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CHAPTER
32
Principles of
Asepsis
© 2011 The McGraw-Hill Companies, Inc. All rights reserved.
32-2
Learning Outcomes
32.1 Explain the historical background of
infectious disease prevention.
32.2 Identify the types of microorganisms that
cause disease.
32.3 List some infectious diseases, and identify
their signs and symptoms.
32.4 Discuss the importance of preventing
antibiotic resistance in a health-care setting.
32.5 Describe ways you can help prevent
antibiotic resistance in health-care settings.
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32-3
Learning Outcomes (cont.)
32.6 Explain the disease process.
32.7 Explain how the body’s defenses protect
against infection.
32.8 Describe the cycle of infection.
32.9 Identify and describe the various methods of
disease transmission.
32.10Explain how you can help break the cycle of
infection.
© 2011 The McGraw-Hill Companies, Inc. All rights reserved.
32-4
Introduction
Our bodies are amazing
structures that defend us
against infections under
normal circumstances
You will learn about:
– Disease-causing
microorganisms
– How the body fights
disease
– Ways infections occur
– Antibiotic-resistant
organisms
– Importance of patient
education on the proper
use of antibiotics
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32-5
History of Infectious Disease Prevention
• Throughout history
people have
attempted to discover
– Causes of infection
– How to prevent
infections
– How to treat infections
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32-6
History of Infectious Disease Prevention
(cont.)
Scientist
Contribution
Edward Jenner (1749–1823)
• Developed first effective
vaccine
• Used cowpox to vaccinate
against smallpox
Ignaz Semmelweis (1818–1865)
and Oliver Wendell Holmes (1809–
1894)
• Promoted handwashing as a
means of reducing the spread
of puerperal fever to women in
childbirth
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History of Infectious Disease Prevention
(cont.)
Scientist
Contribution
Louis Pasteur (1822–1895)
• Helped develop the germ
theory of infectious disease,
stating that disease is
caused by microorganisms
Joseph Lister (1827–1912)
•
•
Helped develop germ theory
Introduced aseptic techniques
through the use of antiseptics
on wounds, surgical sites, and
surgical instruments
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History of Infectious Disease Prevention
(cont.)
Scientist
Contribution
Robert Koch (1843–1910)
• Developed a set of proofs,
known as Koch’s postulates,
claiming that microbes cause
disease
Sir Alexander Fleming
(1881–1955)
•
Discovered penicillin
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32-9
History of Infectious Disease Prevention
(cont.)
• Remarkable advances in the past century
• Threat of infection still present
– New infectious diseases
• AIDS
• Ebola
– Resistant diseases
• MRSA
• VRSA
• Multidrug-resistant TB
© 2011 The McGraw-Hill Companies, Inc. All rights reserved.
32-10
Apply Your Knowledge
Why is the threat of infection still present even
though great advances have been made in
controlling infections over the past century?
ANSWER: The threat of infection is still present because
of new diseases and diseases that have become
resistant to treatments.
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32-11
Microorganisms and Disease
• Microorganisms live all around us
• Pathogens
– Microorganisms capable of causing disease
– Evade host defenses
• People avoid infections most of the time
– Many microorganisms are beneficial or harmless
– Normal defenses resist infection
– Conditions are not favorable for pathogens to grow
and be transmitted
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Microorganisms and Disease (cont.)
Classification
Prions*
Characteristics
• Infectious particle
made of protein
Example
Pr P
Disease
• No nucleic acid
CreutzfeldtJakob
disease
• Reproduction
unknown
Mad cow
disease
* Experts disagree as to whether prions are directly responsible
for disease or merely aid an unknown agent in causing disease.
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32-13
Microorganisms and Disease (cont.)
Classification
Viruses
Bacteria
Characteristics
• DNA or RNA
surrounded by protein
coat
• Reproduced in living
cells
• Very small
• Single-celled
• Reproduce quickly
• Mostly asexual
reproduction
Example
Disease
Varicellazoster virus
Chickenpox
Vibrio
cholerae
Cholera
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Microorganisms and Disease (cont.)
Classification
Characteristics
Example
Disease
Protozoans
•
•
Single-celled
Reproduction
mostly asexual
Entamoeba
histolytica
Amebic
dysentery
Fungi
•
•
Multicellular
Reproduction is
sexual and asexual
Candida
albicans
Candidiasis
Helminths
• Multicellular
parasitic
• Contain specialized
organs
• Sexual reproduction
Enterobius
vermicularis
Pinworms
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Apply Your Knowledge
In many cases, we avoid contracting infections when
exposed to microorganisms. What are the reasons for
this?
