Unit 3: Harm of Microbes

consists of favorable environment, susceptible host, and virulent pathogen

bacterial communication that “counts” cells based on secreted compounds (autoinducers)

class of autoinducers; trade language that all/most bacteria share (how many of all bacteria are there in the area)

class of autoinducers; within species how many of us (ie E. coli) are there in the area

biofilms formed by disease-causing bacteria are held together by these

(n) number of microbes encountered

(V) virulence factors

(R) host immunity

minimal number of microbes necessary for an infection

the number of microbes necessary to kill 50% of the animals infected

the ability to cause disease

measure of pathogenicity, encompasses two types of virulence factor

allow microbes to escape destruction by the host immune system (adhesins, capsules, antigenic variation, etc)

result in damage to host (exoenzymes, exotoxins, endotoxins, etc)

glycoprotein found on some viruses such as influenza, used in attachment and entry of host cell

enzyme found in some viruses responsible for allowing exit out of the host cell

uses blood serum in order to transfer antibodies from a person who has been infected and recovered from a virus to someone who has not yet been infected

treatment used if flu is caught early, prevents exit of virus out of cells

allow bacteria to adhere and give resitance to phagocytosis

powerful early defenders of a vertebrate body

vaccine that protects against most of the Streptococcus pneumoniae strains (generates antibodies)

defensive stratgy - changing proteins that the immune system “sees”

can change surface antigens to avoid host antibodies

small mutations

leads to new strain (H's and N's exchanged)

defensive strategy - inhabited area is changed to better suit microbe

bacterium that causes peptic ulcers, secretes urease (basic compound) that allows it to survive in highly acidic environment of the stomach

offensive strategy - proteins released that help invading bacteria to spread throughout this tissues

enzyme that breaks down hyaluronic acid content of connective tissues

enzyme that breaks down collagen which can result in necrotic (dead) tissue that requires debridement

enzyme that destroys red blood cells

enzyme that break down clots

enzyme that destroys white blood cells

offensive strategy - release of substances that damage host cells

part of the LPS in the outer membrane of gram-negative cells, causes shock, chills, fever, weakness, small blood clots, and possibly death (always gram negative)

proteins synthesized by the microbe and secreted into the host’s tissue, high toxicity, unstable in heat

toxin that kills or damages cells

toxin that blocks nerve impulse transmission

toxin that affects cells lining gastrointestinal tract

inactivated toxin that is still recognized by the immune system (used for vaccines - DTaP)

carrier of a transmissible disease

individuals who have a microbial disease and show symptoms

have no symptoms and may unwittingly pass the disease on to others

continue to harbor the microbe after recovery, this state can continue indefinitely without illness (Typhoid Mary)

diseases in which animals serve as reservoirs

endemic --> epidemic --> pandemic

physical contact, aerosol or droplets

contaminated food or water, fomites (inanimate objects), vector is an animal carrier

important for the outcome of an infection, includes mouth, skin, urethra, vagina

first stage of disease course, period between initial infection and appearance of symptoms, considerable variation among diseases

second stage of disease course, period in which early symptoms appear, usually short and not always well characterized

third stage of disease course, period where disease is most acute and is accompanied by characteristic symptoms

fourth stage of disease course, period in which symptoms gradually subside

fifth stage of disease course, period in which symptoms disappear and recovery ensues

type of disease classification - occurs only occasionally and in unpredictable fashion (tetanus)

disease classification - regularly found at a steady level in a particular location (common cold)

disease classification - sudden increase in morbidity (illness rate) and mortality (death rate) above the norm (plague)

disease classification - epidemics that spread across continents (1918 influenza)

type of epidemic - involves contact with a single contamination source (contaminated water)

type of epidemic - results from person-to-person contact (mumps and chickenpox)

measures the potential for transmission of a disease, mean number of secondary cases, occurring in a nonimmunized (susceptible) population in the wake of a particular infection

refers to the proportion of immunized individuals in a population, the smaller the number of susceptible individuals, the less opportunity for contact between them and infected individuals

