Rational antimicrobial therapy Flashcards
Grampositiveaerobicbacteria
Strep
Staphaureus
Gramnegativeaerobicbacteria
E coli
Helicobacter
Anaerobicbacteria
Clostridiumperfringens
Atypical bacterial species
Rickettsia Mycoplasma Chlamydia Borrelia Bartonella Mycobacterium
Bacterialresistance
some bacteria have resistant genes
use of antimicrobials creates a selective pressure
Whentouseantimicrobials?
definitivelydiagnosed/likelydiagnosis
diseaselikelytoprogresswithoutmedicaltherapy
Wouldcausecriticalillnessifitwasnotrecognisedortreated
factors to consider when choosing antimicrobial
likelybacteriainvolved
likelysusceptibility
cultureneeded/feasible?
pharmacokineticfactorsyouneedtoconsider?
potentialsideeffects+incrriskinyourpatient?
clientcomplianceissues?
costconsiderations?
Factors affecting the success of antibacterial therapy
Whatbugslivewhere? Bacterialsusceptibility Distributiontothesiteofinfection(pharmacokineticphase) Localconditions(pharmacodynamic phase) Clientcompliance
Bacterialsusceptibility
if not susceptible in vitro - resistant in vivo
if susceptible in vitro - may work in vivo
resistancemaybeovercomebyhighconcsachievedinurineortopicalapplication
MIC
MIC=Minimuminhibitoryconcentration
Lowestconcofdrugthatwillinhibitbacterialgrowth
MIC90 usualmeasureusedtodeterminetherapeuticdose - Concthatwillinhibit90%ofisolates
Inhibitionofcellwallsynthesis
penicillins
cephalosporins
bacitracin
Inhibition of cell membrane function
polymyxins
amphotericinB
imidazoles
nystatin
Inhibition of protein synthesis
chloramphenicol macrolides lincosamides tetracyclines aminoglycosides
Inhibition of nucleic acid synthesis
sulphonamides trimethoprim quinolones metronidazole rifampin
Bacteriostatic - define
Tempinhibitthegrowthoforganisms
Effectisreversibleoncethedrugisremoved
drugconc atthesiteoftheinfectionshouldstayabovetheMICthroughoutdosinginterval
Manybacteriostaticdrugscanbebactericidalifdrugexposureissufficientlyhighorprolonged
Bacteriostatic drugs
Chloramphenicol Lincosamides Macrolides Tetracyclines Non-potentiatedsulphonamides (mostly inhibit protein synthesis)
Bactericidal - define
Underidealconditionskillbacteria
preferredwhenconcernabout siteofinfectionorhostdefence
gram+veinfections - susceptibility ofbacteriaandabilityto
penetratetissuemoreimportantconsiderations
Bactericidal drugs
Penicillins Cephalosporins Aminoglycosides Fluoroquinolones Potentiatedsulphonamides(TMPS) Metronidazole
why not to give Penicillins, Cephalosporins + TMPS with bacteriostatic drugs
Bacterianeedtobemultiplyingfordrugstobeeffective
concentration dependant drugs
Aminoglycosides Fluoroquinolones Metronidazole Peakconcentrationachievedorareaunderthecurvepredictstherapeuticsuccess can be given with bacteriostatic drugs
drugs v. bad against gram +ve aerobes
Aminoglycosides
Metronidazole
drugs v. bad against gram -ve aerobes
Metronidazole
Penicillin G
Lincosamides/Macrolides
drugs v.bad against obligate aerobes
Fluoroquinolones
Aminoglycosides
drugs v.bad against penicillinase producing staph
Penicillin G
Aminopenicillins
Metronidazole
drugs v. good against gram +ve aerobes
Penicillin G Aminopenicillins Lincosamides/ Macrolides Tetracyclines
drugs v. good against gram -ve aerobes
Fluoroquinolones
Aminoglycosides
Ticarcillin-clavulanate
Cephalosporins
drugs v.good against obligate aerobes
Penicillin G Amoxy-clav Clindamycin Metronidazole Chloramphenicol Rifampin
drugs v.good against penicillinase producing staph
Amoxy-clav Cephalosporins Cloxacillin Fluoroquinolones Rifampin
drug most good but leaves some important gram +ve aerobes
Fluoroquinolones
drug most good but leaves some important penicillinase producing staph
Clindamycin
drug most good but leaves some important gram -ve aerobes
Amoxy-clav
cephalosporins,cefovicinandamoxycillin
50/50 susceptible/resistant - obligate anaerobes + -ve aerobes
TMPS
50/50 susceptible/resistant all quadrants
Tetracyclines
50/50 susceptible/resistantallquadrantsexceptgrampositive
aerobes
Difficult to access areas
Brain Eye Prostate Bronchus Mammarygland Intracellular Poorlyvascularisedtissues - Bonefragments, Heartvalves
Intracellular bacteria
Bartonella Brucella Chlamydophila Mycobacterium Rickettsia Staphylococcus
poor penetration
Penicillins Cephalosporins Betalactamase inhibitors Polymixins Aminoglycosides
good penetration
Sulphonamides Trimethoprim Lincosamides Macrolides Tetracycline
great penetration
Chloramphenicol Fluoroquinolones Lipophilic tetracyclines minocycline doxycycline Metronidazole Rifampin
Environmentalconditions - Foreignmaterial
phagocytesdegranulatetotrytodestroytheforeignmaterial
inefficientinkillingbacterialpathogens
canprotectbacteriafromantibacterialdrugsandphagocytosis - bacteria can form a biofilm
Penicillinactivityreducedinpresenceof
haemoglobin
Post operative infection risk factors
Clinicalstatusofpatient - Incrriskforshocked/emaciatedpatients
Natureofsurgery - Incrriskforemergencyprocedures
Useofimplants
Experienceofsurgeon
duration of operation
Administeringpropofol - 3.8x more at risk
Clipping - before induction 3x more likely
poor BCS
concurrentendocrinopathies
when to use prophylactic antimicrobials
non-clean surgery
dentalprocedures?
patientswithleukopenia(viral,druginduced)
orthopaedicandmajorabdominalandthoracicsurgery
surgicaltime>90mins
consequencesofinfectionwouldbedisastrous
Antibiotics can not compensate for
grosscontamination
Localtissuetrauma
Compromisedpatienthealth
Surgicalprophylaxis ‐ timing
Administerbeforeprocedure
drugmustbepresentinthewoundatthetimeofbacterialcontamination
LAformulationofamoxycillintakes12hourstoreachtherapeuticconcs
situations when antimicrobials are inappropriate
Dogspresentingforvomiting d/tacutegastritis
YoungcatswithsignsofLUTdisease
Bloodinfaeces
Routinesurgery
