Antimicrobial therapies Flashcards
describe 3 properties of aminoglycosides
.Bactericidal
.target protein synthesis, RNA proofreading ,damages cell membrane
Toxic
name two aminoglycosides
- Gentamicin, streptomycin
Give 4 features of rifampicin
•Bacteriocidal
Targets RpoB subunit of RNA polymerase
.Spontaneous resistance is frequent
. makes secretions orange/red
I target lipid II component of cell wall biosynthesis as well as wall cross linking via D-ala residues, i am bactericidal, i am toxic, what antibiotic am i?
Vancomycin
give me 3 features of vancomycin
.Bactericidal
. TARGET lipid II components of cell wall biosynthesis as well as wall crosslinking via d-ala residues
.toxic
I inhibit the initiation of protein synthesis by binding to 50S rRNA subunit, i am bacteriostatic, i exhibit gram positive spectrum activity, i am…
linezolid
give 3 features of linezolid
.BACTERIOSTATIC
. inhibits initiation of protein synthesis by binding to 50S rRNA subunit
Gram-positive spectrum of activity
I am bactericidal, target cell membrane, gram positive bacteria are affected, toxic, what i am i?
Daptomycin
GIVE 4 features of daptomycin
.Bactericidal
.Gram positive bacteria
.Targets cell membrane
.toxic
i inhibit synthesis of petidioglycan by binding to Penicillin-binding proteins (PBP). E.g i am Penicillin and methicillin. What kind of antibiotic am i?
BETA LACTAMS
Give 2 examples of beta lactams
penicillin and methicillin
what do beta lactams do?
interfere with synthesis of petidoglycan component of cell wall by binding to Penicillin-binding proteins (PBP)
give 2 examples of macroslides
erythromycin, azithromycin
describe macrolides
.gram positive+ gram negative
. Targets 50s ribosomal subunit preventing amino-acyl transfer hence truncates polypetides
I am synthetic, broad spectrum, bactericidal.
I target DNA gyrase and topoisomerase IV in both gram + and - bacteria
what am i?
quinolones
Explain the function of quinolones
.synthetic, bacteriocidal, broad spectrum
. TARGET DNA gyrase and topisomerase IV in + and - bacteria
describe the interaction of DNA gyrase and quinolone
QUINOLONE stabalises the DNA-DNA gyrase complex hence broken strands cant be released and DNA REPLICATION IS BLOCKED
what are the 4 machanisms that cause antibiotic resistance
. altered target site
.altered metabolism
. inactivation of antibiotic
.decreased drug accumulation
how can an altered target site arrise?
via acquistion of alternative gene or gene that encodes a target-modifying enzyme
streptococcus pneumoniae resistance to erythromycin occurs how?
via acquisition of erm genes which encodes an enzyme that methylates the AB target site in the 50S ribosomal subunit
Methicillin-resistant Straphylococcus aureus (MRSA) encodes…
an alternative PBP with low affinity to beta lactams
2 examples of enyzmes which degrade antibiotics
beta-lactamse and cat ( chloramphenicol acetyl transferase)
give 2 broad spectrum beta lactamases
ESBL, NDM-1
explain altered metabolism in antibiotic resistance
. Increased production of enzyme substrate can out compete antibiotic inhibitor (e.g increased PABA allows resistance to sulfonamides)
.Bacteria switch to other metabolic pathways reducing need for PABA.
3 sources of antbiotic resistant genes
plasmids
transposons
naked DNA
explain the three sources of antibiotic resistant genes
PLASMIDS-extra chromosomal circular DNA, carries multiple AB resistant genes
TRANSPOSONS- integrate into chromosomal DNA, allow transfer of genes from plasmids to chromosome and vice versa
.Naked DNA- DNA from dead bacteria released into environment
WHAT ARE THE 5 NON GENETIC MECHANISMS OF RESISTANCE TO ANTIBIOTICS
.Biofilm .intracellular location .slow growth .spores .Persisters
Reasons antibiotic treatment fail are..
. Inappropiate choice for organism Poor penetration of ab into target site .INAPPROPIATE dose wrong administration e.g oral v.s IV) PRESENCE OF AB within commensal flora e.g secretion of beta-lactamase
what 3 misconceptions were made at dawn of antibiotic era
.RESISTANCE WOULD NOT HAPPENS TO MORE THEN ONE CLASS OF ANTIBIOTICS AT THE SAME TIME
. Horizontal gene transfer would not occur
RESISTANT ORGANISMS WOULD BE LESS ‘FIT’.
5 RISK FACTORS OF HOSPITAL AQQUIRED INFECTIONS
.crowded wards immunosupression broken skin e.g surgical wound/IV catheter AB therapy may supress normal flora transmission by staff
How can antibiotic resistance be overcome?
modify meds e.g prevent cleavage of beta lactams or enhance efficacy e.g METHICILLIN
combinations of antibiotic+inhibitor e.g Beta lactamase+Augmentin