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10
Microbiology
Important People in Microbiology
• Anton Van Leeuwenhoek
– Magnifying glass
• Saw microorganisms from teeth for the first time
• Ferdinand Julius Cohn
– Classified bacteria as plants
– Divided bacteria into four groups
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Important People in Microbiology
• Louis Pasteur
– Process of fermentation
• Proved bacteria causes disease
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Important People in Microbiology
• Robert Koch
– Koch postulated that organisms must be:
• Present in all cases of the disease
• Isolated in pure culture
• Capable of producing the disease in another
person or animal
• Recovered again in pure culture
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Important People in Microbiology
• Richard Julius Petri
– Petri dish
– Further developed technique for
dispensing the bacteria onto the medium
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Groups of Microorganisms
• Bacteria and virus groups
– Gram stain used to differentiate
• Gram positive if they keep their dark purple color
• Gram negative if they lose the color
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Bacteria
• Need for oxygen
– Aerobic bacteria must have oxygen to grow
and live
– Anaerobic bacteria are destroyed in the
presence of oxygen
– Facultative anaerobic bacteria grow with or
without oxygen present
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Diseases Caused by Bacteria
• Tuberculosis
– Bacteria found in lungs
– Fatigue, fever, weight loss, persistent cough
– Airborne
• Dental personnel must wear masks
– Detected by a skin test and/or chest x-ray
– Treatment is antibiotics or other drugs
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Diseases Caused by Bacteria
• Diphtheria
– Severe throat infection and fever
• Pertussis
– Respiratory disease
– Mainly affects infants and young children
• Tetanus
– Stiffness of the jaw (“lockjaw”)
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Diseases Caused by Bacteria
• Strep throat
– Very common
– Sore throat, fever, general malaise
– Streptococcus mutans
• Species of the same bacteria
• Implicated in dental caries and endocarditis
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Diseases Caused by Bacteria
• Staphylococcal infections
– Bacteria groups grow in clusters
• Antibiotics are the first line of treatments
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Diseases Caused by Bacteria
• Anthrax
– Humans can get disease through cuts in
skin or eating diseased meat
– Powder form
• Symptoms within 1 to 6 days
• Fever, weakness, dry hacking cough
• Prevention by vaccination or antibiotic
treatment before symptoms
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Diseases Caused by Bacteria
• Chlamydiae
– Microorganisms somewhere between
bacteria and viruses (small in size)
• Genital, eye, and lymph node infections
• Most common sexually transmitted disease in
the United States
• Antibiotics used as treatment
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Protozoa
• Just below visibility of the naked eye
• Always dividing and changing shape
• Flagella
– Many have this long, threadlike appendage
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Diseases Caused by Protozoa
• Amebic dysentery
– Severe diarrhea
• Abscesses may develop in liver
– Prevalent in countries where drinking water
is contaminated and poor hygiene
conditions prevail
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Diseases Caused by Protozoa
• Periodontal disease (protozoa and
bacteria)
– Both found in inflamed tissue around the tooth
– Protozoa is found in the plaque in the periodontal
pockets around the tooth
– Treatments include removal, cleaning of plaque
and tissue, and oral hygiene maintenance
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Diseases Caused by Protozoa
• Malaria
– Symptoms during the first two weeks
• Fever and soreness at point of entry
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Rickettsiae
• Parasites cannot live outside a host
– Lice, fleas, ticks, and mites transmit
disease to humans
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Diseases Caused by Rickettsiae
• Head lice
– Common among children in schools
– Transmitted easily through direct contact
– Eggs reproduce in hair shafts
– Treatment
• Medicated shampoo and cleaning bedding,
brushes, and clothing with very hot water
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Diseases Caused by Rickettsiae
• Rocky Mountain Spotted Fever
– Rare, curable
– Small pink dots appear
• Typhus
– Rare, treatable
– Severe headache, back and limb pain,
constipation, rash, and confusion
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Yeasts and Molds
• Includes bread yeast, mushrooms, and
bread molds
• Cannot be killed by bacterial antibiotics
– Made from mold but does not act on it
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Diseases Caused
by Yeasts and Molds
• Candidiasis
– Covered by mucus in areas such as the inside
of the mouth or the vaginal area
– Treated by antibiotics
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Diseases Caused
by Yeasts and Molds
• Tinea
– Appearance named according to site
infected
• Tinea pedis (Athlete’s foot)
• Tinea corporis (Ringworm)
• Tinea unguium
– White patches on toe or fingernail
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Diseases Caused
by Yeasts and Molds
• Prion (pree-on)
– Proteinaceous infectious particles made of
only protein
• Mad Cow Disease
• Creutzfeldt-Jacob Disease
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Viruses
• Must live inside hosts
• Antibiotics cannot kill the virus
• Treatment is primarily to ease the
