Resistant Infections

Question 1

What are the three types of bacteria we discussed that exhibit multiple drug resistance?

Answer 1

Methicillin Resistant Staphylococcus sp (MRS)

Extended Spectrum B-Lactamase bacteria (ESBL)

Enterococcus

Question 2

What is MRSA?

Answer 2

Staph aureus organisms resistant to the anti-staphylococcal penicillins, methicillin and oxacillin

Question 3

T/F: If a staph organism is resistant to oxacillin or methicillin, there is still a chance it could be susceptible to cefazolin.

Answer 3

False - will be resistant to ALL beta-lactam antibiotics

Question 4

Resistance is MRS is mediated via _________

Answer 4

MecA gene

Question 5

How does MecA work to promote resistance?

Answer 5

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

Question 6

Risk factors for MRSA

Answer 6

Prior administration of antimicrobial drugs (FQs and beta-lactams in dogs)

IV catheterization

Question 7

Most common site for MRSA infections

Answer 7

Ear, skin

Question 8

Which MRS is a common cause of canine pyodermas?

Answer 8

Methicillin Resistant Staph Pseudintermedius (MRSP)

Question 9

T/F: treatment of MRS should be based on culture and sensitivity

Answer 9

True

Question 10

ESBLs are found in gram ______ bacteria

Answer 10

(-)

Question 11

What do ESBLs produce?

Answer 11

Beta-lactamases…duh

Question 12

What drugs do ESBLs like to inactivate?

Answer 12

The beta-lactams (again, duh)

Question 13

How can we identify ESBLs in veterinary medicine?

Answer 13

Resistance to cefpodoxime (3rd gen cephalosporin) on C&S

Question 14

Resistance for ESBLs is __________-mediated

Answer 14

Plasmid

Encode genes that infer resistance to antimicrobial of other classes

Question 15

What are some common options for treating ESBL infections?

Answer 15

Amikacin

Imipenem/meropenem (look out for those carbapenemases though)

Clavamox might be an option for urine b/c has BLI and concentrates in urine

Question 16

What bacteria is the most common ESBL in veterinary medicine?

Answer 16

E. coli

We also can see pseudomonas, salmonella, klebsiella

Question 17

What is enterococci?

Answer 17

Opportunistic pathogen that likes to poke its head out when there are other powerful bacteria around

Commensal organism in the GIT

Question 18

T/F: Enterococci are typically virulent and multi-drug resistant, so we must treat them immediately.

Answer 18

False - not typically virulent, but do express multi-drug resistance

We do not commonly treat these

Question 19

Enterococci like to tango with _________

Answer 19

E. coli

Question 20

In general, how do we treat enterococci?

Answer 20

Treat the primary organism and enterococci will go away

Question 21

When do we treat enterococci?

Answer 21

Pure heavy growth is cultured

Animal has clinical signs

Question 22

What are the two most commonly used drugs to treat enterococci?

Answer 22

Ampicillin
Vancomycin in people

Question 23

SoA of Rifampin

Answer 23

Gram-positive and gram-negative aerobes

Question 24

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?

Answer 24

Using in combination with other drugs

Short treatment times

Question 25

The most common veterinary uses of rifampicin…

Answer 25

Rhodococcus in foals MRSP pyodermas in dogs/cats (10d treatment)

Question 26

Adverse effects associated with rifampin

Answer 26

Dogs - elevated liver enzymes +/- hepatotoxicity Turns urine, sweat, and tears a red or orange color Foals when combined with doxy - hemolytic anemia, hepatotoxicity

Question 27

Rifampin is almost always combined with a second drug like __________ for the treatment of R equi in foals

Answer 27

A macrolides (clarithromycin)

Question 28

Carbapenems are part of the major class of __________

Answer 28

Beta-lactams

Question 29

Name the two carbapenems

Answer 29

Imipenem Meropenem

Question 30

SoA of carbapenems

Answer 30

Incredibly broad spectrum Gram (+) and (-) aerobes and anaerobes NOT for MRS and enterococci

Question 31

What are carbapenems reserved for in veterinary medicine?

Answer 31

Life-threatening, multi-drug resistant ESBL infections, pseudomonas

Question 32

Because imipenem can cause _______toxicity, it is combined with _________.

Answer 32

Nephro Cilastatin

Question 33

Adverse effects with carbapenems

Answer 33

V, D, HSR Nephrotoxicity Rapid IV admin or pre-existing renal disease can lead to seizures

Question 34

SoA of vancomycin

Answer 34

Gram positive aerobes and anaerobes only!!

Question 35

Vancomycin is a _________ and its mechanism of action is _____________

Answer 35

Glycopeptide Cell wall inhibition

Question 36

Vancomycin is the first line treatment for ___________ and _________ in people

Answer 36

Enterococcus MRSA

Question 37

Oxazolidinone has a ______________ spectrum

Answer 37

Gram positive aerobic

Question 38

MoA of oxazolidinone, a linezolid

Answer 38

Protein synthesis inhibitor (50s)

Question 39

Oral availability of oxazolidinone is _______ in dogs

Answer 39

100%

Question 40

MoA of Nitrofuran

Answer 40

Blocks bacterial energy producing pathways

Question 41

Nitrofuran is bactericidal in what body fluid

Answer 41

Urine ONLY

Question 42

SoA of Nitrofuran

Answer 42

Gram negative and gram positive aerobic bacteria in URINE ONLY

Question 43

What is the most common veterinary use of Nitrofuran?

Answer 43

Resistant UTIs - gets aerobic bacteria in the URINE

Question 44

T/F: if you have a resistant UTI, ask the lab for nitrofurantoin susceptibility before reaching for imipenem

Answer 44

True - Nitrofuran is used to treat resistant UTIs b/c it is rapidly excreted unchanged in the urine and reaches high urine concentrations

Question 45

Fosfomycin hasn’t been used for much in veterinary medicine, but it has been used for __________

Answer 45

UTIs in dogs