1. Chapter 18
Microbiology

2. Introduction Microbiology: The study of microorganisms
Micro means “microscopically small,” and bio means “living organisms”
Dental assistant needs a foundation in microbiology to understand the nature of pathogens and how to prevent the transmission of disease in the dental office
The two major oral diseases are bacterial infections:
Dental caries (decay) and periodontitis
What are pathogens? (Disease-producing microorganisms)
Are all microorganisms bad? (No. Most microorganisms are nonpathogenic—they do not produce human illness—and some are helpful.)
Can you think of ways microorganisms are helpful? (Microorganisms are used in the production of flavorful cheeses and yogurt, in the disposal of waste products, in the fertilization of soil, and in the production of lifesaving drugs.)

3. Major Groups of Microorganisms
Bacteria
Rickettsiae
Algae
Protozoa
Fungi
Prions
Viruses
Members of the first four groups are easily recognized with the aid of a microscope.
Viruses can only be viewed under a powerful electron microscope.

4. Types of Infections
Acute infection: Symptoms are often quite severe and appear soon after the initial infection occurs
Chronic infection: The microorganism is present for a long period; sometimes for life
Latent infection: A persistent infection in which the symptoms come and go; cold sores fall in this category
Oral herpes simplex and genital herpes are latent viral infections
Opportunistic infection: Caused by normally nonpathogenic organisms, opportunistic infections occur in individuals whose resistance is decreased or compromised
A patient contracts a common cold. Which one of the four types of infection does he have? (The common cold is an acute infection.)
If a patient is undergoing chemotherapy for breast cancer, which one of the four types of infection would she be concerned about? (She would be concerned about opportunistic infections.)
Shingles is an example of which of the four types of infections? (This is a chronic infection.)
Hepatitis C virus is an example of what type of infection? (This is a chronic infection.)

5. Bacteria
A large group of one-celled microorganisms that vary in shape, size, and arrangement
Pathogenic bacteria usually grow best at 98.6˚ F (37˚ C) in a moist, dark environment
Skin, respiratory tract, and gastrointestinal tract are inhabited by a great variety of harmless bacteria, called the normal flora
Infection occurs when bacteria occurring naturally in one part of the body invade another part of the body and become harmful
What is the function or purpose of the normal flora? (These bacteria protect the human host by aiding in metabolism and preventing the entrance of harmful bacteria.)
What are bacteria in the normal flora considered when they invade another part of the body? (Opportunistic bacteria that cause infection)
What is an example of an opportunistic bacterium? (Cystitis-causing Escherichia coli)

6. Viewing Bacteria Bacteria is not visible with the naked eye.
it must be viewed through a microscope
For optimal viewing bacteria should be stained with special dyes for better visualization
Both gram-negative and gram-positive
Gram-positive
appear blue or purple
Gram-negative
Appear pink or red
Both gram-negative and gram-positive bacteria are present in the oral cavity and are involved in the development of caries and periodontal disease.
Oral bacteria can cause infections in soft tissues and the bloodstream

7. Shapes of Bacteria Spherical (coccus, plural cocci)
Reproduces by dividing in two
Cocci that form chains as they divide are called streptococci
Cocci that form irregular groups or clusters are called staphylococci
Rod-shaped (bacillus, plural bacilli)
Spiral (spirillum, plural spirilla)
The shapes of bacteria can be viewed under a microscope.
What are examples of illnesses caused by coccus-shaped microorganisms? (Strep throat, tonsillitis, pneumonia, and endocarditis)
What is an example of an illness caused by rod-shaped microorganisms? (Tuberculosis)
What are examples of illnesses caused by spiral-shaped bacteria? (Syphilis and Lyme disease)

8. Three Basic Shapes of Bacteria
Three shapes of bacteria are pictured: coccus (round or spherical), bacillus (rod-shaped), and spirochete (helical).
Even through the bacteria are classified in three different shapes, the individual classifications of shapes can vary. Cocci and rods can be single or paired or actually form a chain. Rods can also appear to grow what looks like a tail, which acts as a propeller to guide the bacterium through its environment.
The spiral-shaped bacteria can take on variations of waves and spirals.
From Stepp CA, Woods M: Laboratory procedures for medical office personnel, Philadelphia, 1998, Saunders.

9. Size of Bacteria
The common diameter of a coccus is about one micrometer or micron (µm). A micrometer is one-millionth of a meter or one-thousandth of a millimeter.
The common size of a bacilli are about one mm wide and five to ten mm long.
Spirilla are .2 to 1.0 µm wide and up to 30 µm long.
Pictured on the slide are bacteria that cause infections such as pneumonia.
Are there single, paired, or chainlike cocci? (Mostly chainlike but also single and paired cocci)
From Stepp CA, Woods M: Laboratory procedures for medical office personnel, Philadelphia, 1998, Saunders.

10. Gram-Positive and Gram-Negative Bacteria
Hans Christian Gram (1853–1938) developed a four-step staining process for separating bacteria into two groups
Gram staining requires the sequential use of a crystal violet dye, iodine solution, alcohol solution, and a safranin dye
The bacteria that are stained by the dye are classified as Gram positive (they appear dark purple under the microscope)
The bacteria that are not consistently stained are classified as Gram variable (e.g., Mycobacterium tuberculosis)
How is Gram staining used today? (A physician can make a diagnosis on the basis of the Gram stain and begin the appropriate antimicrobial therapy.)

