Chapter 10: Infection, Infectious Diseases, and Epidemiology

number of ways Diseases can be classified in

How (and if) they are spread to their host, Their extent, Their longevity and severity, Their frequency and geographical distribution

Germ theory of disease

Hypothesis formulated by Pasteur in 1857 that microorganisms are responsible for disease.

Numbers of Invaders & Chances of Infection

If just a few microbes gain entrance into the body, a disease is not likely to occur; Likelihood of disease generally increases with as the number of pathogens increase LD50 : Lethal Dose of a microbes toxin that will kill 50% of experimentally inoculated test animal. ID50 : infectious dose required to cause disease in 50% of inoculated test population. What amount of a toxin causes disease?

Carrier

In human pathology, continuous asymptomatic human source of infection

Signs

In pathology, objective manifestations of a disease that can be measured or observed by others.

Mucous membranes (portal of entry)

Include the lining of body cavities open to the outside world; lining of the respiratory, gastrointestinal, urinary, and reproductive tracts. Tend to be more hospitable for pathogens because they are warm, moist, and relatively thin.

Genitourinary Tract

Includes UTI's and pathogens that are contracted sexually

five stages following infection of infectious disease

Incubation period: time between infection and the first appearance of any signs/symptoms Prodromal: short period of time; characterized by early, mild symptoms of disease (aches, fatigue, etc.) Period of illness: time period when disease is most severe; overt symptoms/signs of disease (fever, muscle pain, sore throat, enlarged lymph nodes, etc.) Period of decline: signs/symptoms subside as immune response/medications take effect Period of convalescence: body returns to pre-diseased state; recovery

5 stages/periods of disease development

Incubation, Prodromal, Illness/Invasive Phase, Decline, and Convalescence(recovery)

Adhesion:

Process by which microorganisms attach themselves to cells Pathogens use adhesion factors to attach to hosts; Includes specialized structures; Suckers on helminths or adhesion disks on protozoa

Exotoxins

Produced within bacteria cell, but secreted outside the cell into the surrounding medium; Exotoxins are proteins; Soluble in water and transported by blood; Exotoxins have a relatively small LD50

Koch's Postulates

Published in 1877: showed that Bacillus anthracis was causative agent of anthrax. Outlined the criteria that need to be met in order to link a specific pathogen to a specific disease

Mutualism

Symbiotic relationship in which both members benefit from their interaction.

Commensalism

Symbiotic relationship in which one member benefits without significantly affecting the other member.

Severity and Longevity of Disease Acute disease:

Symptoms develop rapidly, but lasts a short time e.g., common cold

Diseases may become manifest in different ways:

Symptoms: Subjective characteristics of disease felt only by the patient; Such as pain and tiredness.....feelings. Signs: Objective manifestations of disease observed or measured by others; Such as fever and swelling....measurements. Syndrome: Symptoms and signs that characterize a disease or abnormal condition; example: malaise, loss of helper T cells, diarrhea, weight loss, toxoplasmosis, and tuberculosis characterize AIDS

Adhesion

The attachment of microorganisms to host cells.

Etiology

The study of the causation of disease.

Epidemiology

The study of the occurrence, distribution, and spread of diseases in humans.

Prevalence

The total number of cases of a disease in a given area or population during a given period of time; # of new and old cases/# of people at risk.

Illness

Third stage of disease; Signs and symptoms are most evident during this stage. The body's immune system has not fully responded to pathogens and their presence is harming the body. The stage when a patient is first seen by a physician.

Vehicle Transmission:

Through a medium

Exotoxins

Toxin secreted by a pathogenic microorganism into its environment; Example: clostridia which causes gangrene, botulism, and tetanus.

Enterotoxins

Toxins which affect cells lining the gastrointestinal tract.

Cytotoxins

Toxins which kill host cells or affect their function.

Neurotoxins

Toxins which specifically interfere with nerve cell functions.

Eye Diseases

Trachoma; Chlamydia trachomatis; Conjunctivitis; Pink eye

Airborne transmission

Transmission of pathogens usually occurs when an aerosol is formed from changing linen, dry mopping, or anything that stirs dust. Spread of pathogens to the respiratory mucous membranes of a new host via the air or in droplets carried more than 1 meter.

Droplet

Transmission via airborne droplets of mucus that exit body during exhaling, coughing, and sneezing. example: cold and flu HOWEVER, if droplets travel more than 1 meter, the mode is considered airborne transmission

Common Diseases contracted via the Respiratory Tract

Tuberculosis, Whooping cough, Pneumonia, Measles, Strep Throat, Diphtheria

2 types of flora; Resident flora (microbiota) &Transient flora (microbiota):

remain part of the normal flora of a person through life; mostly commensal remain in the body for only a few hours, days, or months before disappearing; competition from other microbes, body's defense, or chemical/physical changes destroy them

direct contact transmission

requires person-to-person contact; sex,shaking hands

Epidemiology

study of where and when diseases occur and how they are transmitted within populations.

Symptoms versus Signs

subjectively felt by patient / outside observable

Ligands:

surface molecules on bacteria and viruses (attachment sites) that allow them to attach to host cell receptor sites; Often found on fimbriae and glycocalyses of bacteria

pathogenicity

the ability of an organism to incite a disease state.

Decriptive epidemiology

the careful recording of data concerning a disease; it often includes detection of the index case.

sequela

the effects seen even after the recovery of some diseases. Ex: Reyes's syndrome after the flu, encephalitis after the measles, heart valve damage after strep infections.

index case

the first case of the disease in a given area or population

infection

the growth and development of a pathogen on or in a host's body

primary infection

the initial infection in a previously healthy person.

