Wk 8 Flashcards
(22 cards)
What are the two ways of microscopic counting?
Direct smear and counting chamber
What is direct smear?
Counts carried out on a fixed and stained smear from a define volume of fluid
What is counting chamber?
Counts carried out on a fixed volume of bacterial suspension using a calibrated slide
What is a disease?
A disorder of structure or function in the host that adversely impacts the host and is not simply a direct result of physical injury
Define infectious disease
Disease caused by pathogens and transmittals to other hosts
Define pathogenesis
Biological mechanisms that lead to a disease
Define pathogenicity
Ability of microorganism to damage a host
Define infection
The invasion and multiplication of pathogens in an individual or population
What is virulence?
Relative capacity of a pathogen to damage a host (pathogens express wide range of virulence)
To act as a pathogen, what at the four things one must do?
- Find an appropriate niche within a host
- Compete with normal micro iota to adhere to host tissues
- Evade or overcome normal host defenses
- Express genes that encode the factors causing disease
What is inflammation?
Biological host tissue response to harmful stimuli such as pathogens and/or their metabolites
How can inflammation manifest?
Local tissue damage, toxemia, acute systemic disease, chronic disease
What is virulence factor? Is it intracellular or extracellular, and in what ways?
Def: bacterial traits that confer pathogenicity & enable pathogenic bacteria to colonize extracellular or intracellular niches in hosts
Majority of pathogenic bacteria are extracellular pathogens
Obligate intracellular pathogens need host to replicate while facultative intracellular pathogens can multiply in phagocytes or non-phagocytes
Define superantigen. What does it result in/cause?
Def: exotoxin causing dysfunction of immune system. It subverts the adaptive immune response by cross linking two of the most important antigen-recognition receptors
Results in: massive T-cell proliferation and cytokine release & no immune protection
Define biofilm.
Bacterial populations adherent to each other and/or surfaces and enclosed in a bipolymer matrix (can be planktonic (free) or sessile (attached))
How is a biofilm formed?
- Attachment of bacteria to surface and formation of mono layer of cells
- Clustering of cells and formation of micro colonies
- Maturation with production of extracellular polymers and hydrated eco polymer matrix
How can a biofilm manifest?
Dental plaques, biofilms in catheters, UTI’s
Define quorum sensing.
Bacteria produces small signal molecules to communicate with others. When the population reaches a define density, the signal attains a critical threshold concentration at which they coordinate expression of bacterial genes to act as a community rather than alone.
Similarity and difference between plasmid and bacteriophages.
Both may carry genes for antibiotic resistance, toxin, and other virulence factors between bacteria.
Plasmid: small, circular DNA present in bacteria
Bacteriophage: virus that infected and replicates within bacteria
Define conjugation
Transfer of genetic material through direct contact between donor and recipient
Define transformation
Alteration of a cell resulting from the direct uptake and incorporation of exogenous genetic material
Define transduction
Foreign DNA is introduced into another cell via a viral vector
