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Background: The first instance of Legionella infection in a Norwegian hospital was confirmed in 2005. We describe the best-known methods of eradicating Legionella in hospitals., Materials and Method: The article is based on the authors' experience of measures to prevent Legionnaires' disease in hospitals and on a non-systematic search in PubMed., Results: There are several methods of combating Legionella in hospitals. These include chlorination, heat treatment, and the use of filters. However, recontamination easily re-occurs after eradication. The silver and copper ionisation treatment of water is a well-documented method for the systematic and long-term eradication of Legionella in water. The disadvantages of this method are that it is expensive, that there is a risk of discolouring the water, and that there is a possibility of developing resistance in environmental bacteria. This resistance mechanism can theoretically be transferred to bacteria that cause illness., Interpretation: We recommend the silver and copper ionisation treatment of water as a method of preventing nosocomial Legionnaires' disease when standard methods fail and there is a high prevalence of Legionella in the water. The discolouration of operation instruments that occurs as a result of high silver concentrations can be avoided by using a separate water supply for operation units.

Since 1987 we have analysed throat samples from 1,086 healthy contacts of 32 patients with meningococcal disease. The disease-causing strain was found in contacts of 17 out of the 32 patients. 161 (18%) of the contacts carried meningococci, and 30 (3%) of them were carriers of the disease-causing strain as determined by DNA fingerprinting. The carrier strain was eradicated in 29 of these 30 contacts by treatment with rifampicin. No secondary case of meningococcal disease was observed. During the four-year period 1984-87, there were 39 confirmed cases of meningococcal disease, including 12 verified and four suspected secondary cases of meningococcal disease. Therefore identification and eradication of the disease-causing strain seems to prevent secondary cases. A change in the Norwegian recommendations for preventing secondary cases of meningococcal disease should be discussed.

During the period from January 1987 to June 1988 DNA fingerprinting was used to identify carriers of the disease-causing strain of Neisseria meningitidis among the patients contacts. A total of 432 persons were screened during nine episodes. The overall carrier-rate was 16.2%, and the causative strain was found in 3.4% of the contacts. Eleven carriers were successfully treated with rifampicin, whereas two of three carriers treated with penicillin remained carriers. We conclude that DNA fingerprinting is a valuable tool for rapid identification of carriers of the causative organism in order to eradicate the epidemic strain of N. meningitidis.