Dental Pathology and
Microbiology
Unit 1 Classifications of
Microorganisms
Unit 1
• Definition: Microbiology
– Micro
– Bio
– Ology
• Oldest form of life
• Most are Beneficial
• Only a few are harmful
Why do we study Microbiology?
The world we live in…..
• People live longer
• Diseases are now controlled
• Healthier Food
• Better conditions
• Medical Advances
• Environmental advances
Microbiology & Medicine
• Science MUST be ready to face the challenge
• Knowledge of transfer of microorganisms can
reduce spread of disease
• Knowledge of immunity can reduce disease
• Knowledge of sterilization & disinfection
procedures will reduce or prevent spread of
disease
• Not all microorganisms are harmful, some are
even helpful
Theory of Spontaneous
Generation
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Mold on food
Spoiled drinks & spoiled food
Theory was = caused by devil or curse of God
Seemed to be no physical cause
Some scientists attempted to disprove theory
“Catching” diseases spread by contact with
humans and animals
Leeuwenhoek
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Dutch merchant & Amateur scientist
Hobby of grinding lenses to observe microbes
“Animalcules” = small moving objects
Drew pictures and wrote volumes
Early lenses led to early microscopes
Took scrapings from teeth to observe
appearance
• Referred to as Father of Microbiology
Pasteur
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Professor of chemistry in France
Experimented with heating liquid
Process of pasteurization
Process used for wine, beer & Milk
Food canning process
Discovery labeled “Germ Theory of Disease”
proved that airborne bacteria was the cause of
some diseases
Golden Age of Microbiology
• Many new discoveries 1880-1910
• Communication was limited
• Scientists and doctors in all countries were
working on theories
• Numerous causes of disease & death;
patients died in hospitals; women died in
childbirth
• Physicians wore street clothes in surgery
Holmes
• Physician in Boston
• Studied “child bed” fever in new mothers
• Suggested nurses and physicians wash
hands
Semmelweis
• Hungarian doctor
• Explored use of antiseptics with washing
• Number of deaths were reduced
• Both Holmes & Semmelweis were working
on same experiments in different countries
Lister
• English Surgeon
• Set out to prove that wound infection due to
microbes
• Tried carbolic acid (PHENOL)
• Soaked surgical dressings & instruments &
tables
• Asked staff to use phenol on hands after
washing
• Established aseptic techniques
Koch
• German biologist & physican
• Proved ‘specific bacteria causes disease’
• Developed rules
– 1. Organism must be present
– 2. Organism must be isolated
– 3. Organism must produce disease in
another
– 4. Organism must be recovered
Miller
• American dentist & researcher
• Theory: connection between bacteria,
carbohydrates & tooth disease
• BACTERIA + FOOD = Produce Acids
• Acids on teeth = cause decay (cavities)
Review
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Leeuwenhoek –
Pasteur –
Koch –
Lister
Holmes Semmelweis Miller -
Summer Fun
Normal Flora
• Resident microbial population of human
body
• Microorganisms live (reside) in and on
body
* Always present
Activities of Microbes
• Bacteria in soil converted to usable nutrients
• Bacteria cultured to make vinegar, vitamins,
antibiotics
• Bacteria or fungi used to pickle cucumbers;
• Produce cultured dairy: yogurt & sour cream
• Yeast makes bread dough & used in beer
production
GROUPS OF
MICROORGANISMS
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BACTERIA
VIRUSES
FUNGI – Yeasts & Molds
PROTOZOA
– Bacteria & viruses are concern in dental office
– Some fungi can cause dental problems
BACTERIA
• Small cells
• Divide by binary fission
• SHAPES:
– COCCI
– BACILLI
– SPiRILLA
– VIBRIOS
Bacteria
• Grow in COLONIES
• Bacterial growth = increase in cell
numbers
• Cells divide by BINARY FISSION
• Division of cells occurs every 20-30
minutes
• Some bacteria have ability to grow
• Some bacteria do not survive
Growth Requirements of
Bacteria
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Temperature
Acidity
Nutrients
Oxygen Metabolism
Water
Bacteria
• Culturing Bacteria – grow bacteria in
laboratory
• Nutrient base called medium
• Preventing growth – changing
requirements
• Bacteriostatic
• Bacteriocidal
Infections/Diseases from
bacteria
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TUBERCULOSIS
DIPHTHERIA
PERTUSSIS
TETANUS
STREPTOCOCCAL Infections (caries)
STAPHLOCOCCAL Infections
FUNGI: Yeasts & Molds
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Larger than bacteria
Disease: Candidiasis (known as thrush)
Found inside mouth
Cannot be killed with antibiotics
Usually cause problems after use of too
much antibiotics
Candidiasis/Yeast/Thrush
Baby thrush
VIRUS
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Smaller than bacteria
Have many shapes
Cause disease by changing cells
Cannot be killed with antibiotics
Some antiviral drugs
Best approach is immunization or Infection
Control Procedures
Viral Diseases
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Measles, Mumps, Rubella
Poliomyelitis
Chicken Pox (Varicella)
Common Cold
Influenza
Herpes Simplex
Hepatitis
Shingles
VIRAL
NO PPE???
• Herpetic
conjunctivitis- Herpes
of eye
• Herpetic WhitlowHerpes on hand
Protozoa
• Live in bloodstream,
mouth & digestive
tract
• Contaminated
drinking water
• Gum disease
(Periodontal disease)
Rickettsiae
• Parasites – cannot
live outside a host
• Diseases are Typhus
& Rocky mountain
fever
THE END
• Grandpuppies