chpater 13: microbe-human interactions

What happens when you are exposed to microbes

You either fight it off, learn to live with bacteria, or die

Microbiota

Normal inhabitant, typically dont cause disease (mutual/ commensal relationships)

Pathogens

Not normally found in/on body. Cause disease (parasitic relationship)

Urine in your bladder should be

Sterile but not when it comes out

Microbiota include

Bacteria, fungi, protozoan, animals, viruses

A fetus is what prior to birth

Fetus is a sterile tissue

What happens after birth

Pick up all types of batceria and microbiota

Microbiota is typically very stable, changing only when the body changes like

• first solid food

• Eruption of teeth

• Puberty/ menopause

• Long term antibiotic therapy

Microbiota only found in SKIN in upper epidermis, glands, and follicles

• staphylococcus

• Streptococcus

• Micrococcus

• Propionibacterium

• Fungi

• Arthropods

Gastrointestinal tract : mouth- very diverse environment

• Streptococcus

• S. Mutants

• S. Sanguinis

Gastrointestinal tract: esophagus/ stomach/ small intestine

Little microbiota

Gastrointestinal tract: large intestine - obligate anaerobes

Clostridium

Gastrointestinal tract: large intestine - facultative anaerobes

E. Coli

Where are microbiota found in the upper respiratory Tracy

Only found in the upper end of the respiratory tract (nasal cavity - trachea)

Upper respiratory tract (nasal - trachea)

Same microbiota found in the mouth

What does the body do to the microbiota found in the upper respiratory trachea

Body defenses prevent the migration of microbes to bronchi and beyond

Genitourinary Tract in Males

Support microbiota only in the outermost portion of the urethra

Genitourinary tract in females

Microbiota found on the external genitalia and part of the urethra

How has most of the information on the effect of microbiota been discovered

Through axenic (germ free) animals

How to raise axenic animals

• birth via C- section

• Sterile existence

General studies is

What does microbiota do

Gnotobiotic studies is

Add back one microbe

Do we need microbiota if so what would happen without them

• undeveloped immune system

• Absence of dental caries

• Vitamin deficiency

• Heightened susceptibility to enteric pathogens (salmonella, shigella, vibrio cholera)

• Less body fat

Progress of an infection Step 1

Finding a portal of entry

• skin

• GI tract

• Respiratory tract

• Urogenital tract

• Endogenous biota

Progress of an infection Step 2

Attaching firmly

• fimbrae

• Capsules

• Surface proteins

• Viral spikes

• Hooks

Progress of an infection Step 3

Surviving host defenses

• avoiding phagocytosis

• Avoiding death inside phagocyte

• Evading actions of the immune system

Progress of an infection Step 4

Causes of damage and disease

direct damage

• Toxins, enzymes, lysis Indirect damage

• Host response is inappropriate and excessive

True pathogens

Capable of making a person with a fully functioning immune system ill

Opportunistic pathogens

Only capable of causing disease in a weakened host

Pathogens that infect during pregnancy and birth include TORCH which is defined as

Common infections of infants, neonates

TORCH- T stands for

Toxoplasmosis

TORCH- O stands for

Other (Hep B, HIV, Chlaymidia)

TORCH- R stands for

Rubella

TORCH- C stands for

Cytomegalovirus

TORCH- H stands for

Herpes simplex virus

Attachment to host: what must pathogens bind to

Must bind to host cells to initiate infections using fimbriae, capsules, spike, hooks, ect

Non- infectious microbes are

Microbes that have lost the ability to bind to host cells

Virulence Fcators: Host point of view

Characteristics of mirrors that make us sick

Virulence Factors : microbes point of view

Characteristics that allow microbes to become established in the tissues

Virulence factors include

• exoenzymes

• Toxins

• Anti-phagocytic factors

• Invasion factors

Bacteria produce exoenzynmes that do what

Destroy the proteins and matrix holding cells together

What do exotoxins do

Kill cells that block the movement of pathogens or attempt to destroy them

Phagocytosis cells

Patrol the body, looking for foreign organisms, like bacteria, to engulf and destroy

Thick capsules

Neisseria and streptococcus

Thick capsules- neisseria, streptococcus

Make it difficult for WBCs to engulf pathogens

What pathogens have the ability to live and grow inside white blood cels

Listeria, hiv

Exotoxins are

• produced by living cells

• Toxic in small doses

• Effects are cell type specific

• Hemolysins found in staphylococcus and streptococcus causes lysis of red blood cells

Endotoxins are

• the lipopolysaccharide (LPS) layer of the cell wall has toxic effects on cells

• Found only in gram neg bacteria

• Toxin only in high doses

• Released when cell die

• Effects are systemic (fever, shock, pain)

Types of infections: Local

Infection is restricted to a specific location

EX: pimple, wart

A types of infections: systemic

Infection spreads throughout body

EX: flu

A types of infections: focal

Infections is local but effects are systemic (often due to toxins)

EX: tetanus infection

A types of infections: toxinoses

Illness is due to toxins.

Botulism Toxin that paralyses your body

Tetanus Toxin

Mixed infection

Infection contains more than one microbe

Primary infection

First of multiple infections (chicken pox because that is what alllows for staphylococcus aureus to enter and infect you)

Signs of disease

Objective (measurable)

• fever , ski eruptions, swollen lych nodes

Secondary infection

Only occurs because primary infections weakens the host defense (staphylococcus that is in your finger nails and you begin to scratch your chicken pox open sores which is infecting)

Symthoms of disease

Subjective (defined by patient)

• chill is , nausea, pain, irritation, headache, sore throat, ect

Portal of exit

Characteristics route microbes take to leave the body

• cough, sneeze, urine

Persistence of microbes

Latency (recurrent disease)

Sequelae (long term damage)

Where microbes live : reservoir

Primary habitat of a microbe

• only reservoir of SHIGELA is HUMAN FECES

• Non living reservoirs include soil and water

Where microbes live: source

The actual source of infection

• contaminated food

Carriers

People who carry pathogens without showing overt signs of disease but may pass the pathogens to other s

Passive carriers

Transfer of infectious agent through contact

vectors

Animals that transmit pathogens

• insects

Biological vectors

Animals that participate in the life cycle of the pathogens like malaria

• mosquitos

Mechanical vector

Animals that do not participate in the life cycle of the pathogens like E. Coli

• cockroaches and flies

Zoonotic infections

Normally found i animals buy may spread to humans

• tracked via sentinel animals

• Mostly include people who are around animals like veterinarians, zoo keepers, people who hike, ect

Spread of disease: communicable

May be spread person to person