Exam 3 - Microbiology

presence of microbes that live and grown 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 microbes living on and in the body

human microbiome

also known as a resident or indigenous biota or normal biota

human microbiome

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

• these organisms have a profound effect on human biology

human microbiome

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

biota

for example, differences in the gut microbiome have preliminarily been associated with differences in the risk for:

• crohn’s disease

• obesity

• diabetes

• asthma

• heart disease

• mental health (anxiety, depression)

traditional sites of microbiota

• skin and adjacent mucous membranes

• upper respiratory tract

• gastrointestinal tract, including mouth

• outer portion of urethra

• external genitalia

• vagina

• external ear canal

• external eye (lids, conjunctiva)

newly described sites of microbiota

• lungs (lower respiratory tract)

• bladder (and urine)

• breast milk

• amniotic fluid and fetus

sites where you can find DNA from microbiota

• brain

• bloodstream

the new information of sites of microbiota comes from the ___________________ - an international collaboration aimed to characterize the microbiome in health and disease

human microbiome project

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

• these microbes are important for healthy full-term pregnancies and healthy newborns

utero

during birth - baby becomes colonized with mother’s ________

vaginal biota

during breast feeding - breast milk contains around ___ species of bacteria

• also 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

600

previously thought to be sterile, the womb probably has its own microbiota

in utero

vaginal and c-section deliveries contribute different initial microbiomes to baby

birth

breast milk and formula have differing microbes in them

milk

family, siblings, and others share microbes with baby

caregivers

baby can pick up microbes from anything she comes in contact with

environment

benefits of normal biota

• influence the development of organs

• prevent the 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

• results in infection and disease

pathogen

capable of causing disease in healthy persons with normal immune systems

true pathogens

cause disease when:

• the host’s defenses are compromised

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

opportunistic pathogens

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

• ex. influenza infection frequently leads to bacterial pneumonia

polymicrobial

factors that weaken host defenses and increase susceptibility to infection

• old age and extreme youth (infancy, prematurity)

• genetic defects in immunity and acquired defects in immunity (AIDS)

• surgery and organ transplants

• underlying disease: cancer, liver malfunction, diabetes

• chemotherapy/immunosuppressive drugs

• physical and mental stress

• pregnancy

• other infections

not all ______ causes the same severity of disease

pathogens

degree of pathogenicity

virulence

indicated by a microbe’s 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 (ID)

determine experimentally for many microbes

infectious dose (ID)

microbes with a ______ infectious dose have greater virulence (i.e. need fewer cells/viral particles to cause disease)

smaller

steps involved when a microbe causes disease in a host

• finding a portal of entry

• attaching firmly and negotiating the microbiome

• surviving host defenses

• causing damage (disease)

• exiting host

a characteristic route taken by a microbe to initiate infection

portals of entry

originating from outside the body

• the environment, another person, or animal

exogenous

already existing on or in the body

• normal biota or a previously silent infection

endogenous

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

________ pathogens usually transmitted via sexual contact

urogenital

the _____ is an exchange organ

placenta

formed by maternal and fetal tissues

placenta

separates the blood of the 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 ________ and are spread by the umbilical vein into the fetal tissues

placenta

other infections 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 between specific molecules on both the host and pathogen

• ex. fimbriae on bacteria

• ex. spike proteins on viruses

attaching to the host

a particular ____ is limited to only those cells and organisms to which it can bind

pathogen

once attached, a _______ can invade body compartments

pathogen

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 (ex. antibodies, complement)

capsules

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

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 imune system

intracellular survival

direct damage by enzymes and toxins

causing disease

secreted by pathogenic bacteria, fungi, protozoa, and worms

exoenzymes

break down and inflict damage on tissues

exoenzymes

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

exoenzymes

ex. mucinase, keratinase, gelatinase

exoenzymes

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

toxin

secreted by a living bacterial cell to the infected tissues (ex. tetanus toxin, botulism toxin (botox), shiga toxin)

exotoxin

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

endotoxin

many cases of microbial diseases are the result of indirect damage or the host’s excessive or inappropriate response to a microorganism

• ex. fever, chills, malaise

inducing an injurious host response

is a trait not solely determined by microorganisms

pathogenicity

is a consequence of an interplay between microbe and host

pathogenicity

specific avenue by which pathogens exit

portal of exit

shed through secretion, excretion, discharge, or sloughed tissue

exiting the host

high number of microbes in these materials increases the likelihood that the pathogen will reach other hosts

exiting the host

is usually the same as the portal of entry, but some pathogens use a different route

portal of exit

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

• skin conditions, ex. warts, boils

• upper respiratory infections, cold

localized infection

infectious agent spreads from a (usually asymptomatic) 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

• viral: measles, rubella, chickenpox, HIV

• bacterial: brucellosis, anthrax, typhoid fever, syphilis

• fungal: histoplasmosis, cryptococcosis

systemic infection

infectious agents can also travel by means of nerves (rabies) or cerebrospinal fluid (meningitis)

systemic infection

come on rapidly and have short-lived effects (i.e. are resolved)

acute infections

progress and persist over a long period of time

chronic infections

host is infected but does not manifest the disease

• most infections are attended by some sort of sign

asymptomatic, subclinical, or inapparent infections

a dormant state of an infectious agent

latency

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

• ex. HSV-1, chickenpox/shingles, tuberculosis, and malaria enter into latent stages

latency

long-term or permanent damage to organs and tissues

• ex. meningitis can result in deafness, strep throat can lead to rheumatic heart disease, lyme disease can cause arthritis, and polio can product paralysis

sequelae

objective evidence of disease as noted by an observer

• ex. elevated body temperature, decreased blood pressure

sign

subjective evidence of disease as sensed by the patient

• ex. feeling nauseous, dizzy

symptom

a disease identified by a certain complex of signs and symptoms

syndrome

no noticable symptoms are produced

• microbe is active in host tissues

• host does not seek medical attention

• these infections are known as asymptomatic, or subclinical (inapparent)

silent

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 phase

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

acute period

patient responds to infection and symptoms decline

convalescent period

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

the cause of infection and disease

etiologic/causative agent

a series of guidelines that became the standard for determining causation of infectious disease

koch’s postulates

step one of koch’s postulates

find the evidence of a particular microbe in every case of a disease

step 2 of koch’s postulates

isolate that microbe from an infected subject and cultivate it in pure culture in the laboratory, characterize it fully

step 3 of kochs postulates

inoculate a susceptible healthy subject with the laboratory isolate and observe the same resultant disease

step 4 of kochs postulates

reisolate the same agent from this subject