Micro 2460 Chapter 13

Infection

A condition in which pathogenic microorganisms penetrate host defense, enter the tissues and multiply.

Pathologic State

Cumulative effects of infection

disruption of tissues and organs

Results in disease

Disease

Any deviation from health factors that cause disease

-Infections, diet, genetics, aging

Infectious Disease

Disruption of tissues or organs caused by microbes or their products

Normal Biota

Large and diverse collections of microbes living on and in the body

"resident" or "indigenous biota" "normal flora"

Include an array of bacteria , fungi, protozoa and viruses

Human cells contain ______ protein encoding genes: microbes that inhibit humans contain ___ million

22,000

8 million

All healthy people harbor potentially dangerous pathogens,

but in low numbers

Benefits of normal biota

-influences the development of organs

-prevent the overgrowth of harmful microorganisms

Microbial antagonism

-General antagonistic effect "good" microbes have against intruder microorganisms

-Microbes in a steady established relationship and unlikely to be displayed by incoming microbes

Differences in gut biota put you at risk for...

-heart disease

-asthma

-austism

-rheumotiod arthritis

-even thoughts, moods, possibly even mental illness

Endogenous infections

-Caused by biota already in the body

-can occur when normal biota is introduced to a site that was previously sterile

Examples: E.coli entering the bladder resulting in a UTI

A growing number of doctors and scientists believe...

fetuses are seeded with normal microbiota in utero.

Breast milk contains about ____ species of bacteria and sugars that babies cannot digest

600

Pathogen

-Microbe whose relationship with its host is parasitic

-Result in infection and disease

Pathogenicity

Describes an organisms potential to cause infection of disease

True pathogens

Capable of causing disease in healthy people with normal immune defenses

Opportunistic Pathogens

Cause disease when

-the hosts defense are compromised

-when they become established in a part of the body that is not natural to them

Virulence

The relative severity of the disease caused by a particular microorganism

Virulence factor

Any characteristic or structure of the microbe that contributes to toxin production or induction of an injurious host response

Biosafety Levels

A system of biosafety categories adapted by the centers for disease control and prevention

Portal of entry

-a characteristic route taken by a microbe to irritate infection

-usually through skin or mucous membrane

Exogenous

Originating from outside the body environment, another person or animal

Endogenous

Already existing in the body normal biota or a previously silent infection

Sites of Entry

Nicks, abrasions, punctures, some tiny and inapparent, conjunctive. Intact skin is a very tough barrier that few microbes can penetrate

GI tract as portal

Entry through food, drink or other ingested substances

-adapted to survive digesting enzymes and abrupt pH changes

Respiratory portal of entry

Oral or nasal cavity.

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

Sexually Transmitted Infections

Pathogens transmitted by sexual means

-Account for 4% of infections worldwide

-13 million new cases in the US every year

STI Entry points through skin or mucosa of...

penis, external genitalia, vagina, cervix, urethra

Placenta is an exchange organ...

-Separates blood from fetus and mother

-Permits diffusion of the dissolved nutrients and gases to the fetus

-few microbes are passes by the umbilical cord vein into the fetal tissue

-other infections transmitted to child through passing the birth canal

TORCH stands for...

Toxoplasmosis, Other diseases: syphillis, coxsackievirus

Rubella, Cytomegalovirus, Herpes simple virus

TORCHs are..

common infections of the fetus and neonate

Infectious dose (ID)

Minimum number of microbes required for an infection to proceed.

Adhesion

A process by which microbes gain a more stable foothold on host tissues

Phagocytes

White blood cells that engulf and destroy pathogens by means of enzymes and antimicrobial chemicals

Antiphagocytic factors

-Virulence factor used by pathogens to avoid phagocytes

-Circumvent some part of the phagocytic process

Toxin

A specific chemical product of microbes, plants, and some animals that is poisonous to other organisms

Exotoxin

Secreted by a living bacterial cell to the infected tissues

Endotoxin

-Not actively secreted

-Shed from the outer membrane

-Only found in gram-negative bacteria

Localized infection

Microbe enters the boy and remains confined to a specific location

-boils, warts, fungal skin infections, warts

Systemic Infection

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

Viral: measals, rubella, chicken pox, AIDS

Bacterial: brucellosis, anthrax, typhoid fever, syphilis

Fungal: histoplasmosis, cryptococcosis

Infectious agents can travel by means of...

nerves or cerebrospinal fluid

Focal Infection

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

• Tuberculosis

• Streptococcal pharyngitis: scarlet fever

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

Mixed Infection

Several agents establish themselves at the infection site

- In synergistic infections, microbes cooperate in breaking down tissue

- In other mixed infections, one microbe greatest an environment that enables another microbe to invade

