Four media containing 4-methylumbelliferyl-beta-D-glucuronide were evaluated as a non-confirmatory procedure for E. coli detection in recreational water surveillance. The media included ECD-Agar for membrane filtration and laurylsulphate-tryptose, brilliant-green-bile and lactose as broth media in a three tube most probable number procedure. From six representative water sites, samples were collected weekly over a typical summer season (17.05-27.09.1994) and processed as parallels, using each media at two different incubation temperatures (36 degrees/44 degrees C). Results showed that incubation temperature had no impact on E. coli counts. Each media at a given temperature could be regarded as individual enrichment procedure. None of these enrichment procedures showed a constant and predictable higher sensitivity during the sampling period at all sites compared to the others tested. For parallel results, the rate of agreement, based upon EC-guideline (76/160/EWG) staging of recreational water quality, was 85% for membrane filtration and 75% for the MPN-procedure results. Marked differences could be observed in false-positive specificity showing correlation to the selective characteristics of the media. Subsequently lactose-broth at 44 degrees C performed worst with 30% non verifiable results, while ECD-agar and laurysulphate-tryptose-broth, both at 44 degrees C, had a nearly 100% confirmation rate. Thus, combining high specificity with no lack in sensitivity these two MUG-supplemented media seem to be best suited for E. coli detection in routine recreational water surveillance.
In many cases, the increasing knowledge about the causes of occupational diseases has led to improved preventive actions at the working place. This made it possible to achieve a general decrease in the incidence of occupational diseases--except for some illnesses such as asbestos-related and obstructive lung diseases. An opposite trend can be noticed in the field of work-related illnesses, which especially includes cardiovascular, psychiatric and psychovegetative diseases, and musculoskeletal disorders. In contrast to the occupational diseases, in this context work factors are only of less importance and interact with intrapersonal, social and environmental aspects. Since the associations between the working world and the disease are normally too weak due to the multiple causes involved, what is therefore required for researching these multifactorial relationships are most sensitive epidemiological examination methods including large populations and at the same time avoiding or controlling bias and confounding. Most of the recent studies are based on secondary evaluations of already existing data (premature incapacity, inability to work, results from special preventive checks at the working place). Although this leads to large populations, a considerable bias is caused at the same time since these data in most cases are collected for administrative purpose rather than for epidemiological reasons. Moreover, when looking at the different load factors, only the work aspects are mainly taken into consideration, which leads to considerable confounding due to the omitted other concurring causes. Thus, most of the associations discovered so far are not strong enough to allow for a general deduction of special preventive measures at the working place. For further investigation of these relationships, prospective cohort and intervention studies are therefore required.