ANSWER: This is because:
 many microorganisms are beneficial or harmless
 we have normal defenses to resist infection
 conditions are not favorable for the pathogen to grow
and be transmitted.
Correct!
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Infectious Diseases
• Knowing signs and
symptoms of common
infectious diseases
can help protect
against exposure
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Infectious Diseases (cont.)
Chickenpox
(Varicella)
• Contagious viral infection
• Incubation period of 7 to 21 days
• Itchy rash  fluid-filled blisters
• Slight fever, headache, general malaise
• Spread by direct, indirect, droplet, or
airborne transmission
• Isolate until all blisters have scabbed over
• 1996 – live vaccine approved
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Infectious Diseases (cont.)
Common
cold
•
•
•
Viral infections of upper respiratory tract
No isolation needed
Commonsense precautions to prevent
spread
–
–
–
•
Use tissues when coughing or sneezing
Wash hands frequently
Use disposable dishware, if possible
Incubation – 2 to 3 days
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Infectious Diseases (cont.)
Croup
• Most often caused by a virus
• Characterized by a harsh, barking cough,
difficulty breathing, hoarseness, and lowgrade fever
• Most common in infants and young children
• Symptoms lessened by humidification of air,
rest, and clear fluids
• Commonsense precautions to prevent
spread
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Infectious Diseases (cont.)
Diphtheria
• Bacterial infection of nose, throat, and
larynx
• Symptoms: pain, fever, respiratory
obstruction
• Incubation – 2 to 5 days
• Isolation required
• Antibiotic therapy (fatal if untreated)
• Immunization available
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Infectious Diseases (cont.)
Epstein-Barr
Virus
• Common human virus
• 95% of adults have had virus
– 35 – 50% of teens develop mononucleosis
• Symptoms – fever, sore throat, swollen
lymph nodes
• Virus remains dormant for life
• Occasionally reactivates as tumors
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Infectious Diseases (cont.)
Haemophilus
Influenzae
Type B
• Bacterial infections in infants and young
children
• Spread – direct, indirect, and droplet
transmission
• Incubation – 3 days
• Upper respiratory symptoms, fever,
drowsiness, body aches, diminished
appetite
•
Monitor closely – bacterial meningitis
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Infectious Diseases (cont.)
Hepatitis
• Viral infection of liver
• Spread through blood or fecal-oral route
HIV/AIDS
• Human immunodeficiency virus
• Acquired immune deficiency syndrome
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Infectious Diseases (cont.)
Influenza
(Flu)
• Symptoms – fever, chills, headaches,
body aches, upper respiratory congestion
• Isolation and commonsense precautions
• Vaccines
– Live, attenuated virus – nasal spray
– Inactivated virus – IM injection
• Annual vaccination
– People at risk for complications
• People older than 50 years old
• People in close contact with persons at
risk for complications
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Infectious Diseases (cont.)
Measles
(Rubeola)
• Infectious viral disease
• Spread by droplets or direct transmission
• Initial symptom of fever develops 8 to 13
days after exposure, followed by a
characteristic itchy rash 14 days after
exposure
• Isolation for 7 days after rash appears
• Keep children under 3 years old away
from anyone with the disease
• Reportable to state or county health dept.
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Infectious Diseases (cont.)
Meningitis
• Inflammation and infection of protective
coverings of brain and spinal cord and
the fluids around them
• Viral – milder form
– Clears in 1 to 2 weeks without treatment
– Aseptic meningitis
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Infectious Diseases (cont.)
Meningitis
• Bacterial – serious, life-threatening,
requiring immediate treatment
– Vaccination available for people in high-risk
groups
– Symptoms – red, blotchy rash, confusion,
delirium, light sensitivity, headache, fever and
chills, nausea and vomiting, sleepiness, stiff neck
– May spread through exchange of respiratory and
throat secretions
– Reportable to state or county health dept.
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32-28
Infectious Diseases (cont.)
Mumps
• Viral infection
– Primarily affects salivary glands
• Incubation – 2 to 3 weeks
• Pain related to inflammation of parotid
gland and fever
• Isolate until glandular swelling stops
• Reportable to state or county health
dept.
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32-29
Infectious Diseases (cont.)
Pertussis
(Whooping
Cough)
• Highly contagious bacterial infection of
respiratory tract
• Symptoms – fever, sneezing, runny nose,
quick short coughs, characteristic “whoop”
during inhaled breath following coughing fit
• Isolate for 3 weeks following onset of
spasmodic coughs
• Reportable to state or county health dept.
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32-30
Infectious Diseases (cont.)
