Micro Exam 3

presence of microbes that live and grow in/on host without disease

colonization

a condition in which pathogenic microorganisms penetrate host defenses, enter the tissues, and multiply

infection

any deviation from health

disease

factors that cause disease:

infections/genetics/aging/malfunctions of systems or organs

disruption of tissues or organs caused by microbes or their products

infectious disease

large and diverse collection of microbe living on and in the body

human microbiome

other names for human microbiome

resident or indigenous biota or normal flora

include an array of bacteria, fungi, protozoa, and viruses

human microbiome

differences in gut microbiome have preliminary been associated with differences in the risk for what?

• crohns disease

• obesity

• diabetes

• asthma

• heart disease

• mental health

the makeup of your ____ can influence many facets of your overall health

biota

traditional sites of microbiota

• skin & adjacent mucous membranes

• upper respiratory tract

• gastrointestinal tract

• outer portion of urethra

• external genitalia

• vagina

• external ear canal

• external eye

newly described sites of microbiota

• lungs

• bladder

• breast milk

• amniotic fluid and fetus

sites in which DNA from microbiota has been detected:

• brain

• bloodstream

an international collaboration aimed to characterized the microbiome in health and disease

Human microbiome project

current understanding is that fetuses are seeded with normal microbiota in ___

utero

during birth - baby becomes colonized with mothers ______ ?

vaginal biota

during breast feeding - breast milk contains around _______?

600 species of bacteria

contains sugars that babies cannot digest, but are used by healthy gut bacteria

breast milk

may be necessary for maintaining a healthy gut microbiome in the baby

breast milk

benefits of normal biota:

• influence the development of organs

• prevent overgrowth of harmful microorganisms

the general antagonistic effect “good” microbes have against intruder microorganisms

microbial antagonism

microbes in a steady, established relationship are unlikely to be displaced by incoming microbes

microbial antagonism

a microbe whose relationship with its host is parasitic

pathogen

results in infection and disease

pathogen

capable of causing disease in healthy persons with normal immune systems

true pathogens

cause disease when the hosts defenses are compromised

opportunistic pathogen

cause disease when they become established in a part of the body that is not their natural habitat

opportunistic pathogen

majority of infections are ______ with contributions from more than one microbe

polymicrobial

example of polymicrobial infection

influenza infection frequently leads to bacterial pneumonia

factors that weaken host defenses & increases susceptibility to infection

• old age & extreme youth

• genetic defects in immunity

• surgery ad organ transplants

• underlying disease

• chemotherapy/immunosuppressive drugs

• physical and mental stress

• pregnancy

degree of pathogenicity

virulence

indicated by a microbes ability to establish itself in the host and cause damage

virulence

any characteristic or structure of the microbe that helps it successfully infect its host, often associated with increased disease

virulence factor

a minimum number of microbes required for an infection to proceed

infectious dose

determined experimentally for many microbes

infectious dose

microbes with a smaller infectious dose have ____?

greater virulence

steps involved when a microbe causes disease in a host

1. finding portal of entry

2. attaching & negotiating the microbiome

3. surviving host defenses

4. causing damage

5. exiting host

a characteristic route taken by a microbe to initiate infection

portal of entry

originating from outside the body (the environment, another person, animal)

exogenous portal of entry

already existing on or in the body (normal biota or previous silent infection)

endogenous portal of entry

very tough barrier that few microbes can penetrate, requires breakage (abrasions, nicks/cuts, bug/animal bites)

skin

entry via ingested substances, pathogen has to withstand digesting enzymes and pH changes

