Rational antimicrobial therapy Flashcards Preview

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Flashcards in Rational antimicrobial therapy Deck (46):
1

Gram positive aerobic bacteria

Strep
Staph aureus

2

Gram negative aerobic bacteria

E coli
Helicobacter

3

Anaerobic bacteria 

Clostridium perfringens

4

Atypical bacterial species

Rickettsia
Mycoplasma
Chlamydia
Borrelia
Bartonella
Mycobacterium

5

Bacterial resistance

some bacteria have resistant genes
use of antimicrobials creates a selective pressure

6

When to use antimicrobials?

definitively diagnosed/likely diagnosis
disease likely to progress without medical therapy 
Would cause critical illness if it was not recognised or treated 

7

factors to consider when choosing antimicrobial

likely bacteria involved
likely susceptibility
culture needed/feasible?
pharmacokinetic factors you need to consider?
potential side effects + incr risk in your patient?
client compliance issues?
cost considerations?

8

Factors affecting the success of antibacterial therapy

What bugs live where?
Bacterial susceptibility
Distribution to the site of infection (pharmacokinetic phase)
Local conditions (pharmacodynamic phase)
Client compliance 

9

Bacterial susceptibility

if not susceptible in vitro - resistant in vivo
if susceptible in vitro - may work in vivo
resistance may be overcome by high concs achieved in urine or topical application 

10

MIC

MIC = Minimum inhibitory concentration
Lowest conc of drug that will inhibit bacterial growth
MIC90 usual measure used to determine therapeutic dose - Conc that will inhibit 90% of isolates

11

Inhibition of cell wall synthesis 

penicillins
cephalosporins
bacitracin

12

Inhibition of cell membrane function

polymyxins
amphotericin B
imidazoles
nystatin

13

Inhibition of protein synthesis

chloramphenicol
macrolides
lincosamides
tetracyclines
aminoglycosides

14

Inhibition of nucleic acid synthesis

sulphonamides
trimethoprim
quinolones
metronidazole
rifampin

15

Bacteriostatic - define

Temp inhibit the growth of organisms
Effect is reversible once the drug is removed
drug conc at the site of the infection should stay above the MIC throughout dosing interval
Many bacteriostatic drugs can be bactericidal if drug exposure is sufficiently high or prolonged

16

Bacteriostatic drugs

Chloramphenicol
Lincosamides
Macrolides
Tetracyclines
Non-potentiated sulphonamides
(mostly inhibit protein synthesis)

17

Bactericidal - define

Under ideal conditions kill bacteria
preferred when concern about site of infection or host defence
gram +ve infections - susceptibility of bacteria and ability to 
penetrate tissue more important considerations

18

Bactericidal drugs

Penicillins
Cephalosporins
Aminoglycosides
Fluoroquinolones
Potentiated sulphonamides (TMPS)
Metronidazole

19

why not to give Penicillins, Cephalosporins + TMPS with bacteriostatic drugs

Bacteria need to be multiplying for drugs to be effective

20

concentration dependant drugs

Aminoglycosides
Fluoroquinolones
Metronidazole
Peak concentration achieved or area under the curve predicts therapeutic success
can be given with bacteriostatic drugs

21

drugs v. bad against gram +ve aerobes

Aminoglycosides
Metronidazole

22

drugs v. bad against gram -ve aerobes

Metronidazole
Penicillin G
Lincosamides/Macrolides

23

drugs v.bad against obligate aerobes

Fluoroquinolones
Aminoglycosides

24

drugs v.bad against penicillinase producing staph

Penicillin G
Aminopenicillins
Metronidazole

25

drugs v. good against gram +ve aerobes

Penicillin G
Aminopenicillins
Lincosamides/
Macrolides
Tetracyclines

26

drugs v. good against gram -ve aerobes

Fluoroquinolones
Aminoglycosides
Ticarcillin-clavulanate
Cephalosporins

27

drugs v.good against obligate aerobes

Penicillin G
Amoxy-clav
Clindamycin
Metronidazole
Chloramphenicol
Rifampin

28

drugs v.good against penicillinase producing staph

Amoxy-clav
Cephalosporins
Cloxacillin
Fluoroquinolones
Rifampin

29

drug most good but leaves some important gram +ve aerobes

Fluoroquinolones

30

drug most good but leaves some important penicillinase producing staph

Clindamycin

31

drug most good but leaves some important gram -ve aerobes

Amoxy-clav

32

cephalosporins, cefovicin and amoxycillin

50/50 susceptible/resistant - obligate anaerobes + -ve aerobes

33

TMPS

50/50 susceptible/resistant all quadrants

34

Tetracyclines 

50/50 susceptible/resistant all quadrants except gram positive 
aerobes

35

Difficult to access areas

Brain
Eye
Prostate
Bronchus
Mammary gland
Intracellular
Poorly vascularised tissues - Bone fragments, Heart valves

36

Intracellular bacteria

Bartonella 
Brucella
Chlamydophila
Mycobacterium
Rickettsia
Staphylococcus

37

poor penetration

Penicillins
Cephalosporins
Beta lactamase
inhibitors
Polymixins
Aminoglycosides

38

good penetration

Sulphonamides
Trimethoprim
Lincosamides
Macrolides
Tetracycline

39

great penetration

Chloramphenicol
Fluoroquinolones
Lipophilic 
tetracyclines
minocycline
doxycycline
Metronidazole
Rifampin

40

Environmental conditions - Foreign material 

phagocytes degranulate to try to destroy the foreign material
inefficient in killing bacterial pathogens
can protect bacteria from antibacterial drugs and phagocytosis - bacteria can form a biofilm

41

Penicillin activity reduced in presence of 

haemoglobin

42

Post operative infection risk factors

Clinical status of patient - Incr risk for shocked/emaciated patients
Nature of surgery - Incr risk for emergency procedures
Use of implants
Experience of surgeon
duration of operation
Administering propofol - 3.8x more at risk
Clipping - before induction 3x more likely
poor BCS
concurrent endocrinopathies

43

when to use prophylactic antimicrobials

non-clean surgery
dental procedures? 
patients with leukopenia (viral, drug induced)
orthopaedic and major abdominal and thoracic surgery
surgical time > 90 mins
consequences of infection would be disastrous

44

Antibiotics can not compensate for

gross contamination
Local tissue trauma
Compromised patient health

45

Surgical prophylaxis ‐ timing

Administer before procedure 
drug must be present in the wound at the time of bacterial contamination
LA formulation of amoxycillin takes 12 hours to reach therapeutic concs

46

situations when antimicrobials are inappropriate

Dogs presenting for vomiting d/t acute gastritis
Young cats with signs of LUT disease
Blood in faeces
Routine surgery