Microbiology Exam 3. Ch 14 Study Guide

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Pathology

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The scientific study of disease

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Etiology

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The cause of disease

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Infection

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The invasion or colonization of the body by pathogenic microorganisms

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Disease

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An abnormal state in which part or all of the body is not properly adjusted or incapable of performing its proper functions

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Normal Microbiota

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(Also Normal Flora) The microorganisms that establish permanent residence (colonize) but do not produce disease under normal conditions

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Transient Microbiota

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Microorganisms present for several days, weeks or months than disappear

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Commensalism

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A symbiotic relationship where on organism benefits and the other is unaffected

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Mutualism

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A type of symbiosis that benefits both organisms

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Parasitism

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A type of symbiosis where one organism benefits by deriving nutrients at the expense of the other

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Microbial Antagonism

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(Also Competitive Exclusion) The competition among microbes. This helps normal microbiota benefit the host by preventing overgrowth of harmful microorganisms

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Competitive Exclusion

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(Also Microbial Antagonism) Normal microbiota prevents overgrowth of harmful microorganisms by competing for nutrients, producing substances harmful to invaders and affecting PH levels and O2 availability

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Symbiosis

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(Includes Mutualism and parasitism) The relationship between two organisms in which at least one organism is dependent on the other

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How does Mutualism pertain to Probiotics

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Probiotics are live microbial cultures that are applied or ingested. They are intended to have a beneficial affect.
EX. Ingesting LActic Acid Bacteria (LAB) can alleviate diarrhea and prevent colonization of Salmonella. IN return the microbe receives nutrients for survival

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Opportunistic Microorganisms

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Microbes that do not cause disease in their normal habitat in a healthy person but may do so in a different environment

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Opportunistic Pathogens

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Microbes that do not cause disease in their normal habitat in a healthy person but may do so in a different environment. In addition, they may possess other features that contribute to their ability to cause disease.
EX. They are present in or on the body or in the external environment in large numbers
EX E.Coli is generally harmless as long as it remains in the large intestine but if it gains access to other sites such as the urinary bladder spinal cord or wounds it may cause urinary tract infection, meningitis, or abscesses.

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What are Koch's Postulates?

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There are four (4) Koch's Postulates. They provide a framework for the study of the etiology of any infectious disease
1) The same pathogen must be present in every case of the disease
2) The pathogen must be isolated from the disease host and grown in a pure culture
3) The pathogen from the pure culture must cause the disease when it is inoculated into a healthy, susceptible laboratory animal
4) The pathogen must be isolated from the inoculated animal and shown to be the original organism

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What are the exceptions to Koch's postulates?

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Koch's postulates are useful in determining the causative agent of most bacterial diseases however, there are some exceptions.
1) Some microbes have unique culture requirements. (ex. Treponema pallidum is known to cause syphilis but virulent strains have never been cultured)
2) Some pathogens do not display clear-cut or specific symptoms (ex. nephritis [inflammation of kidneys] can involve several different pathogens, all of which show the same signs and symptoms)
3) Some pathogens cause several disease conditions (ex. Mycobacterium tuberculosis is implicated in diseases of the lungs, skin, bones, and internal organs)
4) Ethical considerations because some agents that cause disease in humans have no other known host. (ex HIV)

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Communicable Disease

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Any disease that spreads from one host to another, either directly or indirectly

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Non-Communicable Disease

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Is not spread from one host to another. These diseases are caused by microorganisms that normally inhabit the body and only occasionally produce disease or by microorganisms that reside outside the body and produce disease only when introduced to the body (ex tetanus)

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Contagious Disease

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Disease that are easily spread from one person to another

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Symptoms

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Changes in body function such as pain or malaise. These subjective changes are not apparent to the observer

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Signs

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Objective changes that the physician can observe and measure. These include lesions, fever, swelling and paralysis

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Syndrome

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A specific group symptoms or signs may always accompany a specific disease

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Frequency of Occurrence: Incidence

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The number of people in a population who develop a disease during a particular time

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Frequency of Occurrence: Prevalence

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The number of people in a population who develop a disease at a specified time, regardless of when it first appeared. Prevalence takes into account both new and old cases. It's an indicator of how serious and how long a disease affects a population

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Frequency of Occurrence: Sporadic

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A disease that occurs only occasionally

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Frequency of Occurrence: Endemic

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A disease that is constantly present in a population. (Ex. the common cold)

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Frequency of Occurrence: Epidemic

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Many people in a given area acquire a certain disease in a relatively short period

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Frequency of Occurrence: Pandemic

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An epidemic disease that occurs worldwide

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Severity and duration: Acute

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A disease that develops rapidly but lasts only a short time. Influenza

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Severity and duration: A Chronic disease

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A disease that develops slowly, and the body's reaction may be less severe, but the disease is likely to continue or recur for long periods

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Severity and duration: a Subacute disease

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A disease that is intermediate between acute and chronic

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Severity and duration: A Latent disease

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A disease in which the causative agent remains inactive for a time but then becomes active to produce symptoms of disease (Ex. Shingles)

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Severity and duration: Herd Immunity

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When many immune people are present in a community

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Extent of host involvement: A local infection

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An infection in which the invading microorganisms are limited to a relatively small area of the body (ex. boils or abscesses)

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Extent of Host involvement: A systemic (generalized) infection

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An infection in which microorganisms or their products are spread throughout the body by the blood or lymph (ex. measles)

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Extent of Host involvement: A Focal Infection

