Electron Microscopy of Infectious Agents

Infectious Agents

Case 1
Case 2
Case 3
Case 4

Introduction

I have selected a series of 8 infections studied by electron microscopy for this Case of the Month format, and divided them into two groups, with group 1 featuring opportunistic organisms included here. Group 2, which features viral infections, will be presented next month. The series of cases selected is not intended to be all-inclusive. Rather, the series is a brief treatment of some of the more unusual examples of infectious agents that may be referred for electron microscopic review.

In our facility, microbiological specimens are too infrequently submitted, and represent only about 0.2% of our total. This is a shame because EM can be so useful in identifying infectious agents, providing a very definitive documentation of the offending organisms, changing the course of the disease, and improving the treatment. On the other hand, of the number of microbiological cases submitted, the percentage of those with positive findings is relatively small, so I can understand why the clinician may be reluctant to take the additional step of having EM studies performed. Here, I think, is where the Pathologist plays a critical role by working with the clinician to recommend EM studies where appropriate, and to discourage the clinician when indications suggest that EM studies would have little or no yield. In addition, the Pathologist can advise/assist the clinician on the most suitable specimen selection and ensure proper handling for optimum results. Equally important when the specimens are submitted without consultation, the Pathologist can correlate the histology samples with the tissue selected for EM to ensure that the organisms are likely to be included in the EM sample. This may avoid the needle-in-the-haystack phenomenon or, at least, improve the probability that the haystack is included in the EM specimen.