Infection

the invasion of the host by a pathogen

Animal Reservoirs; Zoonoses

Wild and domestic animals; Diseases that can be transmitted from animal host to humans.

symptom

a characteristic of disease that can be observed or felt only by the patient. ex: pain nausea, headache, chills, itching,, abdominal cramps

sign

a characteristic of disease that can be observed or measured when examining a patient. ex.swelling, rash, pulse, pus formation, vomiting, tachycardia, bradycardia.

aerosol

a cloud of small droplets and solid particles suspended in the air.

virulence factors

a collective term used to describe the characteristics of an organism that enable it to invade, colonize, and promote disease in a host.

syndrome

a combination of signs and symptoms that normally occur together.

Which of the following phrases describes a contagious disease?

a disease that is easily passed from host to host in aerosols.

Contagious disease

a disease that is easily transmitted from a reservoir or patient.

zoonosis

a disease that is transmitted from animal to human

Syndrome

a group of symptoms and signs that collectively characterizes a particular abnormal condition.

Pathogenicity

a microorganisms ability to cause disease

super infection

a secondary infection that results from the destruction of normal flora. ex: yeast infection

Kochs Postulates

a series of essential conditions to prove the cause of infectious diseases. Some circumstances can make the use of these postulates difficult or even impossible.

Prodromal Period

a short period during which non-specific symptoms such as malaise and muscle aches appear; not apparent in the course of all diseases.

disease

a situation (that can arise from an infection) in which the state of health of the host is altered in such a way that normal functions cannot be carried out.

commensalism

a symbiosis in which one of the organisms involved benefits, while the other is neutral(unaffected) neither benefited nor harmed; humans have skin, eye, and ear commensals.

mutalism

a symbiotic relationship in which both of the organisms involved benefit; humans have a mutualistic relationship with our intestinal flora.

parasitism

a symbiotic relationship in which one of the organisms(the parasite) benefits at the expense of the other organism(the host); pinworms(helminths)

skin

the largest organ of the body. When unbroken is an effective barrier for most microorganisms.

morbidity rate

the number of cases in relation to the total number of people in the population in a given year; expressed in 1000.

mortality rate

the number of deaths due to a certain disease in relation to the total population in a given year; expressed per 1000.

incidence

the number of new cases seen in a specific period of time.

Toxemia

the presense of poisons called toxins in the blood

The most frequent portal of entry for pathogens is

the respiratory tract

portals of entry

the sites at which microorganisms gain entry to the body and tissues; include: skin , mucous membrane of the digestive, respiratory and urogenital systems, through the placenta, and parenteral route.

portals of exit

the sites at which microorganisms leave the body; usually associated with bodily secretion or feces.

epidemiology

the study of factors and mechanisms involved in the spread of a disease within a certain population.

Etiology

the study of the cause of a disease

etiology

the study of the cause of a disease

Epidemiology:

the study of the location, course, and transmission of diseases within populations; An epidemiologist looks for patterns in disease; age, sex, occupation, lifestyle, socioeconomic status, immunizations, geography; concerned about methods for controlling disease; drugs, vaccines, water treatment, food inspection, personal habitats; concerned about frequency of disease

Incubation Period

the time b/w the onset of exposure and the appearance of signs and symptoms.

Illness/Invasive Phase

the time during which the disease develops its most severe signs and symptoms; fever is an important component of this phase; fever is caused by the production of pyrogens by the pathogens (as well as by the host immune system).

prevalence

the total number of cases at any one time.

Disease:

abnormal body function or deviation from health; "homeostatic imbalance"

Biofilms:

about 65% of all bacterial infections

Nosocomial infections and nosocomial diseases

acquired by patients in health care facilities

Hospital Epidemiology Nosocomial Infections:

acquired by patients or workers in health care facilities; Includes hospitals, dental offices, nursing homes, clinics

non-communicable

acquired from the environment (not spread from one host to another)

exogenous

acquired from the health care environment

Extent of Disease Primary Infection & Secondary Infection

acute infection that causes initial illness infection caused by an opportunistic pathogen after the primary infection has weakened the body's defenses e.g., bacterial pneumonia followed by influenza, e.g., sinus infection following a cold, e.g., yeast infections after antibiotic treatment

The process by which microorganisms attach themselves to cells is

adhesion

Virulence Factors affect the relative ability of a pathogen to infect and cuase disease. What are the factors?

adhesion factors extracellular enzymes toxins antiphagocytic factors

The nature of bacterial capsules

affects the virulence of these bacteria

vehicle transmission

airborne transmission, waterborne transmission, and foodborne transmission.

Which of the following types of epifemiologists is most like a detective?

an analytical epidemiologist

microbial antagonism

an effect where the normal flora populations serve to compete (for space and nutrients) with pathogenic species to inhibit their growth and decrease the probability of disease.

secondary infection

an infection that arises after the primary infection and usually is a result of the primary infection.

Three types of reservoirs

animal reservoirs, Human carriers, Nonliving reservoirs

Antitoxins

antibodies the host forms against toxins

Noncommunicable disease

arise from either outside of hosts or from normal microbiota.

common source epidemic

arises from contact with contaminated substances. ex: food poisoning

propagated epidemic

arises from person-to-person contact. ex: common cold

Infections that may go unnoticed due to the absence of symptoms are called _____ infections.

asymptomatic

When pathogenic bacterial cells lose the ability to make adhesions, they

become avirulent

vector transmission

biological and mechanical vectors.

