Considerations for environmental and microbiological studies (tool 7)
This tool contains a brief discussion of the subject with emphasis on the use of typing in outbreak investigations. The emphasis here on typing is because the classical microbiological isolation methods, as for instance those used for detection of agents in food samples, are well established and performed according to uniform, standardised protocols.
Epidemiological methods are central tools in most outbreak investigations; however, depending on the specific outbreak circumstances, environmental, microbiological or molecular epidemiological investigation methods may be equally important tools.
Outbreak investigations are generally more successful and give more convincing evidence when both epidemiological, microbiological, site-inspections, risk-assessments and food-tracing approaches are applied in parallel. Detection of the disease agent in food or water is obviously something that should always be attempted; however, to be able to conclude that a particular disease agent found in a food is closely related or indistinguishable from one isolated from humans will often require sub-typing, and it is important to agree on the best methods to use. Furthermore, detection of organisms in patients and comparisons of isolates using typing methods are often a prerequisite for establishing that an international outbreak is taking place.