Micro Chapter 14: Microbial Interactions

a parasite capable of causing disease in a host

any organism that harbors another organism

an association between two (or more) species

"living together"

both members benefit from the relationship

one organism benefits from the relationship, where as the other organism

two species live together in a relationship such that one benefits and the other one neither benefits nor is harmed

both species harm each other without ether benefiting

microorganisms are present

the multiplication of any parasitic organism within or on the host's body

the presence of larger parasites, such as worms or arthropods, in or on the body

a disturbance in the state of health wherein the body cannot carryout all its normal functions

the capacity to produce disease

the intensity of the disease produced by pathogens

the rapid transfer of the pathogen through animals of a species susceptible to infection by that pathogen

the weakening of the disease-producing ability of the pathogen

a laboratory technique in which a pathogen is passed from its normal host to a new host species and then passed sequentially through many individuals of the new host species

organisms that live on or in the body but do not cause disease

comprise microbes that are always present on or in the human body

microorganisms that can be present under certain conditions in any of the locations

organisms that do not usually cause disease but can do so under certain conditions

• 1. Failure of the Host's Normal Defenses
• 2. Introduction of the Organisms into Unusual Body Site
• 3. Disturbances in the Normal Microflora

• 1. the specific causitive agent must be observed in every case of a disease
• 2. The agent must be isolated from a diseased host and must be grown in pure culture
• 3. when the agent from the pure culture is inoculate into healthy, but susceptible, experimental hosts, the agent must cause the same disease
• 4. The agent must be re-isolated from the inoculate, diseased experimental host and identified as being identical to the original specific causative agent

diseases caused by infectious agents such as bacteria, viruses, protozoa, and helminths

caused by any factor other than infectious organisms

caused by errors in genetic information

structural and functional defects present at birth, caused by drugs, excessive X-ray exposure, or certain infections

disorders that develop in one or more body systems as aging occurs

lower resistance to infectious deseases and contribute to the severity of infections

due to excesses or deficiencies of hormones

can be caused by a variety of factors, including those of an emotional, or psychogenic nature, as well as certain infections

caused by malfunction of the immune system

involve abnormal cell growth that leads to the formation of various types of generally harmless, or cancerous growths or tumors

caused by medical preocedures and/or treatments

diseases whose cause is unknown

some infections that can be spread from one host to another

highly communicable diseases

are not spread from one host to another

structural or physiological characteristics that help organisms cause infection and disease

a critical point in the production of bacterial disease (attachment)

proteins or glycoproteins found on attachment pili (fimbrae) and capsules

the growth of microorganisms on epithelial surfaces, such as skin or mucous membranes

its ability to invade and grow in host tissues

spreading factor

Streptococci produce this enzyme to digest hyaluronic acid

• a bacterial enzyme that accelerates the coagulation (clotting) of blood
• 1. keeps organisms from spreading
• 2. helps wall organisms off from immune defenses that might otherwise destroy them

dissolves blood clots

any substance that is poisonous to other organisms

soluble substances secreted into host tissues

more powerful toxins produced by several Gram-positive and a few Gram-negative bacteria

part of the cell wall and are released into host tissues from Gram-negative bacteria

the action of these exotoxins is to lyse (rupture) red blood cells

hemolyze blood cells, partially break down hemoglobin, and produce a greenish ring around colonies

hemolyze blood cells but completely break down hemoglobin and leave a clear ring around colonies

exotoxins produced by many bacteria

damage or destroy certain kinds of white blood cells called neutrophils and macrophages

interferes with the ability of leukocytes to engulf microorganisms that secrete the exotoxin

the spreading of exotoxins by blood from the site of infection

disease that result from the ingestion of a toxin

are exotoxins that act on tissues of the nervous system to prevent muscle contraction (botulism) of muscle relaxation (tetanus)

are exotoxins that act on tissues of the gut

an altered toxin that has lost its ability to cause harm but that retains antigenicity

in tissue culture systems, once inside a cell, viruses cause observable changes

consist of nucleic acids and proteins not yet assembled into viruses, masses of viruses, or remnants of viruses

occurs when viruses enter a cell and produce infectious offspring

occurs when viruses enter a cell but are unable to express all their genes to make infectious offspring

the virus may retreat into the nervous system and remain inactive, or latent

stress, other infections, or fever can reactivate the virus

involve a continued production of viruses over many months or years

certain fungi parasites produce which cause disease in human

a characteristic of a disease that can be observed by examining the patient

a characteristic of a disease that can be observed or felt only by the patient

combination of signs and symptoms that occur together and are indicative of a particular disease or abnormal condition

an increase in the number of white-blood cells circulating in the blood

some disease leave aftereffects, even after recovery

develops rapidly and runs its course quickly

develops more slowly, is usually less severe, and persists for a long, indeterminate period

characterized by periods of inactivity

confined to a specific area, but pathogens, or their toxins, can spread to other areas

generalized infection

affects most of the body, and the pathogens are widely distributed in many tissues

an intial infection in a previously healthy person (many are acute)

follows a primary infection, especially in individuals weakened by the primary infection

the time between infection and the appearance of signs and symptoms

a short period during which nonspecific, often mild, symptoms such as malaise and headache sometimes appear

a symptom indicating the onset of a disease

the period during which the individual experiences the typical signs and symptoms of the disease

when the signs and symptoms reach their greatest intensity

• act on a center in the hypothalamus, referred to as the body's thermostat.
• Pyrogens set the thermostat at a higher-than-normal temperature

the period of illness during which host defenses and the effects of treatment finally overcome the pathogen

tissues are repaired, healing takes place, and the body regains strength and recovers