Quiz 1 Flashcards
What are the 5 types of infectious agents?
Bacteria
Viruses
Fungi
Parasites
Prions
What is the difference between a commensal organism and a symbiotic organism
a commensal organism benefits from close proximity to its host, while the host is unaffected (one-sided symbiosis)
Define immunogenicity
the ability of an organism to generate an immune response
What is colonization resistance?
the natural phenomena where microbiota inhibits colonization by newcomers
What are the most notable differences between eukaryotic cells and bacterial cells (prokaryotes)?
What is the main component of the bacterial cell wall?
peptidoglycan
What are two important cell wall polymers found in gram-positive bacteria?
What two peptides are commonly found in the peptidoglycan cell wall surrounding bacteria?
What are the four most notable components of the outer membrane of gram-negative bacteria?
What three elements compose the structure of lipopolysaccharide (LPS)?
Lipid A
Core oligosaccharide
O antigen
Which element of the structure of LPS is the endotoxin responsible for fever and shock?
Lipid A
Which element of the structure of LPS accounts for the virulence of gram-negative bacteria?
O antigen
What are examples of three genus of gram-positive cocci/diplococci?
Staphylococcus
Streptococcus
Enterococcus
What are examples of three genus of gram-positive bacilli/rods?
Bacillus
Clostridium
Listeria
What is an example of a gram-positive pleomorphic rod?
Corynebacterium
What are three examples of gram-negative cocci/diplococci, or coccobacilli?
Neisseria
Moraxella
Hemophilus
What are three examples of gram-negative bacilli/rods?
E- coli
Klebsiella
Psuedomonas
What are three examples of gram-negative curved/spiral rods?
Vibro
Campylobacter
Helicobacter
Why do ureaplasma and mycoplasma not gram stain? What is the clinical significance?
they lack a cell wall
they are insenstivie to beta-lactam antibiotics
Mycobacteria can stain gram-positive weakly; what are two notable molecules found in their cell wall?
mycolic acids
lipoarabinomannan (LAM) (a glycolipid)
What three antigens serve as the basis for serotyping pathogens?
O antigen (LPS)
K antigen (capsule)
H antigen (flagellin)
What is the maximum net yield of ATP in bacteria performing aerobic respiration?
36-38 ATP
What is the maximum net yield of ATP in bacteria performing anaerobic respiration?
2-36 ATP (can use non-oxygen final electron acceptor)
What is the maximum net yield of ATP in bacteria performing fermentation?
2 ATP
How is a bacteria that requires oxygen for metabolism classified?
Obligate aerobe
How is a bacteria that can grow with or without oxygen for metabolism classified?
Facultative anaerobe
How is a bacteria that can survive with only very little oxygen for metabolism classified?
Microaerophilic bacteria
How is a bacteria that is poisoned by oxygen classified?
Obligate anaerobe
What three enzymes can play a role in detoxification in aerobic or facultative bacteria?
superoxide dismutase
catalase
peroxidase
What is the difference in thickness of the peptidoglycan layer in gram-positive vs gram-negative bacteria?
gram-positive- 20-80nm
gram-negative- 5-10nm
Which bacteria are catalase positive?
Staphylococci
Pseudomonas aeruginosa
Enteric bacteria
Mycobacterium tuberculosis (at low body T)
What are protein secretion systems?
Which protein secretion system type is known as an injectosome or needle-like protein, and is commonly found in Yersinia, Psuedomonas, Salmonella, Shigella, and E. coli?
Type III secretion system
What is the major determinant of virulence in virulent strains of bacteria?
Exotoxins
T/F: Secretion is the exclusive method of trasmitting exotoxins for bacterial cells
F: Exotoxins can also be released by lysis of the bacterial cell in some cases
T/F: Endotoxins are cell-associated substances that are structural components of the peptidoglycan layer of bacterial cells
F: Endotoxins are structural components of the outer membrane (LPS) of gram-negative bacteria
Many (not all) bacterial exotoxins have an A-B structure for their components. What are the functions of each subsection?
B- binding component that triggers uptake
A- active component that has enzymatic activity
Though there are other types of exotoxins, what are the four major types of exotoxins taught in H&D? Give a short description of each type
Enterotoxins- act in GI to cause increased fluid secretion
Neurotoxins- act on nerves to cause paralysis
Pyrogenic exotoxins- stimulate cytokine release (rash, fever, TSS)
Tissue invasive exotoxins- allow bacterial to circumvent cell/tissue barriers
How does a superantigen present itself to T cells? What characterizes the reaction after binding?
How are endotoxins secreted from a bacteria into the host during an infection?
via cell lysis or detachment (not actively secreted)
Are either exotoxins or endotoxins heat stable?
Which part of the LPS structure is most responsible for endotoxin release?
Lipid A
What important virulence factor is associated with H antigen?
flagella
Bacterial adhesin proteins are most often associated with hair-like fibers called what?
pili or fimbriae
Some gram-positive bacteria can form spores. What are three notable facts about spore formation?
spores form during a nutrient shortage
spores lack metabolic activity
spores contain dipicolonic acid (granting heat resistance)
Will most antibiotics and hand sanitizers kill spores?
No
Does the replication fork in bacterial DNA replication proceed in one or two directions?
two directions
By what four processes does bacterial gene exchange occur?
Transformation
Conjugation
Transduction
Transposition
What are the three types of bacterial horizontal gene transfer (HGT)?
What is meant by labeling a bacteria as “competent”
It is able to take up DNA
During bacterial conjugation, the donor cell with the pilus is referred to as F+ or F-?
F+
What are transposable elements in bacterial DNA?
DNA elements that can jump from one place in bacterial DNA to another, transferring genes or disrupting genes when they insert
What is the main advantage that capsules give to encapsulated bacteria?
