PRELIM: Unit 3 infections and diseases

Mutualism

organism 1: benefits organism 2: benefits

Commensalism

organism 1: benefits organism 2: neither benefits nor is harmed

Parasitism

organism 1: benefits organism 2: is harmed

Escherichia coli (human)

synthesize vitamin K and some B vitamins; provide nutrients

Protozoa (termites)

digest wood/cellulose; provides food and place to live

Algae (fungi-lichens)

provides food by photosynthesis; chitin in CW provides protection for the algae

Mutualistic synergism

Two organisms work together to produce a result neither could accomplish alone

Fusobacteria and Spirochetes

causes "trench mouth"

Legumes and Nitrogen

fixing bacteria

Commensalism

one is benefitted but the other is neither benefitted nor harmed

Commensalism

e.g. most of the body's normal flora

Parasitism

An organism benefits at the expense of the host organism

endoparasites (infection)

Intestinal worms

ectoparasites (infestation)

mites, lice, ticks

Colonization

Contact (beneficial outcome)

Line of defense and sterile areas have been breached

Contact (Adverse Effects)

• Constant source of nourishment and moisture

• Relatively stable pH and temperature

• Extensive surface area available

Proof of Humans as Favorable Hosts:

toxoplasma gondii (toxoplasmosis)

pathogens that cross placenta : protozoan

• treponema pallidum (syphilis)

• listeria monocytogenes (listeriosis)

pathogens that cross placenta : bacteria

• cytomegalovirus (usually asymptomatic-herpes)

• parvovirus b19 (erythema infectiosum)

pathogens that cross placenta : DNA virus

• lentivirus (HIV (AIDS)

• rubivirus rubella (german measles)

pathogens that cross placenta : RNA virus

Bacteriophage

viruses that attacks bacteria

Defenses hold pathogen in check

infection (beneficial outcome)

Tissue injury or disruption

infection (adverse effects)

One: Maintaining a reservoir Two: Leave its reservoir and enter a host Three: Adhesion to the surface of the host (Adhesion Factors / Adhesins) Four: Invading the Body (Invasiveness) Five: Evading the Body's Defenses Six: Multiply within the body Seven: Leave the body and return to its reservoir or enter a new host

Capabilities of a Pathogen

• Humans

• Animals

• Environment

list of reservoir

incubatory carriers

acquire organisms until one shows signs and symptoms

1. helminthic

2. protozoan

3. fungal

4. bacterial

5. viral

common zoonoses

1. respiratory tract

2. gastrointestinal tract

3. genitourinary tract

4. skin or parenteral route

Portals of entry

Lethal Dose (LD50)

The number of microorganisms that must enter the body to cause the death of 50% of the test animals.

Infectious Dose (ID50)

The number of microorganisms that must enter the body to establish an infection in 50% of the test animals.

toxic dose

the median toxic dose of a substance at which toxicity occurs in 50% of the cases (human)

1. contact transmission

2. vehicle transmission

3. vector transmission

Modes of Transmission

1. adhesins (adhesive factors)

2. extracellular enzymes

3. toxins

4. actin tail formation

Virulence Factors

Hyaluronidase

spreading factor

siderophores

Obtaining Iron

acute disease

symptoms develop rapidly but the disease lasts only a short time (and that runs its course quickly)

chronic disease

a disease with usually mild symptoms that develops slowly and continues over a long period of time

subacute disease

disease with time course and symptoms between acute and chronic

asymptomatic disease

disease without symptoms

latent disease

disease that appears a long time after infection

communicable disease

disease that is transmitted from one individual to another

contagious disease

a disease that is easily spread from one host to another

noncommunicable disease

disease arising from outside of hosts or from opportunistic pathogen

local infection

infection confined to a small region of the body

systemic infection

widespread infection in many systems of the body; often travels in the blood or lymph

focal infection

infection that serves as a source of pathogens for infections at other sites in the body

primary infection

initial infection within a given patient

secondary infection

infection that follows a primary infection, often by opportunistic pathogens

prodromal period

mild signs or symptoms

acme period

signs and symptoms are most intense (peak)

period of convalescence

the recovery period, when the body returns to its predisease state

endemic disease

disease constantly present in a population

sporadic disease

disease that occurs occasionally in a population

epidemic disease

certain area; higher frequency of disease

pandemic disease

worldwide epidemic, one or more continent

Serology

Study of In Vitro Antibody-Antigen Reaction

Precipitation test

Useful in detecting Antibody of exotoxin of Tetanus, Diphtheria and Scarlet fever

Precipitins

antibody involved in formation of visible precipitate

Radio Immuno Assay (RIA)

Use of radioactive labelled antigen

Agglutination test

formation of large clumps/aggregates

Agglutinins

antibody

Widal Test

diagnosis for typhoid

Weil felix

Rickettsia

VDRL, RPR

Syphilis

hemagglutination rxn

blood typing

ELISA (Enzyme Linked Immunosorbent Assay)

used to detect AIDS and Rubella virus

Immunofluorescence / Fluorescent Antibody (FA) Technique

use antibody molecule with a fluorescent dye ; detected using UV light

Immunofluorescence / Fluorescent Antibody (FA) Technique

for detection of Streptococcus pyogenes, Treponema pallidum, Neisseria meningitidis, Salmonella typhi, Haemophilus influenzae, Rabies virus

Opsonization

antibody added on the surface of bacteria to make them readily phagocytised

Capsular swelling

Quellung test

Capsular swelling

test for encapsulated microorganisms e.g. Streptococcus

Schick test

SC injection of Diphtheria toxin

Dick test

Intracutaneous injection

Dick test

Susceptibility test of Scarlet Fever

Schultz - Charlton test

test to determine if rashes is produced by scarlet fever (diagnosis for scarlet fever) common test to babies

nosocomial infection

hospital acquired infection

exogenous infections

enter patient from environment

endogenous infections

Caused by biota already in the body ; Can occur when normal biota is introduced to a site that was previously sterile

iatrogenic infections

doctor induced infections; materials used

superinfections

use of antimicrobial drugs inhibits some resident microbiota allowing other microbes to thrive; taking strong antibiotic

Nationally notifiable infectious diseases

physicians are required to report the incidence of certain infectious diseases

positive air pressure

the situation that occurs when air flows out of a room or area because the pressure in the area is greater than that of surrounding areas.

Negative air pressure

the situation that occurs when air flows into a room or area because the pressure in the area is less than that of surrounding areas.