Chapter 10: Mechanisms of Disease Flashcards
Host
any organism capable of supporting the nutritional and physical growth requirements of another
Infection
the presence and multiplication of microorganisms within a host, causing subsequent injury to the host
Colonization
the act of microorganisms establishing a presence
Normal Microflora
internal and external exposed surfaces of the human body that are normally and harmlessly inhabited by a multitude of bacteria
Commensalism
microorganism receives benefit (i.e. nutrition)
host does not receive benefit or harm
Mutualism
interaction in which both the microorganism and the host derive benefits
(Vitamin K and Vitamin B12)
Parasitic Relationship
the infecting organism benefits from the relationship and the host either gains nothing or sustains injury
Infectious Disease
when the host sustains injury or pathologic damage
Pathogens
microorganisms capable of causing disease
Opportunistic Pathogens
harmless microorgansims that are capable of causing infectious disease when the health and immunity of the host are weakened by illness, malnutrition, or medical therapy (antibiotics, chemotherapy)
Example: E. coli
Prions
lack RNA or DNA
causes neurodegenerative diseases: Mad-Cow disease
occurs primarily from consuming infected meat
Viruses
smallest obligate intracellular pathogens
surrounded by a capsid
live and replicate inside living cells
Examples: influenza, herpes, hepatitis
Bacteria
reproduce outside of the host cells vulnerable to antimicrobials exotoxins and endotoxins cause damage to cells/tissues flagella for motility fimbriae helps adhere to surfaces aerobes and anaerobes
Fungi
Yeasts (Candida) - colonies are smooth with a waxy or creamy texture
Molds (ringworm) - colonies produce a cottony or powdery appearance
Penetration
invasion of microorganisms through disruption in skin or mucous membranes
Examples: abrasions/burns, wounds, surgery, catheterization, surface lesions (chick pox, impetigo)
Direct Contact
transmission directly from infected tissue or secretions to exposed, intact mucous membranes
Examples: STIs (gonorrhea, syphilis, chlamydia, genital herpes)
Vertical Transmission
passed from mother to child (across placenta or during birth)
Examples: TORCH infections
Ingestion
entry of pathogenic microorganisms through the oral cavity and GI tract
contaminated food and water
Examples: food poisoning, traveller’s diarrhea, Hep A, dysentery, cholera/typhoid
Inhalation
droplet and airborne
Examples: bacterial pneumonia, meningitis, tuberculosis
viruses: measles, mumps, chicken pox, influenza, the common cold
Endogenous Source of Infection
acquired form the host’s own microbial flora
opportunistic infection
Exogenous Source of Infection
acquired from sources in the external environment
water, food, soil, air
Fomite
inanimate objects that carry an infectious agent
Zoonoses
infectious diseases passed from another animal species to humans
Examples: rabies, cat-scratch disease, HIV, plague, influenza
Vectors
biting arthropods such as mosquitoes, spiders, and ticks
Examples: Lyme disease, West Nile Virus
Nosocomial (Healthcare-Associated) Infections
infections that develop in people while they are hospitalized (greater than 48 hours)
Community-acquired Infections
infections that occur outside of healthcare facilities
Incubation Period
pathogen begins replicating without producing symptoms
can be short (cholera) or prolonged (Hep B/HIV)
Prodromal Stage
initial vague appearance of symptoms
mild fever, myalgia, headache, fatigue
duration varies host to host
Insidious
extended prodromal stage
Fulminant
abrupt onset of symptoms with little or no prodromal stage
Acute Stage
period during which the host experiences the maximum impact of the infectious process
immune response
symptoms become more pronounced and specific
Convalescent Period
beginning of resolution
the containment of the infection, progressive elimination of the pathogen, and repair of damaged tissue
may be days, weeks, or months
Resolution
the total elimination of the pathogen from the body without residual signs and symptoms of disease
-itis
inflammation of an anatomic location/involved tissue
-emia
presence of a substance in the blood
Septicemia/Sepsis
presence of microbial toxins in the blood causing systemic inflammation
Localized Infection
microorganism is restricted to a certain body part/system
Examples: influenza to respiratory tract
gonorrhea to genitourinary tract
H. pylori to GI tract
Systemic Infections
disseminate from the primary site of infection through the circulatory system to involve other locations and organ systems
Examples: staph aureus, meningitidis, Lyme disease
Virulence Factors
substances or products generated by infectious agents that enhance their ability to cause disease
Exotoxins
proteins released from the bacterial cell during growth that may damage host cells
Examples: pertussis, anthrax, traveler’s diarrhea, TSS, and food-borne illnesses
Endotoxins
found in gram-negative bacteria - potent activators of the regulatory system
Example: endotoxic shock: clotting, bleeding, inflammation, hypotension and fever
Adhesion Factors
microbial attachment to host cell surfaces
slime or mucous layer (anchors and protects bacteria)
Evasive Factors
factors produced by microorganisms to evade the host’s immune system
Examples: encapsulated organisms, H. pylori excretes urease
Invasive Factors
products produced by infectious agents that facilitate the penetration of anatomic barriers and host tissue
most are enzymes capable of destroying: cell membranes, connective tissue, intracellular matrices, structural protein complexes
Culture
growth of a microorganism outside of the body, usually on or in artificial growth media (sugar plates, broth)
microscopic appearance and gram stain for bacteria
cell cultures for viruses
obtain cultures prior to antibiotic administration
Serology
an indirect means of identifying infectious agents by measuring serum anitbodies
anitbody titers and antigen detection
not as accurate as culture but useful in identifying diseases that are not able to be cultured (Hep B)
