AGACNP Barkley Review Antibiotics Exam Questions And Correct Answers

AGACNP Barkley Review
Antibiotics Exam Questions And
Correct Answers

Ways organisms become resistant to antibiotics - ANSWER -1) *spontaneous

mutation* - occurs only to one drug

2) *conjugation* - mostly in GN bacteria, occur b/w normal flora & pathogens -*R-factor* w/c is extra-
chromosomal DNA encoding for resistance that is passed from

one bacteria to the next - responsible for multiple-drug resistant bugs

CDC's campaign to prevent antimicrobial resistance - ANSWER -*Infection Prevention* - vaccinate -
remove catheters

*Diagnose & Tx infections effectively* - target the pathogen - contact the experts

*Use ABX wisely* - practice antimicrobial control - use local data - tx infection, NOT contamination or
colonization - know when to say "NO" to Vanco - stop ABX when infection has cleared or unlikely a
bacterial infection

*Prevent transmission*

- isolate the pathogen - break the chain of contagion

Who should receive ABX prophylaxis? - ANSWER -1) Select *surgical patients* -

cardiac, peripheral vascular, orthopedics, GI, GYN (hysterectomy)

2) *severely neutropenic*

3) pt at risk for *bacterial endocarditis*

4) pts w/ *recurrent UTIs, severe rheumatic endocarditis*

Indications for ABX combinations - ANSWER -1) *initial therapy for severe infection* -

until organism is ID'd

2) *mixed infections* - common in GI, pelvic, brain abscesses

3) *prevent emergence of resistance* - TB, HIV, certain parasites

,4) *to decrease toxicity*

5) *to promote synergistic effect* - PCN + gentamicin, TMP-SMZ*

ABX combination disadvantages - ANSWER -1) increased risk of *adverse effects* like

allergy or toxicity

2) risk of *suprainfection* (ex. C. diff & yeast infection*

3) risk for *drug resistance*

Abx selective toxicity & mechanism of antibiotic action - ANSWER -Abx unique MOA

that makes them selectively toxic to bacteria - ability to disrupt bacterial cell wall or inhibit cell wall
synthesis - lethal or nonlethal inhibition of bacterial protein synthesis - inhibition of bacterial nucleic
acid synthesis - antimetabolites

DNA or RNA synthesis inhibitors - ANSWER -fluoroquinolones, rifampin

T/F: any antibiotic may promote resistance, but *broad spectrum* agents are the most

likely to cause it - ANSWER -True

Mechanisms of antibiotic resistance - ANSWER -1) production of drug-metabolizing

enzymes

2) decreased drug uptake

3) change in drug receptor w/ decreased binding of abx

4) synthesis of compounds that antagonize the antibiotic

4) increase *cost*

Cell wall synthesis inhibitors - ANSWER -PCN, cephalosporins, carbapenems,

aztreonam, vancomycin, fosfomycin, teicoplanin

Penicillins - ANSWER -- *inhibit transpeptidases necessary for cell wall synthesis* &

activate autolysis w/c cleave bonds in the cell wall. - *target the PCN binding proteins (PBP) - PBP1 &
PBP3 (crucial targets) - *resistance* is d/t inability of drug to reach PBPs or enzymatic inactivation of the
drug - PCN resistant drugs produce beta-lactamase which cuts into the beta-lactam ring of

the drug which inactivates the ABX so the ABX is no longer become anti-infective.

•Allergic reactions (1-5%); Anaphylaxis (.004-.015%)

•Cross reaction - 3-7% PCN to Ceph

•Prolonged high dose = granulocytopenia, interstitial nephritis

Bacterial cell wall - ANSWER -Gram positive vs Gram negative

,Gram negative has an outer membrane and gram positive does not w/c prevents PCN

from reaching PBPs (target molecules)

PCN: *Narrow-spectrum PCNase sensitive* - ANSWER -*PCN G, PCN V K*

useful for Strep, Neisseria, many anaerobes, & spirochetes

PCN: *Narrow-spectrum PCNase resistant* - ANSWER -*Nafcillin, Oxacillin*,

Cloxacillin, Dicloxacillin

- useful for Staph aureus

PCN: *Broad-spectrum* - ANSWER -*Ampicillin, Amoxicillin*, Bicampicillin - useful for H. flu, E. coli, P.
mirabilis, N. gonorrheae, enterococci

susceptible to beta-lactamase

PCN: *Extended-spectrum* - ANSWER -- *Piperacillin*, Carbenicillin, Ticarcillin,

Mezlocillin

useful for H. flu, E. coli, P. mirabilis, N. gonorrheae, enterococci

*PLUS*

*pseudomonas*, enterobacter, proteus, *B. fragilis*, & Klebsi

susceptible to beta-lactamase

PCN side effects & toxicities - ANSWER -1) Pain at IM injection site - bec PCN is

thick/viscious

2) reactions to procaine & potassium - from the injection, not PCN itself

3) rare neurotoxicity

4) *ALLERGY* - can occur immediate (2-30 mins), accelerated (1-72h); late (days to

weeks)

*anaphylactic reactions occur w/ PCNs more than any other drugs*

*Incidence is 0.02% but mortality is 10%

Allergy is exposure dependent, NOT dose dependent.

What to do if pt has PCN allergy? - ANSWER -*AVOID PCNs ENTIRELY*

*mild allergy* - can give cephalosporin

*severe allergy or anaphylaxis* - avoid PCN & cephalosporin (5-10% cross-sensitivity)

Alternatives to PCN - Vanco & erythromycin

, *Life-threatening + NO abx alternatives, give PCN according to desensitization

schedule*

PCN Combined with a Beta-Lactamase Inhibitor - ANSWER --cillin/bactam -cillin/clavulanate

limited toxicity; *great for Pseudomonas*

*Ampicillin + sulbactam (Unasyn)*

*Amox + clav (Augmentin)*

Ticarcillin + clav (Timentin)

*Piperacillin + tazobactam (Zosyn)*

Cephalosporins - ANSWER -*widely used abx*

*beta-lactam abx that bind to PBPs*

resistance d/t beta-lactamases (bacteria makes them) w/c cleave open the drugs

•Allergic reactions (1-3%)

•Cefotetan - disulfiram-like reaction with EtOh and hemostasis (hypoprothrombinemia)

1st generation cephalosporins - ANSWER -*Cefazolin, cephalexin*

Use: *Gram- positive cocci*, Proteus mirabilis, E. coli, Klebsiella pneumoniae.

*Cefazolin used prior to surgery to prevent S. aureus wound infections*

2nd generation cephalosporins - ANSWER -* Cefoxitin, cefaclor, cefuroxime*

Use: GP w/ some GN, Haemophilus influenzae, Enterobacter aerogenes, Neisseria

spp., Proteus mirabilis, E. coli, Klebsiella pneumoniae, Serratia marcescens.

3rd generation cephalosporins - ANSWER -*Ceftriaxone, cefotaxime, ceftazidime*

Use: serious gram-negative infections resistant to other β-lactams.

*Ceftriaxone*—meningitis, gonorrhea, disseminated lyme disease

*Ceftazidime* —Pseudomonas

4th generation cephalosporins - ANSWER -*Cefepime* - broadest spectrum

Use: GN, GP, & Pseudo

Cephalosporins: side effects & toxicities - ANSWER -1) Allergy - *maculopapular rash

after several days (most common)*

2) increased *risk for bleeding* (cefotetan, cefmetazole, cefoperazone)

3) *thrombophlebitis w/ IV infusion*