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Microbiology know your enemy From April 2008 newsletter

Solving microbiological problems in food

When microbiological problems strike, rapid and reliable solutions are essential.

Whether it is food safety, spoilage or processing failures, understanding the cause of the problem is the first step in solving it - and preventing recurrences. Using the latest molecular techniques we have extended our portfolio of methods for fast and definitive identification and characterisation of bacteria, yeasts and moulds, as Dr. Suzanne Jordan of our Microbiology Department explains.


Molecular methods such as DNA amplification (PCR) and gene sequencing enable us to put a name to an isolate - quickly. For example, non-pathogenic Citrobacter and Proteus can resemble Salmonella in some tests, giving 'presumptive positives' that can be very costly to companies. Using PCR they can be distinguished in as little as 4 hours. This identification is essential in assessing safety implications or managing 'false positives' from more subjective methods.

Meanwhile, profiling methods such as 'repPCR' and ribotyping enable us to 'characterise' or cluster organisms that share similar DNA profiles - and trace sources of contamination within a laboratory or factory. For example, if a company was concerned that an apparent positive resulted from cross-contamination with a QC sample in the laboratory, repPCR can be used to see whether this is or is not the case. It takes as little as 6 hours and can also be used with yeasts and moulds. Ribotyping has been used to show that a Listeria monocytogenes isolate from a food product shared a DNA fragment pattern with an environmental strain, implicating the source for rapid, targeted remedial action.


Identification is also often important in solving spoilage problems - as it can be used to search for information on similar incidences. For example, an unidentified yeast had been isolated from butter. Using gene sequencing we were able to identify it as a Cryptococcus, a known contaminant of cheese and yoghurt. A spoilage organism isolated from a fruit drink was shown, by DNA sequencing, to be an Asia sp., previously identified as an unusual spoilage organism of fruit flavoured water. A brewery contaminant was shown to be an acid resistant Bacillus, while two thermophiles - Geobacillus and Aneurinibacillus - were implicated as the cause of problems following survival of the heat process.”

These new molecular techniques help industry solve problems quickly and reliably, by identifying the contaminating organisms and their source, so tackling problems at their root cause.

Dr. Roy Betts, Head of Microbiology, concludes: “Our wealth of experience and facilities, housed within the largest microbiology department of its kind in Europe, means we are ideally placed to help industry prevent and solve microbiological problems. Coupling this with our extensive international contacts in food and industrial microbiology, means we are able to host premier events such as our forthcoming international conference and exhibition on rapid microbiological methods - to help industry get the very best from the latest technology.”

Contact: Suzanne Jordan
+44(0)1386 842013