Anti-bacterials

Question 1

Bacterial resistance to antibacterial drugs is less common than viral resistance to antiviral drugs.
a. True
b. False

Answer 1

a. True

Viruses are more likely to have variation and resistance. That is why we have so few effective antivirals against common viral infections (cold, flu, etc)

Question 2

Which antibiotic requires a lower dose for patients on dialysis?
a. Cephalexin
b. Clindamycin
c. Doxycycline
d. Azithromycin

Answer 2

a. Cephalexin

Cleared by the kidneys - the others are not.

Question 3

Among adult women in the US who received oral antibiotics for uncomplicated UTI between 2010 and 2015, more than 75% received:
a. Both the wrong duration and an inappropriate antibiotic
b. Inappropriate antibiotic prescriptions
c. Antibiotics for the wrong duration

Answer 3

c. Antibiotics for the wrong duration

The findings of an observational cohort study published in Infection and Control and Hospital Epidemiology indicated that 76% received antibiotics for the wrong (typically a longer - 14 days!) duration, and 46% received prescriptions for an inappropriate antibiotic. In the same publication, the author reported that things improved in 2019, but not by much. 70% with wrong duration and 40% with wrong drug.

Question 4

Sulfonamides inhibit folic acid synthesis in microbes.
a. True
b. False

Answer 4

a. True

Question 5

A shorter course of antibiotic therapy with a high dose versus a longer course with a lower dose may offer which of the following advantages?
a. Increased adverse effects from therapy
b. Unchanged antibiotic tolerability
c. Markedly higher cure rate
d. Decreased proliferation of antibiotic-resistant flora

Answer 5

d. Decreased proliferation of antibiotic-resistant flora

Question 6

Antibiotics demonstrate selective toxicity. This means….
a. The drug is toxic to pathogens
b. The cytochrome P450 enzymes are able to manage toxicities through metabolism
c. The pathogen is toxic to the drug
d. The drug is toxic only to a few patients

Answer 6

a. The drug is toxic to pathogens

Question 7

The pt refuses to continue to take erythromycin becuase it makes him vomit. This is an example of which pt-drug-pathogen interaction?
a. Pharmacodynamics
b. Resistance
c. Pharmacokinetics
d. Immunity

Answer 7

a. Pharmacodynamics

Question 8

LH is a 78 yo woman who presents to the ED with fever, productive cough, and SOB. She was recently hospitalized for flulike symptoms and d/c’d home after 2 days of antiviral Rx (she tested positive for influenza B). A CXR today shows patchy opacities in the B/L lower lobes and her WBC is elevated to 13K. Her eGFR is 60 mL/min/1.72 m3.

A preliminary dx of hospital-acquired pna is made due to recent hospitalization. What antibiotics are considered?

Answer 8

IDSA recommends broad-spectrum coverage, empiric therapy - obtain a sputum culture if you can. Cover G+ MRSA and G- Pseudomonas.

Can draw a procalcitonin to understand when to de-escalate abx.

Can use Vancomycin 15 mg/kg q8-12 hr IV - requires admission to cover MRSA

Can use cefepime, cetazadime, levofloxacin, or piperacillin-tazobactam to cover everything else.

Treat until absence of elevated WBC or fever is achieved plus one day.

Question 9

Patients with latent TB are treated with the same pharmacological regimen as patients with active TB.
a. True
b. False

Answer 9

b. False

Latent TB is defined as the presence of TB bacteria in the body without signs or symptoms or x-ray evidence of TB. It is detected with the IGRA or TST test. Generally, pateitnes with latent TB cannot spread TB bacteria to others. It is treated with a single drug. Active TB is treated with 3 drugs.

Question 10

A 23 yo M presents with acute appendicitis that ruptures shortly after adm. He is taken to the operating room for surgery, and post surgical cultures reveal E. coli and bacteroides fragilis, susceptibilities pending. Which of he following provides adequate empiric coverage of these two pathogens?
a. Cefepime
b. Piperacillin/tazobactam
c. Aztreonam
d. Ceftaroline

Answer 10

b. Piperacillin/tazobactam

While all of these agents cover most strains of E. coli, pipercillin/tasobactam is the only drug on this list that provides coverage against bacteroides species.

Question 11

A 68 yo M presents from a nursing home with fever, increased urianry frequency and urgency, and mental status cahnges. He has a penicillin allergy of anaphylaxis. Which of the following B-lactams is the most appropriate choice for gram-negative coverage of this patients UTI?
a. Cefepime
b. Ertapenem
c. Aztreonam
d. Ceftaroline

Answer 11

c. Aztreonam

Based on the severity of the allergic reaction, aztreonam is the choice of all the B-lactams. Although cross-reactivity with cephalosporins and carbapenems is low, the risk rarely outweighs the benefit in these cases.

Question 12

A 25 yo man presents to the urgen care center with a painless sore on his genitals that started 2 weeks ago. He reports unprotected sex with a new partner about a month ago. A blood test confrims that the pt has Treponema pallidum. Which of the following is the drug of choice for the treatment of this patient’s infection as a single dose?
a. Benzathine penicillin G
b. Ceftriaxone
c. Aztreonam
d. Vancomycin

Answer 12

a. Benzathine penicillin G

A single treatment with penicillin is curative for primary and secondary syphilis. No antibiotic resistance has been reported, and it remains the drug of choice unless the patient has a severe allergic reaction.

Question 13

Which of the following cephalosporins has activity against gram-negative anaerobic pathogens like Bacteroides fragilis?
a. Cefoxitin
b. Cefepime
c. Ceftriaxone
d. Cefazolin

Answer 13

a. Cefoxitin

The cephamycins (cefoxitin and cefotetan) and the only cephalosporins with in vitro actvity against anaerobic gram-negative pathogens.

