be found and correlation lines/tables between colony counts and detection times are easy to construct.

The figure above is an example of the growth curves, derived by PMEU Spectrion. X axis shows the time scale of the test, y axis indicates the values of RT. This curve shows that PMEU Spectrion actually illustrates the classic growth curves with the lag, log and stat phases (and, if the cultivation will continue long enough, also the kill phase). The moment when the turbidity begins to rise is inversely related to the count of microbes in the original sample.