D&D Unit 4 Flashcards
What are the 3 cytoskeletal elements in bacteria we care about? What do they do?
FtsZ - division. Tubulin-like.
MreB - shape, polarity, chromosome segregation. Actin-like
CreS - shape. Intermediate filament-like
Peptidoglycan is composed of which 2 sugars?
N-acetylglucosamine
N-acetylmuramic acid
How does the amount of cross-linking in peptidoglycan chains vary between gram-positive and negative bacteria?
It is much greater in gram-positive bacteria
Which enzyme made by the body hydrolyzes peptidoglycan?
Lysozyme - it cleaves the glycosidic bond between the 2 sugar types
What extra 2 components does the gram-positive cell surface have compared to the gram-negative cell surface?
Teichoic acid
Lipoteichoic acid
What extra 3 components does the gram-negative cell surface have compared to the gram-positive cell surface?
Lipopolysaccharides
Lipoproteins
Porins
What 2 important antigens does the lipopolysaccharide of gram-negative bacteria contain?
Lipid A - toxic part of endotoxin
O antigen - side chain oligosaccharides
In the middle is the core polysaccharide
What is techoic acid made of?
Repeating polyglycerol-P or polyribitol-P
What makes up biofilms?
Extracellular glycocalyx
What is it calle when bacteria have flagella distributed over their surface? At one end?
Peritrichous
Polar
Where is the bacterial DNA located?
Nucleoid (a region of cytoplasm)
____________ is when a bacteria’s gene expression and thus phenotype is changed because of infection with a bacteriophage
Phage conversion
What are the 4 stages of the bacteria growth curve?
- Lag phase - period of physiologic adjustment for the starting cells
- Exponential phase - rate of increase in cells is proportional to the number already present
- Stationary phase - nutrients are consumed and toxic metabolic byproducts accumulate
- Death (only sometimes occurs)
What is a microaerophilic bacterium?
It grows best at low oxygen concentrations though it can grow without oxygen
What is sporulation?
A response to nutrient-limited conditions. Bacteria differentiate to form highly resistant, dehydrated forms that have no metabolic activity.
Antimicrobial agents work on the principle of ___________
Selective toxicity - selective inhibition of microbial growth at drug concentrations colerated by the host
What is a selective medium for growing bacteria?
One that allows for visible differentiation of organisms
What is an enrichment medium for growing bacteria?
One that allows a particular one to grow more than others
In contrast to a selective medium that suppresses the growth of some bacteria
A plasmid the confers resistance to an antimicrobial is an _________
R factor
What are insertion sequences?
Transposons that encode transposase
What are complex transposons?
Ones that encode transposase and additional genes
What are pathogenecity islands?
Large segments of bacterial genomes that encode genes that contribute to virulence
What is the major cytotoxic agent released by staph aureus?
Alpha-toxin
How does staph aureus reduce phagocytosis?
Coagulase enzyme induces fibrin deposition
What is the primary virulence factor in strep throat? What 2 things does it do?
M-protein
Inhibits phagocytosis/killing by PMNs
Enhances adherence to epithelial cells
What is the difference between tetanus and botulism toxin?
Spastic vs. flaccid paralysis
Most cystic fibrosis patients are chronically infected with ___________ by age 15-20
Pseudomonas aeruginosa
What part of Neisseria gonorrhea is required for virulence?
Pilus
What is trachoma?
Chlamydia infection of the eye
Where does staph aureus normally hang out?
Anterior nares
Perineum
The lupus anticoagulant is what?
IgG against phospholipid
_____________ is the major constituent of fungal membranes vs. _____________ in mammalian membranes
Ergosterol
Cholesterol
What is the difference between a bactericidal vs. a bacteriostatic agent?
Bactericidal - organisms are killed via inhibition of cell wall synthesis, disruption of cell membrane funciton, interference with DNA function or synthesis
Bacteriostatic - organisms are prevented from growing by inhibition of protein synthesis (except animnoglycosides, which are bactericidal), intermediary metabolic pathways
Whdn do you take antibiotics on an empty stomach? When do you take it with food?
