Nguyen Lectures Flashcards
T or F: planktonic bacteria live as communities
F - Planktonic bacteria live as motile single cells
What are biofilms?
Multicellular bacterial communities
T or F: Biofilm formation is limited to only a few unique species (ie. biofilms are unique phenomena)
F
Most bacteria in environment exist as indvl bacteria or as biofilms?
Biofilms
Contrast biotic and abiotic surfaces
Biotic surface = surface on living organism (ex. tissue)
Abiotic surface = surface on non-living thing (ex. rock)
T or F: biofilms can be caused by many bacterial species living together. If true, what is this type of biofilm called?
T, called polymicrobial biofilm
Are antibiotics effective against biofilms?
No
T or F: biofilm-mediated infections are simple to treat
F
Name 2 Gram - models for biofilm formation
- P. aeruginosa
2. E. coli
Name 2 Gram + models for biofilm formation
- B. subtilis
2. S. aureus
Name 2 ways that biofilms can be grown in the lab
- Grown on plastic plates
2. Grown as pedicles in liquid culture
T or F: Biofilms can only form on solid surfaces
F - they can form in liquid broth as pedicles
At which part of a liquid broth culture do pedicles form?
Air-liquid interface
What microscopy technique is commonly used to study biofilms? What is its advantage?
Confocal microscopy. Can study the biofilm structure in 3D, which is useful bc bacteria form complex 3D structures in biofilms
Describe the method used to quantify biofilm formation
Grow biofilms on polystyrene/plastic plates (Calgary device), then stain with crystal violet
Name 5 components in the extracellular polymeric substances matrix
- environmental DNA
- polysaccharides
- proteins
- cellular debris
- membrane vesicles
List 2 reasons why the composition of the matrix can be different
- different bacteria form different matrices
- different matrices form depending on the environment - bacteria will form different proteins and molecules depending on the environment and nutrients available
List 3 properties of the environment that can influence matrix composition
- nutrients
- physical
- chemical
List 2 functions of the matrix
- keeps the cells aggregated
2. keep the aggregated cells stuck to the surface
T or F: transition from biofilm state to planktonic state is an unregulated and random process
F: gene regulation and coordinated gene expression is required for biofilm formation and transition into planktonic state
What does EPS stand for
extracellular polymeric substance
What are 2 properties of EPS polymers?
- adhesive
2. aggregative
Give 2 reasons why biofilms are difficult to get rid of. Consider properties of the EPS matrix
- acts as a protective barrier by slowing diffusion of molecules like antibiotics - prevents these molecules from reaching the bacteria
- acts as a protective barrier by interfering with immune functions (ex. prevents Ab from reaching bacteria)
What is quorum?
Density of bacteria
List 4 things that quorum sensing can regulate
- light production
- virulence factor production
- biofilm formation
- antibiotic production
What is quorum sensing?
- bacterial communication signal based on surrounding bacterial density
- allows bacteria to regulate gene expression
T or F: gene expression correlates linearly with cell density in quorum sensing
F: Cells must reach a critical density before there is enough of an auto-inducing signal that activates a transcriptional regulator to turn on gene expression
T or F: quorum sensing is not a good target for drugs aiming to inhibit biofilm formation
F
List 3 strategies that can be used to treat biofilm infections
- Develop compounds/surfaces that prevent attachment
- Develop matrix-degrading enzymes
- Target biofilm metabolism + dispersion
Name 3 properties of chronic infections
- Less invasive
- More localized
- Less susceptible to antibiotics
Why are biofilm infections considered chronic infections?
- Motility and virulence factor genes are turned off
- Matrix prevents bacteria from disseminating into system/limits bacterial spread
- overall, this promotes low “visibility” of the bacteria to the immune system = less inflammation
- also, immune cells and Ab can’t reach bacteria due to matrix, therefore bacteria persist
T or F: most antibiotics originate from a synthetic/man-made source
F - most are derived from natural compounds produced by environmental bacteria
T or F: bacteriostatic antibiotics kill bacteria
F - they INHIBIT bacterial growth. removing the drug will allow the bacteria to resume growing
Bacteriostatic drugs target what bacterial process?
Cell replication
Bactericidal drugs inhibit a process required for _____.
Cell survival
T or F: Whether a drug is cidal or static depends on concentration and the bacterial species targeted
T
How are antibiotic classes grouped?
Based on what they target
What are the 3 major targets of antibiotics?
- cell wall synthesis
- protein synthesis
- DNA replication
What do beta-lactams target?
Cell wall biosynthesis/peptidoglycan cross linking
Where are drug efflux pumps located on Gram negative bacteria?
Spans the inner and outer membranes
What is the function of a drug efflux pump?
Pumps antibiotics and other bad molecules from cytoplasm to ECS
T or F: drug efflux pumps are specific
F
T or F: drug efflux pumps are mechanisms of multidrug resistance
T - bc the pumps are not specific and can prevent many different antibiotics from reaching their target
T or F: expression of drug efflux pumps can be regulated
T
Give an example of a target mutation.
