Foundations: Infectious Disease 1 Flashcards
What is a primary pathogen?
One capable of causing disease in a normal host
What is a pathogen?
Any microorganism that is capable of causing disease in a susceptible host
What is an opportunist pathogen?
One that primarily causes disease in immunocompromised individuals
What is bacteria?
Single cell organisms that lack membrane-enclosed organelles
What color do gram+ bacteria turn in a gram stain and why?
Purple due to lack of lipopolysaccharide layer and exposed peptidoglycan layer
What color do gram- bacteria turn in a gram stain and why?
Pink due to outer lipopolysaccharide layer
What color do Mycobacteria or Nocardia turn during an acid-fast stain and why?
They turn red due to the high content of mycolic acid in their cell walls
What purpose does mycolic acid serve?
Impedes entry of chemicals and lysosomal components of phagocytes
Fewer and much longer porins
Surface proteins act as adhesins
What do spiral bacteria tend to cause?
Systemic diseases
Treponemes, Borrelias, Leptospiras
What do pathogenic filamentous bacteria tend to cause?
Chronic diseases
Actinomyces, Nocardia, Mycobacteria
What are two examples of Gram + bacteria?
Staphylococcus (skin)
Streptococcus (skin and pneumonia)
What are internal (endogenous) pyrogens?
Cytokine factors that migrate to circumventricular organs of brain to active toll-like receptors
What are the major endogenous pyrogens?
IL-1
IL-6
TNF-alpha
What are exogenous pyrogens?
Usually microbes or their products
Describe a capsule.
Outside of the cell wall Difficult to remove Prevents phagocytosis Helps bacteria adhere to surfaces Most common in gram- bacteria
Describe the slime layer.
Outside of the cell wall
Easily removed
Protects bacteria from environmental dangers
Helps bacteria adhere to surfaces
Describe antigenic variation.
Expression of various alternative forms of antigen/surface proteins in order to evade a host immune response
What do anaerobes cause?
Abscesses
What are 2 examples of obligate aerobes?
Pseudomonas aeruginosa
Mycobacterium tuberculosis
What are Microaerphiles?
Bacteria that require oxygen in another inorganic form, like CO2
What are 3 examples of Microaerphiles?
Neisseria gonorrheae
Neisseria meningitidis
Helicobacter pylori
What is an example of a slow growing bacterium, and what do they tend to cause?
Mycobacterium tuberculosis
chronic infections
What is an example of a rapid growing bacterium?
Vibrio vulnificus (from uncooked seafood)
What are the phases of bacterial growth?
Lag phase
Exponential growth phase
Stationary phase
Death phase
What happens during the lag phase?
Bacteria are adjusting to the environment
What happens during stationary phase?
The death rate is about equivalent to the growth rate
What is an example of a bacterium with a long stationary phase?
Mycobacterium tuberculosis
What is an example of a bacterium with a short stationary phase?
Vibrio vulnificus
What is an example of an obligate intracellular bacterium?
Rickettsia (causes Rocky Mountain spotted fever)
What is an example of an extracellular bacterium?
Helicobacter pylori
What are 2 examples of bacteria with antigenic variation?
Neiseria meningitidis
Neisseria gonorrhoeae
What does it mean for a bacterium to have phase variation?
The phenotype switch is usually reversible
“on/off switch”
What happens during Transcription?
RNA strand synthesized from DNA template
What happens during Translation?
Conversion of mRNA sequence to amino acid sequence
What is a Transition point mutation?
purine to purine (A&G)
pyrimidine to pyrimidine (C&T)
What is a Transversion point mutation?
purine to pyrimidine or vice versa
What are the 4 types of gene transfers?
Conjugation
Transformation
Transduction
Transposition
Describe Conjugation.
Mediated by F plasmid. One cell extends its pilus to another cell to share the F plasmid between cells.
What can result from Conjugation?
Shared DNA
Resistance to antibiotics, immune system
Describes Transformation.
A recipient cell takes up free floating DNA fragments, which enter the cell as exogenous DNA and are incorporated into host cell’s chromosome via recombination
Describe Transduction.
Bacteriophages attach to the bacterial wall to inject infective DNA particles to transfer resistant genes
Describe Transposition.
A transposon induces spontaneous mutations and promotes genome rearrangements to regulate gene expression… spreads traits like antibiotic resistance
What are some characteristics of viruses?