An animal that carries a pathogen and also serves as host for the pathogen is a ____ vector.

biologocal

congenital

born with it-anatomical and physiological (structural and functional) defects present at birth; caused by drugs (legal and illegal), X-ray exposure, or infections

Severity and Longevity of Latent disease:

causative agent remains inactive for awhile, but then becomes active to produce symptoms e.g., shingles caused by the chicken pox virus

necrotizing factors

cause death to body cells; produced by Group A Strep (GAS): S. pyogenes.

Opportunistic Pathogens

cause disease when the immune system is suppressed, when normal microbial antagonism (competition) is affected by certain changes in the body, and when a member of the normal microbiota is introduced into an area of the body unsual for that microbe.

mixed infection

caused by several species of pathogens that are present at the same time such as dental caries and periodontal diseases.

infectious

causes by microbe or an infectious agent

latent

characterized by periods of inactivity either before symptoms appear or between attacks; most common in viral infections.

Aerosols

clouds of water droplets, which travel more than 1 meter in airborne transmission.

normal flora

collectively refers to all the organisms that permanently associate themselves with the body after birth, and under normal circumstances do not produce disease in the host.

Infection:

colonization of the body by pathogens OR presence of a microbe in a part of the body where it is NOT normally found; infection may or may not result in disease example: carriers can have a pathogen but not feel ill

local infection

confined to a specific area of the body.

focal infection

confined to a specific area, but pathogens from the infection, or their toxins, can spread.

Universal Precautions

consists of policy and procedure guidelines regarding sharp (needle, scalpel) disposal, hand-washing, and safety equipment usage.

An axenic environment is one that

contains only one species

formites

contaminated non-living objects such as needles, toys, toothbrushes,diapers, drinking glasses, bedsheets, medical equipment and money-inanimate objects that are inadvertently used to transfer pathogens to new hosts

Virulence Factors

contribute to the ability of pathogens to invade a host

Virulence

degree of pathogenicity.

The length of incubation

depends of the virulence of the pathogen, the initial number of pathogens, the state and health of the host, and the nature of the pathogen and its reproductive time

endogenous

derived from normal microbiota that become opportunistic while in the hospital setting

chronic

develops more slowly, is usually less severe, but persist for a long period of time.

acute

develops rapidly and runs its course quickly.

Contact transmission

direct and indirect transmissions

Infectious Disease:

disease caused by a pathogen (sometimes called infectious agent)

pathogen

disease causing.

zoonotic diseases (zoonoses)

diseases of animals that may be spread to humans via direct contact with the animal or its waste products, or via an arthropod. Humans may be asymptomatic carriers.

Extent of Disease Subclinical infection:

does not cause noticeable illness, However, person carrying the pathogen can still spread it (healthy carrier)

septic shock

drop in blood pressure

iatrogenic

due to medical treatment or procedures. ex: superinfection

mental

emotional or psychosomatic

coagulase

enzyme that accelerates: clot formation

lecithinase

enzyme that destroys cellular membranes.

The study of where and when diseases occur and how they are transmitted within populations is____.

epidemiology

The study of the cause of a disease is___.

etiology

neoplastic

excessive growth. ex. tumors -abnormal cell growth.

Toxoid

exotoxin that has been inactivated by some chemical means no longer causes disease, but still stimulates the production of antitoxin against the toxin. Toxoids are often important components of vaccines example: DPT vaccine; protects against Diphtheria, Pertussis, and Tetanus; contains diphtheria toxoid and tetanus toxoid

Antiphagoctic factors

factors prevent phagocytosis by the host's phagocytic cells

Nonliving reservoirs of disease, such as a toothbrush, drinking glass, and needle, are called ____

fomites

Transmission

from a reservoir or a portal of exit to another host's portal of entry

Hereditary

genetic-caused by errors in the genetic code received from the parents

nosocomial

healthcare setting acquired

Which of the following are most likely to cause disease?

highly virulent organisms

endocrine

hormones (due to excesses or deficiencies of hormones)

immunological

hyperactive or hypoactive immunity

A patient contracted athletes foot after long term use of a medication. His physician explained that the malady was directly related to the medication. Such infections are termed:

iatrogenic infection

optimal opportunities

immune suppression, changes in the normal microbiota(superinfections), movement of the normal microbiota to a new location.

Morbidity rate:

incidence of disease (number of people affected by disease in given time period)

Disease Process (stages of infectious diseases)

incubation period prodromal period illness decline convalescence

iatrogenic

induced by treatment or medical procedures

Nonliving reservoirs

infection include soil, water, and inanimate objects.

nosocomial infections

infections acquired while in a healthcare facility.( ex: hospital, hospice, nursing homes, doctor/dentist office.)

Communicable disease

infectious disease comes either directly or indirectly from another host.

communicable

infectious diseases that can be easily spread from one host to another (contagious)

neurotoxins

inhibit proper nerve impulse transmission; mechanism of botulism (flaccid paralysis) and tetanus (spastic paralysis).

