Rapid monitoring of bacterial growth and metabolism with the PMEU Unit from clinical, environmental, food and process industry samples

THE PRESENTATION OF PMEU TECHNOLOGY AT THE NEW ZEALAND MICROBIOLOGICAL SOCIETY MEETING 2ND OF DECEMBER 2010, AUCKLAND, WITH THE MOTTO “small things, BIG ideas” BY ADJUNCT PROFESSOR ELIAS HAKALEHTO

ABSTRACT


The idea of constructing a cultivator where microbe enrichment could be started on the sampling site has fascinated us for many years. In the PMEU (Portable Microbe Enrichment Unit) one actually intensifies the research on metabolic reactions in a multiplied scale. This equipment also simulates the interactions between different microbes, and it therefore can be used for studying microbial ecosystems.

Sampling in an Austrian hospital during three years from the bile specimens of about 250 patients indicated that coliformic bacteria and fecal enterococci represented around 60% of the microflora in this part of the gastrointestinal tract. The mixed acid fermenting coliformic strains and the neutral end-products producing Klebsiella/Enterobacter group were shown to live in symbiosis in the PMEU cultures implying to their cooperation in the duodenum. This gives an idea how the microbial community maintains intestinal conditions by regulating the pH and other parameters.

The PMEU Spectrion® equipment validated by the State Research Centre of Finland (VTT) has Ethernet connections which make it possible to follow up the microbe enrichment and detection process in real time. The water department field trials are reported. The PMEU can be used to monitor directly both hygiene indicator strains as well as pathogenic bacteria, both in water and in food. A recent report involving the National Institute of Health and Welfare in Finland describes detection of Campylobacter sp. from natural and household waters using the combination of PMEU enrichment and the real time PCR.

In hospital tests at Kuopio University Hospital in Finland, the PMEU Scentrion® gas sensing bacterial cultivator has been validated for the microbiological blood testing of neonatal and cancer patients. The PMEU has also been used for monitoring the development of the microflora after the birth or antibiosis. The enhanced enrichment could be used effectively for improving the recovery of bacterial cells in the detection process.

Biocide testing (KILL tests) with PMEU Spectrion

PMEU Spectrion ® can be applied as a rapid tool for two types of biocide testing.


GROWTH PREVENTION TEST shows the ability of the biocides to prevent microbial growth in processes. Short detection times (typically under 10 hours) indicate poor or lacking effect of the active compound. Long detection times (over 10 hours) show that the biocide can prevent the microbial growth in the target.

This test can be performed in aerobic, microaerophilic or anaerobic conditions.

Temperature control of PMEU unit allows testing of psycrophilic, mesophilic and thermophilic microorganisms.

Turbidity of the test syringes, caused by microbial growth, will be documented automatically and growth curves will be drawn for every syringe. Detection time
(= the moment of the test, counted from the beginning, when the turbidity has increased by a certain factor) can be seen from these growth curves.

PMEU KILL TEST bases on the biocide-dependent change of microbial count. ATP Assay is the fastest method to detect the quantitative increase and the decrease of microbial cells in the samples and is therefore chosen to assist PMEU biocide testing in cases where both the growth prevention and the death of microbes shall be evaluated.

Results of these two types of biocide tests have a significant correlation.

GROWTH PREVENTION TEST can visualize some microbial processes which cannot be detected with traditional colony count method, eg. it shows the prevention of spore germination to vegetative cells by an effective biocide.

All PMEU Spectrion® methods have one excellent property: they indicate the effects of biocides in the original samples, and recovering effect of colony count methods are totally excluded. The user can focus the attention to the biocidic effects which really take place in the paper machine processes.

Modifications of PMEU biocide testing for biofilm control are also available.