General Antimicrobial Pharmacology Flashcards
Define antimicrobials
chemicals that kill microorganisms
Define antiseptics
Chemicals the reduce the microbial population on a living surface
List 2 examples of antiseptics
povidone iodine
chlorhexidine gluconate
What is the mechanism of action of povidone iodine
the free iodine dissociates and interacts with bacterial protein/nucleotides and fatty acids
What is the mechanism of action of chlorhexidine gluconate? How does it compare to povidone iodine?
It disrupts cell membranes
It is better than povidone iodine as a pre-surgical use (except on face) and there is no documented resistance yet
Define disinfectant
A biocide that reduces microorganisms on a non-living surface
Define antibacterials
chemicals that kill or inhibit bacteria
How are antibacterials classified? What are the 6 classifications?
by the site of action in the microbe
- folate synthesis inhibitor
- call wall synthesis inhibitor
- RNA pol inhibitor
- DNA gyrase inhibitor
- cell membrane inhibitor
- protein synthesis inhibitor
Define minimum inhibitory concentration
The lowest concentration needed to completely inhibit bacterial growth
Define minimum bactericidal concentration
The lowest concentration needed to kill 99.9% of bacterial isolates in vitro
Compare bacteriocidal and bacteriostatic
bacteriocides: interfere with the vital processes of the bacteria to kill
- the MIC = MBC
bacteriostatic: prevent bacterial growth but don’t kill
- the MIC is very different from the MBC
What are narrow spectrum antibacterials
they have efficacy against a single or small population of pathogens
associated with low adverse effects and a reduce AMR risk
What are broad spectrum antibacterials
They have efficacy against a wide range of pathogens
What are extended spectrum antibacterials
they have efficacy against an intermediate number of pathogens (not narrow but not broad spectrum)
Give 3 examples of concentration dependent antibacterials
aminoglycosides
fluoroquinolones
metranidazole
Explain what concentration dependent antibacterials are
Their efficacy depends on how high above the MIC they are
- more effective if they are at higher concentrations
What is the post antimicrobial effect
bacterial inhibition after treatment with antibacterials has stopped
removal of the bacteria by the host immune system maintains low levels for a while
Explain what time dependent antibacterials are
Efficacy depends how long that drug is at the site of infection above the MIC
the dosing will maximize the time the concentration is maintained above the MIC
- concentration has no effect on efficacy (as long as it is above the MIC)
Give 5 examples of time dependent antibacterials
penicillin
cephalosporin
macrolide
phenicol
tetracycline
How to plan dosing intervals of antibacterials
give the next dose during the post antimicrobial effect period
- before the bacterial concentrations begin to increase again
What are 3 methods for testing antibacterial susceptibility
broth dilution test
disc diffusion test
e-test method
How does the broth dilution susceptibility test work
add abx + growth media + bacteria
see what concentration of abx is needed to prevent bacterial growth
How does the disc diffusion susceptibility test work
put abx discs on an agar plate innoculated with bacteria
measure zone of inhibition
How does the e-test susceptibility test work
it is a plastic strip with a gradient of abx
How are bacteria deemed susceptible or resistant? What are the 3 categories of susceptibility?
based on the MIC breakpoints
- MIC values are specific to different bacteria
susceptible - MIC < susceptible breakpoint
intermediate
- MIC is between the susceptible and resistant breakpoint
resistant - the MIC is above the resistant breakpoint
What is ‘de-escalating’ and antibacterial treatment plan?
When you switch antibacterials during a treatment to a less important or more specific type
What is empirical treatment
treating based on your knowledge and experience of what is most likely the cause of the problem
What should you consider when thinking about your rationale for using antibacterial
are they needed
is the causative agent susceptible
will they recover without abx
will abx improve the outcome or significantly reduce the risk to other individuals
Provide examples of topical abx
triple abx ointment
silver sulfadiazine cream
betadine ointment
chlorhex gel
honey
What are the 2 types of ways antibacterial can be used
prophylactic/metaphylactic -
preventative use
therapeutic
- to treat infection
What are the 3 types of therapeutic abx treatment? How do they change the type of abx you use?
non life threatening and not serious
- narrow spectrum
- don’t usually need C/S on first treatment
serious but not life threatening
- consider C/S if they need long term abx
- avoid big guns - target common pathogens
life threatening
- target full range of pathogens
- use a combo treatment or big gun abx
What other considerations should you have before using antibacterial
site of infection
- is it immune-privileged or intracellular
treat underlying causes
- lance abcess/remove FB/debride
history
- signalment
- concurrent disease
- hygeine/housing
- diet
- immunosuppressive drugs
Define obligate anaerobe
can only live with oxygen
What is the 4 quadrant approach
categorize bacterial types to choose most effective treatment if you don’t have a C/S
gram (+) aerobe
- include facultative anaerobe + aerotolerant anaerobe
gram (-) aerobe
- include facultative anaerobe + aerotolerant anaerobe
gram (+) anaerobe
- obligate anaerobes only
gram (-) anaerobe
- obligate anaerobes only
Define facultative anaerobe
can use aerobic or anaerobic respiration
Define aerotolerant anaerobe
is anaerobic but can live in the presence of oxygen
Define obligate anaerobe
can only live without oxygen
What enzymes facilitate oxygen metabolism in bacteria
superoxide dismutase
catalse
peroxidase
List 9 categories of antibacterials (not the same as classification)
macrolides
folate synthesis inhibitors
- sulfonamides
- diaminopyrimidines
fluoroquinolones
animoglycosides
lincosamides
-phenicols
nitroimidazoles
beta lactams (cell wall disruption)
tetracycline
List 7 examples of gram (+) aerobes
staphylococcus
streptococcus
enterococcus
truperella
listeria
bacillus
nocardia
Give examples of gram (-) aerobes that affect the GI, resp and opportunistic
enteric:
- e. coli
- kleibsiella
- proteus
- campylobacter
resp:
- manheimmia
- pasturella
- histophilus
- bordatella
opportunistic
- pseudomonas
Give 3 examples of gram (+) anaerobes
clostridium
actinomyces
peptostroptococcus
Give 2 examples of gram (-) anaerobes
fusobacterium
bacteroides
What are the 2 main antibacterial classes that are used to treat Pseudomonas infection in companion animals and horses?
fluoroquinolones and aminoglycosides