11. Gram-Positive Stain
Gram-positive bacteria are stained during the Gram stain process, making them appear darker in color or purple under microscopic examination.
What drugs or medications are most Gram-positive bacteria susceptible to? (Penicillins)
Gram-positive bacteria are stained during the Gram stain process, making them appear darker in color or purple under microscopic examination.
G: Textbook of diagnostic microbiology, ed 4, Philadelphia, 2011, Saunders.

12. Gram-Negative Stain
Gram-negative bacteria are almost colorless or a light pink in color under microscopic examination.
What are bacteria that are inconsistently stained called? (Gram variable)
Gram-negative bacteria are almost colorless or a light pink in color under microscopic examination.
From VanMeter KC, VanMeter WG, Hubert RJ: Microbiology for the healthcare professional, St Louis, 2010, Mosby.

13. Need for Oxygen
Aerobes: A variety of bacteria that require oxygen to grow
Anaerobes: Bacteria that grow in the absence of oxygen and are destroyed by oxygen
Facultative anaerobes: Organisms that can grow in the presence or the absence of oxygen
A good supply of oxygen enhances the metabolism and growth of many bacteria. Obligate or strict aerobes require oxygen to grow. Example: Mycobacterium tuberculosis.
Obligate or strict anaerobes cannot grow in the presence of oxygen. An example is Porphyromonas gingivalis. However, microaerophiles that are also classified as anaerobic bacteria can survive when low levels of oxygen are present. Example: Campylobacter fetus.
Facultative anaerobes use oxygen to generate energy through respiration if it is present. Examples: Mutans streptococci and Escherichia coli.

14. Capsules
Some types of bacteria form a capsule or protective layer that covers the cell wall (e.g, Streptococcus mutans)
Generally virulent (capable of causing serious disease)
Capsule increases the bacteria’s ability to resist the defense mechanisms of the body
Capsule may also prevent antibiotic agents from having an effect on the bacteria
The capsule is an amorphous, gelatinous layer that surrounds the entire bacteria.
Besides providing protection to the bacteria, what other role does the capsule play? (It mediates adhesion of the bacteria to human tissues, which enhances the bacteria’s ability to colonize and begin the infectious process.)

15. Spores Some bacteria change into a highly resistant form called spores
Bacteria remain alive in the spore form but are inactive
Spores represent the most resistant form of life known
Can survive extremes of heat and dryness and even the presence of disinfectants and radiation
Harmless spores are used to test the effectiveness of the techniques for sterilizing dental instruments
What causes the disease tetanus? (The disease tetanus is caused by a spore-forming bacillus.)
When bacteria are inactive in the spore form, they cannot reproduce or cause disease.
Spore tests are performed with the use of biological monitors. Biological monitors are designed to prove sterilization.
If the biological monitor claims that the spores were killed during the sterilization process, is it safe to assume that less resistant bacteria have been destroyed? (Yes)

16. Bacterial Diseases Tuberculosis Legionnaires' disease Tetanus Syphilis
Methicillin-resistant Staphylococcus aureus (MRSA)
Diseases caused by bacteria are also of concern for dental care workers.
Bacterial diseases include tuberculosis, Legionnaires' disease, tetanus, and syphilis.
Bacterial diseases are also categorized as communicable diseases.

17. Tuberculosis Caused by the bacterium Mycobacterium tuberculosis
Leading cause of death resulting from infectious disease worldwide
HIV and tuberculosis are often present together
Of the two diseases, tuberculosis is a greater health risk for healthcare workers
“Tuberculosis kill time” is the benchmark for the effectiveness of a surface disinfectant
Why do HIV and tuberculosis often present together? (Because HIV-infected patients have a weakened immune system, they are highly susceptible to tuberculosis; therefore, they often present together.)
Why is tuberculosis a greater health risk for healthcare workers than HIV? (One reason for this is that the rod-shaped tubercle bacillus is able to withstand disinfectants that kill many other bacteria.)
What are the oral manifestations of tuberculosis? (Oral lesions are usually secondary to primary infections commonly seen in the lungs. Oral lesions include ulcerations, tuberculous lymphadenitis, and periapical granuloma.)

18. Legionnaires' Disease
Legionella pneumophila causes two acute bacterial diseases:
Pontiac fever
Legionnaires' disease
Bacteria are transmitted through aerosolization and aspiration of contaminated water
No person-to-person transmission
Dental personnel have higher titers of antibodies against L. pneumophila than do members of the general public
The less serious form of infection is called Pontiac fever; the more serious form, which causes a very severe pneumonia, is called Legionnaires' disease.
In elderly individuals and those who are already immunocompromised, the disease can be fatal.
Why do you think dental personnel have higher titers of L. pneumophila antibodies? (The presence of these antibodies indicates occupational exposure and resistance to this organism.)
Legionnaires' disease is also more commonly seen in heavy middle-aged smokers.

19. Bacteria Taken from Dental Unit Waterlines
The L. pneumophila bacteria has been found to thrive in lakes, creeks, hot tubs, spas, air-conditioning systems, shower heads, water-distillation systems, and the biofilm found in dental-unit waterlines.
Do you think that dental personnel are at increased risk of contracting a disease caused by the L. pneumophila bacteria? (Answers will vary.)
Courtesy Dr. Shannon Mills, New Hampshire.

