Welcome to the Microbiology Information

Legionella are bacteria that are common in the environment such as rivers and lakes as well as artificial water systems which includes hot and cold water systems such as storage tanks, pipework, taps and showers. In the environment the occurrence of legionella in groundwater is also common.

With Legionella we usually associate it with larger water systems such as those in factories, hotels, hospitals and museums, and cooling towers. However, they can also live in smaller water supply systems used in homes and other residential accommodation.

In addition, other potential sources of legionella include spa and whirlpool baths, humidifiers in factories and fire-fighting systems such as sprinklers and hose reels. Legionella can survive in
low temperatures, but thrive at temperatures between 2OoC and 45oC. At high temperatures, greater than 6O0C legionella will be killed.

Legionella causes Legionnaires’ disease and it is a potentially fatal form of pneumonia. It can affect anybody, however the risk is higher for those over 45 years of age, smokers and heavy drinkers, those suffering from chronic respiratory or kidney disease, and people whose immune system is low or impaired.

Legionellosis is the collective name given to the pneumonia-like illnesses caused by legionella bacteria, including the most serious and well-known Legionnaires’ disease, and also the similar but less serious conditions of Pontiac fever and Lochgoilhead fever.

If you suspect an area may have the potential for Legionella, then it is best to get the water tested using an accredited water testing laboratory.

The 3M Petrifilm Environmental Listeria plates sounds like a great product. It is a sample-ready culture medium containing selective agents, nutrients, a cold-water-soluble gelling agent, and a chromogenic indicator that facilitates Listeria colony detection. 3M claims the plates were designed to analyze environmental samples and to help increase the efficiency of monitoring plant sanitation. The presence of indicator Listeria such as Listeria innocua provides evidence that environmental conditions are suitable for the occurrence of Listeria monocytogenes. As the two usually co-exist together.

Here is the interesting remark, according to 3M the Petrifilm Environmental Listeria plate detects the majority of environmental Listeria, consisting of Listeria monocytogenes, Listeria innocua, and Listeria welshimeri.*. Here is the sub-clause about the other strains of listeria. “* For further information on the prevalence of Listeria species, please contact the official 3M Microbiology representative nearest you. L. ivanovii, L. grayi/murrayiand L. seeligeri grow but do not form typical colonies.”

That’s right, although all listeria colonies will grow, not all strains will form typical colonies and therefore as a selective medium this is deceptive marketing. Interestingly, the first interpretation guides did not mention the strains in question. That is Listeria ivanovii, Listeria grayi/murrayi and Listeria seeligeri.

Normally a good microbiologist will pick this up, however there are some managers or technical personnel who do not have a clue about this product and will be persuaded by one of the 3M sales representative.

Although Listeria monocytogenes is the main organisms of interest, some regulatory bodies will want all listeria species to be detected in their product. Therefore if this is the case then the 3M Petrfilm Environmental Listeria Plates is not a good option for environmental monitoring and I would stick to the normal ELISA based methods. If on the otherhand, you are not concern with other species of listeria, then this product is a great product.

My point is 3M would be better to develop two different plates:
1. a plate that detects Listeria monocytogenes / innocua only
2. a plate that detects all listeria strains (including Listeria ivanovii, Listeria grayi/murrayi and Listeria seeligeri.)

Finally any pathogen testing must be conducted by qualified personnel’s in an accredited laboratory otherwise the risk of further contamination is raised.

Would I buy this product?
No as some listeria strains do not form typical colonies.

Listeria: A Practical Approach to the Organism and Its Control in Foods No Synopsis Available

Did you know that among the E. coli human pathogens, Verotoxin (Shiga-like toxin) forming strains (VTEC) have gained in importance in recent years. The group of enterohaemorrhagic E. coli (EHEC) with its highly pathogenic serovars 0157:H7, 026, 0103, 0111, 0145, and other strains are of particular concern.

Verotoxins can be classified into two main categories Verotoxin 1 (VT1, SLT1, Stx1) and Verotoxin 2 (VT2, SLT2, Stx2). EHEC strains may produce either VT1 or VT2 only or both VT1 and VT2 simultaneously. EHEC are capable of initiating life threatening illnesses, particularly in those with immune deficiency, young children and the elderly.

Detection of verotoxin is the easist way in which you can determine if the E.coli of interest is a pathogen of real concern.

E.coli is common everywhere with the main sources of infection being contaminated, raw or insufficiently heated foods of animal origin, e.g. meat and dairy products.

The reservoir for EHEC is the feces of cattle, sheep and goats. These microorganisms can enter food during the processing of meat and dairy products if hygienic conditions are inadequate. The drastic increase in the incidence of food infection caused by E. coli 0157 demands reliable and rapid methods of detection. In addition to traditional culture methods, immunological techniques are becoming more useful due to their improved specificity and sensitivity.

Duopath® Verotoxins is an immunological screening test based on the immune flow principle. The Duopath® Verotoxins GLISA test is an immunochromatographic rapid test intended to be used in food-analysing laboratories for the qualitative detection of Verotoxins (Shiga-like toxins) 1 and 2 from Verotoxinogenic E. coli (including E. coli O157:H7) isolated from food enrichments using FDA, USDA or other food enrichment methods.

This test has been validated and received AOAC approval for detection of Verotoxins 1 and 2 from isolated Verotoxin-producing E.coli (including E. coli O157:H7). Duopath® Verotoxin is also intended to be used in clinical laboratories for the qualitative identification of Verotoxins 1 and 2 (Shiga-like toxins 1 and 2) produced by E. coli isolated in cultures derived from clinical stool specimens. The identification aids in the diagnosis of diseases caused by enterohemorrhagic E. coli infections.

The third edition of the Dairy Microbiology Handbook is out and this is a must for those microbiologists who works or has an affiliation in the food or dairy industry. This two-volume set focuses on microbial safety issues and readers will find the latest information on public health risks, pathogens (listeria, salmonella, coliform, E.coli, Yersinia entercolitica and so forth, spoilage organisms (pseudomonas etc), the factors affecting growth of these microorganisms in plants, and good manufacturing practice. It also provides thorough coverage of both dairy microbiology principles and practical applications.

If you already have or own the 2nd edition you’ll understand my excitement.