Microbiology: Chapter 14
is the scientific study of disease
the study of the cause of a disease.
the manner in which a disease develops
- the growth of microorganisms in the body
- the invasion or colonization of the body by pathogenic microorganisms
- the presence of a particular type of microorganisms in a part of the body where it is not normally found
- an abnormal state in which part of all of the body is not properly adjusted or is incapable of performing normal functions
- occurs when an infection results in any change of a state of health.
- the microoorganisms that colonize a host without causing disease
- aka normal flora
- the microorganisms that are present in am animal for a short time without causing diease
- may be present for several days, weeks, or months, and then disappear
- growth of some microbes prevents the growth of other microbes
- normal microbiota protect the host against colonization by potentially pathogenic microbes by competing for nutrients, producing substances harmful to the invading microbes.
- aka competitive exclusion
- the living together of two different organisms or populations
-a relationship between two organisms in which at least one organism is dependent on the other
a symbiotic relationship in which two organisms live in association and one is benefited while the other is neither benefited nor harmed.
a symbiotic relationship in which both organisms or populations are benefited
- live microbial cultures applied to or ingested that are intended to exert a beneficial effect
- probiotics may be administered with prebiotics, which are chemicals that selectively promote the growth of beneficial bacteria.
- a symbiotic relationship in which one organisms exploits another without providing any benefits in return
- one organisms benefits by deriving nutrients at the expense of the other
- many disease-causing bacteria are parasites
a microorganism that does not ordinarily cause a disease but can become pathogenic under certain circumstances.
- criteria used to determine the causative agent of infectious disease
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 pure culture
3) the pathogen from the pure culture must cause the disease when it is inoculated in a healthy, susceptible laboratory animal
4) The pathogen must be isolated from the inoculated animal and must be shown to be the original organism
- changes in body functions
- a change in body function that is felt by a patients as a result of a disease
a change due to a disease that a person can observe and measure
a specific group of sings or symptoms that accompany a disease
any disease that can be spread from one host to another, either directly or indirecly
a disease that is easily spread from one person to another
a disease that is not transmitted from one person to another.
the fraction of the population that contracts a disease during a particular period of time
- number of people in a populate who develop a disease at a specific time, regardless of when it first appeared
- takes into account both old and new cases
a disease that occurs occasionally in a population
a disease constantly present in a population
a disease acquired by many hosts in a given area in a short time
epidemic disease that occurs worldwide
develops rapidly but lasts only a short time
develops more slowly, and the body's reactions may be less sever, but the disease is likely to continue or reoccur for long periods.
a disease with symptoms that are intermediate between acute and chronic.
a disease in which the causative agent remains inactive for a time but then becomes active to produce symptoms of the disease
the presence of immunity in most of a population
an infection in which pathogens are limned to a small area of the body
systemic (generalized) infections
- an infection throughout the body
- microorganism or their products are spread throughout the body by the blood or lymph
- a systemic infection that began as an infection in one place
- Agents of a local infection enter a blood or lymphatic vessel and spread to other specific areas of the body
- can arise from infections in areas such as the teeth, tonsils, or sinuses.
- a toxic inflammatory condition arising from the spread of microbes
- the presence of a toxin or pathogenic organism in the blood and tissue
-systemic infection arising from the multiplication of pathogens in the blood
- the proliferation of pathogens in the blood, accompanied by fever; sometimes causes organ damage
- common example of sepsis
- aka blood poisoning
- presents of bacteria in the blood
presents of toxin in the blood
presence of viruses in the blood
- an acute infection that causes the initial illness
- cause by an opportunistic pathogen after the primary infection has weakened the body's defenses.
subclinical (inapparent) infection
- an infection that does not cause any noticeable illness
- makes the body more susceptible to a disease and/or may alter the course of the disease
(1st development of disease)
- the interval between the initial infection and the first appearance of any signs of symptoms.
- no signs or symptoms
- the time of incubation depends on the specific microorganism involved, its virulence, the number of infecting microorganism, and the resistance of the host.
(2nd development of disease
- relatively short period that follows the period of incubation in some disease
- characterized by early, mild symptoms of disease
Period of illness
(3rd development of disease)
- the disease is most sever
- exhibits overt signs and symptoms of disease
- most sever signs and symptoms
period of decline
(4th development of disease)
- signs and symptoms subside
- vulnerable to secondary infections
period of convalescence
(5th development of disease)
- regains strength and the body returns to its prediseased state.
reservoir of infection
-a continual source of infection
organisms (usually refers to humans) that harbor pathogens and transmit them to others.
diseases that occur primarily in wile and domestic animals and ca be transmitted to humans.
spread of agent of disease by direct contact, indirect contract, or droplet transmission
Direct contact transmission
- is the direct transmission of an agent by physical contact between its source and a susceptible host
- no intermediate object is involved
- aka person-to-person
Indirect contact transmission
- occurs when the agent of disease is transmitted from its reservoir to a susceptible host by means of a nonliving object
a nonliving object that can spread disease
- which microbes are spread in droplet nuclei (mucus droplets) that travel only a short distance
- disease agents that travel short distances are not regarded as airborne transmission
- transmission of disease agents by a medium, such as water, food, or air.
- other media include blood and other body fluids,drugs, and intravenous fluids
pathogens are usually spread by water contaminated with untreated or poorly treated sewage
pathogens are generally transmitted in foods that are incompletely cooked, poorly refrigerated, or prepared under unsanitary conditions.
spread of agents of infection by droplet nuclei in dust that travel more than 1 meter from the reservoir to the host.
animals that carry pathogens from one host to another
passive transport of the pathogens on the insect's feet, or other body parts.
- the transmission of a pathogen from one host to another when the pathogen reproduces in the vector.
- arthropod bites an infected person or animal and ingests some of the infected blood.
- an infection that develops during the course of a hospital stay and was not present at the time the patient was admitted.
Nosocomial infection result from the interaction of several factors:
1) microorganisms in the hospital environment
2) the compromised (or weakened) status of the host
3) the chain of transmission in the hospital
- a host whose resistance to infection is impaired.
- two principal conditions can compromise the host: broken skin or mucous membranes, and a suppressed immune system.
emerging infectious diseases (EIDs)
a new or changing disease that is increasing or has the potential to increase in incidence in the near future.
the science that studies when and where diseases occur and how they are transmitted
- entails collecting all data that describe the occurrence of the disease under study.
- relevant information usually includes information about the affected individuals and the place and period in which the disease occurred.
- analyzes a particular disease to determine its probable cause
- case control method: the epidemiologist looks for factors that might have preceded the disease.
- cohort method: epidemiologist studies two population: one that has had contact with the agent causing a disease and another that has now.
-begins with a hypothesis about a particular disease; experiments to test the hypothesis are then conducted with a group of people
Centers for Disease Control and Prevention (CDC)
- a branch of the U.S. Public Health Service located in Atlanta, Georgia, is a central source of epidemiological information in the United States.
Morbidity and Mortality Weekly Report (MMWR)
- CDC issues a publication
- is read by microbiologists, physicians, and other hospital and public health professional.
- contains data on morbidity and mortality
the incidence of specific notifiable diseases
the number of deaths from these diseases
notifiable infectious diseases
are diseases for which physicians are required by law to report cases in the U.S. Public Health service.
the number of people affected by a disease in a given period of time in relation to the total population
the number of deaths resulting from a disease in a population in a given period of time in relation to the total population