Chapter 5: Microbiology Basics Chapter 5: Microbiology Basics.

TheHuman Bodyin Healthand Illness

Barbara Herlihy

Chapter 5: Microbiology Basics

Chapter 5: Microbiology Basics

Copyright © 2007 by Saunders, an imprint of Elsevier Inc.

All rights reserved.

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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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• 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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• 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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• 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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• 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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• 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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• 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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• 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

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Chapter 5: Microbiology Basics Chapter 5: Microbiology Basics.

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