killing or inactivating microbes that cause disease

heat, low temperature control, radiation, physical removal

heavy metals, 70% alcohol, aldehydes, halogens, quaternary ammonia compounds, salt

substance that can be used on inanimate objects and surfaces but is too toxic to the body (lysol/ bleach)

substance that can be used on living body tissues (alcohol on a scrape)

substance that is very commonly added in antibacterial products

antimicrobial characteristic that refers to drugs that harm the pathogen, not the host being treated

range of microbes that are affected by an antimicrobial (broad vs narrow)

first practical antimicrobial medications

drug resistance mechanism, essentially destroys the antimicrobial

drug resistance mechanism, makes it harder for antimicrobial to enter (reduced permeability)

drug resistance mechanism, commom method that gathers and removes antimicrobials via pump

drug resistance mechanism, change in drug binding site

drug resistance mechanism, less common method where product is produced via other metabolic means

substances used to combat antimicrobial resistances

mechanical barrier, first line of defense against microbial infection

chemical barrier, highly acidic environment that inhibits most microbes

physical barrier, line the internal body cavities

reflects the ratio of the white blood cells and is an important tool in the diagnosis of an infection

significant innate defense mechanism, proteins that circulate in the blood in an inactive form that activate upon exposure to bacterial cells and their antigens, complement proteins act to enhance phagocytosis

group of proteins that act to interfere with viral replication, alert other cells of impending attack, triggering them to manufacture virus-blocking enzymes

constant over time, has no memory, eliminates microbes that have penetrated the body, not formed in response to an infection

detect pathogen-unique features, also known as PAMPs (flagella, peptidoglycan, LPS, etc)

specific, has a memory, first exposrue = slower to respond, produces lymphocytes (B or T cells) in response to antigen

antibody mediated, triggers production of anitbodies specific for an antigen, antibodies produced by activated B lymphocytes, helper T cells critical for activating B lymphocytes

production of T lymphocytes directed against an antigen, lymphocytes said to be "sensitized"

binding of these to antigens can have various different outcomes, each of which facilitates the destruction or inactivation of the antigen

cytotoxic cells that can kill tumor or infected cells displaying foreign antigen via cell-meditated cytotoxicity

individuals are challenged with antigens that cause them to develop memory B and T cells leading to a secondary response upon the next exposure

individuals are given pre-made antibodies of immune cells, very quick but does not last long, as the antibodies will be cleared by the recipient’s immune response

Weakened strain of whole pathogen
Advantages: cellular and humoral immunity, long-lasting immunity, transmission to contacts
Disadvantages: difficult to store and transport, risk of infection in immunocompromised patients, risk of reversion

Whole pathogen killed with heat, chemicals, or radiation
Advantages: ease of storage and transport, no risk of severe infection
Disadvantages: weaker immunity (humoral only), higher doses and more boosters needed

Immunogenic antigens
Advantages: lower risk of side effects
Disadvantages: limited longevity, multiple doses required, no protection against antigenic variation

Inactivated bacterial toxin
Advantages: humoral immunity to neutralize toxin
Disadvantages: does not prevent infection

Capsule polysaccharide conjugated to protein
Advantages: T-dependent response to capsule, better response in young children
Disadvantages: costly to produce, no protection against antigenic variation, may interfere with other vaccines

mRNA for a single protein in a lipid vesicle
Advantages: cheaper and quicker to develop
Disadvantages: newer technology, public distrust

immunity gained without direct human intervention

immunity gained with human intervention

10 year campaign where orphans were used to transport vaccine (cowpox) across the Atlantic

Three main tenets:
1. Human subjects must give voluntary consent
2. Any experiments involving humans must be based on prior animal experiments
3. Experiments should benefit society and cannot include procedures likely to cause death or disability

three core principles, created as a result of unethical experiments exposed in the US:
People have the right to make informed decisions
Researchers need to work from a principle of beneficence
The group of people bearing the majority of the risk of an experimental study also benefiting the most from the data gathered