Resistant Infections Flashcards
MRSA resistance is mediated by which gene?
(The MecA gene)
What protein is encoded for by the MecA gene that has a low binding affinity for beta-lactam antibiotics?
(PBP 2a)
(T/F) Any Staph aureus with the MecA gene is resistant to ALL beta-lactam antibiotics, even when paired with a beta-lactamase inhibitor.
(T)
What are the two main risk factors for MRSA infections?
(Prior adm of antimicrobial drugs (specifically beta-lactams, fluoroquinolones, and 3rd generation cephalosporins) and IV catheterization)
Why are MRSA infections not associated with an increased risk of mortality in veterinary medicine species?
(Because the common sites of infection (ear and skin) are not vital and still fairly easy to treat (with topicals))
What is the basis for treatment of MRSA infections in veterinary medicine species?
(Treatment should be based on culture and susceptibility, there is no routine medication that is used for treatment of MRSA, especially bc some 1st tier antibiotics can be used to tx it but you need to know based on c+s)
Extended-spectrum beta-lactamases (ESBLs) are gram positive/negative (choose) bacteria.
(Negative)
(T/F) Extended-spectrum beta-lactamases can not be treated with any penicillins, even those with a beta-lactamase inhibitor.
(F, some still can be inhibited by beta-lactamase inhibitors, but only if you can get a high enough concentration such as clavamox in the urine (so your infection needs to be in the urine))
(T/F) If you culture Enterococcus along with E. coli in the UTI of a cat with clinical signs, you need to treat both the Enterococcus and the E. coli.
(F, treat the E. coli and the Enterococcus will go away; if it were a pure, heavy growth of Enterococcus that is another story (would tx with ampicillin or vancomycin (scary) if clinical signs))
Why is rifampin often combined with other drugs?
(Because resistance to it develops quickly (i.e. in the middle of tx) so other drugs are used in combo to prevent that from happening, short tx intervals also prevent that)
(T/F) Rifampin can be used to treat gram negative, gram positive, and intracellular bacteria.
(T)
What are the most common veterinary uses of rifampin?
(MRSP pyoderma in dogs and cats (10 day course) and R. equi in foals (usually combo’d with a macrolide)
Rifampin causes hemolytic anemia and hepatotoxicity in foals when combined with what drug?
(Doxycycline)
(T/F) Carbapenems are beta-lactam antibiotics.
(T)
Why are carbapenems useless against MRSA infections?
(MRSA are resistant to ALL beta-lactams, guess what carbapenems are (beta-lactams); also useless against Enterococci)
What drug must be given with imipenem to prevent the formation of renal tubular dipeptidase which causes nephrotoxicity?
(Cilastatin; also increases urine concentration of the active drug)
Why is meropenem a better choice for use in small animals (if you have to use it)?
(It is easily administered SC (imipenem is painful given IM or SC), less likely to be nephrotoxic when compared to imipenem, and there is a generic option so cheaper)
(T/F) Vancomycin has zero activity against gram positives.
(F, zero activity against gram negatives, it is used for tx of gram positive aerobes (MRSA, Enterococcus) and anaerobes (Clostridium))
(T/F) Linezolid has ~100% oral bioavailability in dogs, has good intra and extracellular penetration, has a spectrum of gram-positive aerobes (Enterococci, streps, staphs), and is bactericidal.
(F, all true except bactericidal, linezolid is a protein synthesis inhibitor so it can only be bacteriostatic)
Nitrofuran is bactericidal and gets gram negative and gram positive aerobes (such as E. coli and staphs), but that is all if the infection is where in the body?
(The urine)
What is the spectrum for fosfomycin?
(Gram positive aerobes, gram negative aerobes, and some gram positive anaerobes)
There is no evidence for use of fosfomycin in treatment of infections anywhere but where in dogs?
(Urinary tract)
