1 Introduction and basic bacteriology Flashcards
What is Purpura Fulminans?
Small capillary clots due to intra vascular coagulation, leading to tiny spots of necrosis all over the body. Simultaneously, bleeds occur all over the place because clotting factors are used up by all the tiny clots.
Which organisms are the major causes of Purpura Fulminans?
Neisseria meningitidis, Streptococcus pyogenes, Staphylococcus aureus
Which spherical bacterium is named for its golden color?
Staphylococcus aureus
What treatment is used to neutralize superantigen exotoxins, and why is it so rarely used?
intravenous immunoglobulin; it is rarely used in part because it is so expensive ($30K)
What is drotrecogin-alpha, and what is it used to treat?
activated Protein C; it is used to slow clotting to prevent purpura
What illness can develop when a patient has a respiratory viral infection complicated by Staph aureus?
Post-influenza TSS
Which bacterium is the most significant cause of serious infections and deaths due to infections in the United States?
Staphylococcus aureus
Which bacteria constitute the top two causes of bloodstream infections?
1) Staphylococcus epidermidis 2) Staphylococcus aureus
Which bacterium is the number 1 cause of osteomyelitis?
Staphylococcus aureus
T or F: Staph aureus is the number 1 cause of pneumonia.
F; it is the number 2 cause of pneumonia
Thucydides Syndrome is now recognized as what illness?
post-influenza Staph TSS
How many americans die yearly due to seasonal influenza?
3K to 50K
Which two proteins are essential in influenza virus for infecting (i.e. entering and exiting) a host cell?
Hemagglutinin and Neuraminidase
Which protein allows entry of the influenza virus into an epithelial cell, and what does it bind to on the host cell to initiate this process?
Hemagglutinin binds to sialic acid residues on epithelial cells to allow entry of the virus
What needs to occur in order to activate hemagglutinin?
a serine protease needs to cleave the HA and expose the sialic acid binding site on HA
Which protein is required in order for influenza virus to exit a host cell?
neuraminidase
Which viral protein is the target of Tamiflu?
Neuraminidase
How does Staph aureus help to activate influenza HA?
Staph aureus produces a large amount of serine proteases that can cleave and activate HA
T or F: TSST-1+ S. Aureus produces lower levels of proteases
F, it produces exceptionally high levels
T or F: Influenza virus can be activated by Human serine proteases
T
Summarize the pathogenesis of post influenza TSS.
1) Human is co-colonized by influenza A virus and TSST-1+ Staphylococcus aureus
2) S. aureus serine proteases activate the viral HA, and the virus
infects respiratory epithelial cells
3) Virus damages epithelium, allowing for secondary S.
aureus infection and TSST-1 production
4) Post-influenza TSS develops in virally
immunocompromised, susceptible humans
What is a pathogen?
A microbe that causes illness
What is a primary pathogen?
A microbe that typically causes illness whenever present in the host
What is an opportunistic pathogen?
Often normal flora microbe that causes illness when the host is immune compromised
What are normal flora, also known collectively as the microbiome?
Microbes that usually live on the skin and mucous membranes without causing illness
What is virulence factor?
The strength of the microbe in disease causation, and the factors that give them that strength
What are bacilli, and what are some examples?
rod-shaped bacteria; examples include Bacillus cereus [G+], Clostridium tetani [G+], and Escherichia coli [G-]
What are some of the sub types of bacilli?
regular rods, fusiform (with tapered ends) and filamentous (thread-like)
What are cocci, and what are some examples?
spherical bacteria; examples include Staphylococcus aureus [G+], Streptococcus pyogenes [G+], Streptococcus pneumoniae [G+], and Neisseria meningitidis [G-]
What are the major groups of bacteria determined by shape?
bacilli, cocci, coccobacilli, spirilli, spirochetes
What are spirilli, and what is an example?
curved bacteria; an example is Vibrio cholerae [G-]
What are spirochetes, and what is an example?
long spiral-shaped bacteria; an example is Treponema pallidum
Summarize the gram staining process.
1) Stain bacteria for 1 minute with crystal violet and then 2 minutes with Gram’s iodine
2) Decolorize with ethanol
3) Counterstain 30 seconds with safranin
T or F: Both crystal violet and safranin are acidic dyes that bind to peptidoglygan carbohydrates.
F; Both crystal violet and safranin are BASIC dyes that bind to Nucleic Acids
What color do Gram-positive bacteria stain? Gram-negative?
Gram-positive bacteria stain purple, and Gram-negative stain pink
What technique is used to visualize spirochetes?
Darkfield microscopy
T or F: Silver stain is used to visualize Legionella pneumophila
T
Summarize the acid fast coloring technique.
1) stain with hot carbol fuschin (red)
2) counterstain other bacteria with methylene blue
Which organisms is acid fast stain used to visualize, and why is this technique necessary?
mycobacteria and actinomycetes
What are the typical dimensions of prokaryotic organisms?
1 micrometer in diameter by a few micrometers long
What type of ribosomes do most prokaryotes use, and why is this information clinically significant?
70s ribosomes, frequent target of antibiotics.
Describe the typical prokaryotic chromosome.
Circular haploid chromosome, 1-10 megabases in size, contains a few thousand genes