20. Tetanus Also known as lockjaw
An extremely dangerous and often fatal disease caused by a spore-forming bacillus found in soil, dust, or animal or human feces
This microbe is usually introduced into the body through a wound or break in the skin (e.g., a puncture wound caused by a soiled instrument)
The disease can be prevented by the administration of a vaccine; however, immunity must be kept current through booster doses
Why is tetanus referred to as "lockjaw"? (The organism that causes tetanus produces the severe muscle spasms and rigidity that give the disease its popular name of lockjaw.)
What is the best way to protect yourself against tetanus? (Immunization with the vaccine tetanus toxoid, which is a component of the DTP vaccine, with follow-up boosters every 10 years)

21. Syphilis
A sexually transmitted disease (STD) caused by Treponema pallidum pirochetes
Bacteria are quite fragile outside the body, but can cross-infect the dental operator through contact with oral lesions
First stage of syphilis is a painless ulcerating sore, known as a chancre, which is infectious on contact
The second stage is also infectious, and immediate infection may occur as a result of contact with an open sore
The third stage, known as latent syphilis, is usually fatal, and it may occur after the disease has been dormant for 20 years
How can one differentiate the first stage of syphilis from a herpes lesion? (When it occurs on the lip, it may resemble herpes, but the crusting is darker.)
An additional phase, which falls between the second and third stage, is called tertiary syphilis.
This phase occurs 3 to 10 years after the onset of primary syphilis.
Lesions appear as granulomatous nodules of the skin, mucosa, bone, and internal organs.
This phase of the disease is very destructive.

22. Examples of Syphilis A, Chancre on tongue seen in primary syphilis.
This painless ulcerated sore is also called a chancre.
The lesion is very infectious on contact.
Common oral sites include lips and tongue. Lesions on the gingiva and tonsillar area are not as common.
Lesions usually heal within 5 weeks of their first appearance.
Regional lymph nodes will also be enlarged.
B, Chancre on lip.
This primary lesion resembles herpes when it appears on the lip; however, the crusting is usually darker.
From Ibsen OAC, Phelan JA: Oral pathology for the dental hygienist, ed 6, Philadelphia, 2014, Saunders. A, Courtesy Dr. Norman Trieger; B, Courtesy Dr. Edward V. Zegarelli.

23. Methicillin-Resistant Staphylococcus aureus (MRSA)
A bacteria that is resistant to some antibiotics
This type of Staphylococcus aureus has evolved due to the excessive use of penicillin antibiotics over the years
MRSA infections can be on the surface of the skin or can go into the soft tissue and form a boil or an abscess
Staphylococcus aureus is a common bacterium that is carried on the skin or in the nose of healthy people.
It is estimated that 30% of people worldwide carry this bacteria, and most never develop symptoms or illness.
The infection is common in places where people are in close contact.

24. Prevention Tips for MRSA
Always maintain good hand hygiene practices
Never squeeze or try to drain any sore
Keep any wound covered until it has healed
Do not share personal items such as towels, razors, sheets, clothes
Experts say the key to dealing with MRSA is early diagnosis and then completion of a full course of antibiotic treatment.
The public needs to watch for wounds that do not heal and are not helped with normal antibiotic treatment.
Hand hygiene is the very best means to prevent the spread of MRSA and all other diseases.

25. Controlling Growth of Bacteria
Antibiotics
Chemicals that interfere with some metabolic activity of the bacteria without affecting our body cells
Bacteriostatic
Agents that prevent bacteria growth without killing them
Bactericidal
Agents that kill bacteria
Disinfectants
Strong chemicals used on inanimate objects to kill or reduce bacteria levels
Antiseptics
Chemicals used on tissues to kill bacteria

26. Fungi
Fungi are plants, such as mushrooms, yeasts, and molds that lack chlorophyll
Candida is a common yeast found in the oral cavity of about half of the population
It also is found in the gastrointestinal tract, female genital tract, and sometimes the skin
Cross-infection may occur between mother and baby or among infant siblings
The study of fungi is called mycology.
Fungi are eukaryotic microorganisms, as opposed to bacteria, which are known as prokaryotic.
Fungi exhibit two basic structural forms: yeast and mold.
What is the difference between the two fungi forms? (Yeast is unicellular and mold is multicellular.)

27. Oral Candidiasis Caused by the yeast Candida albicans
All forms of candidiasis are considered opportunistic infections; they are found in patients who are very young, very old, or very ill
Characterized by white membranes on the surface of the oral mucosa, tongue, and elsewhere in the oral cavity
Lesions may look like thin cottage cheese and can be wiped off to reveal a raw, red, and sometimes bleeding base
Candida albicans can also be found in the gastrointestinal tract, female genital tract, and sometimes the skin.
What is the common term for an oral candida infection? (Thrush)

28. Treatment of Oral Candiasis
Candida infections of the mouth and throat must be treated with prescription antifungal medication.
The type and duration of treatment depends on the severity of the infection and patient-specific factors such as age and immune status. Untreated infections can lead to a more serious form of invasive candidiasis.
Oral candidiasis usually responds to topical treatments such as clotrimazole troches and nystatin suspension (nystatin “swish and swallow”). Systemic antifungal medication such as fluconazole or itraconazole may be necessary for oropharyngeal infections that do not respond to these treatments.

29. Examples of Oral Candiasis
In patients infected with human immunodeficiency virus (HIV), candidiasis is virtually always mucocutaneous, involving the oropharynx, the esophagus, and the vagina.
HIV infection by itself is not associated with the syndrome of disseminated candidiasis, which is characterized by candidemia, endophthalmitis, and multiple organ involvement.
The precise immunologic processes that control candidal infection in HIV-infected patients are not known. However, mucocutaneous candidiasis is clearly related to the development of clinical cellular immunodeficiency. In fact, oropharyngeal candidiasis is an independent predictor of immunodeficiency in patients with acquired immunodeficiency syndrome (AIDS).
Edentulous patients should have regular soft tissue checks with a dentist to avoid an outbreak of candidiasis-associated denture stomatitis.
Properly fitting dentures and proper daily brushing of appliances and oral tissues will decrease the chance of an outbreak.
From Regezi JA, Sciubba JJ, Pogrel MA: Atlas of oral and maxillofacial pathology, St Louis, 2000, Saunders.

