Oyster-associated gastroenteritis

Rapid estimation of Escherichia coli in live marine bivalve shellfish using automated conductance measurement

Conductance measurement for quantitative estimations of Escherichia coli in live bivalve shellfish was evaluated as an alternative to the conventional most probable number (MPN) method used in France. The sensitivity of the two techniques was comparable. A single regression line (r = -0.968, P < 10(-6)) between log10 MPN and detection time (DT) was used to estimate E. coli concentrations for all shellfish examined. Estimation accuracy was +/- 0.92 log unit. Repeatability was better for DT than the log10 of MPN estimations (average coefficients of variation 2.7 and 9.3%, respectively). The conductance signal was attributable to E. coli in 96% of cases, and only 0.7% of E. coli cultures failed to exhibit a signal within 20 h. The conductance method reduces analysis handling time and is much easier to use than the MPN method. Moreover, results can be obtained within 5-9 h compared to 3 d for the MPN method.

Diagnostic virology using electron microscopic techniques

This chapter illustrates the development of the use of electron microscopy in viral diagnosis. The field covered is confined to medical viral diagnosis, but parallel developments have taken place in both veterinary and botanical fields and techniques derived from both these sources are also included where relevant. It is reported that the scanning transmission mode of operation, which can induce image contrast changes electronically, may enhance studies with unstained sections and perhaps facilitate thin section immune electron microscopy (IEM). The application of negative stain IEM has been particularly useful for the study of the antigenic nature of some of the newly discovered noncultivable viruses. Viral antigens can also be detected in thin sections of infected cells by IEM with suitably labeled specific antibodies. Confirmation of viral infection by electron microscopy on tissues originally processed for light microscopy is also frequently useful.