Antibitoics And Antibiotic Ressistance Flashcards
What are the 4 main mechanisms of action of antibiotics?
- Interfere with nucleic acid synthesis
- Stop cell wall synthesis
- Stop effective cell membrane function
- Stop protein synthesis
What are the characteristics of ideal antibiotics?
- selectivly toxic
- few adverse effects on host
- reaches site of infection
- both oral and IV formulations
- long half life so few administrations
- doesnt interfere with other drugs
How does penicillin (and most beta lactams) work?
Bind to penicillin binding proteins, which prevents crosslinking of peptidoglycans so the cell walls cannot be synthesised.
How does vancomysin (and most glycopeptides) work?
binding to peptidoglycans side chains to prevent them from being crosslinked.
How does tetracyline work?
prevents mRNA- tRNA binding (at 50s subunit)
How do macrolides and aminoglycosides work?
aminoglycosides act at the 30s and macrolides act at 50s subunits of ribosomes which are not present in human ribosomes
How do floroquinolones work?
Bind to nuclear enzymes to prevent supercoiling of DNA and so prevent DNA replication
What 2 subtypes of antibiotics work by preventing folic acid synthesis?
trimethoprim and sulphonamides
what drug is used for bacterial meningitis treatment and why?
ceftriaxone- penetrates CSF well
what drug is used to treat UTIs?
trimethoprim
penicillins, cephalosporins, carbapenems and monobactams are all subtypes of what major group of antibiotics?
Beta lactams- generally active against gram - bacteria
Why should tetracyclin and doxycycline not be used on children less than 12 yrs?
leads to yellowing of teeth
Name the most common aminoglycoside that is generally reserved for gram neg sepsis
gentamicin
What are Azoles and how do they work?
Antifungals active against yeasts and moulds (eg candidia) that work by inhibiting cell membrane synthesis
Which azole is used to treat candidia infections
fluconazole
How do polyenes work as antifungals?
inhibit cell membrane function
What is metronidazole often used to treat?
some anerobic bacteria and protozoal infections- dysentry, giardia, vaginits and C DIFF
State and explain the 3 types of antibiotic ressistance
intrinsic- the drug wont work on that organism, no target or access for the drug (permanent ressistance)
acquired- generic material aqcuired or mutated which gives resistance (also permanent)
Adaptive- organism responds to the stress caused by adapting (overcome by higher dose usually)
What’re the 3 main ways of developing resistance to antibiotics?
- Drug inactivating enzymes
- Altered drug targets so lower affinity to the drug
- Altered uptake of drug or increased efflux
How can bacteria aquire genetic resistance?
Vertical or horizontal transmission, bacteriophages (via transduction) or by free chunks of DNA entering by transformation
How can antibiotic sensitivity be measured?
disc testing- place antibiotic on infected agar disc and measure size of clearance zone
minimum inhibitory concentration- create many differnt concentrations of antibiotic and add organism and see what minimum conc needed to stop growth is
what is the definition of multi drug resistant bacteria?
organism that isnt suseptible to at least one agent in three or more categories
Define extensively drug resistant bacteria
organism not susceptible to at least one agent in all but one or two antimicrobe categories
define pan drug resistant bacteria
not susceptible to any agents in any categories
What is the advantage of having shorter courses of antibitoics? why is this not always feasible?
Some non antibotic resistant bacteria survive to compete with the antibiotic resistant bacteria so the proportion of bacteria that are antibiotic resistant decreases
however shorter courses mean higher likelyhood of treatment failure
Define antimicrobial stewardship
interventions to improve and measure appropriate use of antibiotics by promoting the optimal selection, dose, duration and administration also to improve clinical outcomes, minimize toxicity, side effects and cost
give examples of persuasive interventions for antimicrobial stewardship
education consensus opinion leaders reminders audits feedback
Give examples of restrictive interventions for antimicrobiral stewardship
forumulary restriction
prior authorisation
automatic stop orders
Give examples of structural interventions for antimicrobiral stewardship
computerised records
rapid lab tests
expert systems
quality monitoring
What is a process measures
Attempts to measure the actions, eg. measure use of antibiotics in daily doses per 1000 bed days to make a standardised measure so comparisons can be made
Give examples of outcome measures
emergence of resistance
c. diff infection rates
pt outcomes- death, infection, long term morbidity ect
What are 3 requirements for success of antimicrobial stewardship programmes?
- sustainable
- appropriate rescources and systems in place
- leaders delegate management of it and support them
How did MRSA develop resistance?
- new target protein with lower affinity to beta lactams
- beta lactamases
What is common presentation of MRSA infection
- bacteraemia with no specific site of infection
- elderly/ chronically ill
- with IV line/ catheters/ open wounds/ on antibotics
- general illness
What else can be used to treat MRSA?
flucoxacillin or vancomicin if very bad
What antiviral is often used to treat herpes, encephalitis, chicken pox and shingles?
acyclovir- inhibits viral DNA polymerase
What antiviral can be used against influenza A and B (but isn’t very potent)
oseltamivir (tamiflu)- inhibits viral neuraminidase
What can metronidazole be used to treat?
dysentery, giardia, vaginitis- works against protozoa and some anaerobic bacteria
When is tetracyline used?
- generally good against gram positive bacteria
- can be used in penicillin allergy
When is gentamicin (an aminoglycoside) used?
gram negative bacteria, generally reserved for gram negative sepsis
What can be used to treat C. diff?
vancomysin (a glycopeptide)
How is strep pneumonia treated?
- used to be penicillin G but lots of resistance so vancomysin and ceftriazone generally used now
How is strep pyogenes treated?
- penicillin G still widely used as little ressistance
- if allergic use macrolide like clarithromycin
How is a staph epididermis infection treated?
vancomysin
How is staph aureus treated?
- almost all are penicillin G and methicillin resistant now
- vancomysin, ocacillin and nafcillin can still usually be used
How is neisseria meningitidis treated?
Penicillin G can be used
usually ceftriaxone used
What is the neisseria meningitisis vaccine made of?
capsular material of stereogroups A, C, Y and W
Given that haemophilus influenzae is a gram negative bacteria, which antibiotic is generally used to treat it?
- cephalosporins such as ceftriaxone
Name a very broad spectrum antibiotic against almost all gram negatives which is generally safe in a penicillin allergy
meropenem (a carbapenem)
What types of bacteria is vancomysin active against?
gram positives
What is co- trimoxazole (sulphamethoxazole+ trimethoprim) used to treat?
PCP, can also be used against MRSA