30. Who Gets Oral Candidiasis?
Oral thrush occurs most frequently among babies less than one month old, the elderly, and groups of people with weakened immune systems. Other factors associated with oral and esophageal candidiasis include:
HIV/AIDS
Cancer treatments
Organ transplantation
Diabetes
Corticosteroid use
Dentures
Broad-spectrum antibiotic use

31. Denture Related Candidiasis
Denture-related stomatitis (also termed denture sore mouth, denture stomatitis, chronic atrophic candidiasis, Candida-associated denture induced stomatitis, and denture-associated erythematous stomatitis) is a common condition where mild inflammation and redness of the oral mucous membrane occurs beneath a denture.

32. How Can I Prevent Oral Candidiasis?
Good oral hygiene practices may help to prevent oral thrush in people with weakened immune systems.
Some studies have shown that chlorhexidine (CHX) mouthwash can help to prevent oral candidiasis in people undergoing cancer treatment.
People who use inhaled corticosteroids (used to help treat asthma) may be able to reduce the risk of developing thrush by washing out the mouth with water or mouthwash after using an inhaler.

33. Viruses Much smaller than bacteria
Despite their tiny size, many viruses cause fatal diseases
New and increasingly destructive viruses are being discovered and have caused the creation of a special area within microbiology called virology
Viruses can live and multiply only inside an appropriate host cell
The host cells may be human, animal, plant, or bacterial
A virus invades a host cell, replicates (produces copies of itself), and then destroys the host cell so that the viruses are released into the body
What are some common characteristics of viruses?
(Not visible with a light microscope
Not capable of free growth
DNA and RNA not present together
Do not have a rigid cell wall
Not susceptible to penicillin or tetracycline
Metabolically inactive outside the cells of susceptible hosts)

34. Virus Specificity
Viruses can exhibit specificity (preference) for particular cell types in which to replicate.
For example, HIV infects cells known as CD4+ cells, whereas the hepatitis virus infects only liver cells.
Some other viruses are able to cause disease in more than one organ.
Unfortunately, some viruses can cross the placenta and infect the fetus.
What is an example of viral specificity? (For example, HIV infects cells known as CD4+ cells, whereas the hepatitis virus infects only liver cells.)
Viruses can cause severe acute oral and orofacial disease, may produce oral signs of systemic infection, and may be transmitted to patients and dental staff.

35. Virus Latency
Some viruses establish a latent (dormant) state in host cells
A latent virus can be reactivated in the future and produce more infective viral particles, followed by signs and symptoms of the disease
Stress, another viral infection, and exposure to ultraviolet light can reactivate the virus
HIV has a latency period of months to years
Hepatitis C is known to have a latency period of 15 to 25 years
What is another word for “latent” or “dormant”? (Suppressed)
Why are lengthy latent periods of concern to the dental team? (A patient may be infected but have no signs, symptoms, or knowledge that he or she has an infection.)

36. Treatment of Viral Diseases
Viruses cause many clinically significant diseases in human beings
General antibiotics are ineffective in preventing or curtailing viral infections, and even the few drugs that are effective against some specific viruses have limitations
Viruses are also capable of mutation
It is very difficult to develop vaccines against viruses because of the ability of viruses to change their genetic code
Most viral diseases are treated symptomatically. What does the term symptomatically mean in this context? (Treating the symptoms, not the infective cause)
Why are general antibiotics ineffective against viruses? (Antibiotics either kill or interfere with the metabolic processes of bacteria. Because viruses do not function in the same way as bacteria, antibiotics are not effective against them.)
Why is having the capability to mutate such a powerful defense for viruses? (Changing makes the viruses better suited to survive current conditions and resist efforts being made to kill them.)

37. Transmission of Viral Diseases
Viral diseases are transmitted by the following means:
Direct contact
Insects
Blood transfusions
Contaminated food or water
Inhalation of droplets expelled by coughing or sneezing
Viruses are transmitted from one host to another by way of inhalation through the respiratory tract, ingestion through the gastrointestinal tract, or inoculation through the skin or mucosa.
The ability of organisms to adhere to host surfaces is a prerequisite for the initiation of infection.
Viruses are completely devoid of organelles of transport and are easily spread throughout the body by way of numerous routes.

38. Viruses in the Environment
Viruses are easily destroyed in the external environment
Chemicals such as chlorine (bleach), iodine, phenol, and formaldehyde easily and effectively destroy viruses on surfaces and objects
These agents, however, are too toxic to be used internally
How long do viruses live on surface areas such as countertops in a dental treatment room? (Some viruses can live on countertops for as long as 6 hours. Most viruses cannot live outside the human body for long periods.)

39. Viral Diseases Viral hepatitis Hepatitis A virus (HAV)
There are at least six types of viral hepatitis, each of which is caused by a different virus:
Hepatitis A virus (HAV)
Hepatitis B virus (HBV)
Hepatitis C virus (HCV)
Hepatitis D virus (HDV)
Hepatitis E virus (HEV)
Hepatitis G virus (HGV)
What is viral hepatitis? (Hepatitis is an inflammation of the liver caused by a virus.)
In the United States, hepatitis A, hepatitis B, and hepatitis C are the most common types.