Empty stomach - when a higher pH is needed
Food - when the drug is acid stable but may irritate stomach
What are the 3 stages of peptidoglycan formation?
- Synthesis and assembly of cell wall subunits
- Linear polymerizaiton of subunits at cell membrane
- Cross-linking of peptidoglycan polymers occurring at cell wall
Beta-lactams acetylate _____________
penicillin binding proteins
What bacterial enzyme confers resistance to beta-lactams
Beta-lactamase
Hydrolyzes them - splits the amide bond of the ring
What does diptheria toxin do?
An ADP ribosyltransferase that inactivates elongation factor 2 (required for peptide chain elongation)
1 toxin molecule per eukaryotic cell
What does pseudomonas aeroginosa exotoxin A (PAE) do?
An ADP ribosyltransferase that inactivates elongation factor 2
What 2 bacteria make shiga toxin?
Shigella dysenteriae
E. Coli
What does shiga toxin do?
An RNA N-glycosidase that inactivates ribosomes
What does staphylococcus aureus look like microscopically?
Grapes!
Gram-positive cocci in clusters
Staph alpha-toxin forms a _____________
Heptameric pore
What 3 things made by staph contribute fo impaired phagocytosis?
Coagulase
Fibrinogen-binding protein
Protein A
What 3 cytokines are most excessively produced in the cytokine storm?
IL-2
IFN-Y
TNF-A
Is staph catalase negative/positive? Strep?
Staph = + Strep = -
Which bacteria causes scarlet fever?
Strep
Which bacteria causes rheumatic fever?
Strep
How does M-protein reduce phagocytosis?
Binds factor H, which reduces C3b on cell surface
3 most common organisms that cause rheumatic fever
Staphylococcus aureus
Viridans Streptococci
Coagulase-negative Staphylococci
Which bacteria can we make a vaccine against?
Pneumococcus
Do bacterial spores have detectable metabolism?
No
Do bacterial genomes have introns?
Usually not
What are conjugative and non-conjugative plasmids?
Conjugative plasmids promote sexual conjugation between cells
Non-conjugative plasmids can’t initiate conjugation, so they need assistance of conjugative plasmids to transfer
4 steps needed to demonstrate that a toxin participates in the pathogenesis of an infectious disease
- purified toxin produces characteristic signs/symptoms of infectious disease
- Administration of antitoxin prevents development of the disease if the infectious agent is given
- Virulence of infectious agent reflects the amount of toxin it produces (somewhat questionable)
- Strains lacking ability to produce toxin are decreased in virulence or are avirulent
Which types of bacteria make endotoxin?
Gram-negative bacteria
They shed pieces of lipipolysaccharides
What are superantigens?
Microbial exotoxins that corrupt mechanisms of immunity
They trigger excessive and abberant activation of T-cells
What are the 2 subunits of diptheria toxin?
B-subunit is for cell entry (not all cells have the receptor)
A-subunit is the part that catalyzes transfer of ADP-ribose part of NAD onto EF-2 in the cytoplasm. The EF-2 can’t function in protein synthesis
What is the primary treatment for diphtheria?
Antitoxin
Antibiotics are used to prevent spread
Are diptheria toxin and exotoxin A (pseudomonas aeruginosa) the same?
NO they have no homology
Different cell receptors, cell types, amino acid sequences
What is type III toxin secretion?
Toxins are injected directly into eukaryotic cells
Many gram- bacteria can do this
What is type IV toxin secretion?
Injection of toxin (and nucleic acids too) by conjugation-like bacterial machinery
Which type of bacteria has an outer membrane?
Gram -
What type of stuff do porins allow to pass through the outer membrane of gram- bacteria?
Hydrophilic stuff
What enzymes cross-link peptidoglycan?
Penicillin binding proteins
What does the peptidoglycan precursor have that antibiotics can target?
D-alanine-D-alanine
It is cleaved off during cross-linking
Carbapenemases are __________-mediated
Plasmid
Whatgene confers resistance in MRSA?
mecA
PBP2a - A low affinity penicillin-binding protein
Confers resistance to all beta-lactam agents
Only in staph
What are mosaic PBPs?
