Module 5: Microbial & Host Interactions Flashcards
What are Koch’s Postulates (four other them)?
- Microorganism must be found in every case of disease .
- Microorganism must be isolated from the diseased host and growth in pure culture.
- The specific disease must be reproduced, when injected into the healthy host.
- Microorganism must be recovered from injected host.
What is norma flora?
normal bacteria that is found on the outside surfaces and mucous membranes of the body. Eg. skin, hair, mucous membrane openings.
Transient Normal Flora
bacteria that is different from usual flora and present for a short time. Eg. due to antibiotics or hospitalization
What is contamination of bacteria?
presence of a bacteria in or on a body site. it is just present not growing. Eg. decal matter on our hands.
What is colonization of bacteria?
when the bacteria are growing or have colonized a site, no host reaction.
What is infection of bacteria?
bacteria growing in or on a body site and causing host reaction. Eg. fever, inflammation
Pathogenicity
ability to cause disease
Virulence
degree of pathogenicity
Non-pathogen
not capable of causing disease
Describe Bacterial Virulence Factor: Capsules
prevent phagocytosis
Describe Bacterial Virulence Factor: Hyaluronidase
- extra cellular enzyme produced by gram positive bacteria
- dissolves hyaluronic acid in connective tissue and allows bacteria to spread through tissue.
Describe Bacterial Virulence Factor: Collagenase
-breaks down collagen of connective tissue causing bacteria to spread faster in the connective tissue
Describe Bacterial Virulence Factor: Hemolysins
-lyse RBC’s & this decreases the host’s immunity
Describe Bacterial Virulence Factor: Leukocidins
-kills phagocytic cells (white blood cells) creating pus
Describe Bacterial Virulence Factor: Kinases
-breaks down fibrin clot (breaks through) formed by the body to isolate infected bacteria, bacteria spread into tissue.
Eg. Can be used as “clot busters” to break down fibrin in patients with “thick blood”, stroke victims with clots
Describe exotoxins (gram +) and give an example.
- they are mainly produced in gram positive bacteria
-they are excreted from living bacterial cells
-mostly are protein molecules
-antigenic, causes an immune response
-can be converted to toxoids for immunization
-have specific site of action in host
EG. Botox and tetanus
Describe endotoxins (gram -) and give an example.
- produced by gram negative bacteria
-they are past of the cell wall: lipopolysaccharide (outer part), they are released when the walls are lysed from antibiotics
-NOT antigenic- don’t form toxoids
-non-specific site in hosts
-effects: aches, malaise, fever, decreased blood pressure, shock.
EG. salmonella endotoxin
Give the 6 signs of a bacterial infection.
- Fever
- Lymph node swelling
- Inflammation
- Exudate (accumulation of fluid at the site or infection)
- Granulomatous
- Cellulitis (diffuse pus inflammation)
Describe inflammation.
- Histamine released at site of infection
- Dilation of blood vessels
- Swelling, Redness, pain, heat
Describe the 3 different types of exudate.
- Purulent exudate- many WBC’s or PMN’s (polymorphonuclear neutrophils) at the site of infection causes pus.
- Serous exudate- water fluid with few PMN’s (neutrophils)
- Transudate- non-cellular fluid caused by passive leak from blood & lymph vessels.
Describe granulomatous infection.
- Granuloma at site of infection contains large macrophages
- Epithelioid cells: giant cells caused by macrophages fusing together, wall off infection in body site.
Describe cellulitis.
- subcutaneous loose connective tissue, fluid spreads between layers causing redness and swelling.
Epidemic
outbreak of a disease in a short amount of time.
Endemic
present in small % of population
Pandemic
epidemic that occurs world wide
Endogenous infection
infecting bacteria come from outside hosts body. Eg. UTI
Exogenous infection
infecting bacteria come from outside hosts body. E. Strept throat.
Nosocomial
infection acquired from a hospital environment.
Describe the types of infections by bacteria (primary, secondary, nonspecific, opportunistic).
Primary: initial infection
Secondary infection: an infection following a primary infection and usually caused by a different bacterium
Nonspecific infection: bacterial cause of infection is not identified
Opportunistic: low grade pathogen causes infection in immunosuppressed or chronically ill patients. (takes advantage) Eg. Yeast infection in Chemotherapy patient
Describe acute and chronic infections.
Acute= drastic and short lasting Chronis= low grade and long lasting
Describe localized and disseminated infections.
Localized= restricted to small area Disseminated= spread to most part of body