Vehicle Transmission

involves airborne, waterborne, and foodborne transmission.

parenteral route

involves direct deposition of organisms into the hosts' tissues; ex: punctures, biters, surgery

Eperimental epidemiology

involves testing a hypothesis resulting from analytical studies

endemic disease

is constantly present in the population of a particular geographical area, but the number of cases and the severity of the disease both remain low enough not to constitute a public health problem. ex: chicken pox (prior to vaccine), common cold, allergies.

reasons for notifiable diseases are categorized

it is a zoonosis, sexually transmitted, or routinely immunize against it.

cytotoxins

kill host cells or inhibit their normal function; mechanism of diphtheria and anthrax.

A disease in which a pathogen remains inactive for a long period of time before becoming active is termed a(n)

latent disease

endotoxins

lipid substances produced and released into tissues from the cell walls of Gram-negative organisms as they die and cell wall lysis occurs.

Extent of disease focal infection:

local infection that causes subsequent infection or symptoms in other parts of the body. For example, tetanus(lockjaw) is caused by the release of extoxin from a local infection, perhaps an infected puncture wound of the foot.

3 reservoirs for infection

locations from which pathogens can be spread; Animal reservoirs, Human carriers, and Non-living (Environmental) Reservoirs

Asymptomatic or subclinical infections

may go unnoticed because of the absense of symptoms, even though clinical tests might reveal signs of disease.

Symbiosis

means "to live together" We have symbiotic relationships with countless microorganisms

virulence

measures the intensity of the disease produced.

which of the following is false concerning microbial contaminants?

most microbal contaminants will eventually cause harm

flaccid paralysis

muscles unable to contract. (relaxed)

spastic paralysis

muscles unable to relax (stayed contracted)

In which type of symbiosis do both members benefit from their interaction?

mutualism

Competitive exclusion

no 2 species can simultaneously and continuously occupy the same niche; Thus, normal flora outcompete potentially pathogenic bacteria, protecting their host

Fomites:

non-living object that can transmit disease between hosts. Examples of fomites: bedding, toys, money, thermometers, keyboard, toothbrushes

____ infections are those acquired by patients or staff while in health care facilities.

nosocomial

Epidemiologists track the Incidence/ prevalence of a disease

number of new cases/ total number of cases

Mortality rate:

number of people that died from particular disease in given time period

Control/or Methods of prevention of nosocomial infection(and breaking the chain of transmission)

observance of aseptic technique; frequent hand washing especially between patients; careful handling, cleaning, and disinfection of fomites; where possible use of single-use disposable items; patient isolation; various institutional methods such as air filtration within the hospital; EDUCATION! Prescribe antibiotics only when necessary; avoid invasive procedures if possible

indirect contact transmission

occurs through formites, and droplet transmission.

epidemic disease

occurs when a disease has a sudden, very high incidence in a population; considered a public health problem.

Some microbes can gain entrance thru

openings in the skin:hair follicles and sweat glands; Abrasians and scrapes; Some parasitic worms can burrow thru the skin Some fungi can digest the outer layer of skin

Noraml Microbiota

organisms that live in and on the body. Some are resident and others are transient.

Endotoxins

part of the LPS layer; the Lipid A portion; As such, endotoxins are characteristic of Gram-negative bacteria; Endotoxins are released upon lysis, during reproduction, or are phagocytized Have a relatively large LD50; Endotoxins produce similar effects Fever, inflammation, shock; Antitoxins not generally produced against endotoxins

A microbe that causes disease is called a ___.

pathogen

Extent of disease Local infection:

pathogens are limited to small area of the body

Foodborne:

pathogens in and on foods that inadequately processed, undercooked, or poorly refigerated

Extent of disease Systemic infection:

pathogens or their toxins are spread throughout the body by the blood or the lymph

Doplet Transmission

pathogens travel in droplets of mucus less than 1 meter to a new host as a result of speaking, coughing, or sneezing.

Carriers:

people who carry a pathogen but remain asymptomatic Examples: AIDS, tuberculosis, syphilis

Decline

period when the signs and symptoms begin to subside.

Convalescence(recovery)

period when tissues are repaired, healing takes place, and the body regains strength.

Direct Contact transmission

person-to-person spread by bodily contact.

Notifiable disease:

physicians are required by law to report cases to U.S. Health Official

toxins

poisonous substances produced and released by bacteria.

To total number of cases of a disease in a given area is its ___

prevalence

hemolysins

proteins that enable organisms to degrade red blood cells for access to iron; specifically called streptolysins when produced by the streptococci.

Etiology

refers to the cause of disease. Not ALL diseases are caused by microbes; ex: inherited disorders, obesity

infestation

refers to the growth and development of large pathogens in or on the host. ex. helminths or arthropods

Microbial contamination

refers to the mere presense of microbes in or on the body or object. They include harmless resident and transient members of the microbiota, as well as pathogens, which after a successful invasion cause an infection.

Toxemia

refers to toxins in the bloodstream that are carried beyond the site of infection

Endotoxins (lipid A)

released from the cell wall of dead and dying Gram-negative bacteria and can cause fatal effects.

Notifiable Diseases

those diseases that by law must be reported to public health officials. ex: AIDS, anthrax, botulism, cholera, gonorrhea,mumps, contaminated water,yellow fever, hepatitis, measles, plague, malaria, smallpox,rubella,lyme

degenerative

tissues ie: myopia result from aging

foodborne transmission

transmission of pathogens usually occurs when food has been processed in an unsanitary environment, is incompletely cooked, or was poorly refrigerated.

waterborne transmission

transmission of pathogens usually occurs when the water is untreated or improperly treated. Ex: cholera or hepatitis

idiopathic

unknown agent cause

World Health Organization

use epidemiological data to promulgate rules and standards for clean, potable water and safe food, to prevent disease by controlling vectors and animal reservoirs, and to educate people to make healthy choices concerning the prevention of disease.