Roseola
• Rose-colored rash possibly caused by human
herpes virus
• Infants and young children
• Incubation 5 to 15 days
• Symptoms – sudden, high fever; sore throat;
swollen lymph nodes; rash
Rubella (German •
Measles)
•
•
•
•
•
Highly contagious viral disease
Direct or droplet transmission
Incubation 16 to 18 days
Symptoms – fever and itchy rash
Vaccination available
Reportable
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32-31
Infectious Diseases (cont.)
Streptococcal
pharyngitis
(strep throat)
• Bacterial infection of throat
– Sore throat, swelling of pharyngeal
mucosa, fever, headache, nausea,
abdominal pain
– Treat with antibiotics
• Scarlet fever
– Bacteria becomes systemic
– Characteristic “strawberry rash”
– Incubation 7 to 10 days
– Isolate 7 days
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32-32
Infectious Diseases (cont.)
Streptococcal
pharyngitis
(cont.)
• Rheumatic fever
– Occurs after apparent recovery from strep throat
– Autoimmune disorder – antibodies to
streptococci cross-react with heart tissues
– Symptoms – carditis, ECG changes, joint pain and
inflammation, fever
• Acute post-streptococcal glomerulonephritis
– Inflammation of glomerulus of the kidney resulting
in inadequate filtering of the blood
– Symptoms – swelling of hands and feet,
decreased urine output, hypertension, protein in
urine
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32-33
Infectious Diseases (cont.)
Tetanus
• Acute infectious bacterial disease
following a contaminated puncture wound
• Incubation – 3 to 21 days
• Late symptoms – lockjaw, paralysis
• No isolation needed, but reportable
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32-34
Infectious Diseases (cont.)
Tuberculosis
• Infectious bacterial disease affecting mainly
lungs
• Symptoms – night sweats, productive cough,
fever, chills, fatigue, unexplained weight loss,
diminished appetite, bloody sputum
• Incidence – higher in urban centers
• Transmission
– Mycobacterium tuberculosis
– Droplet
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32-35
Infectious Diseases (cont.)
Tuberculosis
(cont.)
• Increasing resistance to TB
– Early diagnosis, prompt treatment
– Compliance with treatment regimen
• Preventing TB
– Vaccination – BCG (not used in the U.S.)
– Causes false-positive with TB skin test
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32-36
Infectious Diseases (cont.)
Tuberculosis
(cont.)
• Treating TB
– Mantoux TB test
• Positive test = Induration – skin turns red and
becomes raised and hard
• Positive result from immunization or exposure
to TB bacteria
– Treatment based on area affected and type
of TB involved
– Patients must complete entire course of
treatment – 12 to 18 months on medication
– Isolation
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32-37
Preventing the Spread of TB
• Containment of the tuberculosis bacteria
• Patient measures
• Office measures
– Covering mouth
– Proper disposal of
tissues
– Take medication as
directed
– Avoid close contact
with others
– Air out their room
– Use negative pressure
area
– Use personal respirator
– Apply standard
sanitization, disinfection,
and sterilization
techniques
© 2011 The McGraw-Hill Companies, Inc. All rights reserved.
32-38
Apply Your Knowledge
How can the spread of many infectious diseases
can be limited or prevented?
ANSWER: The spread of many infectious diseases can be
limited or prevented by using commonsense precautions:
 Using tissues when coughing or sneezing
 Washing hands frequently
 Using disposable dishware
Excellent!
© 2011 The McGraw-Hill Companies, Inc. All rights reserved.
32-39
Drug-Resistant Microorganisms
• MRSA – methicillin/oxacillin-resistant S. aureus
• VRE – vancomycin-resistant enterococci
• VISA – vancomycin-intermediate S. aureus
• VRSA – vancomycin-resistant S. aureus
• ESBLS – extended-spectrum beta-lactamases
• PRSP – penicillin-resistant Streptococcus
pneumoniae
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32-40
Drug-Resistant Microorganisms (cont.)
• MRSA and VRE
– Most common in non-hospital health-care facilities
• Community-associated MRSA
– Increasing in incidence
• PRSP
– Common in patients seeking care in physicians’
offices and clinics (pediatrics)
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32-41
Drug-Resistant Microorganisms (cont.)
• Risk factors for development of infections
by drug-resistant organisms
– Advanced age
– Invasive procedures
– Prior use of antibiotics
– Repeated contact with health-care system
– Severity of illness
– Underlying diseases or conditions
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32-42
Preventing Antibiotic Resistance
• Four strategies to reduce incidence of
antibiotic-resistant microorganisms
– Prevent infection
– Diagnose and treat infection
appropriately
– Use antibiotics carefully
– Prevent transmission of
infections
© 2011 The McGraw-Hill Companies, Inc. All rights reserved.
