9: Microbiology and Immunology

Microbiology and Immunology

Jessica C. Peek and the publisher acknowledge the past contributions of Marie Collins to this chapter.

Basic concepts of microbiology and immunology relate to transmissible diseases encountered in client care. Using standard precautions in the dental setting greatly reduces the transmission of pathogens. Dental hygienists must prevent and manage potential occupational exposures from infectious diseases.

General Microbiology


General Considerations

Ubiquitous—found virtually everywhere

Only 3% are pathogenic (disease causing); 97% are nonpathogenic

Exhibit characteristics common to all biologic systems: reproduction, metabolism, growth, response to stimuli, adaptability, mutation, and organization

Medically important microorganisms

1. Eukaryotes

2. Prokaryotes (aerobic or anaerobic unicellular bacteria)

3. Viruses; classification based on:

4. Prion

Nomenclature—the binomial system

Methods of Measurement and Observation


Most commonly used units of measurement

Light microscopes illuminate objects by visible light

1. Bright-field microscopy

2. Darkfield microscopy

3. Phase-contrast microscopy

4. Fluorescence microscopy

5. Confocal-scanning laser microscopy

6. Specimen preparation

a. Viewing living organisms

b. Staining

(1) Procedure

(2) Types of dyes

(3) Simple staining procedures

(4) Differential staining procedures (Table 9-1)


Comparison of Gram-Positive and Gram-Negative Bacteria

  Gram-Positive Bacteria Gram-Negative Bacteria
Color after Gram’s stain procedure Blue to purple Pink to red
Peptidoglycan layer in cell walls Thick Thin
Teichoic acid in cell walls Present Absent
Lipopolysaccharide in cell walls Absent Present

(a) More than one dye preparation used

(b) Used for initial bacterial grouping

(c) Most common methods

(5) Special staining procedures—used to color and isolate specific parts of microorganisms

Electron microscopy

Prokaryotic (Bacterial) Cell Structure and Function

Bacterial morphology

External cell structures

1. Appendages

a. Provide motility

b. Allow for movement—spirochetes (e.g., Treponema pallidum, Borrelia burgdorferi) move by this method

c. Provide attachments

2. Surface coating (glycocalyx)

3. Cell wall

Jan 1, 2015 | Posted by in Dental Hygiene | Comments Off on 9: Microbiology and Immunology
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