CHAPTER 8 Microbiology and Immunology
Microorganisms are life forms that normally CANNOT be seen with the unaided human eye. Possess characteristics common to ALL cellular life in terms of physiology, morphology, reproduction. Inhabit MOST niches of environment. Normal inhabitants of human body (normal flora). A medically IMPORTANT microorganism is one that inhabits human host and is considered a pathogen (causes disease).
Microbiology spectrum includes prokaryotes, eukaryotes, viruses. Classification of prokaryotes and eukaryotes employs Latin binomial system of genus and species. Ultrastructures have important MAIN differences.
Specimens MUST be prepared and then stained to be seen under light microscope because refractive index of MOST organisms is clear. Basic dyes (e.g., crystal violet, methylene blue, safranin) are positively charged and combine with negatively charged cell constituents. Acidic dyes (e.g., eosin, nigrosin, basic fuchsin) possess negative charge and combine with positively charged cell components.
Small bacteria possess variety of shapes and sizes and internal or external structures that aid in survival and are useful in identification of different bacteria. Survival is KEY to involvement with infectious processes.
Bacterial growth is the increase in the numbers of bacterial cells by binary fission. Growth is influenced by the physical environment and the availability of essential nutrients. This is important NOT only in pathogenesis of systemic infections but also with development of infectious oral disease (periodontal disease and caries) and its MAIN etiological factor, dental biofilm (dental plaque).
|Parasitism||Benefits||Benign or harmed|
Microorganisms generally MUST breach host defense barriers to initiate disease-causing reactions and transfer to new hosts, whether it involves bacteria or viruses. EXCEPTION is transmission by ingestion of preformed microbial (bacterial) toxin that can cause toxemia (poison in the bloodstream) (see later discussion). There are many overlaps between the routes of transmission of infectious materials, since the overwhelming goal of the microorganism is to survive at ANY means; there are also nonspecfic and specific host defenses.
Each route of transmission is discussed here with the MOST common examples of infectious disease that have practical association with major risks for exposure in the dental setting. Risk factors for NOT achieving oral health are also listed when involved. Infection control protocol and standard precautions to prevent transmission are discussed later.
Many infections are bacterial in origin, but many have vaccinations developed against them or are sensitive to antibiotics and other infection control procedures. However, resistant strains are now a developing problem in healthcare. See later discussion on antibiotics.
|Sex||Male Female||The patient presents at a walk-in medical and dental clinic with weight loss, fever, oral sore. A sputum smear shows the presence of acid-fast bacilli. A chest radiograph shows evidence of pulmonary lesions. Two days later, a test the patient took on his skin is determined to be positive; however, he says he has never received any vaccinations since he was a baby.|
|Chief Complaint||“I am coughing all the time now.”|
Some bacteria may cause disease in humans because of toxic (poisonous) properties present in protein molecules (toxins), which they carry and release, producing a toxemia. Disease from toxin exposure may NOT require bacterial replication in the body, because in some cases exposure to the toxin alone is sufficient.