Streptokinase -

used to dissolve blood clots in the Heart (heart attacks due to obstructed coronary blood vessels)

antitoxin

what The body produces antitoxins; an antibody designed to bind to a specific toxin; neutralizes toxin, making it harmless

pandemic disease

when an epidemic occurs simultaneously on more than one continent.

biological vector

when the agent of transmission is necessary for the multiplication or development of the microorganism; the vector is not only contaminated, but also infected; ex including: most biting insects like mosquitoes and ticks.

mechanical vector

when the agent of transmission is not necessary for the multiplication or development of the microorganism; only provides a "ride" for the organism; ex include: the legs of flies or cockroaches and contaminated unwashed hands.

bacteremia

where bacteria are simply transported in the blood, but do not multiply.

septicemia

where pathogens are present and multiplying in the blood. (cell division)

toxemia

where toxins are release by pathogens, are present in the blood.

viremia

where viruses are in the blood.

droplet transmission

which occurs when a person in close proximity to others cough, sneezes, or even speaks.

Examples of zoonoses

yellow fever, anthrax, bubonic plague, and rabies.

Diseases that are naturally spread from their usual animal hosts to humans are called___.

zoonoses

Parasitism

One (parasite) benefits; one is harmed (host)

Symptoms

Subjective characteristics of a disease that can be felt by the patient alone.

Infection

Successful invasion of the body by a pathogenic microorganism.

Direct contact transmission

Spread of pathogens from one host to another involving body contact between hosts.

symbiosis

"to live together"

Portals of Exit

(ex nose, mouth, and urethra) allow pathogens to leave the body and are of interest in studying the spread of disease.

streptokinase

(fibrinolysin)-enzyme that degrades clots; produce by Strep. pyogenes; direct injection into blocked blood vessels to treat myocardial infarction.

systemic infection

(generalized) infection-affects the entire body, and the pathogens are widely distributed in the blood and lymph.

hyaluronidase

(the spreading factor)-enzyme that digests hyaluronic acid which is part of all-connective tissues; produced by most species of streptococcus

eg of Opportunistic Pathogens:

1. Introduction of normal flora into unusual site. E. coli is non-pathogenic in the large intestine; certain strains become pathogenic when it gets into the urethra leading to urinary tract infection 2. Immune suppression, immunocompromised Disease, malnutrition, extremes of age, chemotherapy, immunosuppresant drugs, HIV (AIDS) 3. Changes in the normal microbiota e.g.,vaginitis resulting from a broad spectrum antibiotic killing resident Lactobacillus

criteria Koch's Postulates

1. The same pathogen must be found in all organisms suffering from the disease but not necessarily in healthy organisms 2. The pathogen must be isolated from a diseased organism and grown in pure culture 3. The cultured pathogen must cause the disease when introduced into a healthy organism. 4. microorganism must be re-isolated from the inoculated, diseased host and identified as being identical to the original specific pathogen

Diseases can be descibed as 1. acute 2. subacute 3. chronic 4. latent

1. disease develops rapidly but lasts only a short time (common cold) 2. have durations and severities that lie somewhere between acute and chronic. (endocarditis, a disease of heart valves) 3. develop slowly and are continual or recurrent. (mononucleosis, hep C, TB, leprosy) 4. a pathogen remains inactive for a long period of time before becoming active. (Herpes)

1. Vectors 2. Biological vectors 3. Mechanical vectors

1. transmit pathogens between hosts. 2. animals (usually biting arthropods) serve as both host and vector pathogens. 3. not hosts to the pathogens they carry.

classification of disease outbreaks as 1. endemic 2. spiradic 3. epidemic 4. pandemic

1. usually present 2. occasional 3. more cases than usual 4. epidemic or more than one continent

Pathogen

Any parasite that causes disease

Nosocomial disease

A disease acquired in a healthcare facility.

Contagious disease:

A disease that is easily spread from one host to another A sub-category of communicable disease; Ex: chickenpox

Noncommunicable disease:

A disease that is not transmitted from one host to another. many normal flora that are opportunistic pathogens Examples: tooth decay, urinary tract infections

Communicable disease:

A disease that is spread from one host to another. Examples: tuberculosis, influenza, herpes, HIV

Epidemic

A disease that occurs at a greater than normal frequency for a given area or population

Endemic

A disease that occurs in a relatively stable frequency within a given area or population.

Sporadic

A disease that occurs in only a few scattered cases within a given area or population during a given period of time.

Syndrome

A group of symptoms, signs, and diseases that collectively characterizes a particular abnormal condition.

Virulence

A measure of pathogenicity.

Pathogenicity

A microorganism's ability to cause disease.

pathogen

A parasite that causes disease; disease causing microbe

Opportunistic Pathogens

A pathogen that doesn't affect healthy host, but do in weakened immune states or abnormal body conditions

Biofilm

A slimy community of microbes growing on a surface, example: dental plaque

Morbidity

AKA disease- a condition sufficiently adverse enough to interfere with normal functioning of the body.

Pathogenicity

Ability of a microorganism to cause disease; In order for disease to result from an infection, the pathogen must evade the host's defense system

Skin (portal of entry)

Access can be gained via (normal) openings such as hair follicles and sweat glands. Other openings such as abrasions, cuts, bites, scrapes, and surgeries may also open the body to infection.

