Wk 1 Infectious Agents Flashcards
Bacteria
can grow under appropriate conditions in the absence of a host.
* Some exceptions (i.e. Rickettsia is an obligate intracellular bacterium)
Viruses
obligate intracellular parasites that must replicate inside cells, using cellular machinery.
Fungi
non-motile filamentous, branching strands of connected cells: replicate as yeasts or molds.
Parasite
Eukaryotic organism that lives on or in a host organism and gets its food from or at the expense of its host.
* Protozoa (unicellular)
* Helminths (tapeworms, hookworms, roundworms, etc.)
* Ectoparasites (ticks, mites, fleas, lice).
Prion
“infectious proteins”
non-replicating
Size comparison of microbes
Symbiosis
2+ organisms living in close proximity
-usually mutually beneficial
Pathogen
organism that usually lives as a symbiont, but under the right circumstances an organism that causes disease in its host
Pathobiont
organism that becomes a pathogen under certain circumstances
Commensal
an organism that benefits due to close proximity to its host, while the
host remains unaffected (one-sided symbiosis)
Parasitism
one organism benefits from the relationship at the expense of the other
Virulence
characteristics of an organism that influence its ability to cause disease (pathogenesis)
Immunogenicity
the ability of an organism to induce an immune response in the host
Sepsis
Acute illness caused by infectious agents and/or their products circulating in the bloodstream
Bacteremia
bacteria circulating in bloodstream
Viremia
viruses circulating in bloodstream
Fungemia
fungi circulating in bloodstream
parasitemia
parasites circulating in the bloodstream
Successful pathogen features
- Gains access to the host (contamination)
- Adheres to the host (adherence)
- Replicates on host surfaces (colonization)
- Invades tissues (invasion)
- Produces toxins (damage)
- Eludes host immune responses (immune evasion)
- Propagates (replication)
- Sheds (transmission)
*** The vast majority of microbes are not pathogens
What is the chain of infection?
How is bacterial nomenclature identified?
By genus and species
ie. staphylococcus aureus or Escherichia coli
- always italicized
Bacterial infections classified by disease/location
5 modes of direct transmission
- Skin to skin contact
- Droplet (short-range aerosol due to coughing, talking, etc.)
- Kissing
- Sexual contact
- Contact with soil or vegetation
3 modes of indirect transmission
- Droplet (organisms carried in small droplets, dust, etc.)
- Vehicles: food, water, biologic products (i.e. blood), fomites (inanimate objects that can transfer disease)
- Vectors: mosquitoes, fleas, ticks, etc.
5 routes of transmission
- Respiratory tract
- Fecal oral (GI pathogens)
- Skin
- Blood
- Mucous membranes
The triad of infectious disease
4 categories of antimicrobial therapy
- Antibiotics: against bacteria
- Antivirals: against viruses
- Antifungals: against fungi
- Antiparasitics: against parasites
What are 4 modes of antimicrobial use?
- Prophylactic: used to prevent infection based on risk factors
- Empiric: used to treat based on experience and relevant information available when you do not know the pathogen causing disease
- Preemptive: used to prevent based on preliminary data anticipating an infection
- Definitive: used to treat and expect cure after etiology has been identified
Bactericidal
cause death and disruption of the bacterial cell, include drugs that primarily act on the cell wall (i.e., beta-lactam antibiotics), cell membrane (i.e., daptomycin), or bacterial DNA (i.e., fluoroquinolones)
Bacteriostatic
inhibit bacterial replication without killing the organism. Most bacteriostatic drugs, including sulfonamides, tetracyclines, and macrolides, act by inhibiting protein synthesis
What is MIC?
= minimum inhibitory concentration
-lowest [] that prevents visible growth after 18-24h of incubation
What is MBC?
= minimum bactericidal concentration
-lowest [] that totally suppresses growth or results in >99.9% decline in colony count after overnight incubation
4 direct types of adverse events
- Allergy
- Toxicity
- Drug-drug interaction * Therapeutic failure
Epidemiologic distribution of disease
Sporadic: normally absent, but can occur without predictability
Endemic: predictable regularity
Epidemic: greater frequency than expected Outbreak: mini-epidemic, restricted in time and place
Pandemic: globally spread large epidemic affecting several countries and/or continents
Notifiable Diseases
Voluntary reporting to CDC by state for monitoring disease data
-list is modified annually by CDC
Reportable Diseases
Mandatory reporting by state
-uses personal identifier
-each state has its own laws and regulations for defining list
-list varies among states and over time
