Antibiotic resistance in SA (NAVDF Papich) Flashcards
Which animals are more likely to have resistant strains of fecal bacteria (E coli)
*Previously hospitalized
*Previous antibiotic tx within 1 year
Also: raw meat diet, dogs in shelters/breeders
Which antibiotic may be associated with antibiotic resistant E coli in dogs
Fluoroquinolones
(Also amoxicillin, clavamox, cephalosporins)
T or F: The amount of resistant bacteria will return to pre-treatment levels within days to weeks after antibiotics are discontinued
True
But the resistant bacteria can linger in small numbers for a very long time
T or F: It has been reported that there is transfer of resistant E coli from humans to their dogs and back
True
Biggest risk factor for developing MRSP in dogs
Previous antibiotic exposure
T or F: MRSP from pets is a serious health risk for humans
False. They CAN have transfer of MRSP to humans, but infection is unlikely.
Only a few isolated reports
Do pets give their owners MRSA
Pets can be transient carriers for MRSA (from a human origin)
T or F: resistance genes from E coli can be spread to other Enterobacteriaceae bacteria
True
Can pets transmit Salmonella, Campylobacter, Clostridium difficile?
Yes, but usually from contaminated meat or the environment. Healthy pets can be carriers. BUT not related to antibiotic administration.
No evidence dog spread of these bacteria are associated with drug-resistant strains in people.
Salmonella CAN be spread to people. Control measures when Salmonella outbreaks are identified
T or F: evidence has shown spread of antibiotic-resistant Pseudomonas from a dog to humans
FALSE. No evidence as of yet
T or F: large animals can be a source of a “serious threat” for drug resistant bacteria (Campylobacter, ESBL E coli)
TRUE. But not seen in small animals
Cause of Staphylococcal methicillin resistance (gene, protein)
mecA gene
Altered Penicillin-binding protein (PBP-2a)
T or F: Adding a beta lactamase inhibitor can overcome methicillin resistance
False
T or F: methicillin resistant Staph are very likely to be resistant to other antibiotics
True.
>90% are resistant to >4 drugs
T or F: most MRSP are susceptible to TMS, clindamycin, FQs
FALSE. This is different than community acquired MRSA in humans, where these antibiotics usually work
Rifampin: describe lipo vs hydrophiliic, volume of distribution, absorption
Lipophilic
Good volume of distribution
Good absorption
Which antibiotic is a good options for Mycobacterium (intracellular bacteria)
Rifampin
(also macrolides)
Should rifampin be combined with other antibiotics to minimize MRSP?
No. Can be used as effectively as a monotherapy
Rifampin can induce cytochrome p450 enzymes, for faster clearance of other drugs. How long after discontinuing rifampin does it take for the enzyme effects to recover?
4 weeks in people
Can inhibit intestinal transport of other meds too! Which really limits the amount of active medications
When doxycycline is compounded into an aqueous suspension, how potent is it at 14 days
20%!
Stable at 7 days though
T or F: doxycycline can cause dental enamel discoloration and chelates with calcium-containing oral products
False. But that is a concern with other tetracyclines
Other than Staphylococcus, what other bacteria is chloramphenicol often used for
Enterococcus
AEs chloramphenicol in dogs
*GI disturbance = common
*Decreased protein synthesis in Bone marrow with chronic use (esp CATS!)
*Hind limb weakness, ataxia -> peripheral neuropathy. Large breed dogs
*Drug interactions! Cytochrome p450 and CYP2B11 inhibitor!
Aplastic anemia in humans, irreversible
Implications of combining chloramphenicol with other drugs
*Cytochrome p450 and CYP2B11 inhibitor!
Increases concentration of opiates, barbituates, propofol, salicylate
T or F: gentamicin is absorbed well SC and IM
True. Water soluble. BUT painful
Are aminoglycosides better for gram negative bacteria or gram positive (like Staphylococcus)
Gram negative. They disrupt gram - outer membrane.
