Biology Terms for Micro Exam 3: Drug Toxicity & More

sterilization

the mechanical removal of most microbes from an animate or inanimate surface

ex. heat (autoclave), sterilants

disinfection

the destruction or removal of vegetative pathogens but not bacterial endospores

usually used only on inanimate objects

ex. bleach, iodine, heat (boiling)

decontamination

the mechanical removal of most microbes

ex. soaps, detergents, dishwashers

antisepsis

reduces the number of microbes on the human skin

a form of decontamination but on living tissues

ex. alcohol swabs, surgical hand scrubs

types of physical control

heat, radiation, filtration

heat

elevated temperatures are microbicidal

lower temperatures are microbiostatic

moist heat

hot water, boiling water, or steam between 60-135C

boiling water --> disinfects

dry heat

hot air or an open flame, which ranges from 160-1000C

thermal death time

shortest length of time required to kill all test microbes at a specified temperature

thermal death point

the lowest temperature required to kill all microbes in a sample in 10 min

radiation- ionizing

gamma rays and x-rays

highly effective alternative for sterilizing materials that are sensitive to heat or chemicals

radiation-nonionizing

UV rays

not as penetrating as ionizing, the object is disinfected

filtration

effective method to remove microbes from air and liquids

fluid is strained through a filter with openings large enough for the fluid to pass but not microbes

pore sizes can be controlled to permit true sterilization

uses of filtration

Used to prepare liquids that cannot withstand heat such as serum, blood products, vaccines, drugs, IV fluids, enzymes, and media

Alternative method for decontaminating milk and beer without altering their flavor

Important step in water purification

High-efficiency particulate air (HEPA) filters are used in hospital rooms and sterile rooms

chemical control

can be liquid, gaseous, or solid

germicides and sterilants

ex. Lysol sanitizing wipes, Purell instant hand sanitizer

antimicrobial chemotherapy

the use of drugs to control infection and kill infected cells without killing the host's cells

antibiotics

originally metabolic products of bacteria and fungi

produced to inhibit the growth of competing microbes in their habitat

before starting antimicrobial therapy you must

1. identify the microorganism

2. identify the degree of the microorganism's susceptibility to various drugs

3. the overall medical condition of the patient

Kirby-Bauer Technique

surface of an agar plate is spread with test bacterium

small discs containing a prepared amount of antibiotic are placed on the plate

zone of inhibition surrounding the disc s is measured and compared with a standard for each drug

therapeutic index

the ratio of the dose of the drug that is toxic to humans as compared to its minimum effective dose

the smaller the ratio, the greater the potential for toxic drug reactions

the drug with the highest therapeutic index has the widest margin of safety

selective toxicity

antimicrobial drugs are selectively toxic

this means that they kill or inhibit microbial cells without damaging host tissues

selective toxicity application

drugs with excellent selective toxicity block the synthesis of the bacterial cell wall (penicillin)

human cells lack the chemical peptidoglycan and are therefore unaffected by the drug

selective toxicity decreases when the infectious agent is closer in structure to the host cell

antimicrobial drugs get classified into 5 categories

1. inhibition of cell wall synthesis

2. inhibition of nucleic acid (RNA and DNA) structure and function

3. inhibition of the ribosome in protein synthesis

4. interference with cytoplasmic membrane structure or function

5. inhibition of folic acid synthesis

broad-spectrum

effective against more than one group of bacteria

narrow-spectrum

target a specific group

penicillin

Antibiotic that interferes with the synthesis of the peptidoglycan portion of bacterial cell walls

original penicillin was narrow-spectrum but molecule has been altered and improved on over the years

antifungal

an agent that destroys or inhibits the growth of fungi

fungal cells are eukaryotic; therefore, present special problems in drug treatment

similarities between fungal and human cells mean that drugs toxic to fungi will also harm human tissues

anti-protozoal

an example of an anti-protozoal drug is metronidazole, a widely used drug for amoebas

anti-helminthic

A drug used to treat helminth infections

ex. Ivermectin

the most effective drugs immobilize, disintegrate, or inhibit the metabolism of all stages of the helminth life cycle

antiviral

drug used to treat viral infections

infectious agent relies on a host cell for most of its metabolic functions. Therefore, disrupting viral metabolism requires disruption of cellular metabolism of host

ex. measles, mumps, hepatitis are prevented with vaccines

actions of antiviral drugs

1. Inhibition of virus entry

2. Inhibition of nucleic acid synthesis

3. Inhibition of viral assembly/release

antiretroviral

used to manage HIV infections

drug resistance

an adaptive response in which microorganisms begin to tolerate an amount of the drug that would be normally inhibitory