40. Hepatitis A (HAV) Can affect anyone
Spread from person to person when something is put in the mouth that has been contaminated with the stool of a person with hepatitis A (fecal-oral transmission)
Good personal hygiene and proper sanitation can also help prevent hepatitis A
Always wash your hands after changing a diaper or using the bathroom
The least serious form of viral hepatitis
A vaccine is available that provides long-term prevention in persons older than 2 years
HAV is a small virus belonging to the picornavirus group (which also includes poliovirus and coxsackievirus).
HAV is inactivated by ultraviolet light, by exposure to 100° C water for 5 minutes, and by exposure to 2% glutaraldehyde for 15 minutes.
What is the incubation period for HAV? (Between 2 and 7 weeks)

41. Bloodborne Pathogens
May infect different blood cells or other tissues of the body
Pathogens may exist or be released into the blood or other body fluids
Diseases of concern in dentistry are:
HBV, HCV and HIV
Diseases can be spread from one person to another by contact with the fluids
Body fluids (OPIM’s) include:
Semen
Vaginal secretion
Intestinal secretions
Tears
Mother’s milk
Synovial fluid (joints)
Pericardial fluid
Amniotic fluid
Saliva

42. Hepatitis B (HBV)
A very serious disease that may result in prolonged illness, liver cancer, cirrhosis of the liver, liver failure, and even death
Bloodborne disease that may also be transmitted by other body fluids, including saliva
Anyone who has ever had the disease, and some persons who have been exposed but have not been actually ill, may be carriers of HBV and may actually be spreading the infection to others
This presents a high risk for dental personnel because dental treatment brings them into contact with saliva and blood
What is the incubation period of HBV? (Between 1 and 6 months)
Types of carriers of HBV:
People with chronic persistent hepatitis, or “healthy carriers,” usually have no liver damage and are generally in good health.
People with chronic active hepatitis are extremely infectious because they harbor infectious particles in their blood.

43. Hepatitis B
It is a major health problem in the United States and is endemic in other parts of the world
Between 200,000 to 300,000 people are infected with the hepatitis B virus each year
Approximately 10,000 people require hospitalization
About 250 people will die of fulminant hepatitis
Approximately 15,000 will become chronic carriers
About 4,000 people die of hepatitis related cirrhosis of the liver and 800 from related liver cancer
CDC suggests that there are approximately 1 to million HBV carriers in the United States that have potential to spread the disease

44. Hepatitis B
A milliliter of blood from an infected person can contain as many as 100 million virus particles
A very small amount fluid can easily transmit the disease
Three important parts:
Surface antigen: HBsAg
2 inside antigens: HBcAg & HBeAg

45. Hepatitis B Carrier State
About 90% of those infected recover completely
Approximately 5-10% become carriers; ½ of them eliminate the disease from their bodies within 2 ½ years
The other ½ become chronic carriers
The carrier state is called: HBsAg-positive on at least two occasions when tested at least 2 months apart or being HBsAg positive and IgM anti-HBc negative at a single test
HBsAg positive have a great chance to spread the disease
HBeAg positive have very high concentration of the virus in their blood and are considered very infectious
Persons with chronic hepatitis have greater chance of later developing liver cancer

46. Spreading Hepatitis B Percutaneously Permucosally
Spreading through blood transfusion or blood products is rare because of testing
High risk activities that increase chance of exposure:
Sharing contaminated needles during intravenous drug abuse
Homosexual, bisexual or heterosexual behaviors with multiple partners
Injuries with sharp objects contaminated with blood or other body fluids
Exposure of non-intact skin or mucous membranes to blood or other body fluids

47. Symptoms of Hepatitis B
If they develop they begin 2 ½ - 6 months after exposure
About 1/3 show regular symptoms
Regular symptoms:
Yellowing of skin & whites of eyes (jaundice)
Light colored stools, Dark urine, Joint pain
Fever, Rash, Itching
Additional 1/3 show mild symptoms:
Malaise
Loss of appetite
Nausea
Abdominal pain
Additional 1/3 show no symptoms
Because many bloodborne diseases show little or no symptoms the person can still spread the disease
Standard and Universal Precautions must always be followed

48. Symptoms of Hepatitis B

49. Hepatitis B

50. Hepatitis B Immunization
Highly effective vaccine is available to prevent hepatitis B
All dental personnel with a chance of occupational exposure should be vaccinated against hepatitis B
The OSHA Bloodborne Pathogen Standard requires that the employer offer the hepatitis B vaccination, at no cost to the employee, within 10 days of initial assignment to a position in which there is chance of occupational exposure to blood or other body fluids
The employee has the right to refuse the offer of vaccination; however, that employee must sign a release form indicating that the employer did offer the vaccine and that the employee understands the potential risks of contracting hepatitis B
Who is at greater risk of contracting HBV in a dental setting, the dental staff or the patient? (The usual mode of transmission is from the patient to the dental operator.)
Where is the greatest intraoral concentration of HBV? (Because of continuous serum exudate, in the gingival sulcus)

51. Hepatitis B Vaccine Adult vaccine regimen consists of:
1 mL doses given at 0, 1, and 6 months
Injection given into deltoid muscle
Single antigen vaccines:
Recombivax HB (Merck & Co., Inc.)
Engerix-B (GlaxoSmithKline Biologicals)

52. Hepatitis B Vaccine Combination vaccines:
Twinrix: adults (HBsAg and inactive hepatitis A)
Comvax: infants and young children (hepatitis B and Haemophilus influenzae type b (HIB) )
Pediarix: infants and young children(hepatitis B, diphtheria. pertussis and tetanus
Postscreening for antibody level is recommended 1-2 months after 3 dose vaccination
Anti-HBsAg
If a person does not seroconvert they should have a 2nd series of three injections and then be retested
If still no seroconversion then test for HBsAg the presence of which would indicate a hepatitis B carrier state or current infection
One indication of chronic HBV is inability to produce defensive antibody

