One August morning in 2008, a large proportion of the inmates at a Wisconsin county jail awoke complaining of nausea, vomiting, and diarrhea. The local health department suspected an outbreak of food- borne illness, and along with the Wisconsin Division of Public Health, initiated an investigation. Because of the strict routine and controlled environment of prison life, it was relatively easy to find out what the inmates had eaten in the past 24 hours and how their food had been prepared. A written questionnaire distributed to the inmates revealed 194 probable cases of food intoxication. Four respondents commented on the unusual taste of the casserole they had eaten the night before, which contained macaroni, ground beef, ground turkey, frozen vegetables, and gravy. Stool samples were obtained from six symptomatic inmates and cultured for the presence of pathogenic bacteria. ◾ What five basic techniques are used to identify a microorganism in the laboratory? ◾ What types of media might a lab technician use to differentiate bacteria from one another? Continuing the Case appears on page 66. Outline and Learning Outcomes 3.1 Methods of Culturing Microorganisms: The Five I’s 1. Explain what the five I’s mean and what each step entails. 2. Name and define the three ways to categorize media. 3. Provide examples for each of the three categories of media. 3.2 The Microscope: Window on an Invisible Realm 4. Convert among different lengths within the metric system. 5. Describe the earliest microscopes. 6. List and describe the three elements of good microscopy. 7. Differentiate between the principles of light and electron microscopy. 8. Name the two main categories of stains. 9. Give examples of a simple, differential, and special stain. Case File 3 Tools of the Laboratory The Methods for Studying Microorganisms 55