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organisms that colonize the body's surfaces without normally causing disease

- normal flora
- indigenous microbiota

normal microbiota in hosts (synonyms)

- normal flora
- indigenous microbiota

remain part of normal microbiota of a person for life

resident microbiota

microbiota that remain in body for few hours, days, months before disappearing

transient microbiota

sites that are free of any microbes (microbiota) and in absence of disease, are never colonized by normal flora

axenic sites

examples of axenic areas of the body

- alveoli of lungs
- central nervous system
- circulatory system
- upper urogenital regions
- uterus

areas of normal microbiota

- upper respiratory tract
- upper and lower digestive tract
- female and male urinary and reproductive system
- eyes
- skin

when does microbiota begin to develop

during first month of life
- birthing process
- first breath
- handling by family
- mouth and nose through birth canal

normal microbiota that cause disease under certain circumstances

opportunistic pathogens

conditions that provide opportunities for pathogens

- introduction of normal microbiota into unusual site in body
- immune suppression
- changes in normal microbiota

sites where pathogens are maintained as a source of infection

reservoirs of infection

three types of reservoirs of infection

- animal reservoir
- human carriers
- nonliving reservoir

diseases that naturally spread from animal host to humans


ways in which zoonoses are acquired

- direct contact with animal or its waste
- eating animals
- bloodsucking arthropods

infected individuals who are asymptomatic but infective to others


carriers who develop illness


the mere presence of microbes in or on the body


when an organism evades the body's external defenses, multiplies, and becomes established in the body


sites through which pathogens enter the body

portals of entry

three major pathways of entry to the body

- skin
- mucus membrane
- placenta

line the body cavities that are open to the environment and provide a moist, warm environment hospitable to pathogens

mucus membranes

most common site of entry for pathogens

respiratory tract

table on page 17

pathogens that cross the placenta

means by which the portal of entry can be circumvented

parenteral route

what does inability of adhesion do to microorganisms

makes them avirulent

results if the invading pathogen alters normal body function


disease is also referred to as


group of symptoms and signs that characterize a disease or abnormal condition






gen-, -gen

give rise to




literally rotting; refers to presence of pathogens





haemophilus influenza B causes influenza

FALSE; meningitis in children

disease caused by infections of pathogenic microorganisms

germ theory of disease

statements to prove a particular pathogen causes a particular disease

Koch's postulates

exceptions to Koch's postulates

- some pathogens cannot be cultured in lab
- diseases caused by a combination of pathogens and other cofactors
- ethical considerations

difficulties in satisfying Koch's postulates

- disease can be caused by more than one pathogen
- some pathogens have been ignored as potential causes of disease

ability of a microorganism to cause disease


degree of pathogenicity


pathogenicity and virulence refer to severity of the disease


virulence factors

- adhesion
- biofilms
- extracellular enzymes
- toxins
- antiphagocytic factors

where are extracellular enzymes secreted from


function of extracellular enzymes

- dissolve structural chemicals in the body
- help the pathogen maintain infection, invade, and avoid body defenses

chemicals that harm tissues or trigger host immune responses that cause damage


toxins in the bloodstream that are carried beyond the site of infection


two types of toxins

- exotoxins
- endotoxins

lipid A is an example of

an endotoxin

protective molecules, antibodies, formed by the host


the ability of a chemical to trigger a specific immune response, particularly the formation of antibodies


factors that prevent phagocytosis by the host's phagocytic cells

antiphagocytic factors

a structure composed of chemicals not recognized as foreign that make it difficult for phagocytes to engulf bacteria

bacterial capsule

five stages of infectious disease in sequence

- incubation period
- prodromal period
- illness
- decline
- convalescence

period between infection and occurrence of first symptoms or signs

incubation period

short period of generalized, mild symptoms

prodromal period

most severe stage of infection where signs and symptoms are most evident


when the body gradually returns to normal as immune response/treatment vanquish pathogens


patient recovers from illness, tissues repaired and returned to normal


transport of pathogens from a reservoir or portal of exit to another host's portal of entry


five groups of transmission

- contact transmission
- vehicle transmission
- vector transmission
- airborne transmission
- perinatal transmission

ways in which disease can be classified

- the body system they affect
- taxonomic categories
- their longevity and severity
- how they are spread to their host
- the effects they have on populations

occurrence of disease is measured in two ways

- incidence
- prevalence

number of new cases of a disease in a given area during a given period of time


number of total cases of a disease in a given area during a given period of time


disease that normally occurs at regular intervals at a relatively stable incidence within a given population or geographical area


only a few scattered cases within an area or population


occurs at a greater frequency than is usual for an area or population


an epidemic that occurs simultaneously on more than one continent


careful tabulation of data concerning a disease

descriptive epidemiology

first case of a disease identified and reported

index case

observational studies and experimental studies

analytical epidemiology

infections acquired in health-care setting

nosocomial infections

percentage of americans that acquire nosocomial infection yearly


types of nosocomial infections

- exogenous
- endogenous
- iatrogenic

pathogen acquired from the health care environment

exogenous nosocomial infection

pathogen arises from normal microbiota due to factors within the health care setting

endogenous nosocomial infection

infection that results from modern medical procedures

iatrogenic nosocomial infection

the most effective way to reduce nosocomial infection

hand washing

disease acquired by inhaling aerosolized deer-mouse urine or feces stirred up by sweeping

Hantavirus pulmonary syndrome

table 14.12

classification of diseases

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