53. Hepatitis C (HCV)
Most efficiently transmitted through blood transfusion or percutaneous exposure to blood
Can occur as a result of an accidental needlestick injury to an employee in a dental office, through the sharing of contaminated needles among users of injection drugs, or through use of contaminated tattoo needles
The carrier rate for HCV is higher than that of HBV
No vaccine against hepatitis C at this time, nor is there a cure for the disease
Treatments available to control effects of the disease
Why is the use of standard precautions when dealing with all patients, especially those with a history of HCV infection, of the utmost importance? (Hepatitis C is caused by an enveloped RNA virus. The viral RNA can remain intact for at least 7 days at room temperature.)
What is the incubation period of HCV? (Two weeks to 26 weeks)
Possible oral manifestations of HCV include: lichen planus, oral malignancy, and salivary gland disease.

54. Hepatitis D (HDV)
HDV is a defective virus that cannot replicate itself without the presence of HBV.
Therefore, infection with HDV may occur simultaneously as a coinfection with HBV or may occur in an HBV carrier.
Persons with a coinfection of HBV and HDV often have more severe acute disease and a higher risk of death than do those infected with HBV alone.
Vaccination against HBV also prevents infection with HDV.
HDV is the smallest animal virus known.
What is the incubation period of HDV? (Between 2 and 12 weeks)

55. Hepatitis E (HEV) Not transmitted through bloodborne contact
Most frequently transmitted by way of the fecal- oral routes through contaminated food or water
HEV is most frequently seen in the form of an epidemic in developing countries
Transmission is not a major concern in a standard dental setting
Where are HEV outbreaks most common? (Hepatitis E outbreaks are common in Africa, Asia, and Latin America.)
HEV does not pose a major risk of cross-contamination in dentistry.

56. Human Immunodeficiency Virus
HIV is a bloodborne viral disease
An infection in which the body’s immune system breaks down
AIDS is caused by HIV
When HIV enters the body, it infects special T cells and slowly kills them
As more and more of the T cells die, the body’s ability to fight the infection weakens
A person with HIV infection may remain healthy for many years
AIDS is considered to have developed in an HIV-positive person when he or she becomes sick with serious illnesses and infections that can occur with HIV
T cells are responsible for supporting immunity.
HIV is spread by way of sexual contact with an infected person and by needle-sharing among drug users.
Before the advent of blood-donor screening, HIV was transmitted during transfusions of infected blood products.
HIV is destroyed easily by heat from an autoclave or hot-air oven.
The virus can survive for 15 days at room temperature and at body temperature.
Disinfectants, including 2% glutaraldehyde and hypochlorite, are effective in killing HIV on surfaces within a few minutes.

57. Human Immunodeficiency Virus
HIV is spread by sexual contact with an infected person and through needle sharing among drug users
Now that blood is screened for HIV antibodies, the blood supply in this country is safe
Babies born to HIV-infected mothers may become infected before or during birth or, after birth, while breastfeeding
In (nondental) healthcare settings, workers have been infected with HIV after being stuck with needles containing HIV-infected blood
In nondental healthcare settings, workers have also been infected (less frequently) when infected blood has gotten into a worker’s bloodstream through an open cut or been splashed onto a mucous membrane (e.g., eyes, the inside of the nose).
The virus can enter the body through the lining of the vagina, vulva, penis, rectum, or mouth.
The virus can also be transmitted in infected blood or other body fluids, such as breast milk.
Is saliva considered a body fluid that can transport HIV? (No)

58. Viruses in the Environment
Viruses are easily destroyed in the external environment.
Chemicals such as chlorine (bleach), iodine, phenol, and formaldehyde easily and effectively destroy viruses on surfaces and objects.
These agents, however, are too toxic to be used internally.

59. Herpesviruses
The herpesvirus is a double-stranded DNA virus that causes infection in human beings.
What are some common herpes infections? (Fever blisters and genital herpes are common infections.)
The herpesvirus may stay dormant for years, then become activated and cause disease.
There are two types of herpes simplex viruses. What are their names? (Herpes simplex virus type 1 [HSV 1] and herpes simplex virus type 2 [HSV 2])
Diseases caused by herpes simplex virus are either primary infections resulting from a first encounter with the virus or a reactive or recurrent infection resulting from activation of the latent virus.
Primary infections have an incubation period of 2 to 20 days.

60. Herpes Simplex Virus Type 1
A viral infection that causes recurrent sores on the lips
Because these sores frequently develop when the patient has a cold or fever of other origin, the lesions have become commonly known as fever blisters or cold sores
Type 1 herpes simplex primarily causes oral lesions.
Primary infectious lesions called primary gingivostomatitis are located on the lips and mouth.

61. Primary Herpes
This disease, which is highly contagious, makes its first appearance in very young children (1–3 years of age) and is known as primary herpes
Child may have a slight fever, pain in the mouth, increased salivation, bad breath, and a general feeling of illness
Inside of the mouth becomes swollen, and the gingivae are inflamed
Healing begins naturally within 3 days, and the illness is usually over in 7 to 14 days
Supportive measures can be taken to make the child more comfortable, relieve the pain, and prevent secondary infection
What are some supportive measures to take in patients infected with primary herpes? (Over-the-counter pain medication can be given to the child. Elimination of cross-contamination among family members—hand washing, no sharing of contaminated cups or utensils, and so on—should also be discussed.)

