Microbe human interactions

Dynamic equilibrium

The human body exists in a state of dynamic equilibrium.

Biofilms

Many interactions between human body and microorganisms involve the development of biofilms.

Colonization

Colonization of the body involves a constant 'give and take'.

Infection

A condition in which pathogenic microbes penetrate host defenses, enter tissues, and multiply.

Infectious Disease

An infection that causes damage or disruption to tissues and organs.

Pathogen (true)

Any agent capable of causing disease in a healthy person with normal immune defenses.

Opportunistic pathogen

One that invades the tissues when the body defenses are suppressed.

Virulence

The degree of pathogenicity of a parasite.

Avirulent

Lacking the ability to cause disease.

Normal Flora

Most areas of the body in contact with the outside environment harbor resident microbes.

Transients

Microbes that occupy the body for only short periods.

Residents

Microbes that become established.

Microbial antagonism

Bacterial flora benefit host by preventing overgrowth of harmful microbes.

Endogenous infections

Occur when normal flora is introduced to a site that was previously sterile.

Initial Colonization of the Newborn

Uterus and contents are normally sterile and remain so until just before birth.

Flora of the Skin

Skin is the largest and most accessible organ.

Flora of the Gastrointestinal Tract

hollow tube, bounded by mucous membranes. Tube is exposed to the environment

Flora of the Mouth

Most diverse and unique flora of the body.

Bacterial count of saliva

5 x 10^9 cells per milliliter.

Flora of the Large Intestine

Has complex and profound interactions with host.

Microbes per gram of feces

10^8-10^11 microbes per gram of feces.

Flora of the Respiratory Tract

Flora found in upper respiratory.

Lower respiratory flora

Larynx, trachea = flora; Bronchi, bronchioles, lungs = sterile.

Aerosols

Produced by sneezing, coughing, or even just speaking are an important mechanism for respiratory pathogen transmission.

Flora of the Genitourinary Tract

Sites that harbor microflora: Females - Vagina, distal urethra, and external genitalia; Males - Distal urethra, external genitalia.

Normal Resident Flora

essential to the health of humans. create an environment that may prevent infections and can enhance host defenses

Role of Flora

Flora create an environment that may prevent infections and can enhance host defenses.

Factors Altering Flora

Antibiotics, dietary changes, and disease may alter flora.

Probiotics

Introducing known microbes back into the body.

Sterile Areas of the Body

All internal tissues and organs; all fluids within organs or tissue.

Pathogen's Goal

find a good place to live and multiply = perpetuate its species.

Severity of Disease

Severity of the disease depends on the virulence of the pathogen.

Virulence Factor

Characteristic or structure that contributes to the ability of a microbe to cause disease.

Portal of Entry

Site where the parasite enters the host

Exogenous

Source outside the body

Endogenous

Source on or inside the body

Skin

Enter via nicks, abrasions, punctures, incisions

Gastrointestinal tract portal

Enter via food, drink, and other ingested materials

Respiratory tract

Enter via respiratory droplets into oral and nasal cavities

Urogenital tract

Sexual, displaced organisms

Transplacental

Some pathogens have the ability to move from mother's bloodstream and into baby's bloodstream via the placenta

Insect Bite

Arthropods that feed (blood meal) on animals and humans

STORCH

Syphilis, Toxoplasmosis, Other diseases (hepatitis B, AIDS and chlamydia), Rubella, Cytomegalovirus and Herpes simplex virus

Infectious Dose (ID)

Minimum number of microbes required for infection to proceed

Virulence factors

Traits used to invade and establish themselves in the host, also determine the degree of tissue damage that occurs

Exoenzymes

Enzymes that chemically break down or dissolve host's barriers and promote the spread of microbes into deeper tissues

Mucinase

Dissolve mucus coating

Keratinase

Dissolve keratin of skin or hair

Collagenase

Dissolve collagen

Hyaluronidase

Digests hyaluronic acid

Exotoxin

Protein secreted that goes to site of action = target tissue

Hemotoxins

Lyse blood cells

Enterotoxins

Affect intestinal mucosa

Neurotoxins

Affect nerve tissue

Cytotoxins

Affect general tissues

Endotoxin

Composed of lipopolysaccharide (LPS), part of the outer membrane of gram-negative cell walls

Nosocomial Infections

Diseases that are acquired or developed during a hospital stay

Epidemiology

The study of the frequency and distribution of disease and health-related factors in human populations

Prevalence

Total number of existing cases with respect to the entire population usually represented by a percentage of the population

Incidence

Measures the number of new cases over a certain time period, as compared with the general healthy population

Mortality rate

The total number of deaths in a population due to a certain disease

Morbidity rate

Number of people afflicted with a certain disease

Endemic

Disease that exhibits a relatively steady frequency over a long period of time in a particular geographic locale

Epidemic

When prevalence of a disease is increasing beyond what is expected

Pandemic

Epidemic across continents