Polymicrobial diseases

Gas gangrene, wound infections, dental caries, human bite infections

Primary Infection

Initial infection

Secondary Infection

Occurs when a primary infection is complicated by another infection caused by a different microbe

Acute Infections

-Come on rapidly

-Have short lived effects

Chronic Infections

Progress and persist over a long period of time

Sign

Any objective evidence of disease as noted by an observer

Symptom

Subjective evidence of disease as sensed by the patient

Syndrome

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

Inflammation

Earliest symptoms of disease

Edema

Accumulation of fluid in affected tissue

Granulomas/Abscesses

Walled off collections of inflammatory cells and microbes in the tissues

Lymphadenitis

Swollen lymph nodes

Leukocytosis

Increase in the level of white blood cells

Leukopenia

Decrease in the level of white blood cells

Septicemia

General state in which microbes are multiplying in the blood and are present in large numbers

Bacteremia

Small numbers of bacteria are present in the blood but not multiplying

Viremia

Presence of viruses in the blood, whether or not they are actively multiplying

Asymptomatic, subclinical or inapparent infections

Host is infected but does not manifest the disease

-patients experience no symptoms or disease and does not seem medical attention

-Most infections are attended by some sort of sign

Port of Exit

Avenue of departure for pathogens to exit the host

-secretion, excretion, discharge, sloughed tissue

Respiratory and Salivary Portals

Escape media for pathogens that infect the upper and lower respiratory tract

-mucus,sputum, nasla drainage, moist secretions

Blood feeding animals are the most common transmitters of pathogens. They are..

ticks, fleas, mosquitoes

Latency

A dormant state of an infectious agent

During this state, a microbe can periodically become active and produce recurrent disease

Sequelae

Long term or permanent damage to organs and tissues

Incubation Period

The time from initial contract with the infectious agent to the appearance of first symptoms

Prodromal Period

When the earliest notable symptoms of infectious appear

Period of Invasion

Infectious agent multiplies at high levels and exhibit greatest virulence

Convalescent Stage

Patient responds to infection and symptoms decline

Reservoir

A permanent place for an infectious agent to reside

Source

Distinct from a reservoir

Carrier

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

Vector

In epidemiology, a live animal that transmits an infectious agent from one host to another

-Majority of vectors are arthropods: insects and Spiders

Biological Vector

Actively participates in a pathogens life cycle

-Serves as a site in which it can multiple or complete its life cycle

Mechanical Vector

Not necessary to the life cycle of an infectious agent

-Merely transport it without being infected

Zoonosis

An infection indigenous to animals but naturally transmissible to humans

-humans are the dead end host and doesn't contribute the natural persistence of the microbe

Communicable Disease

Occurs when an infected host can transmit the infections agents to another host and establish infection in the host

Contagious

Agent is highly communicable, especially through direct contact

Noncommunicable

Does NOT arise through transmission of the infectious agent but from host to host

Horizontal Transmission

Disease is spread through a population from one infected individual to another

Vertical Transmission

Transmission from parent to offspring via ovum, sperm, placenta or milk

Vehicle

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

Fomite

An inanimate object that harbors and transmits pathogens

Oral fecal Route

Fecal carrier with inadequate personal hygiene contaminates food during handling and an unsuspecting person ingests it.

Oral Fecal Route Examples

Hepatitis A

Amoebic dysentery

Shigellosis

Typhoid fever

Droplet Nuclei

Dried Microscopic residues created when microscopic pellets of mucus and saliva are ejected from the mouth or nose

Aerosols

Suspensions of fine dust or moisture particle in the air that contain live pathogens

Healthcare associated infections

Infectious diseases that are acquired or develop during a hospital stay or stay in another health care facility.

-Rates of HAIs can range from 0.1-20% of all admitted patients

Medical Asepsis

Goal: limit the spread of infectious agents from person to person

Surgical Asepsis

Ensuring all surgical procedures are conducted under sterile conditions

Infection Control Officer

Implements proper practices and procedures through the hospital

Infection Control Officers are charged with...

-Tracking potential outbreaks

-Identifying breaches in asepsis

- Training other healthcare workers in ascetic technique

Bioterrorism

International or threatening use of microorganism or toxins from living organisms to cause death or disease in humans, livestock or plants

Emerging diseases: Newly identified microbes

HIV, SARS, Novel strain of influenza

Reemerging Diseases

Yellow fever, Tuberculosis, Dengue fever

Point Source Epidemic

One in which the infectious agents came from a single source

Common Source Epidemic

Result from common exposure to a single source of infection that can occur over a period of time

Propagated Epidemic

An infectious agent that is communicable from person to person and is sustained over time in a population

Pandemic

Spread of an epidemic across continents