Mostly in strep pneumoniae and Neisseria gonorrhoeae
They can pick up pieces of genetic material from other bacteria and swap them with similar pieces of DNA of their own
What are the 2 places superantigens (made by bacteria) bind?
MHC class II Vd chains on T cells
Thus, they activate much larger numbers of T cells than any specific antigen does
What are the 3 ways bacteria can get new genetic material?
Conjugation - bacteria
Transduction - virus (that took the genes from another bacteria)
Transformation - environment
What are the heat-labile enterotoxins of Vibrio cholera and E. coli?
ADP ribosyltransferases that cause active chloride secretion leading to secretory diarrhea
Which 2 bacteria cause secretory diarrhea caused by chloride secretion?
Vibrio cholera
E. coli
Which 5 bacteria make ADP ribosyltransferase toxins?
Inactivation of EF-2: diptheria, pseudomonas aeruginosa (the toxins are different though!)
Secretory diarrhea - Heat-labile enterotoxins of Vibrio cholera and E. coli
Pertussis
What are the gram+ cocci we care about? 2 (2,4)
Staph: Aureus, SSNA (staph specia, not aureus)
Strep: Pyogenes, pneumoniae, ‘viridans’, Enterococcus faecalis, Enterococcus faecium
Which bacteria causes toxic shock syndrome?
Staph
Which bacteria makes slime and adheres to foreign bodies like implants?
Staph epidermidis
SSNA/CNS (staph species, not aureus/coagulase-negative staph)
What does strep pneumoniae look like under the microscope?
Gram positive
Pairs
3 bactericidal mechanisms
Inhibition of cell wall synthesis
Disruption of cell membrane function
Interference with DNA function/synthesis
2 bacteriostatic mechanisms
Inhibition of protein synthesis (except amnoglycosides, which are bactericidal)
Inhibition of intermediary metabolic pthways
What is the rule of thumb for determining which antibiotics can cross the placenta?
The ones taken orally usually can
Where do the following antibiotics distribute? Clindamycin Macrolides Tetracyclines Nitrofurantoin Aminoglycosides
Clindamycin - bone
Macrolides - pulmonary cells
Tetracyclines - gingival crevicular fluid, sebum. Also developing bone and teeth.
Nitrofurantoin - urine
Eminoglycosides - inner ear and renal brush border
What 2 things do we use to monitor renal status?
Seum creatinine
Creatinine clearance
The persistent suppression of bacterial growth that may occur after limited exposure to some antibacterial drugs is called ____________
Post antibiotic effect
What are 2 gram negative rods we care about?
E. coli
Pseudomonas aeroginosa
What is the gram positive rod anaerobe we care about? The gram negative rod anaerobe?
Clostridium difficile
Bacteroides fragilis
What is the distribution for penicillins?
They are ionized at physiological pH so they mostly enter inflamed tissues
How are penicillins excreted?
Mostly excreted as an active drug via the kidney (remember that they used to reuse penicillin from people’s urine)
How is vancomycin administered?
IV (unless it’s for stuff in the GI tract like C. difficile)
Which 2 bacterial groups is vancomycin used for?
Gram positive cocci: staph and strep
Anaerobes: C. difficile
What does the heat-stable enterotoxin of E. coli di?
Increase cellular cGMP, leading to secretory diarrhea
What are the 3 main toxins E. coli produces?
Shiga
Heat-labile enterotoxin
Heat-stable enterotoxin
What toxin does Bacillus anthracis produce?
Anthrax edema factor
What is intrinsic drug resistance?
MIcrobes lack a target for drug action
What are 2 advantages to bactericidal agents?
Act more quickly and irreversibly (sustained effect)
Macrolides (MAC) are effective against:
MRSA
Atypical bacteria
the Clap
What are the narrow spectrum-prototype penicillins?
Penicillin G - Penicillin V
Which penicillin is penicillinaseresistant
Dicloxacillin
Which 3 penicillin drugs that are extended spectrum?
They have increased hydrophilicity so they can get through the pores of gram-negative bacteria
Amoxicillin
Ampicillin
Piperacillin
Which penicillin is anti-pseudomonal?
