Antimicrobial Selection Flashcards
what are the 3 indications for antimicrobials
- infection
- prophylaxis
- metaphylaxis
prophylaxis
short term administration to prevent infection during surgery
metaphylaxis
treatment of a group of animals that aren’t diseased but are in proximity to diseased animals
what are the main considerations when choosing a specific antimicrobial
- susceptibility of organism
- infection site
- administration route, frequency, and adverse effects
- cost/owner compliance
- drug label and WDTs
- concurrent medications
- host factors
broad spectrum antimicrobials
active against a wide spectrum of bacteria
- carbapenems
- fluoroquinolones
- chloramphenicol
- 2nd/3rd generation cephalosporins
- tetracyclines
- clavamox
pros and cons of broad spectrum antibiotics
pros:
- effective against a wide variety of bacteria
cons:
- greater disruption of normal flora
- increased risk of resistance
narrow spectrum antimicrobials
active against a selected group of bacteria
- erythromycin
- penicillin
- clindamycin
- aminoglycosides
- rifampin
pros and cons of narrow spectrum antimicrobials
pros:
- less disruption of normal flora
- decreased risk of resistance
cons:
- may not be effective if organism is unknown
what are limited sites
body sites that only certain drugs are able to reach
- abscesses
- brain/CNS
- eye
- prostate
- bronchial epithelium and secretions
can all drugs penetrate intracellularly
NO - only certain drugs are able to be effective against intracellular organisms
- tetracyclines
- fluoroquinolones
- macrolides
local factors that effect drug penetration
- purulent material and necrotic debris
- foreign material
- acidic environment
- anaerobic environment
- poor vascularization
- biofilms
- abscesses
1st line drugs
used for empirical selection in the absence of/pending results of C&S testing
- will treat a LIKELY cause of infection
- amoxicillin
- cephalexin
- doxycycline
- TMS
- penicillin
+/- fluoroquinolones
2nd line drugs
used on the basis of C&S testing with the lack of susceptibility to 1st line drugs
- if results show susceptibility to a 1st line drug, use the 1st line drug
- piperacillin
- amikacin
- gentamicin
- 3rd generation cephalosporins
- fluoroquinolones
3rd line drugs
reserved drugs - only used when absolutely necessary
- MUST have documented susceptibility
- must not be susceptible to any 1st or 2nd line drugs
- infection must be serious/life threatening
- infection should be treatable
- vancomycin
- linezoid
- carbapenems
considerations for equine antimicrobials
- poor oral absorption of drugs
- requires large volume of parenteral drugs
- potential for GI upset
considerations for food animal antimicrobials
- cost
- withdrawal times
- label and ELDU of drugs
- large volume required
- effect on meat/milk quality
- often parenteral drugs
when is it indicated to use a combination of antimicrobials
- resistance is rapidly generated against a single antimicrobial
- poolymicrobial infection in which one antimicrobial will not provide wide enough spectrum
- unknown organism w/ life threatening infection
- mixed infections with anaerobic bacteria
synergistic response
ability to kill is enhanced over the additive effect of 2 drugs
indifferent response
no enhanced ability to kill bacteria, additive only
antagonistic response
the drug combination is less effective than the individual drug
avoid using the two drugs together when this is the result
when is antimicrobial prophylaxis recommended
risk of infection outweighs the adverse effects of the drug
what type of antimicrobial should be used for prophylaxis
different antimicrobial than one used to treat the infection that would occur at the site
should prophylactic antimicrobials be used for IV or urinary catheters
no - will increase the risk of infection
goal of surgical prophylaxis
prevent the development of a SSI and reduce the duration of hospitalization
indications for surgical prophylaxis
- procedure has a high rate of infection
- contaminated and clean-contaminated - consequence of infection is high (even if chances of getting infection are slim)
should prophylactic antimicrobials be used in clean orthopedic surgeries without an implant
no
should prophylactic antimicrobials be used in clean orthopedic surgeries with an implant
yes - implant can cause biofilm formation
should prophylactic antimicrobials be used in clean-contaminated surgeries
yes
should prophylactic antimicrobials be used in contaminated surgeries (ex. into the GIT)
yes
should prophylactic antimicrobials be used in spays/neuters
no
what is the most common antimicrobial used for surgical prophylaxis in small animals
cefazolin
when should prophylactic antimicrobials be administered
30-60 minutes before incision
short sx: single dose prior to surgery
long sx: use throughout surgery then stop immediately after