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Agents of a local infection enter a blood or lymphatic vessel and spread to other parts of the body, where they are confined to specific areas of the body. These can arise from infections in areas such as the teeth, tonsils, or sinuses

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Extent of Host involvement: Sepsis

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

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Extent of Host involvement: Septicemia

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Also called Blood Poisoning. Is a systemic infection arising from the multiplication of pathogens in blood. Septicemia is a common sepsis

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Extent of Host involvement: Bacteremia

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The presence of bacteria in the blood

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Extent of Host involvement: Toxemia

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The presence of toxins in the blood. Occurs in Tetanus

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Extent of Host involvement: Viremia

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The presence of Viruses in the blood

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Extent of Host involvement: A Primary Infection

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An acute infection that causes the initial illness

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Extent of Host involvement: A Secondary Infection

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An infection that is caused by an opportunistic pathogen after the primary infection has weakened the body's defenses

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Extent of Host involvement: A Subclinical Infection

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An infection that does not cause any noticeable illness

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What are the four predisposing factors of disease?

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A predisposing factor is anything that makes the body more susceptible to disease
1) Genetic background (Ex. sickle cell)
2) Gender (Ex. females have a higher incidence of UTI)
3)Climate and weather (stay indoors because of cold, closer contact with other people)
4) Nutrition (inadequate)
5) Fatigue
6) Age
6) Others Environment, lifestyle, occupation, preexisting illness, chemotherapy, emotional distress

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Development of Disease: Incubation Period

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The interval between the initial infection and the first appearance of signs or symptoms. The rime of incubation depends of the specific microorganisms involved, virulence (degree of pathogenicity) the number of infecting microorganisms, and the resistance of the host

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Development of Disease: Prodromal Period

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A relatively short period that follows the period of incubation. Characterized by early, mild symptoms or disease, such as general aches and malaise

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Development of Disease: Period of illness

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The period in which the disease is most severe. The person exhibits overt signs and symptoms of disease

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Development of Disease: Period of Decline

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The period where the signs and symptoms subside

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Development of Disease: The Period of Convalescence

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The period where the person regains strength and the body returns to its prediseased state

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Reservoirs of Infection

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A continual source of the disease organism. The source can be either a living organism or an inanimate object that provides the pathogen with adequate conditions for survival and multiplication and an opportunity for transmission

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Reservoirs of Infection: Human Reservoirs (carriers)

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The human body is the principal reservoir for human disease. People harbor pathogens and transmit them directly or indirectly to others. Carriers are people who harbor pathogens and transmit them without exhibiting signs of illness

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Reservoirs of Infection: Animal Reservoirs and Zoonoses

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Disease that occur in wild or domestic animals that can be transmitted to humans are called Zoonoses (ex. Rabies or Lyme disease)

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Reservoirs of Infection: Non-living Reservoirs

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Two major Soil and water. Soil harbors pathogens such as fungi. Water can be contaminated by feces

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What are the three principle routes of infection?

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1) Contact Transmission
2) Vehicles Transmission
3) Vectors

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Routes of Infection: Contact transmission (3 types)

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1) Direct Contact -- Person to person. Physical contact with the host (touching, kissing, sexual intercourse)
2) Indirect contact transmission. Agent of disease is transfered from its reservoir to a susceptible host by means of a non-living object (ex. Fomites: Towels, handkerchief, cups etc.)
3) Droplet Transmission. microbes are spread though droplet nuclei (mucus droplets). These are discharged in the air through coughing, sneezing, laughing, or talking (normally travel less that 1 m)

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Routes of Infection: Vehicle transmission

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The transmission of water by a medium such as water, food or air.
1) Waterbourne
2) foodbourne
3) Airbourne (more than 1m)

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Routes of Infection: Vectors

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Animals that carry pathogens from one host to another (arthropods and other insects)
1) Mechanical transmission: Passive transport on insects feet etc.
2) Biological transmission: An active process. A bite or an injection

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Fomite

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Non-living object involved in transmission. Ex. Handkerchief, cup, toys, keys, etc

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Nosocomial (Hospital acquired) Infections

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An infection that does not show any evidence of being present or incubating at the time of admission to a hospital. It is acquired as a result of hospital stay. They are the 8th leading cause of death in the US.
Factors: Microorganisms in the hospital, compromised (weakened) host, the chain of transmission

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Compromised host

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An individual whose defenses have been weakened by illness ,therapy or burns. Two principle conditions can compromise a host
1) Broken skin/mucous membranes
2) Suppressed immune system

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Which Microorganisms are most often involved with Nosocomial infections?

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1) Coagulase-negative staphylococci- 25%, resistant 89% Most common cause of sepsis
2) Staphylococcus Aureus- Most frequent cause of pneumonia
3) Enterococcus - Most common cause of surgical wound infection
4) Escherichia Coli - Pneumonia and surgical wound infection
5) Clostridium- causes half of nosocomial diarrhea
6) Fungi - Urinary tract infections and sepsis
7) Other gram negative - Urinary tract infections and surgical wound infections

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Chain of transmission in nosocomial infections

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1) Direct contact transmission from hospital staff to patient and from patient to patient. Can happen while changing a dressing
2) Indirect contact transmission through fomites and the hospitals ventilation system (airborne) or urinary catheter

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How to control nosocomial infections?

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1) Use aseptic technique. Handle contaminated materials carefully.
2) Hand washing is the single most effective means of preventing disease infection