SID dosing is based on gram neg bacteria. May need more frequent injections if used for gram + bacteria.
What can inhibit the efficacy of aminoglycosides
Pus, cell debris
(ears, wounds)
What increases the risk of aminoglycoside toxicity
Renal disease
Dehydration
Electrolyte imbalances (Na, K)
Septicemia
Persistent drug levels (esp high trough concentrations —> nephrotox can be decreased with extended dosing intervals
How is vancomycin administered
IV only
Vancomycin: bacteriocidal or bacteriostatic?
Bacteriocidal
Vancomycin: time or concentration dependent?
Time dependent
What happens if vancomycin is giving RAPIDLY IV?
HISTAMINE RELEASE
*Flushing of skin
*Pruritus
*Tachycardia
ALSO: nephrotoxicity, ototoxicity
What happens if vancomycin is given IM?
Painful, irritating
Which antibiotics are concentration dependent
*Fluoroquinolones
*Metronidazole
*Aminoglycosides
Which antibiotics are time dependent
*Beta lactams
*Macrolides
*Glycopeptides
*Tetracyclines
What class of antibiotics is linezolid in
Oxazolidinones
Is Linezolid better for gram + or gram - bacteria
Gram +
How does resistance occur in Linezolid
Multiple sequential mutations, so incredibly rare
How can linezolid be administered
PO or IV
100% absorbed when given PO, not affected by food
MOA of linezolid
Mild, reversible inhibitor of monoamine oxidases A and B
AE of linezolid long term
Reversible, mild bone marrow suppressio, if given >14d in humans
Not reported in dogs, cats.
Caution linezolid with what other medications
Adrenergic agents: Phenylpropanolamine, selegiline
Other MAO drugs: SSRIs, TCAs
Has not been studied
T or F: cefpodoxime can be effective for Pseudomonas and Enterococcus
False
T or F: Cefovicin has a lower MIC for Staphylococcus than first gen cephalosporins
TRUE. Also better for gram - infections.
How do cefovicin and cefpodoxime work for gram negative infections compared to injectable 3rd gen antibiotics (ie ceftazidime)
Poorer activity than IV antibiotics
Which cephalosporins are effective against Pseudomonas
*IV 3rd gen (Ceftazidime > cefoperazone)
*IV/SC/IM 4th gen (cefepime)
Which beta lactam antibiotics have the greatest activity against Enterobacteriaceae (E coli, Klebsiella) and Pseudomonas
Carbapenems (imipenem, meropenem)
Ertapenem does not have anti-Pseudomonas activity
Why is imipenem given with cilastatin?
To minimize renal tubular metabolism
Should imipenem be used against MRSP or Enterococcus
No
Why does imipenem have high antimicrobial activity?
*Stable against most beta latamases (including ESBL)
*Penetrates porin channels that exclude most drugs
Are carbapenems or cephalosporins more likely to induce release of endotoxin from gram negative sepsis?
Cephalosporins
Are carbapenems or cephalosporins more rapidly bactericidal
Carbapenems
Does imipenem or meropenem have greater antibacterial activity
Meropenem
Does imipenem or meropenem have more CNS AEs (seizures)
Meropenem
What penicillin is effective against Pseudomonas, Enterobacter (including ESBL), and gram negative bacteria?
Ureidopenicillins– ie Piperacillin-tazobactam
Needs to be given IV q6hr. No PO option
Antibiotics for gram negative infections (like Pseudomonas) E coli, Klebsiella
*Aminoglycosides (amikacin, tobramycin)
*IV 3rd and 4th gen cephalosporins; ceftazidime, cefperazone, cefepime
*Carbapenem (Imipenem-cilastatin, Meropenem)
*Ureidopenicillins (piperacillin-tazobactam)
Antibiotics for MRSP
*Rifampin
*Tetracyclines
*Chloramphenicol
*Aminoglycosides (gentamicin, amikacin; but best for gram neg!)
*Glycopeptides, vancomycin
*Oxazolidinones; Linezolid
