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