2 Bacteriology 1 Flashcards
What are the types of prokaryotic pathogens?
Bacteria, mycoplasma (bacteria w/o cell wall), rickettsia (bacteria that must live inside host cell)
What are the eukaryotic microbial pathogens?
Fungi
Define bacteriophage
A virus that infects bacteria
What is a plasmid, and what types of plasmids are there?
Extra-chromosomal bacterial DNA.
R-plasmids: antimicrobial resistance plasmids
Virulence plasmids: virulence factors
What is an R plasmid?
An antimicrobial resistance plasmid
Gram ____ bacteria have a thick peptidoglycan layer and will stain ____.
Positive; purple
Gram ______ bacteria have a thin peptidoglycan layer and will stain ____.
Negative; pink
What type of bacteria typically have an outer membrane?
Gram -
Bacteria that require reduced oxygen are called _______
Microaerophilic aerobes
What is MacConkey agar selected for?
Gram - enterobacterales (rods) and some non-enterobacterales (bile salts inhibit a lot of other bacteria)
What are siderophores?
A ‘virulence-lifestyle’ protein that helps microorganisms bind iron from the environment to persist in the host.
What are the major types of bacterial toxins?
Endotoxins and exotoxins
What type of toxin is LPS, and what are its components?
Endotoxin; lipid a – biological action, core polysaccharide – structural link, carbohydrate O side chain – length determines virulence
What kind of bacteria produces endotoxins and why can other types of bacteria not produce endotoxins?
Gram - bacteria, because it ONLY produced in the outer membrane
What is the effect of LPS/endotoxins on the hosts’ tissues?
Inflammation
What is the effect of bacterial exotoxins on the host cells?
Host cell damage or disruption of function
What is a toxoid?
An inactivated exotoxin used in a vaccine.
What are the three types of bacterial exotoxins?
A-B toxins (simple and compound), superantigens, and disorganizers of host cell membranes
What is the function of the “B” component of an A-B toxin?
B is for Binding! Binds to the host cell receptor and determines toxin specificity.
What is the function of the “A” component of an A-B toxin?
A is for Activity! Responsible for the enzymatic action and toxicity after translocation into the host cell
What is the difference between a simple and complex A-B toxin?
A complex toxin has multiple B subunits.
What are the two MOA’s of membrane disrupting exotoxins?
- Channel into the host cell membrane and swell to cause cell/vacuole rupture
- Enzyme that compromises phospholipid membrane integrity
What is the MOA of superantigens?
Bridges MHC-II of macrophages and T cells outside of the antigen groove, causing MASSIVE T-cell stimulation.
Why is the host response to superantigens dangerous?
MASSIVE release of cytokines, esp. IL-2 leading to fever, vomiting, shock
T or F: only G+ bacteria have capsules.
Gram- AND Gram+ bacteria can have capsules
What is the function of a bacterial capsule?
Inhibits complement fixation and phagocytosis
In general, what kind of bacteria make spores?
Gram +
What is the advantage of a bacteria forming spores?
They are metabolically inactive and extremely environmentally resistant so they can survive adverse conditions.
What are the four ways that bacteria can acquire new genetic material?
Conjugation
Transduction
Transposition
Transformation
Describe conjugation.
Transfer of plasmids via sexual pilli.
Describe transduction.
Genetic material is transferred via bacteriophages.
Describe transposition.
Uptake of naked DNA.
Describe transformation.
Transfer of mobile DNA.
List each step of performing a Gram stain and include the purpose of each step.
- Crystal violet - stains peptidoglycan
- Iodine - fixes crystal violet to cells
- Alcohol - decolorizes (removes crystal violet stain from gram negative bacteria and most of the stain from gram positive bacteria)
- Safranin - counterstains the gram negative bacteria pink
What are the differences between Gram staining and Diff-Kwik?
Gram staining is better for bacteria, whereas Diff-Kwik is better for WBCs/RBCs and cellular components. Gram stains appear purple and pink, whereas Diff Kwik is blue and pink.
What are the four morphologies of bacteria microscopically?
Rods, cocci, coccobacilli (short rods), and filamentous (long rods)
What color is yeast on Gram stains?
Variable shades of both pink and purple
What type of agar is used to test hemolysis?
Blood agar
What are the types and appearances of the results of a hemolysis test on blood agar?
Complete hemolysis - yellowing of agar
Partial hemolysis - greening of agar
Non-hemolysis - no change in agar
Define alpha, beta, and gamma hemolysis.
Beta hemolysis - complete hemolysis by Streptococcus
Alpha hemolysis - partial hemolysis by Streptococcus
Gamma hemolysis - non-hemolysis by Streptococcus
What reagents are used to stain spore-forming bacteria, and what is the function of each reagent?
Malachite green - stains spores dark green
Carbol fuschin - counterstains vegetative bacteria pink
What layers make up the bacterial envelope in G- and G+ bacteria?
BOTH - cell membrane, peptidoglycan layer
G- only - outer membrane (contains LPS)
What are exotoxins made of?
Protein