Protection from opsonization/phagocytosis
Which 5 notable encapsulated bacteria are opsonized and cleared by the spleen?
Streptococcus pneumoniae
Hemophilus influenzae
Escherichia coli
Neisseria meningitidis
Salmonella typhi
Peptidoglycan is especially suceptible to what enzyme created by the human body?
lysozyme
Bacterial flagella depend on what substrate instead of ATP?
protons
What is the general function of quinolone medications?
inhibition of unwinding of DNA by DNA gyrase during DNA replication
What virulence factor is presented in the capsule of encapsulated bacteria?
K antigen
What important diseases/infections are associated with Streptococcus pneumoniae?
Bacterial meningitis
Otitis media
Pneumonia
Sinusitis
What important diseases/infections are associated with Streptococcus agalactiae?
Bacterial meningitis
What important diseases/infections are associated with Staphylococcus aureus?
Pneumonia
Eye infections
Skin infections
Food poisoning
What important diseases/infections are associated with Streptococcus pyogenes?
Skin infections
Upper respiratory tract infections
What important diseases/infections are associated with Psuedomonas aeruginosa?
Skin infections
UTI
What important diseases/infections are associated with Escherichia Coli?
Food poisoning
UTI
What important diseases/infections are associated with Staphylococcus saprophyticus?
UTI
When possible, should bacterial samples be collected before or after administration of microbial agents?
before
When would electron miscroscopy be used in direct visualization of bacteria?
In order to view bacterial structures
What is the main difference between the Ziehl-Neelson acid-fast staining method, and the Kinyoun acid-fast staining method?
Ziehl-Neelson: specimen is heated during staining
Kinyoun: cold acid-fast
What is the color visualized for both acid-fast positive and acid-fast negative bacteria?
Acid-fast positive is RED
Acid-fast negative is BLUE
*counterstain is methylene blue
Which types of bacteria undergo alpha hemolysis when plated on a blood agar?
Streptococcus pneumoniae
Viridians group Streptococci
What types of bacteria undergo beta hemolysis when plated on a blood agar?
Streptoccocus pyogenes
Streptococcus agalactiae
Staphylococcus aureus
Psuedomonas aeruginosa
What notable bacteria undergoes gamma hemolysis (no hemolysis) when plated on a blood agar?
Enterococcus faecalis
What two fastidious organisms are selective for chocolate agar?
Haemophilus influenzae
Neisseria species
What is a Colistin and Nalidixic acid (CNA) agar selective for?
Gram-positive bacteria
What does a MacConkey agar select for? What additional differentiation can it provide?
Gram-negative bacteria
It can differentiate lactose fermenters vs. non-lactose fermenters
What color will lactose fermenters turn on a MacConkey agar?
pink
What four notable bacteria are lactose fermenters? (CEEK)
Citrobacter
Enterobacter
E. coli
Klebsiella
What is the Thayer-Martin media selective for?
Neisseria sp.
What is the presentation of a positive catalase test in the lab?
Visible O2 bubbles
A rapid agglutination test can be used to identify what type of bacterial infection?
Group A streptococcus
The complement system consists of proteases in ________ form?
inactive
What are the three anti-microbial functions of complement?
Direct destruction of pathogen
Opsonization
Inflammatory response
What are the three pathways of complement activation?
What characterizes the Alternative pathway of complement activation?
-Activated by exposure to pathogen membranes
-First pathway to act- immediate
What characterizes the Lectin pathway of complement activation?
-Activated by mannose-binding lectin (MBL)
-MBL produced by liver during systemic inflammation (24-48 hours post infection)
What characerizes the Classical pathway of complement activation?
-Activated by antibodies
-5-7 days after 1st exposure
-immediately after second exposure
What are the three main effector functions of the C3 convertase?
What are the main effector functions of the C5 convertase?
How do phagocytes (macrophages, neutrophils and eosinophils) detect opsonized targets?
What are the three main actions of C3a and C5a in promoting inflammation?
- Activation of endothelial cells to induce vasodilation and migration of leukocytes into tissue
- Increased activation of leukocytes, including mast cell and basophil degranulation
- Acting as chemotactic factors
How is the C3 convertase formed in the classical pathway?
Components of C1 cleave C2 and C4 to induce the formation of the C3 convertase (C4bC2b)
How is the C3 convertase formed in the lectin pathway?
MASP proteases cleave C2 and C4 to induce the formation of the C3 convertase (C4bC2b)
How is the C3 convertase formed in the alternative pathway?
Factor D cleaves C3 into C3a and C3b
C3b binds to bacterial surface
Factor D cleaves Factor B to form Bb fragment
C3b and Bb form C3 convertase (C3bBb)
How does C1 INH regulate activation of complement?
It is a regulator of C1 in the classical pathway
How do Factors H and I, as well as DAF and MCP regulate activation of complement?
They destabilize the C3 convertase in the alternative pathway
How does CD59 regulate the activation of complement?
It destabilizies the membrane attack complex (MAC)
What occurs when the pattern recognition receptors (PRRs) on a macrophage or dendritic cell bind a pathogen?
What are 5 principle examples of pattern-associated molecular patterns (PAMPs)?
- LPS
- Peptidoglycan
- flagellin
- Viral dsRNA, ssRNA
- Lipoproteins/fungal sugars
What are toll-like receptors (TLRs)?
A type of PRR used by immune cells to bind PAMPs
LPS, a major PAMP, is recognized by what receptor/receptor combination?
TLR4 paired with CD14
What is the immediate effect of a PAMP binding a TLR?
activation of NFkB and cytokine production
What are the 3 most important cytokines in the immune response (for H&D)?
IL1, IL6, and TNF
What is the acute phase response?
The production of serum proteins by the liver during systemic inflammation?