Download The Human Body in Health and Illness

Human Body
in Health and Illness
The
Barbara Herlihy
Chapter 5:
Microbiology Basics
Lesson 5.1 Objectives
• Define disease and infection.
• Describe the types of bacteria by shape and
staining characteristics.
• List the characteristics of the different types of
pathogens.
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2
Lesson 5.1 Objectives
(cont’d.)
• Define portals of exit and portals of entry.
• List common ways in which infections are
spread.
• Identify the microbiological principles described
in six germ-laden stories.
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Elsevier Inc.
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3
What is Disease?
• Disease: failure of the body to function normally
• Pathogens: disease-producing microorganisms
• Infection: invasion of the body by a pathogen
– Localized: restricted to a small area
– Systemic: more widespread; usually spread through
blood
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Elsevier Inc.
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4
Key Microbiological Terms
Term
Definition
Antibiotics
Chemicals used to treat bacterial
infections
Communicable
disease
Any disease that can be spread from one
host to another
Epidemic disease Disease acquired by many people in a
given area over a short period of time
Epidemiology
Study of occurrence and distribution of a
disease in a population
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Elsevier Inc.
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5
Key Microbiological Terms
(cont’d.)
Term
Definition
Incubation
period
Lapsed period of time from exposure to a
pathogen to the development of the
symptoms of the disease
Normal flora
Group of microorganisms that colonize a
host without causing disease
Nosocomial
infection
Reservoir of
infection
Hospital-acquired infection
Continual source of infection
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Elsevier Inc.
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6
Key Microbiological Terms
(cont’d.)
Term
Definition
Resistance
Ability to ward off disease
Sterilization
Process that destroys all living organisms
Vector
Carrier of pathogens from host to host
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7
Types of Pathogens
•
•
•
•
•
•
Bacteria
Viruses
Fungi
Protozoa
Worms
Arthropods
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8
Microorganisms (Microbes)
• Bacteria: single-celled organisms
– Have a cell wall, not just a cell membrane like
human cells
– Form spores to survive in harsh environments
• Normal flora: organisms that harmoniously live
in body without causing disease
• Pathogenic bacteria cause damage by:
– Entering and growing in cells
– Releasing toxins that damage cells
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9
Microorganisms (Microbes)
(cont’d.)
• Three shape groups of bacteria:
– Cocci (round): diplococci, streptococci, staphylococci
– Bacilli (rod-shaped)
– Curved rods: vibrios, spirilla, spirochetes
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10
Microorganisms (Microbes)
(cont’d.)
• Rickettsiae and chlamydiae
– Parasites classified with bacteria, but smaller
than bacteria
– Reproduce within living cells
• Viruses
– Smallest pathogens
– Formed of either RNA or DNA surrounded by
protein shell
– Reproduce within living cells
– Difficult to kill without damaging host’s cells
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Elsevier Inc.
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11
Microorganisms (Microbes)
(cont’d.)
• Fungi
– Plantlike organisms
– Pathogenic fungi cause mycotic infections
– Mycotic infections usually localized, but can
be systemic
• Protozoa
– Single-cell, animal-like organisms
– Types of protozoa: amebas, ciliates, flagellates, and
sporozoa
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Elsevier Inc.
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12
Multicellular Pathogens
• Parasitic worms (helminths)
– Includes roundworms, flatworms, and pinworms
– Usually transmitted by fecal-oral route: from feces
to mouth, usually carried by the hands
• Arthropods
– Some arthropods are ectoparasites: parasites
that live on the surface of the body and
mucous membranes
– Other arthropods can act as vector organisms
for pathogens
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Elsevier Inc.
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13
Identifying Pathogens
• Bacteria can be identified by staining with a dye:
– Gram stain
• Gram-positive (purple or blue)
• Gram-negative (pink or red)
– Acid-fast stain (retains red stain)
• Culture: pathogen sample collected and grown
in a medium in a laboratory
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14
The Spread of Infection
• Portals of entry: where pathogens enter
–
–
–
–
–
–
Respiratory tract
Gastrointestinal tract
Genitourinary tract
Eyes
Skin
Parenteral route
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Elsevier Inc.
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15
The Spread of Infection
(cont’d.)
• Portals of exit: how pathogens leave
–
–
–
–
–
–
Respiratory tract
Gastrointestinal tract
Genitourinary tract
Eyes
Skin
Breasts
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The Spread of Infection
(cont’d.)
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17
The Spread of Infection
(cont’d.)
• Pathogens spread through:
– Person-to-person contact, either directly or by way of
a contaminated object (fomite)
– Environment-to-person contact
– “Tiny animal”-to-person contact, either as part of the
life cycle (biological vector) or by contact (mechanical
vector)
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18
Six Germ-Laden Stories
• Dr. Semmelweis Screams “Wash Those Mitts!”
– Puerperal fever common in clinic
– Dr. Semmelweis’s observations led him to believe that
the infection was transmitted by particles
– Dr. Semmelweis began requiring handwashing, and
infection rate dropped
– Nosocomial infection: hospital-acquired infection
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19
Six Germ-Laden Stories
(cont’d.)
• Flora and Her Vaginal Itch
– Antibiotic prescribed for sinus infection
– Normal flora: microbes that inhabit an area without
causing harm
– Superinfection: an infection occurring during
treatment for another infection; normal flora are
disturbed, allowing an overgrowth of organisms
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20
Six Germ-Laden Stories
(cont’d.)
• Rick, Nick, and the Sick Tick
– Tick carrying Rickettsia rickettsii transferred
pathogen to Rick
– Host: organism infected with a pathogen
– Animal vector: organism that transmits a pathogen
– Arthropod: class of tiny animals with jointed legs
– Rick treated with an antibiotic for Rocky Mountain
Spotted Fever (RMSF)
– Rick’s friend Nick didn’t get sick because RMSF is
communicable but not contagious
– Zoonosis: animal disease transmissible to humans
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21
Six Germ-Laden Stories
(cont’d.)
• Why Typhoid Mary Needed to Lose
Her Gallbladder
– Cook infected with Salmonella typhi unknowingly
caused typhoid outbreak
– Carrier: person or animal that shows no symptoms
of a disease but harbors the infectious agent of
that disease and transmits it to others
– Typhoid carriers harbor S. typhi in bile of gallbladder
– Only way to end carrier status is to remove
gallbladder
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22
Six Germ-Laden Stories
(cont’d.)
• A Pox News Alert!
– Pox: disease that causes skin lesions
– Pox diseases are not limited geographically or to
humans
– Chickenpox: disease of children caused by VaricellaZoster (a herpes virus)
– Some people believe the chickenpox vaccine is unsafe
and deliberately expose children to the virus
– Great Pox: a name for syphilis, which is not a pox
(lesion)
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23
Six Germ-Laden Stories
(cont’d.)
• The Chief of Staph Reports . . .
– Staphylococcus-induced skin conditions include
impetigo, boils, and Scalded Skin Syndrome
– Antibiotic-resistant strains of staph are on the rise
– Staphylococcus aureus: gram (+) strain that causes
gold-colored exudate
– MRSA (methicillin-resistant S. aureus): a major cause
of resistant nosocomial infection
– Vancomycin-resistant strains have also appeared
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