No cells not alive DNA/RNA coated in protein no ribosomes no nucleus
What traits differ in bacteria?
Unicellular
DNA/RNA free floating
ribosomes
Describe vertical transmission of viruses.
Transmitted mother to child.
Describe horizontal transmission of viruses.
Transmission between members of the same species that are not in a parent-child relationship.
How are viruses mainly classified?
By phonotypic characteristics
How does the International Committee on Taxonomy of Viruses classify viruses?
Order, Family, Subfamily, Genus, Species
How does the Baltimore Classification classify viruses?
Nucleic acid combination
Stranded-ness
Sense
Method of replication
What are the steps of viral replication?
Attachment/adsorption Penetration Uncoating Viral genome replication Maturation Release (lysis, budding)
Discuss some characteristics of fungi.
Nuclei with chromosomes Heterotrophic (no photosynthesis) Osmotrophic (absorb food) Develop hyphae Reproduce by spores
What are some principal manifestations of fungal disease?
Dermatophytosis (skin)
Onychomycosis (nail)
Coccidioidomycoses (systemic)
Mycotoxicoses (poisoning)
Define Morbidity.
Relative incidence of a particular disease in a specific locality.
Define Mortality.
Number of deaths in a population at risk during one year.
Define Prevalence.
The number of people in a population who have a disease at a given time.
Define Incidence.
Probability of developing a particular disease during a given period of time.
What is an epidemic?
When new cases of a disease exceed what is expected based on recent experience.
What is a pandemic?
An epidemic that spreads to other countries or continents and affects a substantial number of people
What are some examples of past pandemics?
Cholera Influenza Measles Tuberculosis Malaria Typhus
How would you describe a disease that occurs among family members, usually by heredity?
Familial
What is a “healthy carrier”?
One that carries the infection but never gets infected
What is a “convalescent carrier”?
A carrier that is recovering from the disease
What is a “temporary carrier”?
Only carries it for less than 6 months
What is a “chronic carrier”?
A carrier that carries the disease for several years or for the rest of their life
What are commensal microbes?
Microbes that live with the host in complete harmony without causing damage.
What is an opportunistic pathogen?
A pathogen that is usually safe but can become dangerous when the host’s immunity is lowered
What are 2 examples of opportunistic pathogens?
Herpes zoster
C diff
What is a way to prevent opportunistic pathogens from causing disease?
Treat with probiotics like acidophilus
What is a zoonoses?
An infectious disease transmitted between species
What are some examples of zoonoses?
Rabies Cholera Ebola HIV Cat Scratch Disease (Bartonellosis) Salmonellosis Rotavirus
What is an example of a bacterial zoonoses?
Bacillus anthracis (inhalation/ingestion of bacterial spores)
What is an example of a viral zoonoses?
Rabies (Rhabdovirus via virus-laden saliva during a bite or scratch)
What is an example of a protozoal zoonoses?
Toxoplasmosis gondii (ingestion of raw/undercooked meat, fecal-oral)
What is an example of a helminthic zoonoses?
Trichinella spiralis (an intestinal nematode from ingesting undercooked meat)
What is an example of a fungal zoonoses?
Ringworm (tinea capitis, athlete’s foot or jock itch)
What is a primary infection?
Exposure to the pathogen for the first time
What is a reinfection?
Exposure to the same pathogen for the second or many times
What is a secondary infection?
Infected by one pathogen
Immunity lowered
Invasion by another pathogen
What is an iatrogenic infection?
Caused by a medical examination or treatment
What is a nosocomial infection?
Caused by a hospital environment
What percentage of American hospital patients acquire a nosocomial infection?
About 10%
What is an endogenous infection?
When a commensal enters places where it should not be
What is an example of an endogenous infection?
E. coli to the urinary tract causing a UTI
What is an exogenous infection?
When a pathogen comes from another source
When is an infection inapparent?
When the individual is asymptomatic
When is an infection atypical?
When it presents with different symptoms or concurrently with another disorder
What is a latent period?
When a pathogen is capable of causing disease at a later date but is currently dormant in the host
What is bacteremia?
Presence of bacteria in the blood
What is sepsis?
Bacteremia associated with an inflammatory response (endocarditis)
What kind of receptors does gut flora have?
Toll-like receptors to activate the immune system (macrophages)