The Movement of Microbes into Hosts:

Adhesion

Virulence factors include:

Adhesion factors, Biofilms, Antiphagocytic factors, Extracellular enzymes, Toxins

Nosocomial infection

An infection acquired in a healthcare facility.

Vectors

Animals that carry pathogens from one host to another, Most notably: arthropods, especially fleas, ticks, and mosquitoes

Disease

Any adverse internal condition severe enough to interfere with normal body functioning.

Biological vector

Biting arthropod or other biting animal that transmits pathogens and serves as a host for the multiplication of the pathogen during some stage of the pathogen's life cycle.

Hyaluronidase

Breaks down hyaluronic acid, The "glue" that holds cells together, Also known as the "Spreading Factor": helps bacteria spread thru a tissue, Sometimes mixed with a drug to help spread the drug thru a body tissue, Released by sperm cells to help penetrate egg

Compromised Host 2 principal conditions compromise the host:

Broken skin/Mucous Membranes: Intact skin and mucous membranes provide a physical barrier against pathogen/ first line of defense: Burns, surgical wounds, trauma, invasive procedures, urinary catheters, etc. all breakdown this barrier and/or produce a pathway into host Suppressed immune system: Adversely affect the actions of white blood cells and antibody production

Coagulase

Cause blood to clot "hiding" the bacteria; converts fibrinogen to fibrin, which forms blood clots; The fibrin coated bacteria is thus protected from phagocytosis from WBC's. e.g., Staphylococcus aureus, boils, abscesses

Illustrations of the different terms for the occurrence of disease-overview

Centers for Disease Control and Prevention (CDC) Main source epidemiological information in the U.S. Issues Morbidity and Mortality Weekly Report; Available at website: www.cdc.gov Contains information on the morbidity and mortality of nationally notifiable diseases

Where are normal flora found?

Certain regions tend to see more, some areas none; Distribution/Composition determined by: Nutrients (secretions, body fluids, food in GI tract), Physical and Chemical factors (pH, oxygen, salt), Mechanical factors (chewing, flow of mucus and urine, muscular movements of throat, stomach, etc.) Normal flora vary, affected by: Age, diet, health, emotional stability, stress, climate, occupation

Toxins

Chemicals that either harm or trigger host immune responses that cause damage.

Toxins

Chemicals that harm tissues or trigger host immune responses that cause damage (aka poisons); Toxins are the primary factor contributing to a bacteria's ability to cause disease; There are 220 known bacterial toxins

Bacterial capsules

Composed of chemicals not recognized as foreign, Slippery (hard to attach to) Example: Streptococcus pneumoniae can only cause disease if it has a capsule. Unencapsulated cells are quickly engulfed and killed by body defenses

3 modes of infectious disease transmission

Contact transmission, vehicle transmission, and vector transmission.

Three groups of transmission

Contact transmission; Direct, indirect, or droplet Vehicle transmission; Airborne, waterborne, or foodborne Vector transmission; Biological or mechanical

Exposure to Microbes:

Contamination vs. Infection

Exotoxins 3 main types:

Cytotoxins: kills host cells in general Neurotoxins: interfere with nerve cells Enterotoxins: affects cells lining the GI tract

Virulence

Degree of pathogenicity; The relative ability of a pathogen to invade a host and cause disease

contamination

state where microbes are present.

IgA Proteases

Destroys IgA antibodies; Main antibody found in mucosal secretions, such as tears, saliva, vaginal secretions, respiratory secretions, digestion secretions; e.g, N. gonorrhoeae and N. meningitidis

Acquisition of normal flora

Development in womb is essentially axenic Microbe free; During the birthing process, our first normal flora acquired; Intestinal bacteria acquired from first meals; Skin flora acquired from contact with parents and others

Kinases

Digest blood cots by breaking down fibrin, allowing bacteria to spread. e.g., streptokinase produced by Streptococcus pyogenes, e.g, staphylokinase produced by Staphylococcus aureus

Chain of Transmission

Direct contact between hospital staff and patients AND between patients themselves; Hospitals create unsavory environment for multiple microbe transmissions in immuno-suppressed patients Still home efficient than home treatment Indirect contact transmission through fomites and ventilation systems; Fomites include bedding, urinary catheters, IV catheters, needles, etc.

various routes zoonoses r acquired

Direct contact with animal or its waste; Eating animals; Bloodsucking arthropods Over 150 zoonose have been identified Rabies, Lyme disease, Malaria

Severity and Longevity of Disease Chronic

Disease develops slowly and bodies reaction may be less severe; however, it tends to last a long time. Tuberculosis, hepatitis B

Zoonoses

Diseases that are naturally spread from usual animal hosts to humans.

Clostridium perfringens

Gas Gangrene uses collagenase to spread thru muscle tissue

Common sexually transmitted disease

Gonorrhea; Neisseria gonorrhoeae; Syphilis; Treponema pallidum; Chlamydia; Chlamydia trachomatis; HIV; Herpes; Genital Warts

Both Organisms Benefit

E. coli of the large intestine synthesize vitamin K and some B vitamins (We use vitamins to assist with clotting and as co-enzymes E. coli get a free meal in our gut. We provide the bacteria with food)

urinary tract catheterization

E. coli responsible for nosocomial infection

Portal of entry

Entrance site of pathogenic microorganisms, including the skin, mucous membranes, and placenta.

