Week 8 Flashcards
What are the four major antibiotic resistance mechanisms? Describe them
Prevent access to target - drug can’t get in or drug gets in but cant get pumped back out before affecting target
Modify or protect antibiotic target - target is altered structurally OR target is overexpressed (so you need much more drug)
Modification/inactivation of antibiotics - drug is inactivated before affecting target.
Modify expression of Bactrian factors needed to activate the antibiotic (prodrug)
Name three antibiotic tolerance mechanisms
Biofilm formation
Spores
Persister cells
What are two ways bacteria may restrict access of antibiotic to target?
Alter envelope to inhibit uptake
Boost expression of efflux pumps (gene amplification)
The ____ mutation in ____ rRNA protects against macrolides like erythromycin
A2580G
23S
Tetracycline binds ____ rRNA in ____ subunit, and distorts the ___ site
16S
30S
A
Bacteria may grow resistant to tetracycline by protecting their ribosomes via ___ or via ___ of a ____ that pertubs the ____ in 16S rRNA that is involved in tetracycline binding
Mutation
HGT acquisition
GTPasse
Helix
*basically, an enzyme is activated to unwind an rRNA so that it is not recognized by tetracycline. Note that this make the ribosome less effective, but it is resistant to tetracycline
How does vancomycin kill bacteria?
Prevents normal cross-linking of peptidoglycan.
Vancomycin binds to D-Ala-D-Ala preventing cross linking
Describe vancomycin resistance
Involves four enzymes that prevents vancomycin from preventing peptidoglycan cross-linking
The multiple enzymes that are required for resistance is what caused bacteria to take so long to grow resistant to vancomycin.
Enzymes are VanH, VanA, VanB, VanX
VanX will reform peptidoglycan cross-linkage
How do some bacteria grow resistant to penicillin by modifying the target?
Penicillin normally binds to transpeptidase to prevent cross-linking.
Point mutations in transpeptidase causes resistance. (Note, however that transpeptidase will be less effective with these point mutations)
What are two ways in that bacteria can grow resistant to antibiotics by modifying or inactivating the antibiotic?
Inactivation by hydrolysis
Inactivation by steric hinderence.
B-lactamases do this
How do B-lactamases work?
Break a bond in the B-lactam ring of penicillins to disable the molecule.
How do B-lactamase inhibitors work? (Like clavulanic acid)
Clavulanic acid is a suicide molecule. It interacts with B-lactamases to be cleaved but remains attacahed to B-lactamase to inactivate it.
**note that bacteria have also developed anti-B-lactamase inhibitors
What are three ways in which antibiotics can e modified for deactivation? What enzymes accomplish this? How is it that these modifications are detrimental?
N acetylation
O phosphorylation
O adenylation
Aminoglycoside inactivating enzymes
Modifications disrupt hydrogen-bonding network used to bind 16S RNA
Some bacteria can gain resistance by modifying expression of bacterial factors needed to activate the antibiotic (prodrugs). Give two examples of prodrugs
Metronidazole is activated by the bacterial factor flavodoxin in H. Pylori and P. Gingivalis
Isoniazid is activated by the bacterial catalase/peroxidase enzyme KatG in. MTB. Isoniazid will then continue to inhibit the synthesis of mycolic acid required for MTB cell wall
In what two ways is resistance acquired?
Mutation
Horizontal gene transfer
Note that E. Coli has a one in a billion chance of becoming resistant to streptomycin. But because of fast growth rates and high numbers, this probability becomes meaningful
What four things are contributing to the spread of resistant bacteria?
Overuse of antibiotics
Overpopulation
Poor hygiene
Travel
Name four pathogens that are becoming increasingly resistant
Extended-spectrum B-lactamase producing enterobactericae
Carbapenem-resistant enterobacteriacae
Clostridium difficile
Super neisseria gonorrhea
What are the three different priority pathogens in the list for R&D of new antibiotics?
Priority 1: Critical
Priority 2: High
Priority 3: medium
What are the three bacteria that are classified under priority 1 (critical)?
Acinetobacter baumannii, carbapenem-resistant
Pseudomonas aeruginosa, carbapenem-resistant
Enterobacteriaceae, carbapenem-resistant, ESBL-producing
What are 6 bacteria that are considered priority 2 (high)?
Enterococcus faecium, vancomycin-resistant
Staphylococcus aureus, methicillin-resistant, vancomycin intermediate and resistant
Helicobacter pylori, clarithromycin-resistant
Campylobacter spp. Fluoroquinolone-resistant
Salmonella, fluoroquinolone-resistant
Neisseria gonorrhoeae, cephalosporin-resistant, fluoroquinolone resistant
Name three bacteria that are considered under the priority 3 (Medium)?
Streptococcus pneumoniae, penicillin-non-susceptible
Haemophilus influenzae, ampicillin-resistant
Shigella spp. Fluoroquinolone-resistant
Antibiotic tolerance contributes to ___ and ____ infections. What are some methods bacteria use to tolerate antibiotics?
Chronic
Recurrent
Spores
Biofilms
Persister cell formation
Intracellular niches
> ___% of human infections may involve biofilms
65
What are six ways in which biofilm formation enhances the ability of bacteria to tolerate antibiotics?
Extracellular matrix
Altered protein expression
Decreased metabolism
Increased stress resistance
Increased gene exchange
Persister cell formation