Chapter 4 Safety and Infection Control 111 Copyright Goodheart-Willcox Co., Inc. In addition, people who have compromised immune systems are susceptible to infections and may become ill from microorganisms that do not usually affect individuals with healthy immune systems. Nonpathogenic organisms can become pathogens to such patients. For microorganisms to live and thrive, they must have certain elements in their environment. For example, some microorganisms require oxygen to live. They are called aerobes. Others live in an environment with little or no oxygen. They are called anaerobes. Bacteria Bacteria are initially classifi ed by their morphology (form and structure) as seen under a microscope. After observing bacteria under the microscope, a clinical microbiologist identifi es the actual family of the bacteria through testing. The basic forms of bacteria are spherical (coccus) and rod-like shapes (bacilli). Figure 4.11 illustrates several shapes of bacteria, including those that appear as twisted cylinders (spirochetes), spherically-shaped cocci arranged in clusters (Staphylococcus), cocci forming chains (Streptococcus), and cocci in pairs (Diplococcus). aerobe an organism that requires oxygen to live anaerobe an organism that requires little or no oxygen to live morphology the science or study of the form and structure of organisms coccus diplococci Staphylococci diplococci encapsulated (Pneumococcus) Streptococci sarcina tetrad Cocci Bacilli Budding and appendaged bacteria Others coccobacillus bacillus diplobacilli palisades Streptobacilli stalk hypha Vibrio Comma’s form Bdellovibrio Club Rod Corynebacteriaceae Helical form Helicobacter pylori Corkscrew’s form Borrelia burgdorferi Filamentous spirochete enlarged rod Fusobacterium Goodheart-Willcox Publisher Figure 4.11 These illustrations show a few simple representations of the many different shapes and sizes of bacteria. Which bacteria names do you recognize?