Microbiology- Chapter 14

Biological Vectors

(transmission) actively participate in a pathogen's life cycle

Mechanical Vector

(transmission) not necessary to the life cycle of an infectious agent and merely transports it without being infected

Maintenance of the Normal Resident Flora

-Normal flora is essential to the health of humans -Flora create an environment that may prevent infections and can enhance host defenses -Antibiotics, dietary changes, and disease may alter and compromise normal flora

Initial Colonization of the Newborn

-Uterus and contents are normally sterile and remain so until just before birth -Breaking of fetal membrane exposes the infant; all subsequent handling and feeding continue to introduce what will be its normal flora

Disease

-an abnormal state in which part or all of the body is not properly adjusted, or is not functioning normally -when the infection results in any changes from a state of health

Infection

-invasion or colonization of the body by pathogens -the presence of a particular microbe in a part of the body where it is not normally found Ex: E. coli a normal inhabitant of the intestines, infecting the urinary tract -a condition in which pathogenic microbes penetrate host defenses, enter tissues, and multiply -Can be undetectable (no symptoms) Ex: HIV

Direct Contact

-physical contact (touching, kissing, intercourse) -requires close association between infected and susceptible host Ex: HIV, common cold, influenza, measles rabies

Antiphagocytic Factors

-some bacteria kill phagocytes in our immune system -slimes or capsules cam make it physically difficult for the phagocyte to engulf the pathogen

3 Concerns of Pathology

1. Etiology 2. Pathogenesis 3. Structural and functional changes brought about by disease, and their final effects on the body

True Pathogens

Capable of causing disease in healthy persons with normal immune defenses -Example: influenza, plague, malarial protozoan

Koch's Postulates

Determining the causative or etiologic agent of infectious disease: - Find evidence of a particular microbe in every case of a disease - Isolate that microbe from an infected subject and cultivate it artificially in the laboratory - Inoculate a susceptible healthy subject with the laboratory isolate and observe the resultant disease - Reisolate the agent from this subject

Transmission of Disease

Disease-causing agents can be transmitted from the reservoirs to a host by: -direct contact -indirect contact

Nosocomial Infections

Diseases that are acquired or developed during a hospital stay -From surgical procedures, equipment, personnel, and exposure to drug-resistant microorganisms -2 to 4 million cases/year in U.S. with approximately 90,000 deaths -Most commonly involve urinary tract, respiratory tract, and surgical incisions -Some of the most common organisms involved: E. coli, Pseudomonas, Staphylococcus

Signs and Symptoms

Earliest signs or symptoms of disease as a result of the activation of the body defenses -fever, pain, soreness, swelling

Universal Precautions

Stringent measures to prevent the spread of nosocomial infections from patient to patient, from patient to worker, and from worker to patient

Symbiosis

Symbiosis is the relationship between 2 organisms (such as normal microbiota and the host) in which at least one organism is dependent on the other -Most areas of the body in contact with the outside environment harbor resident microbes -Generally, internal organs, tissues, and fluids are microbe-free

Us and Microbes

The human body exists in a state of dynamic equilibrium with microorganisms. A healthy individual is able to maintain a balanced coexistence with them. However, the balance can be disrupted and result in infection and disease. Many interactions between human body and microorganisms involve the development of biofilms Microbial cells bind to our cells and to other microbes Colonization of the body involves a constant "give and take"

Epidemiology

The study of the frequency and distribution of disease and health-related factors in human populations -Surveillance - collecting, analyzing, and reporting data on rates of occurrence, mortality, morbidity and transmission of infections -Reportable, notifiable diseases must be reported to authorities

Sign

a change in a body that can be measured or observed as a result of disease

Symptom

a change in body function that is felt by a patient as a result of disease

Vector

a live animal (other than human) that transmits an infectious agent from one host to another

Syndrome

a specific group of signs and symptoms that accompany a disease

Septicemia

a systemic infection arising from the multiplication of pathogens in the blood -microorganisms are multiplying in the blood and present in large numbers

Edema

accumulation of fluid

Secondary Infection

acquired after the initial (primary) infection, due to the weakening of the body's defenses -caused by a different microbe (an opportunistic pathogen) than what caused the primary infection

Latency

after the initial symptoms in certain chronic diseases, the microbe can periodically become active and produce a recurrent disease; person may or may not shed it during the latent stage -shingles

Asymptomatic (subclinical) infections

although infected the host doesn't show any signs of disease -HIV -Genital Herpes -Inapparent infection, so person doesn't normally seek medical attention

Carriers

an individual who inconspicuously shelters a pathogen and spreads it to others; may or may not have experienced disease due to the microbe

Koch's Postulates

are used to prove the cause of an infectious disease -some pathogens can cause several disease conditions -some pathogens cause disease only in humans

Bacteremia

bacteria present in blood

Mutualsim

both organisms benefit

Toxigenicity

capacity to produce toxins at the site of multiplaction

Opportunistic Pathogens

cause disease when the host's defenses are compromised or when they grow in part of the body that is not natural to them

Virulence Factor

characteristic or structure that contributes to the ability of a microbe to cause disease, and that determine the degree of tissue damage and severity of the disease

Acute Infection

comes on rapidly, with severe by short-lived effects -influenza

Passive Carrier

contaminated healthcare provider who is not infected, but picks up pathogens and transfers them to other patients, such as from not washing hands

