topic 8 Flashcards
What are 4 different kinds of microbes and some of their general characteristics? What are some of their structural differences/sizes?
Bacteria – first and smallest independently living cells known. Size in the Light microscope range, smaller than fungi/protozoa, bigger than viruses.
– prokaryotic cells (no nucleus, one chromosome, no membrane bound organelles, cell wall, etc.)
– Typical: most bacteria; typical cell wall structure; typical metabolic growth
– Atypical: lack characteristic components (mycoplasma, chlamydia, rickettsia, mycobacteria)
- Fungi: eukaryotic molds (filamentous) or yeasts (single cells). Bigger than bacteria, but normally not seen by human eye.
- Protozoa/Helminths (single cell protozoa/worms– eukaryotic parasites). Bigger than bacteria, but normally not seen by the human eye.
- Viruses: intracellular parasites with no cellular structure;consist of either DNA or RNA, a capsid, and can either be naked or enveloped. They direct their own replication. Smaller than bacteria, most can only be seen by electron microscropes.
What are some general steps of the viral life cycle?
Virus adsorbed and binds to a specific receptor at a specific type of cell.
Virus is endocytosed and then the DNA/RNA is released
DNA/RNA is copied.
DNA/RNA is transcribed and translated in the various proteins that are needed to make a virus.
Viral proteins, DNA/RNA, etc. are put on the cell membrane and together, as a unit, they bud off the cell membrane.
Any action performed such as duplication, transcription, transport, etc. uses the host cells machinery.
All of these steps vary from virus to virus (whether they kill cell or not, how long it takes, how much of their own machinery they have, etc.).
How do much bacteria duplicate? How does chlamydia duplicate?
Most bacteria duplicate by binary fission.
Chlamydia enters a host cell in a phagosome. It begins to replicate itself inside the phagosome. These cells then condense into elementary bodies which are released when the host cell is lysed.
How do fungi duplicate? What is the lifecycle of candida? What determines which conformation it will take?
Fungi mainly replicate by budding.
Candida are an opportunistic microbe meaning they take advantage of a weakened system. Therefore, when antibiotics are taken, they’ll take the opportunity to grow b/c antibiotics aren’t there.
Their conformation depends on the temperature of their environment.
What is an example of a protozoa’s lifecycle?
Malaria is a protozoa. its lifecycle is rather complex. It has 3 different lifecycles. On is in the mosquito, one is in the human liver, and one is in human blood (fevers, etc., when we can actually see the malaria). Mosquitos are considered to be a vector (if mosquitos didn’t exist, malaria wouldn’t either).
What is an example of a worm’s life cycle?
A schistosome also has a complex lifecycle and requires a vector. They have a life cycle within snails until the snails release them into water where they enter into humans. They have a life cycle in humans. Humans release many eggs in their feces in urine that end up in water and then end up in snails to mature.
What is the definition of an infection? What do they cause at the site of infection?
Infection – theoretically just growth of microbes
– but…commonly used to mean disease
– pyogenic (pus-neutrophils)
– granulomatous (cellular build up)
What is the definition of a disease?
Disease - harm/damage caused by an infection
– Extracellular bacteria
– Intracellular bacteria
– Obligate intracellular parasites (can’t live outside cells)
• Viruses, Chlamydia & Rickettsia (bacteria)
What is a pathogen? What is an opportunistic pathogen-how is it treated?
Pathogen – microbe capable of causing disease
• Opportunistic pathogen - takes the opportunity to cause disease, typically in a compromised host (often are normal flora). You don’t try to get rid of the bacteria, but find out the opportunity that made them act pathogenically.
Pathogens may be normal flora in one organism or site but a pathogen in others.
What is virulence? What are virulence factors?
- Virulence - quantitative measure of pathogenicity (# orgs necessary to cause disease) - ~Infectious Dose
- Virulence factors - properties of the pathogen (virus/bacteria/fungus/parasite) which enable virulence
What are two ways of measuring virulence?
ID50-Amt. of organisms needed to infect 50% of subjects.
LD50-Amt. of microbes needed to kill 50% of subjects
What are some terms involved with the source of an infection?
- Nosocomial - hospital acquired infection
- Iatrogenic - physician (healthcare worker)- induced infection
- Communicable - host to host
– contagious - highly communicable
What is an epidemic, endemic, and pandemic?
- Epidemic - infections much more freq. than usual
- Endemic - constant low level infection
- Pandemic - world-wide distribution
What are subclinincal/inapparent infections, latent infections? What are carriers? What is colonization?
• Subclinical/inapparent infections – no disease
– may detect organism or antibody to it
• Latent infection – organism is dormant, little or no symptoms
- can be reactivated (e.g., Herpes)
- Carrier - growth without symptoms (e.g., Staph. Aureus)
- Colonization - growth in a specific site (e.g., nasal passages)
What is epidemiology? What are some associated terms and their definition?
• Epidemiology - factors that influence the acquisition and
spread of ID
- Reservoir – normal habitat of organism (e.g., rodents for Hantavirus)
- Source – where the actual infection was acquired
- Vectors - mode of transmission (food, water, insect)
