Microbiology 3 -The Prokaryotes Strike Back (Antibiotic resistance) Flashcards
State the mechanism of action of b-lactams
Inactivates PBP’s (crossliking step of peptidoglycan synthesis)
State the mechanism of action of Glycopeptides
Binds to precursor of peptidoglycan
State the mechanism of action of Aminoglycosides
Inhibits protein synthesis (binds to 30s subunit)
State the mechanism of action of Microlides
Inhibits protein synthesis (binds to 50s subunit)
State the mechanism of action of Quinolones
Inhibits Topiosomerases (DNA synthesis)
State 2 things that determine Acquired resistance
1) Acquisition of plasmids or transposons
2) Mutation in chromosomal genes
What is Intrinsic resistance determined by ?
- Genetic material in chromosome
What is Horizontal gene transfer ?
The process of swapping genetic material between neighbouring bacteria -a means by which antibiotic resistance can be acquired.
Horizontal gene transfer may occur via three main mechanisms. Name them
1) Transformation
2) Transduction
3) Conjugation
What are Transposons ?
Discrete genetic elements capable of moving (transposing) within the bacterial genome
Transposons are found in all organisms. TRUE or FALSE
TRUE
Transposons are capable of independent replication. TRUE or FALSE
FALSE. Transposons aren’t capable of independent replication
Transposition provides multiple copies. TRUE or FALSE
TRUE
Describe composite transposons
Consists of 2 copies of insertion sequence (IS) flanked by inverted repeats
Composite transposons display Replicative transposition. TRUE or FALSE
FALSE. They display conservative transposition; DNA replication doesn’t occur
Name 2 types of Transposons
1) Simple transposons
2) Composite transposons
What type of transposition does Simple transposons express ?
Replicative transposition
What is the role of Resolvase
Responsible for resolution of the transfer
What is the role of Transposase
Responsible for excision and transfer of transposon
State 4 types of b-Lactam antibiotics
1) Penicillins
2) Cephalosporins
3) Carbapenems
4) Monobactams
What are PBP’s ?
Penicillin binding proteins
PBP’s catalyse final steps of peptidoglycan synthesis. TRUE or FALSE
TRUE
State 3 things the activity of b-lactams is determined by
1) Affinity for PBP’s
2) Stability of b-lactamases
3) Membrane permeabilty
Most MRSA are multi-drug resistant but susceptible to Vancomycin. TRUE or FALSE
TRUE
MRSA contains novel PBP1a. TRUE or FALSE
FALSE. MRSA contains novel PBP2a
MRSA chromosome contain around 50kb mec region. TRUE or FALSE
TRUE
What is PBP2a encoded and controlled by
Encoded by mecA gene and controlled by mecl, mecR1 and other factors
What family of antibiotics does Vancomycin belong to
Glycopeptide
Name 2 processes inhibited by Vancomycin
1) Transglycosylation
2) Transpeptidation
Vancomycin is only active against Gram negative bacteria. TRUE or FALSE
FALSE, it cannot cross outer-membrane of gram negative bacteria so only active against gram positive bacteria
What is Vancomycin primarily used for
Primarily for multi drug resistant (MDR) Staphylococci infections,
patients with penicillin allergy or C. difficile infections
Name the antibiotic used as a last resort
Cabapenem