62. Recurrent Herpes Labialis
After the initial childhood infection, the HSV lies dormant and reappears later in life as the familiar recurring fever blister or cold sore
Recurrences tend to take place when the patient’s general resistance is lowered as a result of stress, fever, illness, injury, or exposure to the sun
The use of sunscreen with a sun protective factor of 15 helps to prevent sun-induced recurrences of herpes
Attacks may recur as infrequently as once a year or as often as weekly or even daily
Like primary herpes, recurrent herpes labialis sores heal by themselves in 7 to 10 days, leaving no scar.
About one third of patients who have had a primary infection experience herpes labialis in later life as a result of reactivation of the latent virus.
Lesions develop at the mucocutaneous junction of the lip or on the skin adjacent to the nostrils.

63. Herpes Labialis A, 12 hours after onset. B, 48 hours after onset.
Characteristically the lesions are preceded, some 24 hours before, by itching, prickling, or a burning sensation.
Blisters then develop, enlarge, coalesce, rupture, become encrusted, and heal within 10 to 14 days.
Intraoral recurrent herpetic infections are infrequent. They usually involve the hard palate, alveolar ridges, and gingiva.
From Ibsen OAC, Phelan JA: Oral pathology for the dental hygienist, ed 6, Philadelphia, 2014, Saunders.

64. Herpes Simplex Virus Type 2
Genital herpes is one of the most common sexually transmitted diseases in the United States
Initial symptoms: (generally appear 2 to 10 days after infection) tingling, itching, and a burning sensation during urination
Once a person is infected with the virus, outbreaks will recur
The disease can be transmitted only during these recurrences
A mother with active vaginal or cervical herpetic lesions at the time of delivery can pass the virus to her newborn
The lesions are vesicular and painful.
How likely is it a mother with active lesions will pass along the disease? What are some possible outcomes? (About 50% of such newborns will be infected as they pass through the birth canal. Of the infants infected, at least 85% will be severely damaged or killed by the virus.)

65. Other Herpes Viruses Herpes zoster virus (HHV3)
Causes both varicella (chickenpox) and herpes zoster (shingles)
Chickenpox is the primary infection, and zoster represents reactivation of the illness
Epstein-Barr virus (HHV4)
Responsible for infectious mononucleosis, nasopharyngeal carcinoma, lymphoma, and oral hairy leukoplakia
Cytomegalovirus (HHV5)
Can affect the fetus during pregnancy
Roseola (exanthema subitum) (HHV6)
Roseola occurs as a high fever and a skin rash in infants.
This virus also may cause infectious mononucleosis symptoms.
Human herpesvirus type 7
is isolated from saliva in as many as 70% to 80% of adults and children but has not yet been associated clearly with any particular disease state.
Human herpesvirus type 8
has been associated recently with Kaposi sarcoma
a condition seen in many AIDS patients.
Additional herpes-type viruses:
Herpes zoster virus (HSV type 3) causes both varicella (chickenpox) and herpes zoster, also known as shingles.
Cytomegalovirus (CMV) (HSV type 5) rarely causes disease unless factors such as a compromised immune system are present.
Epstein-Barr virus (HSV type 4) causes infectious mononucleosis, nasopharyngeal cancer, lymphoma, and oral hairy leukoplakia.

66. Herpes Transmission
Major transmission route for herpesvirus is through direct contact with lesions
Even when there are no active lesions, there is still the possibility of transmission of the virus through saliva or the aerosol spray from the dental handpiece
Because there is no preventive vaccine against herpes, it is essential that precautions be taken to prevent exposure
Protective eyewear is particularly important because a herpes infection in the eye may cause blindness
Gloves protect against infection through lesions or abrasions on the hands
The primary lesion is associated with fever and is more painful than the secondary lesions.
Why would asymptomatic secondary lesions pose an increased danger? (The spread of secondary lesions is more common because the infected person is unaware that a breakout is occurring.)

67. Herpetic Whitlow Herpetic whitlow—also called digital herpes simplex
finger herpes, or hand herpes—is a painful viral infection occurring on the fingers or around the fingernails.
Herpetic whitlow is caused by infection with the herpes simplex virus (HHSV).
DHCW must always wear proper PPE especially on hands to protect against exposure to HHSV 1.
Don’t treat patients when they have active cold sores; reschedule them for at least 2 weeks
Keep hands in good shape; no nail biting or skin biting

68. Enteroviruses Enteroviruses
It is a type of enterovirus; it is a virus that enters the body through the gastrointestinal tract and thrives there, often moving on to attack the nervous system. The polioviruses are enteroviruses.
Enteroviruses can be found in the respiratory secretions (for example, saliva, sputum, or nasal mucus) and stool of an infected person.
Other people may become infected by direct contact with secretions from an infected person or by contact with contaminated surfaces or objects, such as a drinking glass or telephone.
Infections caused by enteroviruses are most likely to occur during the summer and fall. Most people who are infected with an enterovirus have no disease at all. Infected people who become ill usually develop either mild upper respiratory symptoms (a "cold"), a flu-like illness with fever, and muscle aches, or an illness with rash.
In early fall 2014, an outbreak of infection with a non-polio enterovirus known as enterovirus D68, or EV-D68, sickened many children across multiple U.S. states, many of whom required care in a hospital intensive- care unit.
Enterovirus infections have been suspected to play some role in the development of type 1 diabetes, although they do not directly cause the condition. Newborns who become infected with an enterovirus may rarely develop an overwhelming infection of many organs, including the liver and heart, and die from the infection.

