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Tissue Damage and Disease

Stages of Infection

Patient responds to infection and symptoms decline

Invasion

Agent multiplies at high levels and exhibits greatest virulence

Prodromal

earliest notable symptoms of infection appear

Incubation

Initial contact appearance of first symptoms

Types of Carriers

Passive

medical and dental personnel who must constantly handle contaminated materials and risk picking up pathogens mechanically and accidentally transferring them to other patients

individuals who shelter the infectious agent for a long period after recovery from latency of the infectious agent

Convalescent

they continue to shed viable microbes and convey the infection to others

recuperating patients without symptoms

Incubating

microbes are multiplying

infected but shows no symptoms of disease

Persistence of Pathogen

Sequelae

Long-term or permanent damage to organs and tissues

Latency

microbe can periodically become active and produce recurrent disease

A dormant state

Carrier

An individual who inconspicuously shelters a pathogen and can spread it to others without knowing

Source

Distinct from a reservoir

Reservoir

A permanent place for agent to reside

Blood Infection Signs

Viremia

Presence of viruses in the blood, maybe actively multiplying

Bacteremia

Small numbers of bacteria are present in the blood

not multiplying

Septicemia

General state

microbes are multiplying in the blood and are present in large numbers

Leukopenia

Decrease in white blood cells

Leukocytosis

Increase in white blood cells

Inflammation

Earliest symptom of disease

Abscess

Granuloma

Edema

Accumulation of fluid in afflicted tissue

Disease signals

Infections that go unnoticed:

Inapparent

Host is infected -> no disease

Subclinical

Patient experiences no symptoms or disease and does not seek medical attention

Asymptomatic

Syndrome

A disease identified or defined by a certain complex of signs and symptoms

Symptoms

Subjective evidence of disease as sensed by the patient

Signs

Any objective evidence of disease as noted by an observer

Patterns of Infection

Chronic

Progress and persist over a long period of time

Acute

Have short-lived effects

Come on rapidly

Secondary

Primary infection is complicated by another infection caused by a different microbe

Primary

initial infection

Mixed

Polymicrobial diseases:

human bite infections

dental caries

wound infections

gas gangrene

Several agents establish themselves simultaneously at the infection site

other mixed infections

one microbe creates an environment that enables another microbe to invade

synergistic infections

microbes cooperate in breaking down tissue

Focal

Examples:

Toxemia:

infection remains localized, toxins are carried through the blood to the target tissue

Streptococcal pharyngitis:

scarlet fever

Tuberculosis

Exists when the infectious agent breaks loose from a local infection and is carried to other tissues

systemic

Infectious agents can travel by means of nerves or cerebrospinal fluid

When an infection spreads to several sites and tissue fluids, usually in the bloodstream.

Fungal:

cryptococcosis

histoplasmosis

Bacterial:

typhoid fever

anthrax

brucellosis

Viral:

chickenpox

rubella

measles

Localized

Microbe enters the body and remains confined to a specific tissue

Warts

Fungal skin infections

Boils

Attachment

Spikes

Capsule

Subtopic

Fimbrae

Patterns of Transmission

Vectors

Mechanical

Merely transport it without being infected

Not necessary to the life cycle of an infectious agent

Biological

Site of multiplication or end of life cycle

Actively participates in a pathogen’s life cycle

live animal that transmits an infectious agent from one host to another

Majority of vectors are arthropods (insects)

Noncommunicable

Does not arise through transmission from host to host

Communicable

Contagious

Highly communicable

Infected host can transmit the agent and establish infection in another host

Indirect

Air

Waste

Water

Food

Direct

Peripheral

Droplets

Kissing

Fomite

An inanimate object that harbors and transmits pathogens

Not a continuous source of infection

Vehicle

Any inanimate material commonly used by humans that can transmit infectious agents

Horizontal transmission

Spread from one infected individual to another

Vertical transmission

Transmission from parent to offspring

milk

placenta

sperm

ovum

Survival of Host defenses

Virulence factors

Determine the degree of tissue damage that occurs

Adaptations that a microbe uses

establish itself in a host

invade

Structures, products, or capabilities

allow a pathogen to cause infection in the host

Antiphagocitic factors

Virulence factor used by pathogens to avoid phagocytes

Circumvent some part of the phagocytic process

Phagocytes

White blood cells that engulf and destroy pathogens using enzymes and antimicrobial chemicals

Toxins

Specific chemical product that is poisonous to other organisms

Exotoxin

Many types

Secreted by a living bacterial cell to the infected tissues

Endotoxin

Only found in gram-negative bacteria

Shed from the outer membrane

Not actively secreted

Exoenzymes

Secreted by pathogenic bacteria, fungi, protozoa, and worms

promote the spread of microbes into deeper tissues

Dissolve host’s defense barriers

Break down & inflict damage on tissues

Portal of Entry

Placenta (TORCH)

TORCH: common infections of the fetus and neonate.

Herpes simplex virus

Cytomegalovirus

Rubella

Other diseases:

chlamydia

AIDS

varicella-zoster virus

coxsackievirus

syphilis

Toxoplasmosis

exchange organ

A few microbes cross the placenta and are spread by the umbilical vein into the fetal tissues.

Other infections are transmitted perinatally as the child passes through the birth canal.

Permits diffusion of dissolved nutrients and gases

Formed by maternal and fetal tissues–Separates the blood between mother/fetus

Entry points through the skin or mucosa of:

urethra

cervix

vagina

external genitalia

Penis

Sexually transmitted infections (STI's)

Continuous mucous membrane covering the upper respiratory tract, sinuses, and auditory tubes

Microbes often transferred from one site to another

gateways

nasal cavity

oral cavity

Gastrointestinal

Entry through food, drink, or other ingested substances.

Adapted to survive digestive enzymes and abrupt pH changes

skin

sites of entry

conjunctiva

punctures

inapparent

tiny

abrasions

Nicks

Endogenous

already existing in the body

previously silent infection

normal biota

Exogenous

originating from outside of the body

animal

another person

enviornment

Portal of Exit

Blood

portal of exit when it is removed or released through vascular puncture.

Blood-feeding animals are the most common transmitters of pathogens:

Mosquitoes

Fleas

Ticks

Urogenital

Agents involved in STIs leave the host in vaginal discharge or semen.

Candida albicans

Chlamydia

Herpes simplex

Source of neonatal infections that infect the infant as it passes through the birth canal.