Lecture 1 8/31/23 Flashcards
What are the possible bacteria shapes?
-cocci
-bacilli
-coccobacilli
-spiral
-spirochete
What are the general characteristics of bacteria?
-prokaryotic
-unicellular
-singular cellular chromosome
-complex cell wall
-asexual repro. through binary fission
What is etiology?
cause of disease
What is a pathogen?
microbe that can cause disease
What is transmission?
spread of infectious agents from one host to another susceptible host
What is colonization?
presence of microbes in the body without any disease
What is infection?
invasion or growth of disease-causing microbes in the body
What is pathogenesis?
mechanisms by which pathogens causes disease
What is pathogenicity?
ability of a pathogen to cause disease
What are virulence factors?
properties found in isolates that cause disease not in isolates of the same species that do not cause disease
What is virulence?
pathogen’s ability to cause disease/damage
What is predisposition?
condition of the host that makes it susceptible to infections
What are the potential outcomes of infection?
-disease followed by recovery
-disease followed by death or disability
-disease followed persistence of subclinical/chronic infection
What are the characteristics of obligate pathogens?
-highly virulent
-small # enough to cause infection
-distinct disease presentation
-host does not need any predisposition factors
What are the characteristics of primary pathogens?
-moderately virulent
-moderate numbers to cause infection
-distinct disease
-host needs some level of predisposition
What are the characteristics of opportunistic pathogens?
-no virulence
-non-specific disease
-host has many and/or severe predisposing factors
What is the sequence of events in bacterial pathogenesis?
-entry into host
-evasion of host defenses
-colonization of host systems
-multiplication
-exertion of damage in host
-transmission to other hosts
What is the disease “triangle of tragedy?”
-host: factors that impact susceptibility
-pathogen: factors that impact ability to infect/damage
-environment: factors that impact exposure
What types of damage can infection result in?
-changes in normal physiology
-depletion of nutrients
-inflammation/damaging immune response
-combination
What is the microbiome?
collection of all microbes that naturally live on and inside of a body
What are the characteristics of gram positive bacteria?
-thick peptidodglycan
-contain lipoteichoic acid
-no outer membrane
What are the characteristics of gram negative bacteria?
-thin peptidoglycan
-have outer membrane containing lipopolysaccharide
What are the characteristics of acid-fast bacteria?
-thin peptidoglycan
-no outer membrane
-considered gram pos.
-have mycolic acid
What happens when gram negative bacteria die?
-release lipid A/endotoxin into bloodstream
-results in stimulated immune system and endotoxic or septic shock
What are the two types of bacteria without a cell wall?
-mollicutes: genetically have no cell wall
-L-forms: once had cell wall but it has degraded
Why can gram-staining not be used on bacteria without cell walls?
cell walls are what keep the gram-staining dyes in the cell
What must be considered when treating an infection caused by cells lacking cell walls?
antibiotics that act by damaging the cell wall will not work on these bacteria
What are the characteristics of flagella?
-filamentous structures used for motility
-number and arrangement can be used for ID
What are endoflagella?
flagella inside the cell surface (like in spirochetes)
What are the characteristics of pili/fimbriae?
-small, thread-like
-virulence factor
-facilitate adherence
-contribute to antigenicity/protection
What are the characteristics of the capsule?
-outer polysaccharide coating on some bacteria
-helps with evading phagocytosis
-significant virulence factor
What are the characteristics of endospores?
-dormant forms
-highly resistant
-produced when bacteria are exposed to adverse conditions
-essential when nutrients are depleted
-survival mechanism
What are exotoxins?
proteins produced inside bacteria and secreted into the surrounding medium
What are endotoxins?
constitutive elements of the bacteria membrane that are liberated when bacteria die
What are the characteristics of exotoxins?
-heat labile
-exert action on specific target cells
What are the characteristics of endotoxins?
-heat stable
-induce inflammation
What do super antigens do?
-bind and cross link to MHC classical II on APCs and T helper cell receptor
-result in T cell activation and massive cytokine release
-end result is symptoms of shock
How do super antigens differ from conventional antigens?
super antigens can activate any T cell, while conventional antigens only activate antigen-specific T cells
What are the characteristics of biofilms?
-extracellular polymeric substances
-bacteria in masses
-increased clinging to surfaces
-promote chronicity
-reduce antimicrobial penetration/susceptibility
What is quorum sensing?
molecular communication system that synchronizes expression of certain genes
What are plasmids?
circular extrachromosomal elements containing virulence factors that are transferred via conjugation
What are bacteriophages?
virus particles that attack bacteria and transfer or mutate virulence factors via transduction
What are the three bacterial locations?
-extracellular (most common)
-obligate intracellular
-facultative intracellular
What properties are used to classify bacteria?
-staining properties
-metabolic properties
-biochemical characteristics
-fatty acid profile
-DNA sequencing
What DNA sequence is most often used for bacteria classification?
16s ribosomal gene