32-43
Apply Your Knowledge
What strategies reduce the incidence of antibioticresistant microorganisms?
ANSWER: Strategies to reduce the incidence of
antibiotic-resistant microorganisms include:
 Prevent infections
 Diagnose and treat infections appropriately
 Use antibiotics carefully
 Prevent transmission
Good
Job!
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32-44
Disease Process
•
Begins with
microorganisms finding
host
• Virulence –
microorganism’s diseaseproducing power
•
Grows with specific
requirements
• Damage is caused by:
– Proper temperature
– Depleting nutrients
– pH
– Reproducing themselves
– Moisture level
– Making body cells the
target of body’s own
defenses
– Producing toxins
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32-45
Disease Process (cont.)
• Once exposed to a pathogen, the body goes
through 4 stages of illness:
– Incubation – begins at first exposure; ends when first
symptom appears
– Prodromal – begins at first onset of symptoms;
generally short
– Invasion – numbers of organisms are greatest;
symptoms are most pronounced
– Convalescent – patient regains normal health status
© 2011 The McGraw-Hill Companies, Inc. All rights reserved.
32-46
Apply Your Knowledge
What are the four stages of illness?
ANSWER: The four stages of illness are:
 Incubation – begins at first exposure; ends when first
symptom appears
 Prodromal – begins at first onset of symptoms; generally
short
 Invasion – numbers of organisms are greatest;
symptoms are most pronounced
 Convalescent – patient regains normal health status
© 2011 The McGraw-Hill Companies, Inc. All rights reserved.
32-47
The Body’s Defenses
•
Immunity – condition
of being resistant to
pathogens and the
disease they cause
•
First lines of defense








Skin
Sweat glands
Mucous membranes
Cilia
Lacrimal glands
Saliva
Hydrochloric acid
Lysozyme
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32-48
The Body’s Defenses (cont.)
• Resident normal flora – microorganisms found
in the body
– Provide a barrier against pathogens
– Normally live in balance
– Become pathogenic when host’s defenses are
compromised
• Opportunistic infections
– Infections occurring when a host’s resistance is low
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32-49
Nonspecific Defenses
• Inflammation
– Signs
•
•
•
•
Redness
Localized heat
Swelling
Pain
– Purpose
• Summon immunologic
agents to site
• Begin tissue repair
• Destroy invading
microorganisms
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32-50
Nonspecific Defenses (cont.)
– Steps of inflammation
1.Initial constriction, then dilation of blood vessels,
causing redness and heat
2.Fluid leakage from local vessels  swelling
3.Scar tissue formation
– Chronic inflammation
• Damage to tissues
• Loss of function
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32-51
Nonspecific Defenses (cont.)
• Phagocytosis
– White blood cells (phagocytes)
engulf and digest pathogens
– Three types
• Neutrophils – found in pus
• Monocytes – formed in bone marrow and
become
• Macrophages when they migrate to specific
tissues
– Found in lymph nodes, liver, spleen, lungs, bone marrow,
and connective tissue
– Deliver antigens (foreign substances) to lymphocytes
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32-52
Humoral Immunity
• Lymphocytes – B cells and T cells
– T cells activate B cells to produce antibodies
to neutralize an antigen
– Memory B cells respond quickly to produce
antibodies in later invasions
– Specific antibodies are produced in response
to specific antigens
– Antibodies attract phagocytes, which destroy
antigens
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32-53
Humoral Immunity (cont.)
• Types of immunity
– Active – body produces own antibodies
• Natural active
• Artificial active
– Passive – antibodies that are produced
outside body enter the body
• Natural passive
• Artificial passive
• Complement
– Proteins activated by antibodies
– Helps white blood cells destroy pathogens
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32-54
Cell-Mediated Immunity
• T cells attack invading pathogen directly
– Helper T cells
• Activate
– Killer T cells
• Bind with antigen and kill it
– Suppressor T cells
• Slow down or stop attack after antigen is destroyed
– Memory T cells
• Respond quickly to another attack by same
antigen
© 2011 The McGraw-Hill Companies, Inc. All rights reserved.
32-55
Apply Your Knowledge
What is the difference between active and passive
immunity?
ANSWER: Active immunity is long-term immunity in which
the body produces its own antibodies.
Passive immunity results when antibodies produced
outside the body enter the body.
Both can be natural or artificial.
Impressive!