spontaneous mutations

how resistance develops in chromosomal genes

acquisition of entire new genes or sets of genes via horizontal transfer from another species

horizontal transfer

The transfer of DNA from one species to another by conjugation, transformation, or transduction

new gene transfer causes slowing or stopping of metabolism so that the microbe cannot be harmed by the antibiotic

development of resistance and it's long-term therapeutic consequences

any large population of microbes will contain a few individual cells that are already drug-resistant

if the population is exposed to drugs, the drug-resistant population will have a selective advantage

offspring inherit drug resistance

replacement populations evolve to have the drug-resistance form as the dominant species

probiotics

preparations of live microorganisms fed to animals and humans to improve intestinal biota

can replace microbes lost during antimicrobial therapy

augment biota already there

safe, and In some cases, effective

useful in the management of food sensitivities

prebiotics

nutrients like carbohydrates that encourage the growth of beneficial microbes in the intestine that are already there

drug allergy

drug acts as an antigen that stimulates an allergic response

can be provoked by the intact molecule or by substances that develop from the body's metabolic alteration of the drug

penicillin allergy is most common

first exposure sensitizes, second exposure can lead to hives, respiratory inflammation, or anaphylaxis

drug toxicity

drugs can be toxic to different organs in the human body causing adverse reactions

ex. hemolysis, hepatotoxic, nephrotoxic, neurotoxic

infection

microbes that get past "host defenses", enter tissues, and multiply

human microbiome

the sum of all microbes (bacteria) found on and in a human

(skin, mucous membranes, URI, GI tract, urethra, genitalia, vagina, ear canal, external eye, lungs, urine, breast milk, amniotic fluid and fetus)

pathogen

a microbe whose relationship with its host is parasitic and results in infection and disease

true pathogens

capable of causing disease in healthy persons with normal immune defenses

opportunistic pathogens

cause disease when the host's defenses are compromised or when the pathogens become established in a part of the body that is not natural to them

exogenous infectious agents

organisms coming from outside the body

endogenous infectious agents

organisms coming from somewhere in the same human host

infectious dose

the minimum number of microbes "bacteria" necessary to cause an infection to proceed

microorganisms with smaller "infectious doses" have greater virulence

symptom

subjective evidence of disease as sensed by the patient

ex. pain, soreness, swelling

signs

objective evidence of disease as noted by an observer

ex. edema, granulomas, lymphadenitis

incubation period

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

agent is multiplying at the portal of entry but has not caused enough damage to elicit symptoms or disease

prodromal stage

1-2 day period when the earliest notable symptoms of infection appear

acute stage

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

marked by fever and other prominent and specific signs and symptoms

convalescent period

patient begins to respond to the infection and symptoms decline

patient's strength and health gradually return due to the healing nature of the immune response

many patients stop taking their antibiotics during this period

continuation period

**Only some infections have this phase

Either the organism lingers for months, years, or indefinitely after the patient is well or the organism is gone but symptoms continue

zoonotic infections

infections that are transmitted from animals

human-human infections

a great number of infections that affect humans have their reservoirs in other humans

communicable infections

a disease in which an infected host can transmit the infectious agent to another host and establish infection in that host

noncommunicable infections

an infectious disease that does not arise through transmission of the infectious agent from host-host

infected persons cannot spread to another host

horizontal transmission

disease is spread through a population from one infected individual to another

vertical transmission

disease transmitted from parent to offspring

vector transmission

arthropods harbor an infectious agent and transfer it to a human

stages of microbe disease

1. finding a portal of entry

2. attaching firmly and negotiating the microbiome

3. surviving host defenses

4. causing damage/disease

5. exiting host

finding a portal of entry

skin, GI tract, respiratory tract, urogenital tract, endogenous biota

attaching to host

fimbriae, capsules, surface proteins, viral spikes

surviving host defenses

avoiding phagocytosis, avoiding death inside phagocyte, absence of adaptive immunity

causing disease

direct damage via enzymes or toxins, inducing excessive host response, causing epigenetic changes in host chromosome

exiting host

portals of exit: respiratory tract, salivary glands, skin cells, fecal matter, urogenital tract, blood

antibiotic resistance

the evolution of populations of pathogenic bacteria that antibiotics are unable to kill

immunopathology

the study of disease states associated with the overreactivity or underactivity of the immune response

hypersensitivity

allergy and autoimmunity

the tissues are innocent bystanders attacked by immune components that can't distinguish one's own tissues from foreign material

