TheHuman Bodyin Healthand Illness
Barbara Herlihy
Chapter 5: Microbiology Basics
Chapter 5: Microbiology Basics
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2
Lesson 5.1 ObjectivesLesson 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.
• 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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Lesson 5.1 Objectives (cont’d.)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.
• 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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What is Disease?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
• 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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Key Microbiological TermsKey Microbiological Terms
Term Definition
AntibioticsAntibiotics Chemicals used to treat bacterial Chemicals used to treat bacterial infectionsinfections
Communicable Communicable diseasedisease
Any disease that can be spread from Any disease that can be spread from one host to anotherone host to another
Epidemic Epidemic diseasedisease
Disease acquired by many people in Disease acquired by many people in a given area over a short period of a given area over a short period of timetime
EpidemiologyEpidemiology Study of occurrence and distribution Study of occurrence and distribution of a disease in a populationof a disease in a population
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Key Microbiological Terms (cont’d.)Key Microbiological Terms (cont’d.)
Term Definition
Incubation Incubation periodperiod
Lapsed period of time from exposure Lapsed period of time from exposure to a pathogen to the development of to a pathogen to the development of the symptoms of the diseasethe symptoms of the disease
Normal floraNormal flora Group of microorganisms that Group of microorganisms that colonize a host without causing colonize a host without causing diseasedisease
Nosocomial Nosocomial infectioninfection
Hospital-acquired infectionHospital-acquired infection
Reservoir of Reservoir of infectioninfection
Continual source of infectionContinual source of infection
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Key Microbiological Terms (cont’d.)Key Microbiological Terms (cont’d.)
Term Definition
ResistanceResistance Ability to ward off diseaseAbility to ward off disease
SterilizationSterilization Process that destroys all living Process that destroys all living organismsorganisms
VectorVector Carrier of pathogens from host to Carrier of pathogens from host to hosthost
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Types of PathogensTypes of Pathogens
• Bacteria• Viruses• Fungi• Protozoa• Worms• Arthropods
• Bacteria• Viruses• Fungi• Protozoa• Worms• Arthropods
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Microorganisms (Microbes)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
• 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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Microorganisms (Microbes) (cont’d.)Microorganisms (Microbes) (cont’d.)
• Three shape groups of bacteria:– Cocci (round): diplococci, streptococci,
staphylococci– Bacilli (rod-shaped)– Curved rods: vibrios, spirilla, spirochetes
• Three shape groups of bacteria:– Cocci (round): diplococci, streptococci,
staphylococci– Bacilli (rod-shaped)– Curved rods: vibrios, spirilla, spirochetes
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Microorganisms (Microbes) (cont’d.)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
• 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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Microorganisms (Microbes) (cont’d.)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
• 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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Multicellular PathogensMulticellular Pathogens
• Parasitic worms (helminths)– Includes roundworms, flatworms, and pinworms– Usually transmitted by fecal-oral route: from
fecesto mouth, usually carried by the hands
• Arthropods– Some arthropods are ectoparasites: parasites
that live on the surface of the body andmucous membranes
– Other arthropods can act as vector organismsfor pathogens
• Parasitic worms (helminths)– Includes roundworms, flatworms, and pinworms– Usually transmitted by fecal-oral route: from
fecesto mouth, usually carried by the hands
• Arthropods– Some arthropods are ectoparasites: parasites
that live on the surface of the body andmucous membranes
– Other arthropods can act as vector organismsfor pathogens
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Identifying PathogensIdentifying 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
• 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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The Spread of InfectionThe Spread of Infection
• Portals of entry: where pathogens enter– Respiratory tract– Gastrointestinal tract– Genitourinary tract– Eyes– Skin– Parenteral route
• Portals of entry: where pathogens enter– Respiratory tract– Gastrointestinal tract– Genitourinary tract– Eyes– Skin– Parenteral route
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The Spread of Infection (cont’d.)The Spread of Infection (cont’d.)
• Portals of exit: how pathogens leave– Respiratory tract– Gastrointestinal tract– Genitourinary tract– Eyes– Skin– Breasts
• 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.)The Spread of Infection (cont’d.)
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The Spread of Infection (cont’d.)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)
• 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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Six Germ-Laden StoriesSix 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
• 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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Six Germ-Laden Stories (cont’d.)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
• 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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Six Germ-Laden Stories (cont’d.)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
• 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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Six Germ-Laden Stories (cont’d.)Six Germ-Laden Stories (cont’d.)
• Why Typhoid Mary Needed to LoseHer 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 ofthat 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
• Why Typhoid Mary Needed to LoseHer 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 ofthat 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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Six Germ-Laden Stories (cont’d.)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
Varicella-Zoster (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)
• 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
Varicella-Zoster (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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Six Germ-Laden Stories (cont’d.)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
• 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