Piperacillin
What are 2 drugs that can be added in order to inhibit beta-lactamases?
Clavulanic acid + amoxicillin or ticarcillin
Tazobactam + piperacillin
What is the sufix for macrolides?
-mycin
Erythromycin
Clarithromycin
Azithromycin
What are 2 tetracyclines?
Tetracycline
Docycycline
What is the suffix for fluoroquinolones?
-Floxacin
Ciprofloxacin
Levofloxacin
Moxifloxacin
What does staph aureus do on a blood agar plate?
It is beta-heolytic
What is the main virulence factor for staph aureus?
Protein A
Prevents complement from doing its thing by by binding Fc portion of immunoglobulins
Which bacteria usually causes septic arthritis in adults?
Staph aureus
What antibiotic do you use for MRSA? What about regular staph?
Vancomycin
Penicillin - Nafcillin (naph for staph)
What is a mean feature of 3rd generation cephalosporins?
They can penetrate the CNS
What is the definition of minimum inhibitory concentration?
The lowest concentration of antibiotic that prevents visible bacterial growth
Penicillin is for gram-_________ infections
Positive
Cephalosporins have the prefix _________
cef-
Absorption of oral tetracyclines is impaired by _________
Milk
The clostridium genus is gram_________, what sort of metabolism, and does or does not form spores?
Positive
Obligate anaerobes
Forms spores
What does the AmpC gene do?
Beta-lactamases that are cephalosporinases
It is inducibly expressed
Why don’t penicillins or ampicillins work against staph anymore?
Most contain the bla (beta-lactamase) plasmid
What is antiobiotic tolerance/escape?
Bacteria are susceptible to antibiotics but the antibiotics don’t work
Usually because of some metabolic resistance
Which group of bacteria is intrinsically resistant to vancomycin?
Gram-negative rods
What does a positive D-test indicate?
Resistance to clindamycin induced by macrolides
What is endotoxin?
Lipid A, which is part of the lipopolysaccharide of gram- bacteria
2 post-streptococcal diseases
Glomerulonephritis - type III hypersensitivity
Rheumatic fever - type II hypersensitivity
What is the pneumonia vaccine for?
Streptococcus pneumoniae
What bacteria makes alpha toxin?
Clostridium perfringens
What 2 properties of E. coli are essential for GI disease?
Adherence to the intestinal mucosa via pili
Toxins that disrupt the electrolyte balance in teh gut
E. coli UTI strains are _____________-hemolytic
Beta
What do we use to treat pseudomonas?
Piperacillin + tazobactam (piper suitor)
Aminoglycoside and fluoroquinolones
What class of bacteria do penicillins work best against?
Gram positive cocci - purple round ships in Princess Ellen’s New Hope
S. Pneumoniae
S. Pyogenes
Enterococcus
NOT MSSA or MRSA
How are penicillins V and G taken?
V is oral because it is acid stable (oral in Princess Ellen’s New Hope)
G is IV (ivy trapping Princess Ellen)
Where does bacteroides live?
In the gut
What are the 2 E coli enterotoxins?
Heat-stable - cAMP
Heat-labile - cGMP
What toxin does pertussis produce? What does it require?
Adenylate cyclase toxin
Requires activation by calmodulin and calcium
What does anthrax lethal factor do?
It is an endopeptidase that cleaves MAPKK proteins and fucks shit up!
What are the 2 C diff toxins?
They are glucosyl transferases
A - attracts neutrophils
B - alters actin
Tetanus and botulinum toxins are ________-dependent endopeptidases that inactivate _________, preventing ___________
Zinc
SNARE
Neuroexocytosis
What are the 2 parts of an toxin with intracellular targets?
A - active
B - binding
How are beta lactamases conferred?
Plasmids
How is amoxicillin administered? How is ampicillin administered?
Oral - Han Cillin is eating
IV - ivy guitar cord
What confers resistance to aminoglycosides?
Acetyl-phospho-adenylyl transferase
Enterococci
Enterococci drummer throwing ninja stars
What confers resistance to chloramphenicol?
Acetyltransferase
Staph, streph, Neisseria
