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Environmental control – Legionella
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Published March 3, 2006

Medical Microbiology has a well-established range of activities in the field of preventing infections due to environmental exposure. We perform our own laboratory analyses of pathogenic bacteria, and also collaborate closely with the microbiology departments in St. Olav’s Hospital in Trondheim and NTNU.

Our analyses
We carry out holistic studies of Legionella pneumophila, with identification of both genetic material and living cultures, as well as genetic tracing of cause/effect relationships when outbreaks occur. We can also offer quantitative analyses of L. pneumophila.

Our Legionella screening is based on direct studies of water, supported by genome analysis: our RT-PCR is specific to Legionella pneumophila, which is the Legionella species responsible for more than 90 percent of all outbreaks in the western world. Analyses are very rapid, and we can often provide an answer on the same day as the samples arrive in our laboratory. The method demonstrates the presence or absence of genetic material from L. pneumophila bacteria. The test does not distinguish between live and dead bacteria.

Live bacteria are a prerequisite for the start of infection. Demonstration of live bacteria requires cultivation, a process that takes several days (up to a week). Once genetic material from L. pneumophila has been demonstrated, the presence of live bacteria is confirmed or rejected by cultivation. Live bacterial strains are biotyped and genotyped.

Testing of commercially available Legionella tests
One aspect of our policy is to test commercially available tests; for instance, we have tested a rapid test for demonstrating Legionella in the field: Hydrosense® Legionella Field Test™.

In conclusion: The Hydrosense® Legionella Field Test™ is an antigen test which is specific for Legionella pneumophila serotype 1. As an antigen test, the Hydrosense® Legionella Field Test™ gives no information with respect to the concentration of living bacteria. In Legionella-contaminated water, we will expect the majority of antigens to be present as nonliving bacteria or bacterial fragments. When the Hydrosense® Legionella Field Test™ is applied to cultivated Legionella pneumophila serotype 1 strains in the laboratory, the sensitivity of the test is found to be an antigen concentration corresponding to 105-106 cfu/L.

Free-living amoebae and their interaction with L. pneumophila
We are attempting to generate knowledge about relationships between a number of environmental conditions and exposure of  L. pneumophila with regard to risk assessment of water systems. On this background, we are currently demonstrating free-living amoebae using cultivation techniques. Methods for the genetic determination of amoebae will be established.

In addition to causing diseases in human beings directly, free-living amoebae can also act as “culture incubators” for particular strains of L. pneumophila. Bacteria are usually eaten by amoebae, but certain strains of bacteria manage to avoid this fate and instead, use the amoeba as a growth incubator, while obtaining protection against various environmental factors that could be disadvantageous for the growth prospects of L. pneumophila. After spending some time inside amoebae, large quantities leave them and enter the external environment. They may then have a quite different and/or increased potential virulence than when they were absorbed by the amoebae, and this process may increase the chances of an outbreak of legionellosis. Amoebae such as Achantamoeba are particularly associated with the likelihood of acting as “incubators” of this sort for L. pneumophila.

Our goal is to develop a method of testing that can provide an indication of whether environmental conditions at the test site encourage the growth of L. pneumophila in general, in addition to a risk assessment of the potential for the development of virulent strains of L. pneumophila in the environment involved. This would be useful with regard to choosing which measures to implement if L. pneumophila is demonstrated.

Parasites
A parasite is an organism that propagates itself by living on or in and exploiting another organism. The single-celled parasites Giardia and Cyprosporidium are found in rivers and surface water, as well as in the gut of humans and many other species. They can be spread directly between human beings, from animals to humans, or to water sources via contamination with sewage or manure. Even in small amounts, such parasites can cause infections in human beings. While some people become seriously ill, others scarcely notice that they are infected.

Medical Microbiology offers expertise in methodology for demonstrating Giardia and Cyprosporidium in drinking water.

Contact person: Catrine Ahlen, senior scientist.

Senior scientist Catrine Ahlen