Extracellular enzymes

Enzymes that enable pathogens to dissolve structural chemicals in the body and maintain an infection, invade further, and avoid body defenses. Example: Keratinase, an enzyme produced by the fungi that cause ringworm, enzymatically digests keratin - the main component of skin, hair, and nails.

Virulence factors

Enzymes, toxins, and other factors that affect the relative ability of a pathogen to infect and cause disease.

Types of nosocomial infections

Exogenous: Pathogen acquired from the health care environment Endogenous: Pathogen arises from normal flora (microbiota) due to factors within the health care setting, such as compromised immune system; Opportunistic pathogens Iatrogenic: Results from modern medical procedures, such as catheterization

Collagenase

Exotoxin that breaks down collagen, which is the chief structural protein in connective tissue

Two types of toxins

Exotoxins; Endotoxins

The Role of Adhesion in Infection

Once microbe gain access to the body, they need to adhere to cells in order to successfully establish colonies within host

Decline

Final stage of disease; The body gradually returns to normal as the patient's immune response and/or medical treatment vanquish the pathogens. The immune response and its products peak during this stage.

Incubation period

First stage of disease; the time between infection and occurrence of the first symptoms or signs of disease. Length depends on the virulence of the infective agent, the infective dose, the state of health of the host's immune system, the nature of the pathogen and its reproduction time, and the site of infection.

Which of the following statements is the best definition of a pandemic disease?

It is an epidemic that occurs on more than once continent at the same time.

Endotoxin is the part of the cell wall of a Gram-negative bacterium know as ___.

Lipid A

Reservoirs of infection

Living and nonliving continous sources of infectious disease.

Reservoir of infection

Living or nonliving continuous source of infectious disease

Conjuctiva

Membrane that covers the eyeballs and eyelids; Many viruses are introduced into the conjuctiva by contaminated fingers and then washed into the nasal cavity with tests; This is a typical route for the flu virus and common cold

Gastrointestinal (GI) Tract

Microbes gain entrance thru contaminated food and water or fingers and hands; poor personal hygiene. Most microbes that enter the G.I. Tract are destroyed by HCL & enzymes of stomach or bile & enzymes of small intestine. Those that survive can cause disease; eliminated thru feces, and transmitted to other hosts

Subcutaneous (Parenteral) Route

Microorganisms are deposited into the tissues below the skin or mucus membranes. Punctures; Injections; Bites; Scratches; Surgery; Splitting of skin due to swelling or dryness

Opportunistic pathogens

Microorganisms that cause disease when the immune system is suppressed, when microbial antagonism is reduced, or when introduced into an abnormal area of the body.

Respiratory Tract

Most frequently traveled portal of entry; Microbes inhaled into mouth or nose in droplets of moisture or dust particles; Line with mucous membranes, which provide a warm, moist, hospitable environment

Human Carriers

Most important reservoir; it Can be with noticeable symptoms/signs or carriers

Microbes live in Symbiotic relationships.. what are the types?

Mutualism (both members benefit) Parasitism (parasite benefits while the host is harmed) Commensalism (One member benefits while the other is relatively unaffected)

Microbial antagonism

Normal condition in which established microbiota use up available nutrients and space, reducing the ability of arriving pathogens to colonize.

track occurrence of diseases using two measures: Incidence & Prevalence

Number of new cases of a disease in a given area during a given period of time Number of total cases of a disease in a given area during a given period of time Example: The incidence of HIV in the US in 2004 was 40,000; prevalence was 900,000. This means that 40,000 people became infected with HIV that year. This means that in 2004, 900,000 in the U.S. had the HIV virus

Commensalism

One benefits, one is unaffected; Many microbes that inhabit eyes, ears, and genitals; many of the microbes in the intestine. Bacteria benefit: nutrients from secretions and dead cells; protection/place to live Host unaffected: no apparent advantage to us Competitive exclusion may play a role (keeping other harmful microbes away)

Normal flora (aka normal microbiota)

Organisms that colonize the body's surfaces without normally causing disease 10x more bacterial cells than body cells Each square cm of skin contains about 3 million bacteria! Your intestines contain 400-1000 kinds of bacteria!

Adhesion

Pathogens attach to cells via a variety of structures or attachment proteins called adhesion factors. Some bacteria and viruses lose the ability to make a adhesion factors called adhesions and thereby become avirulent.

Resident microbiota

Remain a part of the normal microbiota of a person throughout life. Found on the skin, mucous membrane (of the digestive tract), upper respiratory tract, and the distal portions of the urethra and vagina. Considered commensal - feed on extracellular wastes and dead cells without causing harm to the host.

Transient microbiota

Remain in the body for only a few hours, days, or months before disappearing. Cannot persist in the host due to the competition between indigenous microbiota, elimination by the body's defenses, or chemical and physical changes that dislodge them.

Contact transmission, Direct:

Requires contact between infected and susceptible host. "person to person" (touching, kissing, sex) warts, herpes, gonorrhea. Some zoonoses spread by toucing, scratches, bites, etc. Ringworm, rabies

5 major pathways

Respiratory Tract; Gastrointestinal tract Genitourinary tract; Skin Subcutaneous or intramuscular; (Parenteral) route

surgical wounds

S. aureus responsible for nosocomial infection

Common diseases contracted via the G.I. Tract

Salmonellosis, Salmonella sp., Shigellosis, Shigella sp., Cholera, Vibrio cholorea, Ulcers, Helicobacter pylori, Botulism, Clostridium botulinum

Prodromal period

Second stage of disease; A short time of generalized, mild symptoms that precedes illness. Not all infectious agents have this stage.