hyposensitivity

immune system is incompletely developed, suppressed, or destroyed

Type 1 hypersensitivity

common allergy and anaphylaxis

ex. anaphylaxis, hay fever, asthma

Type II hypersensitivity

IgG and IgM mediated cell damage

ex. blood group incompatibility, pernicious anemia, myasthenia gravis

Type III hypersensitivity

Immune complexes deposit in tissues causing inflammation

ex. systemic lupus, rheumatoid arthritis, serum sickness, rheumatic fever

Type IV hypersensitivity

T-cell response

ex. infection reactions, contact dermatitis, graft rejection

atopy

chronic local allergy such as hay fever and asthma

genetic basis for atopy

1. increased IgE production

2. increased reactivity of mast cells

3. increased susceptibility of target tissue to allergic mediators

Anaphylaxis

systemic, sometimes fatal, reaction that involves airway obstruction and circulatory collapse

degranulation

the release of the contents of mast cell granules that release inflammatory cytokines

Rh factor

Rhesus antigen

Rh+ represent the dominant gene that codes for the antigen; Rh- represents the recessive gene that does not code for the antigen

the only way to develop antibodies against this factor is through exposure to a fetus's antigens while pregnant or transfusion

hemolytic disease of the newborn

happens in a second pregnancy in which the mother's blood type is Rh- and the fetus is Rh+

autograft

tissue transplanted from one site on an individual's body to another site

isograft

tissue from an identical twin is used

allograft

exchanges between genetically different individuals belonging to the same species; the most common types of grafts

xenograft

a tissue exchange between individuals or a different species

graft vs host

graft attacks any host tissue bearing foreign MHC markers

effects are systemic and toxic

occurs within 100-300 days of the graft

host vs graft

cytotoxic T cells of a host recognize foreign class. I MHC markers on the surface of a grafted cells

helper and cytotoxic T cells bind to the grafted tissue and secrete lymphokines that begin the rejection process within 2 weeks of transplantation

antibodies formed against the transplanted tissue contributes to damage

the result is destruction of the vascular supply and death of the graft

phenotypic

observations of traits that an organism is expressing

involves remaining microbe appearance and behavior

considers macroscopic and microscopic morphology, physiology, and biochemistry

stains used: gram stain, acid-fast, KOH.

specimen collection

aseptic technique is imperative

sterile sample containers

prevent contamination

immunologic methods

molecular basis of immunologic testing is the binding of an antibody to a specific site or epitope of an antigen

serology

involves in vitro testing of serum, urine, cerebrospinal fluid, whole tissues, and saliva for the presence of specific antibodies

based on the principle that antibodies have an extreme specificity for antigens

used to determine the immunologic status of patients, confirm a suspected diagnosis, and screen individuals for disease

agglutination and precipitation

in both reactions, one antigen is interlinked by several antibodies to form insoluble aggregates that settle out in solution

agglutination test

antigens are whole cells or organisms such as red blood cells, bacteria, or viruses displaying surface antigens

-forms visible clumps of cells

-used to determine blood compatibility

precipitation test

antigen examined is a small soluble molecule

more difficult to visualize because precipitates are easily disrupted in liquid media

Immunochromatography (lateral flow test)

plastic cartridge contains porous material or polymer that directs fluid to flow in a particular direction

fluid will encounter antibodies along its route of flow

if the sample contains the correct antigen, it will bind to the antibodies and continue to the next station in the cartridge

next stage contains a third molecule that is impregnated on the paper in a stripe pattern

third molecule binds the complexes and eventually, this causes the stripe to change color

ex.) pregnancy test, rapid strep test, COVID-19 test

Western Blot test

antigens within microbial cell lysates are separated via electrical charge within a gel

proteins in the gel are transferred to a special filter

filter is incubated with patient fluid; antibodies are detected when a second, fluorescence-labeled antibody compatible fot the Fc portion of an antibody is added

sites of specific antigen-antibody binding will appear as a pattern of bands that can be compared to known positive and negative controls

verified microbial-specific antigens or antibodies in a patient sample

fluorescent antibodies

monoclonal antibodies labeled by a fluorescent dye

direct fluorescent antibody testing

if antigen-antibody complexes form, they will remain bound to the sample and will be visualized by fluorescence microscopy

valuable for identifying and locating microbial antigens on cell surfaces or tissues and in identifying the causative agents of syphilis, gonorrhea, and meningitis

indirect fluorescent antibody testing

FAbs recognize the Fc region of antibodies in patient sera

known antigen is added to the test serum

binding of the fluorescent antibody is visualized through fluorescence microscopy

fluorescing aggregates or cells indicate the FAbs have complexed with microbe-specific antibodies

used to diagnose syphilis and various viral infections

ELISA (enzyme-linked immunosorbent Assay)

uses an enzyme-linked indicator antibody to visualize antigen-antibody reactions