Host-Microorganism Interactions and Pathogenesis

Vocabulary flashcards covering host-microorganism interactions, clinical microbiology terms, epidemiology, virulence factors, toxins, and immunology based on the lecture notes.

Infection

The growth and multiplication of microorganisms that cause damage to the host, or the invasion of pathogenic microorganisms that can reproduce and cause disease.

Autogenous infection

An infection caused by microorganisms from the microbiota of the host, such as the normal flora Escherichia coli.

Iatrogenic infection

An infection resulting from a medical treatment or procedure, such as surgery.

Opportunistic infection

An infection that affects immunocompromised hosts, with Candida spp. being the most common cause in immunosuppressed patients.

Nosocomial infection

A hospital-acquired infection often caused by Pseudomonas aeruginosa, Acinetobacter baumanii, or Stenotrophomonas maltophilia.

Staphylococcus saprophyticus

The causative agent of "Honeymoon’s cystitis" in sexually active young females.

Staphylococcus epidermidis

The most common cause of hospital-acquired UTIs due to insufficient catheter sterilization.

Aerosol transmission

Transmission where the diameter of particles is less than $5$μm$and can travel up to$3$feet$, such as Tuberculosis.

Droplet transmission

Transmission where the diameter of particles is greater than $5$μm$and travels less than$3$feet$, such as Pertussis.

Handwashing

The cornerstone of modern infection control programs and the most important factor in breaking the chain of infection.

Local Infection

Infection where signs and symptoms are localized in one area, such as wounds, boils, and abscesses.

Focal Infection

An infection that starts as a local infection before spreading to other parts of the body.

Systemic Infection

An infection that has spread throughout the blood or lymph.

Bacteremia

The presence of bacteria in the blood, with the highest concentration occurring before fever spikes.

Septicemia

The active multiplication of bacteria in the blood.

Pyremia

Condition where pus-producing organisms repeatedly invade the bloodstream and become localized at different parts of the body.

Toxemia

The presence of toxins in the blood.

Signs vs. Symptoms

Signs are measurable and observable factors, while symptoms are subjective and felt by the patient.

Sporadic Disease

A disease that occurs only occasionally.

Endemic Disease

A disease constantly present at some rate of occurrence in a particular location.

Epidemic Disease

A larger than normal number of diseased or infected individuals in a particular location.

Pandemic

An epidemic that spans the world.

Carrier

A person who carries the etiologic agent but shows no apparent signs or symptoms of infection or disease.

Typhoid Mary (Mary Mallon)

A famous Chronic Carrier of Salmonella enterica ser. Typhi that causes typhoid fever.

Incubation Period

The time between exposure to a pathogen and the onset of symptoms.

Prodromal Period

The phase characterized by the first appearance of signs and symptoms.

Virulence

The quantitative measure of the degree of pathogenicity of a particular microorganism.

Fomite

A non-living entity contaminated with an etiologic agent that serves as a mode of transmission.

Vector

A living entity that transmits the etiologic agent.

Surveillance

Epidemiologic investigation involving data collection to characterize the incidence or prevalence of an infection or disease.

Symbiosis

An association of two organisms living in close proximity.

Mutualism

A mutually beneficial relationship between two species.

Commensalism

A relationship where the parasite derives benefits from the host without causing harm or injury.

Parasitism

A relationship whereby one organism derives benefits at the expense of another.

Pathogenicity Island

Large groups of genes associated with pathogenicity located on the bacterial chromosome.

Toxoid

A non-poisonous form of a toxin used for vaccination, prepared by aging or exposure to heat, alcohol, formaldehyde, or dilute acids.

Bacteriocins

Antibacterial proteins produced by normal flora that inhibit or kill competing bacteria.

Protein F

A bacterial adhesin that binds to fibronectin on host cell surfaces.

Capsule

A virulence factor that facilitates resistance to phagocytosis by masking cell surface structures and inhibiting complement activation.

Protein A

A protein in the cell wall of Staphylococcus aureus that binds to the Fc portion of IgG, preventing opsonization.

M protein

A heat and acid-resistant protein found in Streptococci that mediates attachment and helps resist phagocytosis.

Hemolysins

Substances produced by Streptococci that lyse red blood cells and induce toxic effects on white blood cells.

Leukocidins

Substances released by pathogenic staphylococci that cause lysosomal discharge into the cell cytoplasm.

Panton-Valentine

A staphylococcal leukocidin that is lethal to leukocytes and contributes to invasiveness.

Adhesins

Cell surface structures, such as fimbriae (pili) and surface polysaccharides, that mediate bacterial attachment to host cells.

IgA protease

An enzyme produced by organisms like Haemophilus influenzae and Neisseria gonorrhoeae that degrades IgA at mucosal surfaces.

Hyaluronidase

An enzyme that hydrolyzes hyaluronic acid in connective tissue, helping organisms like Streptococcus pyogenes spread.

Coagulase

An enzyme produced by Staphylococcus aureus that accelerates the conversion of fibrinogen to a fibrin clot to evade host defenses.

Exotoxins

Highly toxic, heat-labile proteins secreted by gram-positive and gram-negative bacteria that induce antitoxin production.

Botulism toxin

A neurotoxin that blocks nerve impulse transmission, causing flaccid paralysis (often called "Floppy Baby" in infants).

Endotoxins

The lipopolysaccharide (LPS/Lipid A) portion of the outer membrane of gram-negative bacteria, released mainly upon cell lysis.

DIC (Disseminated Intravascular Coagulation)

A condition initiated by endotoxins where the clotting cascade is activated, causing tiny blood clots throughout the body.

Lysozyme

A low-molecular-weight enzyme ($20,000$D$$) that hydrolyzes the peptidoglycan layer of bacterial cell walls.

Β-lysins

Low-molecular-weight cationic proteins in serum, lethal against gram-positive bacteria, released from platelets during coagulation.

Diapedesis

The movement of neutrophils between the endothelial cells of the blood vessels into the tissues.

Opsonization

The coating of a bacterium with antibody or complement components to enhance phagocytosis.

Cardinal Signs of Inflammation

Swelling, redness, heat, pain, and loss of function.

IgG

The most abundant serum immunoglobulin ($70$%$to$75$$) that crosses the placenta and is involved in the secondary immune response.

IgM

A pentameric immunoglobulin involved in the primary immune response and endotoxin neutralization.

IgA

The predominant immunoglobulin in body secretions like saliva and tears that prevents bacterial adherence to mucous membranes.

IgE

An immunoglobulin that increases during parasitic infections and plays a major role in allergic responses.

ID50

The Infectious Dose required to cause infection in $50$%$$ of a sample population.

LD50

The Lethal Dose of a toxin required to kill $50$%$$ of a sample population.