Antibiotic resistance AB Flashcards
What are the three classifications of antibiotic resistance, when described by mechanism?
Antibiotic inactivation
Alteration of target
Decreased uptake
What is an example of antibiotic inactivation?
Betalactamases
Pneumococcus and macrolides (erm)
Enzymatic modification of aminoglycosides
What is an example of alteration of antibiotic target?
Pneumococcus and penicillin
S aureus and methicillin-like antibiotics
What are two mechanisms of decreased uptake?
Reduced penetration
Antibiotic efflux
What is an example of intrinsic antibiotic resistance (i.e. the resistance has always been there) ?
E coli and penicillin or vancomycin
Klebsiella and amoxycillin
What is an example of acquired antibiotic resistance?
S aureus and penicillin
Pseudomonas and ciprofloxacin
Broadly speaking, what are the two genetic mechanisms of developing resistance?
Spontaneous DNA mutations (SNPs)
Acquisition of new DNA
Give an example of spontaneous DNA mutations in genetic mechanisms of resistance?
M tuberculosis
S aureus and Rifampicin
What are the modes of acquisition of new DNA in genetic mechanisms of resistance?
TRANSFORMATION - part of the bacterial chromosome integrated into another bacterial chromosome
CONJUGATION - mobile plasmid enters a different bacterium
TRANSDUCTION - bacteriophage
What is the gene involved in resistance of MRSA?
mecA gene
What is the main mechanism of resistance in MRSA?
Acquisition of altered penicillin binding protein
What are the two genes involved in the resistance of VRE?
VanA
VanB (Australia)
What is the mechanism in the resistance of VRE?
Encode for altered pentapeptide peptidoglycan precursor - decreased affinity
What is the treatment for VRE?
Linezolid
Tigecycline
Daptomycin
What is the mechanism of penicillin-non-susceptible S pneumoniae?
Altered penicillin-binding-protein (not beta-lactamase)
What are the four classes of beta-lactamase enzyme classes
A - Penicillinases
B - Metalloenzymes
C - Cephalosporinases
D - Oxacillinases
What are the genes in penicillinase (A) resistance?
TEM
SHV (Klebsiella)
CTX-M
What are the genes in the metalloenzyme (B) group?
NDM
VIM
IMP
What is an example of inducible beta lactamase activity?
Class C (Cephalosporinases) - AmpC-type
ESCAPPM
What are the ESCAPPM organisms?
Enterobacter Serratia Citrobacter Acinetobacter Proteus (not mirebalis) Providentia Morganella
What is the mechanism of resistance in ESBL?
Mutations in existing beta-lactamase genes (e.g. TEM, SHV)
Plasmid mediated transfer
What is the treatment of ESBL?
Carbapenem
Colistin
Amikacin
What are two examples of class B metallo-beta-lactimases?
Pseudomonas
Acinetobacter
What is the mechanism of resistance in metallo-beta-lactamases
Plasmid mediated transfer (usually)
What is the mechanism of aminoglycoside resistance?
Decreased permeability
What is the mechanism of resistance in VISA?
Thickened cell wall (D-ala-D-ala)
When is VISA commonly seen?
Mainly in dialysis patients or those with infected foreign bodies
What do Van A and B genes code for?
D-ala-D-ala
Which antibiotic should be be avoided with concurrent SSRI or Tramadol use?
Linezolid
What are the anti-pseudomonal antibiotics?
Tazocin Ceftazadime Cefepime Meropenem (not ertapenem) Tobramycin Gentamicin Ciprofloxacin Aztreonam Colistin
Which antibiotics treat VRE?
Linezolid
Daptomycin
Tigecycline
Which antibiotics treat VISA?
Linezolid
In what setting should Fosfomycin be used?
PO agent
Mainly used for resistant UTIs (not pseudomonas)
What does Colistin work well against?
Pseudomonas
Acinetobacter
E coli
Some Enterobacter, Klebsiella, Salmonella and Stenotrophomonas
NOT other ESCAPPM
Which organisms are resistant to Meropenem?
Legionella pneumophila Enterococcus FAECIUM Stenotrophomonas Coxiella burnetti MRSA Candida albicans M pneumoniae
