MLAB 2434 – CLINICAL MICROBIOLOGY SUMMER, 2005 CECILE SANDERS & KERI BROPHY Chapter 8 – Microscopic Examination of Infected Materials

Chapter – 8 - Microscopic Examination of Infected Materials (cont’d) Purposes for direct gram stain from patient specimens Confirm that specimen submitted is representative (ex. Sputum vs. spit) Determine probability of infection by identifying debris of inflammation Identify specific infectious agents

Chapter – 8 - Microscopic Examination of Infected Materials (cont’d) Guide initial antibiotic therapy Use for epidemiologic data Direct gram stains observed with light microscope after staining Preparing smears Using swabs Smears should not be made using swab that has been used to streak cultures

Chapter – 8 - Microscopic Examination of Infected Materials (cont’d) Ideally, if culture AND gram stain are to be done, two swabs of the specimen should be collected and sent to the lab Swab is NOT rubbed on the slide, but rolled back and forth (p. 263) Smears from thick liquids or semisolids (ex: stool) Smears from thick or mucoid material “Pull” slides

Chapter – 8 - Microscopic Examination of Infected Materials (cont’d) Smears from thin fluid (ex: CSF) Mark back of slide with marking pen to show location of specimen on the slide for ease in finding under microscope Cytocentrifuge

Chapter – 8 - Microscopic Examination of Infected Materials (cont’d) Examination of Prepared and Stained Slides If sputum, first evaluate the smear to determine if it is REALLY sputum Unacceptable = squamous epithelial cells/LPF Acceptable = PMN/LPF Evaluate smear first under low power to look for background material, such as WBC (pus), epithelial cells, etc. Search for microorganims

Chapter – 8 - Microscopic Examination of Infected Materials (cont’d) For your ID, use your address Your password is your first name and first letter of your last name, all lower case