Leukopenia

decrease in white blood cells

Endemic

disease that exhibits a relatively steady frequency over a long period of time in a particular geographic locale

Pathogen

disease-causing microorganism

Pandemic

epidemic across continents

Contagious

highly communicable disease

Leukocytosis

increase in white blood cells

Source

individual or object from which an infection is actually acquired

Chronic Carrier

individual who shelters that infectious agent for a long period

Systemic Infection

infection spreads to several sites and tissue fluids usually in the bloodsteam/lymph -measles -influenza

Non-Communicable

infectious disease does not arise through transmission for host to host -Occurs primarily when a compromised person is invaded by his or her own normal microflora -Contact with organism in natural, non-living reservoir

Primary Infection

initial infection

Microbial Antagonism

is a competition between microbes; bacterial flora benefit host by preventing overgrowth of harmful microbes as a result of limited number of attachment sites to host. -competition among microbes for nutrients, space -producing substances harmful to pathogens -affecting pH and oxygen conditions

Vehicle Transmission

is the transmission of disease agents via a medium (or "vehicle) such as water, food, air, blood and body fluids, biological products, fomites -air as a vehicle

Probiotics

live cultures of known microbes that -are applied to or ingested into the body, intended to exert a beneficial effect -are used to re-introduce compromised normal flora back into the body -re-establish normal flora and help prevent susceptibility to infections

Zoonoses

may be transmitted to humans

Incidence

measures the number of new cases over a certain time period, as compared with the general healthy population

Localized Infection

microbes enter the body and remains confined to a specific tissue -boils and abscesses

Residents

microbes that become established

Normal (resident) flora (indigenous flora or microbiota)

microbes that engage in mutual or commensal associations, but do not penetrate into the host's sterile tissues -human body=1 x 10^13 cells harbors 1x10^14 bacterial cells (10 times more)

Transients

microbes that occupy the body for only short periods -may be present for days, weeks or months

Period of Illness

multiplies at high levels, becomes well-established more specific signs and symptoms -disease is most severe -if immune system does not prevail, patient may die

Fomites

nonliving objects involved in the spread of an infection

Morbidity Rate

number of people afflicted with a certain disease

Endogenous Infections

occur when normal flora is introduced to a site that was previously sterile

Endogenous

occurring from within, not form external causes

Parasitism

one organism benefits at the expense of the other -includes many bacterial pathogens

Commensalism

one organism benefits, and the other is unaffected -much of normal microbiota= commensals

Indirect Contact

passes from infected host to intermediate conveyor and then to another host

Normal Microbiota

permanently colonize the host

Convalescent Period

person regains strength, recovers

Toxemia

presence of toxins in blood

Reservoir

primary habitat of pathogen in the natural world -human or animal carrier, soil, water, plants

Centers for Disease Control and Prevention (CDC)

principal government agency responsible for keeping track of infectious diseases nationwide

Chronic Infections

progresses more slowly, may be less severe, but persist over a long period of time -tuberculosis, hepatitis B

Normal Microbiota

protect the host by -Occupying niches that pathogens might otherwise occupy -Producing acids -Producing bacteriocins

Convalescent Carriers

recuperating without symptoms

Virulence

severity of the disease depends on the ____ of the pathogen

Asymptomatic Carrier

show no symptoms

Period of Decline

signs and symptoms subside

Opportunistic Pathogens

some normal microbiota

Incubation Carriers

spread the infectious agent during the incubation period

Aerosols

suspensions of fine dust carrying pathogens in air

Lymphadenitis

swollen lymph nodes

Etiology

the cause of disease (for example, the name of the species that causes the disease)

Pathogenesis

the manner in which a disease develops -how is the infection acquired -what areas of the body does the microbe infect

Pathology

the scientific study of disease

Mortality Rate

the total number of deaths in a population due to a certain disease

Incubation Period

time from initial contact with the infectious agent to the appearance of first signs or symptoms; -agent is multiplying but damage is insufficient to cause symptoms; -several hours to several years

Prevalence

total number of existing cases with respect to the entire population usually represented by a percentage of the population

Sepsis

toxic inflammatory condition arising from the spread of microbes, especially bacteria or their toxins, from a focus of infection

Exotoxin

toxin molecule secreted by a living bacterial cell into the infected tissue -have strong specificity for a target host cell, inflicting damage or death of the cell

Endotoxin

toxin that is not secreted but is released after the cell is damaged -only one type: Lipopolysaccharide (LPS), part of the outer membrane of gram-negative cell walls; can cause fever, inflammation, hemorrhage, or diarrhea

Droplet Nuclei

transmission via airborne droplets of mucus or saliva from coughing, sneezing

Prodromal Stage

vague feelings of discomfort; nonspecific complaints; early mild symptoms; general aches

Viremia

viruses present in blood

Granulomas and Abscesses

walled-off collections of inflammatory cells and microbes

Communicable Disease

when an infected host can transmit the infectious agent to another host and establish infection in that host

Focal Infection

when infectious agent breaks loose from a local infection and is carried to other specific tissues, where is becomes confined

Sporadic

when occasional cases are reported at irregular intervals

Epidemic

when prevalence of a disease is increasing beyond what is expected