Mutation in gyrase so quinolone cannot bind to it
Give an example of an enzyme that performs drug modification
Beta lactamase
What is meant by the spectrum of a beta-lactamase?
How specific the beta-lactamase is - the less specific, the broader the spectrum
What is the consequence of a broad-sepctrum beta-lactamase? What are these enzymes called ?
Called super beta-lactamases - can cleave many beta lactamases
Give 2 examples of drug modification
- Enzymes degrading the antibiotic
2. Enzymes adding moieties to the antibiotic
Which class of drugs are often modified by the additional of chemical moieties?
Aminoglycosides
List 3 methods of horizontal gene transfer
- Transduction - phage injects DNA from bacterium A to B
- Conjugation - direct transfer of plasmids from one bacterium to another
- Transformation - pick up eDNA
What is vertical transmission of antibiotic resistance?
After a selective pressure is applied to a resistance-heterogenous population, all the bacteria are resistant. Only the resistant bacteria survived, so all the others died
T or F: more antibiotics are used on animals than on humans
T
What is the issue with using antibiotics on animals? 2 reasons
- Bacteria on the animal/in the animal may become drug resistant. People will eat the animal + bacteria, and may develop drug-resistant infections
- Antibiotics end up in wastewater and in natural environments, creating a selective pressure - basically brewing antibiotic-resistant environmental bacteria, which may then transfer their DNA to pathogens
Why are new antibiotics quickly become useless because bacteria quickly become resistant to them?
They are based on old antibiotics, so it’s easy to develop a mutation that blocks mechanism of the new antibiotic
List 3 strategies in overcoming antibiotic resistance
- changing human behaviour - use antibiotics properly
- find new antibiotics/use combinations of antibiotics
- inactivating resistance mechanisms (ex. find inhibitors for beta-lactamases, find ways to inhibit efflux pumps)
How were the ESKAPE pathogens selected?
- Associated with multidrug resistance
2. Very common, therefore dangerous if it acquires drug resistance
T or F: antibiotics are only natural compounds
F - can be natural or synthetic (but based on molecules found in nature)
Do all antibiotics kill bacteria?
No, some are bacteriostatic - just need to inhibit replication, then allow immune system to take care of clearing infection
List the 3 main steps of cell wall synthesis
- polyglycan synthesis
- adding peptides to polyglycans (Sortase system)
- transpeptidation - link all the polyglycans
Which step of cell wall synthesis do beta-lactams target? How?
Transpeptidation step; beta-lactams resemble D-Ala-D-Ala which is the normal substrate for penicillin binding protein. Acts as a competitive inhibitor so that the D-Ala-D-Ala are never linked
List some examples of beta lactams
Penicillin Cephalosporin Carbapenem Ampicillin Amoxicillin Monobactam
What do the different substituents on the common beta-lactam ring do?
Make them more resistant to beta-lactamases
Are beta-lactams mostly used against Gram + or - bacteria
Gram +
What part of the elongation step in translation do aminoglycosides inhibit?
tRNA translocation
What part of the elongation step in translation do tetracyclines inhibit?
tRNA delivery
List 2 examples of 30S subunit inhibitors
Tetracyclines
Aminoclycosides
List 3 examples of 50S subunit inhibitors
Chloramphenicol
Lincosamides
Macrolides
What do chloramphenicol and lincosamides do?
Inhibit peptidyl transferase
What do macrolides do?
inhibit peptide exit tunnel so protein cannot be released
T or F: aminoglycosides are effective against Gram +
F
What types of bacteria are aminoglycosides effective against?
Gram negatives
Facultative anaerobes
Are aminoglycosides mainly cidal or static?
Cidal
T or F: most protein synthesis inhibitors have bacteriostatic activity
T
Are quinolones cidal or static?
Cidal
T or F: quinolones have broad spectrum activity against Gram +, -, and quinolones
T
List 2 methods used to improve old antibiotics
- chemical optimization
2. combination therapy
List 3 methods of combination therapy
- combine with another antibiotic
- combine with molecule that overcomes resistance (clavulanic acid)
- combine with molecule to increase penetration into bacterial
List 3 side effects of antibiotics
- antibiotic resistance
- short term infections (C. difficile infections)
- disruptions to microbiota
List 2 new classes of antibacterial molecules
Teixobactin
Odilorhabdins - 30S subunit inhibitor
What are the 5 steps of biofilm formation
- initial attachment
- irreversible attachment + cell replication
- early biofilm formation
- biofilm maturation
- biofilm dispersal
Bacteria in biofilms stick to surfaces via ___ and ___
surface appendages
adhesion molecules
What do surface appendages of bacteria in biofilms include?
Flagella and pili
T or F: molecules mediating attachment can adhere specifically or non-specifically on biotic surface of host
T
T or F: polymer composition of the EPS is species-specific
T
Are there high or low levels of cyclic di-GMP in biofilm state?
High