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32-56
Cycle of Infection
• A reservoir host – animal, insect, or
human body capable of sustaining
pathogen growth
– Carrier – unaware of presence of pathogen
– Subclinical case – unnoticeable infection
– Endogenous infection – normally harmless
microorganisms become pathogenic
– Exogenous infection – pathogen introduced
into the body
Click for Cycle
of Infection
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32-57
Cycle of Infection (cont.)
• Means of exit – how the pathogen
leaves the host
– Nose, mouth, eyes, or ears
– Feces or urine
– Semen, vaginal fluid, or other
reproductive discharge
– Blood or blood products
Click for Cycle
of Infection
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32-58
Cycle of Infection (cont.)
• Means of transmission – how a pathogen
spreads to a host
–
–
–
–
–
Airborne
– Touching
• Direct
Blood-borne
• Indirect through
During pregnancy or birth
fomites
Foodborne
– Inanimate reservoir
of pathogens
Vector-borne
• Living organism that
carries microorganisms
to another person
– Drinking glass, door
knob, etc.
Click for Cycle
of Infection
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32-59
Cycle of Infection (cont.)
•
Means of entrance
– Enter through any
cavity lined with
mucous membrane
• Mouth, nose, vagina,
rectum
• Ears, eyes, intestinal
tract, urinary tract,
reproductive tract,
breaks in the skin
Click for Cycle
of Infection
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32-60
Cycle of Infection (cont.)

Susceptible host

Individual with little or no
immunity to infection by a
pathogen

Host factors influencing
susceptibility







Age
Genetic predisposition
Nutritional status
Other disease processes
Stress levels
Hygiene habits
General health
– Pathogen factors
• Number and
concentration
• Virulence
• Point of entry
Click for Cycle
of Infection
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Cycle of Infection (cont.)
Back
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32-62
Cycle of Infection (cont.)
• Environmental factors
– Dense populations
– Animals – unpasteurized
milk
– Insects
– Economic and political
factors
– Availability of
transportation
– Population growth rates
– Sexual behavior
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32-63
Breaking the Cycle
•
Asepsis – condition in
which pathogens are
absent or controlled
 Maintain strict
housekeeping standards
 Adhere to government
guidelines to protect
against disease
 Educate patients in
hygiene, health
promotion, and disease
prevention
© 2011 The McGraw-Hill Companies, Inc. All rights reserved.
32-64
Apply Your Knowledge
What are fomites?
ANSWER: Fomites are inanimate objects such as clothing,
water, and food that serve as a means of transportation for
microorganisms.
Nice Job!
© 2011 The McGraw-Hill Companies, Inc. All rights reserved.
32-65
In Summary
32.1 Infection control has been a problem throughout
history. Though there have been many advances,
controlling infection continues to be a challenge for
doctors.
32.2 There is great variety in the types of pathogenic
organisms. Types of potentially infectious
microorganisms include prions, viruses, bacteria,
protozoans, fungi, and helminths.
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In Summary (cont.)
32.3 It is important to be familiar with the diseases that
infect people so that you can protect your patients,
coworkers, and yourself. These diseases include but
are not limited to chickenpox, croup, diphtheria,
hepatitis, influenza, measles, mumps, and polio.
32.4 Antibiotic resistance of microbial pathogens is a
growing problem. The number of infections for which
there is little or no treatment is increasing. It is the
responsibility of health-care workers to use antibiotics
wisely.
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In Summary (cont.)
32.5 The CDC began a campaign to prevent antimicrobial
resistance. There are four strategies outlined in the
campaign: 1) prevent infection; 2) diagnose and treat
infection appropriately; 3) use antibiotics carefully;
and 4) prevent transmission of infections.
32.6 There are numerous human pathogens. These
pathogens cause disease by damaging the body in a
number of ways including depleting nutrients needed
by cells, reproducing themselves within body cells,
making body cells the targets of the body’s own
defenses, and producing toxins that damage cells and
tissues.
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32-68
In Summary (cont.)
32.7 The body is able to protect itself from disease through
the use of several lines of defense. These lines of
defense may be nonspecific or specific.
32.8 In order for an infection to occur, five elements must
be in place. There must be a reservoir host, a means
of exit, a means of transmission, a means of
entrance, and a susceptible host.
32.9 Direct disease transmission occurs when the
pathogen moves immediately from one host to
another. Indirect transmission is possible only if the
pathogen is able to survive outside the host for some
period of time.
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32-69
End of Chapter 32
In today's world, new infections
and diseases can spread across
the country and even across the
world in a matter of days, or
even hours, making early
detection critical.
~ John Linder
Member of the U.S. House of
Representatives,
Georgia
© 2011 The McGraw-Hill Companies, Inc. All rights reserved.