5. Microbial and Host Interactions Flashcards
What are Koch’s postulates used for?
Evidence to prove a specific microorganism to be the cause of a given disease.
What is normal flora and transient normal flora?
Normal flora - bacteria normally found on the outer surfaces and mucous membranes of the body
Transient normal flora - bacteria different from usual flora and present for a short time eg. From antibiotic use or hospitalization
What does contamination refer to?
The presence of bacteria in or on a body site that is not a part of the usual flora
Bacteria are present but not growing
What is colonization?
Differs from contamination in that the bacteria are growing or have colonized the site
What does infection refer to?
Bacteria growing in or on a body site and causing a host reaction
What is pathogenicity? Virulence?
Ability of a microorganism to cause disease
Virulence is the degree of pathogenicity
What is a pathogen and a non pathogen?
A Pathogen is a microorganism capable of causing disease
A Nonpathogen is when the microorganism is not capable of causing disease, very few are classified as this
Name the 6 bacterial virulence factors.
- Capsules
- Hyaluronidase
- Collagenase
- Hemolysins
- Leukocidins
- Kinases
Cause damage in the host in the immediate area
Name Koch’s postulates.
- Microorganism must be found in every case of the disease to be called the causative agent
- Microorganism must be isolated from the diseased host and grown in pure culture
- Disease must be reproduced when a pure culture of the microorganism is injected into a healthy susceptible host
- Microorganism must be recoverable once again from the experimentally injected host
What is the function of capsules?
Prevent attachment of phagocyte to bacteria
What is the function(s) of hyalurondiase?
Is an extra cellular enzyme produced by Gram + bacteria
Dissolves hyaluronic acid a compound found in tissue, this allows the bacteria to spread throughout the hosts tissue
What is collagenase?
Brakes down collagen of connective tissue, allowing bacteria to spread faster through connective tissue
What is the function of hemolysins?
Lyse red blood cells which decreases the hosts immunity
What is the function of leukocidins?
Kills phagocytic cells creating pus
What are the functions of kinases?
Break down fibrin clot that’s formed by the body to isolate infection
Bacteria can then break through the clot and spread
Define toxins.
Substances that cause damage to sites far removed from the site of invasion.
What are endotoxins and exotoxins?
Exotoxins - Gram + bacteria, excreted from living cells, protein molecules, causes immune response, can me converted to toxoids for immunization, have a specific site of action in host
Endotoxins - Gram - bacteria, part of the cell wall, released when cell walls are lysed from antibiotic action, do not form toxoids, nonspecific sites of action, cause aches, fever, shock
What are some signs of bacterial infection?
Fever, lymph node swelling, inflammation, exudate (accumulation of fluid), granulomatous infection (granuloma forms), cellulitis (purulent ((pus)) inflammation involving loose connective tissue)
What are the different types of Exudate?
Purulent exudate - many white blood cells, may be called polymorphonuclear neutrophils (PMNs), pus
Serous exudate - watery fluid, few PMNs, less protein
Transudate - noncellular fluid caused by passive leakage from blood or lymph vessels
What is an epidemic?
Many people in a given area having a disease over a shirt period of time
What is an Endemic?
Constantly present in a small percentage of the population
What is a Pandemic?
An epidemic that occurs worldwide
What is Epidemiology?
The study of when and where diseases occur and how they are spread
What is an Endogenous infection?
Infecting bacteria come from the hosts own body
What is an Exogenous infection?
Infecting bacteria come from outside the hosts body
What is a Nonsocomial infection?
Infection is a result of being in a hospital, a hospital acquired infection, or an infection that’s a result of treatment
What is a Carrier?
Potential pathogen carried by the host without any signs of infection
What is a Primary infection?
The initial infection caused by a microorganism
What is a Secondary infection?
Infection following a primary infection caused by a different microorganism
What is a Nonspecific infection?
Microbial cause not identified
What is an Opportunistic infection?
Caused by a low grade pathogen usually in a patient with lowered defences
What is an Acute infection? Chronic infection?
Acute, short lasting
Low grade infection lasting a long time
What is a Localized infection vs. a Disseminated infection?
Localized is restricted to a small area
Disseminated is spread to most parts of the body
