Resistant Infections Flashcards
What are the three types of bacteria we discussed that exhibit multiple drug resistance?
Methicillin Resistant Staphylococcus sp (MRS)
Extended Spectrum B-Lactamase bacteria (ESBL)
Enterococcus
What is MRSA?
Staph aureus organisms resistant to the anti-staphylococcal penicillins, methicillin and oxacillin
T/F: If a staph organism is resistant to oxacillin or methicillin, there is still a chance it could be susceptible to cefazolin.
False - will be resistant to ALL beta-lactam antibiotics
Resistance is MRS is mediated via _________
MecA gene
How does MecA work to promote resistance?
Encodes for penicillin binding protein (PBP) 2a
Low binding affinity for beta-lactam antibiotics
Beta-lactams work by binding and inhibiting PBP, so if they are unable to bind effectively, they won’t work
Risk factors for MRSA
Prior administration of antimicrobial drugs (FQs and beta-lactams in dogs)
IV catheterization
Most common site for MRSA infections
Ear, skin
Which MRS is a common cause of canine pyodermas?
Methicillin Resistant Staph Pseudintermedius (MRSP)
T/F: treatment of MRS should be based on culture and sensitivity
True
ESBLs are found in gram ______ bacteria
(-)
What do ESBLs produce?
Beta-lactamases…duh
What drugs do ESBLs like to inactivate?
The beta-lactams (again, duh)
How can we identify ESBLs in veterinary medicine?
Resistance to cefpodoxime (3rd gen cephalosporin) on C&S
Resistance for ESBLs is __________-mediated
Plasmid
Encode genes that infer resistance to antimicrobial of other classes
What are some common options for treating ESBL infections?
Amikacin
Imipenem/meropenem (look out for those carbapenemases though)
Clavamox might be an option for urine b/c has BLI and concentrates in urine
What bacteria is the most common ESBL in veterinary medicine?
E. coli
We also can see pseudomonas, salmonella, klebsiella
What is enterococci?
Opportunistic pathogen that likes to poke its head out when there are other powerful bacteria around
Commensal organism in the GIT
T/F: Enterococci are typically virulent and multi-drug resistant, so we must treat them immediately.
False - not typically virulent, but do express multi-drug resistance
We do not commonly treat these
Enterococci like to tango with _________
E. coli
In general, how do we treat enterococci?
Treat the primary organism and enterococci will go away
When do we treat enterococci?
Pure heavy growth is cultured
Animal has clinical signs
What are the two most commonly used drugs to treat enterococci?
Ampicillin
Vancomycin in people
SoA of Rifampin
Gram-positive and gram-negative aerobes
Rifampin has a low incidence of resistance currently, but is noted for creating resistance during treatment. What are some ways we an avoid the development of resistance?
Using in combination with other drugs
Short treatment times
The most common veterinary uses of rifampicin…
Rhodococcus in foals
MRSP pyodermas in dogs/cats (10d treatment)
Adverse effects associated with rifampin
Dogs - elevated liver enzymes +/- hepatotoxicity
Turns urine, sweat, and tears a red or orange color
Foals when combined with doxy - hemolytic anemia, hepatotoxicity
Rifampin is almost always combined with a second drug like __________ for the treatment of R equi in foals
A macrolides (clarithromycin)
Carbapenems are part of the major class of __________
Beta-lactams
Name the two carbapenems
Imipenem
Meropenem
SoA of carbapenems
Incredibly broad spectrum
Gram (+) and (-) aerobes and anaerobes
NOT for MRS and enterococci
What are carbapenems reserved for in veterinary medicine?
Life-threatening, multi-drug resistant ESBL infections, pseudomonas
Because imipenem can cause _______toxicity, it is combined with _________.
Nephro
Cilastatin
Adverse effects with carbapenems
V, D, HSR
Nephrotoxicity
Rapid IV admin or pre-existing renal disease can lead to seizures
SoA of vancomycin
Gram positive aerobes and anaerobes only!!
Vancomycin is a _________ and its mechanism of action is _____________
Glycopeptide
Cell wall inhibition
Vancomycin is the first line treatment for ___________ and _________ in people
Enterococcus
MRSA
Oxazolidinone has a ______________ spectrum
Gram positive aerobic
MoA of oxazolidinone, a linezolid
Protein synthesis inhibitor (50s)
Oral availability of oxazolidinone is _______ in dogs
100%
MoA of Nitrofuran
Blocks bacterial energy producing pathways
Nitrofuran is bactericidal in what body fluid
Urine ONLY
SoA of Nitrofuran
Gram negative and gram positive aerobic bacteria in URINE ONLY
What is the most common veterinary use of Nitrofuran?
Resistant UTIs - gets aerobic bacteria in the URINE
T/F: if you have a resistant UTI, ask the lab for nitrofurantoin susceptibility before reaching for imipenem
True - Nitrofuran is used to treat resistant UTIs b/c it is rapidly excreted unchanged in the urine and reaches high urine concentrations
Fosfomycin hasn’t been used for much in veterinary medicine, but it has been used for __________
UTIs in dogs
