In a longitudinal study over a period of ten weeks, the water conduit systems of seven dental surgeries with a total of 20 dental units in which legionellae had been detected in an earlier study (3) were investigated as a complement to extended microbiological tests (4) for the occurrence of free-living amebae and other protozoa. In 96% of all water samples, one or several ameba species were detected. These included 14 strains of the genus Naegleria, but no acanthamoebae. The naeglerias isolated were not thermophilic and thus belong to the N. gruberi complex, which does not contain any pathogenic strains. In two water samples, two different species of small freeliving nematodes were demonstrated. The simultaneous investigation of samples from the warm water supply in the individual dental surgeries revealed an ameba contamination in 24.9% of the samples. A nonpathogenic strain of the genus Protacanthamoeba was demonstrated once. The possible role of the trophozoites of various ameba species as hosts for an intracellular proliferation of the legionella strains demonstrated at the same time (cf. 4) is discussed. The occasional protective intracellular inclusion of legionellae in trophozoites of various species and in cysts of acanthamoebae might be an explanation for the resistance of legionellae to disinfection measures which has been repeatedly observed. This observation will have to be taken into consideration in sterilization and disinfection projects.
For the evaluation of health risks emerging from imported foods data can be utilized which result from national surveillance programmes of member states and which are summarized, e.g. in the WHO Surveillance Programme for Control of Foodborne Infections and Intoxications in Europe. Within this programme annual reports are published reflecting the situation in the various European countries. The epidemiological data allow for long term preventive measures to be developed in an attempt to minimize health risks resulting from foods. Within this programme an Early Warning System has been established to monitor and report on incidents of international concern. The Commission of the European Communities operates an Alert System on contaminated food articles which are in international or intracommunity trade. Thus countries shall be placed in a position to initiate without delay steps for the prevention of current health risks. It is the declared policy of the EEC to dismantle by 1992 all trade barriers between the member countries and thus complete the European domestic market. This situation will make impossible border controls for food within the Community. From that time on import controls will only exist towards so-called Third Countries at the outer border of the Community. The internal free trade with foods on the one hand and the shift of inspection and control measures on the other necessitate a reconsideration of traditional official food inspection procedures. This reorientation has to include risk evaluations and strategies for routine food inspection services as well as questions of judgement criteria for different articles of food, e.g. microbiological criteria, agreement on sampling plans and standardization of examination procedures which would have to be applied.