GI tract

continuous mucus membranes cover upper respiratory tract, sinuses, auditory tubes - microbes can transfer from one site to another

respiratory tract

pathogen usually transmitted via sexual contact

urogenital

an exchange organ

placenta

formed by maternal and fetal tissues

placenta

separates the blood of developing fetus from that of the mother

placenta

permits diffusion of dissolved nutrients and gases to the fetus

placenta

a few pathogenic microbes cross the placenta and are spread by the ______ into the fetal tissues

umbilical vein

other infections during pregnancy and birth are transmitted _____ as the child passes through the birth canal

perinatally

a process by which microbes gain a more stable foothold on host tissues

adhesion

dependent on binding specific molecules on both the host and pathogen

adhesion

examples of adhesion

1. fimbriae on bacteria

2. spike proteins on viruses

a particular pathogen is _____ to only those cells and organisms to which it can bind

limited

all successful pathogens have virulence factors that help them avoid the _______

immune response

act as a shield allowing evasion from phagocytes and preventing attachment of immune proteins

capsules

genetic variation in surface proteins makes it hard for the immune system to recognize the pathoegn

antigenic variation

some target immune cells such as phagocytes, others interfere with immune signaling

toxins

viruses, and bacteria/parasites that replicate in cells are partially hidden from the immune system

intracellular survival

examples of virulence factors that help survive host defenses

• capsules

• antigenic variation

• toxins

• intracellular survival

direct damage by enzymes and toxins

disease

secreted by pathogenic bacteria, fungi, protozoa, and worms

exoenzymes

break down and inflict damage on tissues

exoenzymes

dissolve host defense barriers and promote the spread of microbes into deeper tissues

exoenzymes

examples of exoenzymes

• mucinase

• keratinase

• hylaronidase

a specific chemical product of microbes, plants, and some animals that is poisonous to other organisms

exotoxin

not actively secreted, but shed from outer membrane of gram-negative bacteria

endotoxin

inducing an injurious host response

causing disease

many cases of microbial diseases are the result of indirect damage or the ____________ to a microorganism

hosts excessive or inappropriate response

a trait not solely determined by microorganisms

pathogenicity

pathogenicity is a consequence of an interplay between ____ & ____

microbe & host

specific avenue by which pathogens exit

portal of exit

how do microbes exit the host

shed through:

• secretion

• excretion

• discharge

• sloughed tissue

if there is a high number of microbes in materials like secretions, excretions, discharge, or sloughed tissue it increases the likelihood that the pathogen will reach other ____

hosts

• microbe enters the body and remains confined to a specific tissue

• skin conditions, ex. warts, boils

• upper respiratory infections, colds

localized infections

infectious agent spreads from a local site and is carried to other tissues

ex. periodontal infections leading to cardiovascular consequences

focal infection

when an infection spreads to several sites and tissue fluids, usually in the bloodstream

systemic infection

measles, rubella, chickenpox, HIV

viral systemic infection

brucellosis, anthrax, typhoid fever, syphilis

bacterial systemic infection

histoplasmosis, cryptococcosis

fungal systemic infection

infectious agents can also travel by means of ____ (rabies) or _______ (meningitis)

nerves, cerebrospinal fluid

come on rapidly & have short-lived effects

acute infections

progress and persist over a long period of time

chronic infections

host is infected but does not manifest the disease

asymptomatic, subclinical, or inapparent infections

a dormant state of an infectious agent

latency

most infections are attended by some sort of ____

sign

the microbe can periodically become active and produce a recurrent disease, cycling in and out of _______

latency

long-term or permanent damage to organs and tissues

sequelae

ex. of diseases that can enter into latent stages

• HSV-1

• chicken pox/shingles

• tuberculosis

• malaria

ex. of diseases that can cause sequelae

• meningitis → deafness

• strep throat → rheumatic heart disease

• lyme → arthritis

• polio → paralysis

objective evidence of disease as noted by an observer

sign

subjective evidence of disease as sensed by the patient

symptom

a disease identified by a certain complex of signs and symptoms

syndrome

no noticeable symptoms are produced

silent infections

• microbe is active in host tissues

• host does not seek medical attention

• known as asymptomatic, or subclinical

silent infection

the time from initial contact with the infectious agent to the appearance of first symptoms

incubation period

when the earliest notable symptoms of infection appear

prodromal period

infectious agent multiplies at high levels, exhibits its greatest virulence, and becomes well established in its target tissues

acute phase

patient responds to infection and symptoms decline

convalescent stage

either the organism lingers for months, years, or indefinitely after the patient is well or the organism is gone but symptoms continue (only some infections have this phase)

continuation period