symptoms for the patient’s comfort
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Diseases Caused by Viruses
• Measles
– Rash, fever
– Spread by airborne droplets of nasal
secretions
• Mumps
– Swelling of the parotid (salivary) glands on
one or both sides
– Spread by airborne droplets
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Diseases Caused by Viruses
• Rubella or German measles
– Rash on face may spread to trunk and limbs
– Only serious when it affects women in early
stages of pregnancy
• May cause birth defects
– Vaccines are highly effective and given to
most infants at age 15 months
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Diseases Caused by Viruses
• Poliomyelitis or polio
– Attacks the central nervous system
• Severe paralysis is a possibility
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Diseases Caused by Viruses
• Chicken pox
– Very common and contagious in children
– Rash and fever
– Spread through airborne droplets
– Usually only contract once in a lifetime
• Before age 10 is better than as an adult
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Diseases Caused by Viruses
• Common cold and influenza
– Treatments for fever, upset stomach,
headache, body ache
– Cold is spread through airborne droplets,
contact with contaminated objects, or hand-tohand contact
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Diseases Caused by Viruses
• Common cold and influenza
– Flu vaccines are successful in 60 percent of
patients
– Flu is contagious from 12 to 72 hours after
symptoms appear
– Flu is spread through airborne droplets
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Diseases of Major
Concern to the Dental Assistant
• Herpes simplex virus (HSV)
– Herpes simplex virus I (HSV I) is
associated with infections of the lips,
mouth, and face
– Herpes simplex virus II (HSV II) is
associated with the genital area
• Can also be found in oral cavity
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Diseases of Major
Concern to the Dental Assistant
• Treatment of HSV I
– Depends on its type, site, and severity
– Dental teams may reschedule patient if
sores are apparent
• Primarily for patient comfort, although some
offices may have policies
– Many treatments readily available
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Diseases of Major
Concern to the Dental Assistant
• Bloodborne diseases
– Hepatitis B
– Human immunodeficiency virus (HIV)
• Brain damage and dementia may occur
• May develop into acquired immune deficiency
syndrome (AIDS)
– No cure
– Much research is being done to find a cure
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Diseases of Major
Concern to the Dental Assistant
• High risk behavior
– Injuries or sticks with sharp objects
contaminated with blood or body fluid
– Multiple sexual partners; unprotected sex
– Sharing contaminated needles
– Exposure to non-intact skin or open wound
with contaminated blood or body fluid
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Diseases of Major
Concern to the Dental Assistant
• Viral hepatitis
– Hepatitis A and E
• Transmitted by personal contact or ingestion of
contaminated water or food
• Vaccines and boosters are available for children in
areas at high risk
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Diseases of Major
Concern to the Dental Assistant
• Viral hepatitis
– Hepatitis B (major dental concern)
• Transmitted mainly through needles and syringes
• May or may not have symptoms
– Loss of appetite, abdominal pain and tenderness, fever,
weakness, muscle pain, and jaundice
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How the
Body Resists Diseases
• Infection
– Pyogenic membrane
• Dam built around infected area preventing it to
spread further
– Antibodies
• Produced as a final defense against foreign
substances
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How the
Body Resists Diseases
• Infection
– Antitoxins
• Neutralizes the toxins given off by certain bacteria
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How the
Body Resists Diseases
• Fever
– Fights off infection or pathogens
• Few bacteria can survive beyond 102° F
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How the
Body Resists Diseases
• Inflammation
– Increase in blood vessels to a specific area
allowing antibodies to enter
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•
•
Erythema (redness)
Heat
Edema (swelling)
Pain
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How the
Body Resists Diseases
• Immunity
– Ability to resist disease
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•
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Natural
Acquired
Passive acquired
Active acquired
Natural acquired
Artificial acquired
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How the
Body Resists Diseases
• Antigen substance injected into body to
stimulate specific antibodies
– Allergens
– Hypersensitive
– Anaphylactic shock
• Sometimes fatal
• Requires going through patient’s health history
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Normal Routes of
Microorganism Exposure
• Direct contact
– When a dental provider touches the lesion
or blood of an infected person while
working in the oral cavity
– Standard precautions
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Normal Routes of
Microorganism Exposure
• Indirect contact
– When dental provider or next patient
obtains disease from contaminated
instruments, supplies, or equipment
– Standard precautions
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Normal Routes of
Microorganism Exposure
• Inhalation
– Takes place during use of high-speed
handpiece
• Creates an aerosol spray during patient care
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