Extracellular enzymes

Secreted by the pathogen, Dissolve structural chemicals in the body, Help pathogen maintain infection, invade, and avoid body defenses. Examples: Coagulases, Kinases, Collagenase, Hyaluronidase, IgA Proteases

Portals of exit

Sites through which microorganisms leave the body; examples: nose, mouth, urethra

Portals of Entry

Sites through which pathogens enter the body

Reservoirs of infection

Sites where pathogens are maintained as a source of infection, Most pathogens cannot survive for long outside their host

Indirect contact transmission

Spread of pathogens from one host to another via inanimate objects called fomites; examples: needles, toothbrushes, paper tissues, money, medical equipment, and drinking glasses.

Nonliving Reservoirs

Soil, water, and food can be reservoirs of infection Often due to contamination by feces or urine Clostridium botulinum enters soil from manure Salmonella typhi (typhoid fever) enters water from feces

Nonliving reservoir of infection

Soil, water, food, or inanimate object that is a continuous source of infection

Antiphagocytic chemicals

Some bacteria release chemicals that protect themselves from digestion after being enveloped by phagocytes; Some bacteria make chemicals that help resist a cell becoming phagocytized in the first place; Waxy cell wall of Mycobacterium tuberculosis resists phagocytosis; Some bacteria can release leukocidins, which actually destroy white blood cells

Exceptions to Koch's Postulates

Some microbes cannot be grown on artificial media; e.g., Treponema pallidum (syphillis) and Mycobaterium leprea (leprosy) Different microbes can cause same symptoms (hence same disease); Nephritis (kidneys), pneumonia, meningitis Same pathogen can cause multiple diseases depending on location and host; Mycobacterium tuberculosis can cause diseases of lungs, skin, bones, etc. Ethical considerations; You can't just go around injecting people and animals with disease. For example, humans are the only host for HIV...so Koch's postulates have never been applies to prove that HIV causes AIDS

frequency of Disease

Sporadic disease: disease that occurs occasionally in a population; usually a few scattered cases; e.g., typhoid fever Endemic disease: disease that normally occurs continuously in a population at predictable incidence rates e.g., common cold, malaria (in some parts of the world) Epidemic disease: disease occurs at a greater frequency than what is usual within a population; Note: within a localized area Pandemic disease: worldwide epidemic. AIDS; H1N1 (swine) flu of 2009

Contact transmission; inDirect:

Spread by fomites. For example: HIV and heptatitis B spread thru contaminated needles

Foodborne transmission

Spread of pathogenic microorganisms in or on foods that are poorly processed, undercooked, or improperly refrigerated.

Bodily fluid transmission

Spread of pathogenic microorganisms via blood, urine, saliva, or other bodily fluids.

Waterborne transmission

Spread of pathogenic microorganisms via water.

respiratory tract

Streptococcus responsible for nosocomial infection

Normal microbiota

The group of microbes that normally inhabit the surfaces of the body without causing disease, also known as indigenous microbiota.

An animal was infected with a virus. A mosquito bit the animal, was contaminated with the virus, and proceeded to bite and infect a person. which was the vector?

The mosquito

Incidence

The number of new cases of a disease in a given area or population during a given period of time; # of new cases/ # of people at risk.

Pandemic

The occurrence of an epidemic on more than one continent simultaneously.

Contamination

The presence of microbes in/on the body thru several portals of entry; Some microbial contaminants remain residents of the body and become part of normal flora, while others remain only a short amount of time as transient flora; Others...cause infection

Contamination

The presence of microorganisms in or on the body or other site.

Contact transmission

The spread of pathogens from one host to another by direct contact, indirect contact, or respiratory droplets.

Waterborne:

spread thru water; Especially for many GI diseases Fecal-oral route is a major source of diseases worldwide

high risk procedures for nosocomial infections

Urinary tract catheterization, surgical wounds, and respiratory tract.

when pathogenic bacteria win and disease results:

Vaginitis: results when normal flora population is decreased and pH reaches neutrality; promotes excessive growth of Candida albicans (yeast) Clostridium difficile normally limited by normal flora of intestine; antibiotics can decrease normal flora allowing C. difficile to flourish and cause GI infections (diarrhea or worse!)

Indirect Contact Transmission

When pathogens are transmitted via inanimate objects (fomites)

nutritional

result from lack of some essential nutrients in diet

Fecal-oral Infection

result from sewage contaminated drinking water or from ingesting fecal contaminants.

Disease

results if the invading pathogen alters normal body functions (loss of homeostasis)

Exotoxins

secreted by pathogens into their environment

Analytical epidemiology

seeks to determine the probable cause of a disease.

Portals of entry of pathogens into the body

skin, mucous membranes, the placenta, and the parenteral route, by which microbes are directly deposited into deeper tissues.

exotoxins

soluble protein substances produced (mainly) inside Gram-positive bacteria during normal metabolic processes, which are then secreted into host tissues.

Biofilm

some bacteria interact to produce a sticky web of cells and polysaccharides that adheres to a surface.

opportunists

some of the normal flora, can under special circumstances, produce disease are called

Airborne:

spread of pathogens farther than 1 meter to the respiratory mucous membranes of a new host via an aerosol (cloud of small droplets and particles suspended in the air) Generated from coughing, sneezing, generated from air conditioners, sweeping, changing bed sheets, etc.

Bodily Fluid Transmission

spread of pathogens via blood, urine, saliva, or other fluids