69. Hand, Foot & Mouth Disease
Herpangina: caused by the coxsackie virus
Breakout of ulcers in the posterior part of mouth and last about 1 week
Herpangina is associated with fever, sore throat, and blisters in the back of the mouth.
It is caused by a number of viruses, all part of the enterovirus family, coxsackie virus being the most common.
Most children develop a high fever and complain of a sore throat.

70. West Nile Virus
West Nile virus (WNV) is commonly found in Africa, West Asia, and the Middle East
Has likely been in the United States since the early summer of 1999
Virus is carried by mosquitoes and can infect human beings, birds, horses, and some other mammals
Affects a person’s nervous system, causing inflammation of the brain and spinal cord
Symptoms include fever, headache, tiredness, aches, and sometimes rash
Occurs primarily in the late summer or early fall
Why does WNV occur primarily in the late summer or early fall, or all year-round in the southern U.S.? (Answers will vary, but should include the idea that it is mosquito-borne, and therefore only occurs when mosquitoes are present.)
Symptoms may last for as little as a few days, though even healthy people have been sick for several weeks.
Approximately 80% of people (about four of five) who are infected with WNV will not show any symptoms at all.
WNV is not spread through casual contact.
People typically develop symptoms between 3 and 14 days after they are bitten by the infected mosquito.
People over the age of 50 years are more likely to experience serious symptoms of WNV if they do get sick and should take special care to avoid mosquito bites.

71. H1N1 Flu Virus (Swine Flu)
Not related to previous or current human seasonal influenza viruses
The new H1N1 virus spreads very easily from person to person
The most effective way to protect yourself is to receive the vaccine and practice meticulous hand hygiene
For additional resources, contact:
Describe how most seasonal flu viruses begin. (Most seasonal flu viruses start out infecting pigs in China. These viruses have the ability to infect humans as well as animals. As these viruses work their way around the world, scientists try to predict which are most likely to infect humans. Our vaccines are made of the three top picks, but usually there are about 60 different viruses going around during flu season. This is why you can receive the vaccine and still have the flu.)

72. Rickettsiae
Short, nonmovable rods that normally live in the intestinal tract of insects such as lice, fleas, ticks, and mosquitoes
Very small and require host cells to reproduce
Diseases caused by rickettsiae include typhus and Rocky Mountain spotted fever
Transmitted to humans by way of the bite of an infected insect
Rickettsiae are smaller than bacteria but resemble them structurally and metabolically.
The disease typhus is commonly seen in poor and malnourished individuals.
These bacteria have a round or coccus shape with a multilayered outer cell wall resembling that of Gram-negative bacteria.

73. Algae
Algae range from microscopic single-cell organisms to larger multiple-cell organisms such as seaweed and kelp
All algae contain chlorophyll, as well as pigments that cause them to appear yellow-green, brown, or red
Algae are found in abundance in both freshwater and marine habitats
Most algae do not produce human disease
Which common dental material is made from seaweed (algae)? (Alginate)

74. Protozoa A large group of single-cell organisms
Some can remain viable as cysts for long periods outside their hosts
Most do not cause disease, but some live in hosts and do cause damage
A small number of protozoa are responsible for intestinal infections in human beings; others invade the blood, lungs, liver, or brain
What type of protozoa live in the oral cavity? (Protozoa can live in the oral cavity as large, motile amoebae. The main species is Entamoeba gingivalis.)
Oral protozoa are often found in the periodontal tissues of patients who have just finished radiation therapy.

75. Prions Small proteinaceous infectious particles
They are composed entirely of proteins that lack nucleic acids (DNA or RNA)
Until the discovery of prions, it was believed that any agent capable of transmitting disease had to be made up of genetic material composed of nucleic acids
Prions convert normal protein molecules into dangerous ones simply by causing the normal ones to change their shape
Prions are a new and separate class, unlike bacteria, fungi, viruses, and all other known pathogens
Who discovered prions? (Dr. Stanley Prusiner)
Major characteristics of prions:
Neither viruses nor viroids
Contain no DNA or RNA
Can self-replicate
Have a long incubation period

76. Prion Diseases "Mad cow” disease
Linked to human diseases such as Creutzfeldt-Jacob disease (a rare form of dementia) and possibly Alzheimer’s disease
Prion-caused diseases have been found in human beings and animals
Highly resistant to heat, chemical agents, and irradiation
No treatment or vaccine against prion diseases, and the only preventive measure is not eating suspect food
The prion agent can be transmitted to cows, minks, cats, and mice when fed infected materials.
Prions first appear in the lymphoid tissue and then in brain cells.

77. Future Research on Prions
Ongoing research to determine whether prions that consist of other proteins play a part in more common neurodegenerative conditions such as Alzheimer’s disease, Parkinson’s disease, and amyotrophic lateral sclerosis
These three disorders have marked similarities
As with all prion diseases, these neuropathologic diseases occur sporadically but sometimes run in families
Much remains to be done in researching prions.

78. Pandemic Diseases A global disease outbreak
A pandemic occurs when a new virus or disease emerges for which people have little or no immunity, and for which no vaccine is available
In addition to illness and death, an especially severe influenza pandemic may cause severe disruption resulting from school and business closings and interruption of public transportation and food services
A pandemic is more likely if fewer people are vaccinated. This is why school districts often require children to be vaccinated prior to the school year.

79. Potential Dental Office Exposure
The amount of healthcare exposure has dropped drastically since improvement in infection control protocols
The greatest dental occupational exposures are:
Injuries from contaminated sharps
Needles, instrument punctures, cuts, bur lacerations
Blood and saliva contamination of cuts and cracks on skin on ungloved hands or hands with torn gloves
Spraying of blood or saliva onto open lesions on the skin or onto mucosa membranes