Antibiotics Flashcards
What is a broad spectrum antibiotic?
Kills a lot of species of bacteria
What is a narrow spectrum antibiotic?
Kills few species of bacteria
Which type of antibiotic will have less of an ability to cause superinfection and why?
Narrow-spectrum because it will not kill as many of the normal microorganisms in the body and will cause less resistance
What is the problem with narrow-spectrum antibiotics?
You have to wait for a positive culture and sensitivity assay
What might an antibiotic target?
Cell wall synthesis
DNA replication enzymes
Bacterial ribosomes
How does penicillin target bacteria?
It blocks the transpeptidation step in PG synthesis
What does resistance evolve from?
Overuse and the lack of development of new antibiotics
What is bacterial transformation?
Uptake of free DNA from the environment
What does bacterial transformation require?
Sequence similarity for integration into genome
What is bacterial transduction?
Viral-mediated DNA exchange
How does bacterial transduction work?
A phage accidentally carries bacterial DNA and transfers that to the new host
What is bacterial conjugation?
The direct transfer of plasmid DNA between related species
Plasmid MAY contain resistance genes
What does repeat, short exposure to antibiotics lead to?
Natural selection in which bacteria that can survival antibiotic exposure will predominate
What happens to a population that is mixed with resistant and sensitive individuals?
Resistance can be shared by horizontal gene transfer
What are 4 mechanisms of antibiotic resistance?
Impermeable barrier
Multidrug resistance efflux pumps
Resistance mutations
Inactivation of the antibiotic
How does impermeable barriers cause resistance?
Antibiotics cannot penetrate the barrier or lacks the target of the antibiotic
What are some examples of impermeable barriers?
Mycobacteria
Bacteria in a biofilm
What are multidrug efflux pumps?
Pumps secrete antibiotics from the cell
Some transporters pump them right outside of the cell while Gram-negative bacteria will secrete them into the periplasm
What does exposure to antibiotics increase?
The expression of endogenous pumps
What are ABCs?
ATP-dependent general efflux pumps, broadest class
What is an example of ABCs causing resistance?
E. coli resistance to chloramphenicol
What is the major facilitator family (MFS) and what is an example involving resistance?
Proton-motive force-powered efflux pump
tetracycline resistance
What is the resistant nodule family (NRD) and what is unique about it?
An efflux pump class
Only found in Gram-negative and is also found in P. aeruginosa
What are resistance mutations?
Mutations that modify the target proteins of antibiotics
What are 2 examples of resistance mutations?
Gyrase mutations = allow resistance to fluoroquinolones
Small ribosomal subunit = allows streptomycin resistance
How does inactivation of antibiotics occur?
By covalent modification of the antibiotic
What are 2 ways that an antibiotic could be inactivated?
Catalyzed by acetyltransferase acting on aminoglycoside antibiotics
Degradation of the antibiotic such as that catalyzed by beta-lactamases acting on beta-lactam antibiotics
What are ESKAPE pathogens?
A group of highly antibiotic resistant bacterial pathogens which are responsible for a large portion of hospital acquired infections worldwide
What does Enterococus faecium cause?
Blood infection
UTIs
What is VRE and how does it work?
Vanomycin-resistant Enterococci
Vancomycin binds to D-ala-D-ala peptidoglycan peptide preventing transglycosylation and transpeptidation
What is the resistance mechanism to vancomycin and how is resistance acquired?
Loss of D-lactate in linker peptide so the antibiotic no longer recognizes it
Resistance is acquired by a mutation in PG synthesis
What are some examples of ESKAPE pathogens?
Enterococcus faecium
Ones that form biofilm (MRSA, P. aeruginosa, K. pneumoniae)
Enterobacter spp.
Ones with beta-lactamases
What is beta-lactamase?
Enzymes produced by bacteria and provide resistance to beta-lactam antibiotics such as penicillins
How do beta-lactamases inactivate penicillin?
By digestion
