Lec lesson 5 ni pogi

Pathogen

A microbe capable of causing disease

Pathogenicity

The ability of a microbe to cause disease

Pathogenesis

The steps or mechanisms involved in the development of a disease

True Pathogen

Capable of causing disease in healthy persons with normal immune defenses

Opportunistic Pathogen

Causes disease when host defenses are compromised or when established in an unnatural body site

Infection

Occurs when a microbe penetrates the body and causes harm

Infectious Disease

A disease caused by a microbe; microbes that cause these are called pathogens

Localized Infection

Pathogen confined to the original site (e.g., pimples, boils)

Systemic Infection

Infection spreads throughout the body via blood, lymph, or phagocytes (e.g., tuberculosis)

Primary Infection

The initial disease caused by a microbe

Secondary Infection

A second infection by a different microbe complicating the primary infection (e.g., pneumonia after influenza)

Acute Disease

Rapid onset, short duration (e.g., measles, influenza)

Subacute Disease

Less pronounced but prolonged symptoms (e.g., bacterial endocarditis)

Chronic Disease

Slow onset, long-lasting (e.g., tuberculosis, leprosy)

Latent Infection

Alternates between symptomatic and asymptomatic phases (e.g., herpes, shingles)

Sequelae

Long-term or permanent damage caused by infection (e.g., meningitis → deafness)

Virulence

Degree of pathogenicity; sometimes used synonymously with pathogenic

Virulence Factors

Traits that enable pathogens to establish infection and cause damage

Adhesins (Ligands)

Molecules on pathogen surfaces that allow attachment (e.g., CD4 receptors)

Pili (Fimbriae)

Thin, hairlike projections that enable bacterial attachment

Exoenzymes

Enzymes secreted outside the cell that aid infection

Necrotizing Enzymes

Cause destruction of cells/tissues (e.g., Streptococcus pyogenes)

Coagulase

Promotes clotting of plasma/blood (e.g., Staphylococcus aureus)

Kinases

Dissolve clots

Collagenase

Breaks down collagen fibers (e.g., Clostridium perfringens)

Hyaluronidase

Breaks down hyaluronic acid (e.g., Streptococcus, Staphylococcus)

Hemolysins

Damage red blood cells (e.g., Streptococcus)

Lecithinase

Destroys host cell membranes (e.g., Clostridium perfringens)

Toxins

Poisonous substances produced by microbes that damage host tissues

Exotoxins

Secreted proteins; highly toxic, antigenic, heat-labile (e.g., cholera, tetanus)

Endotoxins

Lipopolysaccharides from Gram-negative bacteria; low toxicity, heat-stable (e.g., sepsis)

Neurotoxins

Damage CNS (e.g., botulinum toxin)

Enterotoxins

Cause gastrointestinal disease

Leukocidins

Destroy leukocytes

Exfoliative Toxin

Causes scalded skin syndrome (S. aureus)

Erythrogenic Toxin

Causes scarlet fever (S. pyogenes)

Diphtheria Toxin

Causes diphtheria (C. diphtheriae)

Symptoms

Subjective evidence of disease (e.g., nausea, dizziness)

Signs

Objective evidence of disease (e.g., abnormal lab results)

Edema

Fluid accumulation in tissues

Granulomas/Abscesses

Walled-off collections of inflammatory cells/microbes

Lymphadenitis

Swollen lymph nodes

Leukocytosis

Increase in WBC count

Leukopenia

Decrease in WBC count

Septicemia

Microorganisms multiplying in blood

Bacteremia/Viremia

Bacteria/viruses present in blood but not multiplying

Portal of Entry

Route microbes take to enter tissues (skin, GI tract, respiratory tract, urogenital tract)

Portal of Exit

Specific avenue pathogens use to leave the host (respiratory secretions, feces, urine, blood)

Incubation Period

Time between pathogen arrival and symptom onset

Prodromal Period

Patient feels unwell but no clear symtomps yet

Period of illness

Patient experienced typical disease symtopms

Convalescene

Recovery phase

Reservoir

Primary habitat where a pathogen originates (living or non-living)

Carrier

Individual who shelters a pathogen and spreads it unnoticed

Transmitter

Individual or object from which infection is acquired

Zoonosis

Infection indigenous to animals but transmissible to humans

Communicable Disease

Can be transmitted from host to host

Noncommunicable Disease

Not transmitted between hosts

Contagious Disease

Highly communicable, especially via direct contact

Horizontal Transmission

Spread from one individual to another in a population

Vertical Transmission

Spread from parent to offspring (via ovum, sperm, placenta, milk)

Healthcare-Associated Infections (HAls)

Infections acquired during hospital/healthcare stay

Nosocomial Infections

Another term for HAls