Microbiology Chapter 14 - Epidemiology

Reservoir of infection

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

Endemic disease

A disease constantly present in a population (common cold)

Chronic disease

A disease that develops more slowly and the body's reactions may be less severe, but the disease is likely to continue or recur for long periods of time (Infectious mononucleosis, tuberculosis, and Hepatitis B)

Acute disease

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

Subacute disease

A disease that is intermediate between acute and chronic (Subacute sclerosing panencephalitis)

Epidemic disease

A disease that many people in a given area acquire in a relatively short period. (Influenza)

Sporadic disease

A disease that occurs only occasionally (ex: typhoid fever in the US)

Pandemic

A disease that occurs worldwide (AIDS)

Latent disease

A disease where the causative agent remains inactive for a time but then becomes active to produce symptoms of the disease (shingles)

Lactobacilli

A newborn's first contact with microorganisms is usually with what bacteria?

Syndrome

A specific group of symptoms/signs that may always accompany a particular disease

Sepsis

A toxic inflammatory condition arising form the spread of microbes from a focus of infection

Biological transmission

An active process/transport of pathogens that may have been caused by an animal biting an infected host, pathogens growing inside the vector, and an increase in the possiblity that they will be transmitted to another host

Primary infection

An acute infection that causes the initial illness

Secondary infection

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

Systemic (generalized) infection

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

Local infection

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

Nosocomial infection

An infection that does not show any evidence of being present or incubating at the time of admission to a hospital, aqcuired during hospital stay

Focal infection

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

Analytical epidemiology

Analyzes a particular disease to determine its probable cause

Vectors

Animals that carry pathogens from one host to another

Noncommunicable disease

Any disease that is not spread from one host to another (Tetanus)

Communicable disease

Any disease that spreads from one host to another, either directly or indirectly (Chickenpox, measles, genital herpes, typhoid fever, tuberculosis)

Septiciemia

Blood poisoning, a systemic infection arising from the multiplication of pathogens in the blood.

Etiology

Cause of the disease

Contagious disease

Disease that is EASILY spread from one person to another

Emerging infectious diseases (EIDs)

Diseases that are new/changing, showing an increase in incidence in the recent past, or potential to increase in the near future

Zoonoses

Diseases that occur primarily in wild and domestic animals and can be transmitted to humans are called...?

Bacteriocins

E.coli in the large intestine produce ________, proteins that inhibit the growth of other bacteria of the same or closely related species, such as pathogenic Salmonella and Shigella.

Descriptive epidemiology

Entails collecting all data that describe the occurrence of the disease under study

Clotridium difficile

If the normal microbiota in the large intestine are eliminated (for example, by antibiotics), what organism can be responsible for nearly all gastrointestinal infections that follow antibiotic therapy?

Virulence, host

Infection depends on _________ which is the degree of pathogenicity and the ______.

Microbial antagonism (competitive exclusion)

Involves competition among microbes. Normal microbiota protect the host against colonization by potentially pathogenic microbes by competing for nutrients, producing substances harmful to the invading microbes, and affecting conditions such as pH and available oxygen.

Morbidity and Mortality Weekly Report

Issued by the CDC, a publication that contains data on morbidity and mortality and is read by microbiologists, physicians, and hospitals

Predisposing factors

Make the body more susceptible to a disease and may alter the course of the disease

Case control method

Method used in analytical epidemiology in which the epidemiologist looks for factors that might have preceded the disease.

Cohort method

Method used in analytical epidemiology in which the epidemiologist studies 2 populations: one that has had contact with the agent causing a disease and another that has not

Transient microbiota

Microorganisms that are present for several days, weeks, or months, and then disappear.

Opportunistic pathogens

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

Signs

Objective changes exhibited by a patient that the physician can observe and measure.

Extent of host involvement

One of 4 factors in classifying infectious diseases. Local vs Systemic

Severity/Duration

One of the 4 factors in classifying infectious diseases. Acute vs Chronic vs Latent

Spreading ability

One of the 4 factors used for classifying infectious diseases. Communicable vs non-communicable disease Contagious -> ease of communicability (chicken pox, measles)

Frequency of Occurrence

One of the 4 factors used for classifying infectious diseases. Incidence Endemic vs Epidemic vs Pandemic

Compromised host

One whose resistance to infection is impaired by disease, therapy, or burns

Foodborne transmission

Pathogens are generally transmitted in foods that are incompletely cooked, poorly refrigerated, or prepared under unsanitary conditions

Waterborne transmission

Pathogens are usually spread by water contaminated with untreated or poorly treated sewage

Carriers

People who are living reservoirs of infection

Period of illness

Period when the disease is most severe

Normal Flora (normal microbiota)

Permanent residents that do not cause disease under normal conditions

Prodromal period

Relatively short period that follows the period of incubation in some diseases (early, mild symptoms such as aches and malaise)

Symptoms

Subjective changes experienced by a patient that are not apparent to an observer

Prevalence

The ________ of a disease is the number of people in a population who develop a disease at a specified time, regardless of when it first appeared.

Incidence

The _________ of a disease is the number of people in a population who develop a disease during a particular time period

Incubation period

The interval between the initial infection and the first appearance of any signs or symptoms

Infection

The invasion or colonization of the body by pathogenic microorganisms

Pathogenesis

The manner in which a disease develops

Mechanical transmission

The passive transport of the pathogens on an insect's feet or other body parts

Period of Convalescence

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

Pathology

The scientific study of disease

Period of decline

The signs and symptoms subside

Airborne transmission

The spread of agents of infection by droplet nuclei in dust that travel more than 1 meter from the reservoir to the host

Contact transmission

The spread of an agent of disease by direct contact, indirect contact, or droplet transmission

Vehicle transmission

The transmission of disease agents by a medium (water, food, air, blood/bodily fluids...)

Droplet transmission

Transmission in which microbes are spread in droplet nuclei (mucus droplets) that travel only short distances (coughing, sneezing,...)

Direct contact transmission

Transmission of an agent by physical contact between its source and a susceptible host (no intermediate object is involved - person to person)

Indirect contact transmission

Transmission that occurs when the agent of disease is transmitted from its reservoir to a susceptible host by means of a nonliving object (thru fomites - tissues...)

1. The same pathogen must be present in every case of the disease 2. The pathogen must be isolated from the diseased 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 must be shown to be the original organism

What are Koch's experimental requirements or postulates for studying the etiology of an infectious disease?

1. Broken skin/mucous membranes 2. Suppressed immune system

What are the 2 principle condition that can compromise a host?

1. Treponema pallidum (can't be cultured in artificial media) 2. Mycobacterium leprae (can only be cultured in armadillo) 3. HIV (can't inoculate humans with infectious agents)

What are the exceptions to Koch's postulates discusses in class?

1. Reservoirs 2. Means of transmission 3. Portal of exit/entry

What are the factors contributing to the spread of infection discussed in class?

1. Spreading ability 2. Frequency of occurrence 3. Severity/Duration 4. Extent of host involvement

What are the four factors for classifying infectious disease discussed in class?

1. Direct contact transmission 2. Indirect contact transmission

What are the principle routes of transmission of nosocomial infections?