Cegepme, ceftriaxone, and cefazolin have no apprecicable activity against Bacteroides fragilis.

Question 14

In which of the following cases would it be appropriate to use telavancin?
a. A 29 yo pregnant women with ventilator-associated pneumonia
b. A 76 yo man with hospital acquired pneumonia also receiving amiodarone for A fib
c. A 36 yo M with cellulitis and abscess growing MRSA
d. A 72 yo F with a diabetic food infection growing MRSA who has moderate renal dysfunction

Answer 14

c. A 36 yo M with cellulitis and abscess growing MRSA

Option A is not good due to the potential of telavancin harming the fetus.

Option B is not a good choice because the patient is on amiodarone and telavancin can cause QTc prolongation.

Option D is not an appropriate choice because the patient has baseline renal dysfunction and telavancin should be avoided unless the benefit outweighs the risk.

Option C is the best choice since telavancin is approved for skin and skin structure infections, and the patient has no apparent contraindications.

Question 15

Which of the following genes produces a change in the PBP rendering treatment with penicillin ineffective?
a. VanA
b. mecA
c. KPC
d. AmpC

Answer 15

b. mecA

The mecA gene alteres the PBPs which makes penicillin treatment ineffective. MRSA occurs due to the presence of the mecA gene is Staphylococcus aureus.

VanA is the gene responsible for resistance to vancomycin in Enterococci.

KPC and AMpC are exaples of B-lactamases.

Question 16

An elderly homeless pt who is known to be noncompliant with medications presents to the ED with an uncomplicated skin and soft tissue infection. Which of the following abx can be used to treat the infection and avoid hospitalization?
a. Daptomycin
b. Ceftaroline
c. Vancomycin
d. Oritavancin

Answer 16

d. Oritavancin

All options can be used to treat skin and soft tissue infections. However, ortavancin is a long-acting lipoglycopeptide and can be administered as a single dose, thereby prevetning hospitalization.

Question 17

Which of the following best describes the reason imipenem is coformulated with cilastatin?
a. To protect imipenem from B-lacatmases
b. To reduce hypersensitivity reactions associated with imipenem
c. To protect imipenem from renal dehydropeptidase
d. To reduce the metabolism of imipenem

Answer 17

c. To protect imipenem from renal dehydropeptidase

Imipenem undergoes cleavage by a dehydropeptidase found in the brush border of the proximal renal tubule. Compounding imipenem with cilastatin protects the parent drug from renal dehydropeptidase and, thus, prolongs the activity in the body.

Question 18

A pt in the MICU is receiving cefepime for the tx of a UTI. The cefepime dose was adjusted due to declining renal function. On day 4 of hospitalization, the urine culture is positive for Proteus mirabilis. Which of the following is most appropriate based on the susceptibility profile below and the pt’s clinical status?

S = susceptible
I = intermediate
R = resistant

ceftriaxone - R
cefepime - R
piperacillin/tazobactam - S
colistin - S

a. Continue cefepime
b. Switch to colistin
c. Switch to piperacillin/tazobactam
d. Swtich to ceftriaxone

Answer 18

c. Switch to piperacillin/tazobactam

Although both colistin and piperacillin/tazobactam are appropriate choices since the bacteria are susceptible, zosyn is a safer selection since colistin is highly associated with nephrotoxicity and the pt already has declining renal function.

Question 19

A 75 yo M is dx’d with ventilator associated pna. A bronchoalvelar lavage is performed and respiratory culture grows carbapenem-resistant E. coli that is found to produce metallo-B-lactamase. Which of the following agents is most likely to have activity against this organism?
a. Ceftolozane/tazobactam
b. Cefiderocol
c. Meropenem/vaborbactam
d. Cefepime

Answer 19

b. Cefiderocol

Cefiderocol is the only abx listed that has activity against all carbapenemases, including metallo-B-lactamases. In addition, cefiderocol is indicated for the treatment of ventilator associated pna. The remaining abx do not provide activity against metallo-B-lactamase-producing organisms.

Question 20

Which of the following describes the mechanism of action of tetracycline antibiotics?
a. Bind the 30S subunit of the bacterial ribocome, preventing binding of tRNA to the mRNA-ribosome complex
b. Binding the 30S ribosomal subunit, interfering with assembly of the functional ribosomal apparatus
c. Bind irreversibly to a site on the 50S subunit of the bacterial ribosome, inhibiting translocation steps of protein synthesis
d. Bind the bacterial 23S ribosomal RNA of the 50S subunit, inhibiting the formation of the 70S initiation complex

Answer 20

a. Bind the 30S subunit of the bacterial ribocome, preventing binding of tRNA to the mRNA-ribosome complex

Tetracyclines enter susceptible organisms via passive diffusion and also by an energy-dependent transport protein mechanism unique to the bacterial inner cytopalsmic membrane. The drugs bind reversibly to the 30S subunit of the bacterial ribosome. This action prevents binding of tRNA to the mRNA-ribosome complex, thereby inhibiting bacterial protein synthesis.

B is the mechanism for aminoglycosides

C is the mechanism for macrolides

D is the mechanism for oxazolidinones

Question 21

Which of the following antibiotic agents should not be given to children less than 8 years of age due to its deposition in bone and teeth?
a. Azithromycin
b. Doxycycline
c. Linezolid
d. Quinupristin/dalfopristin

Answer 21

b. Doxycycline

Tetracyclines are contraindicated in this age group because they are deposited in tissues undergoing calcification, such as teeth and bone, and can stunt growth

Question 22

Aminoglycosides are commonly used for their concentration-dependent bactericidal activity against which of the following group of organisms?
a. Gram-positive aerobes
b. Gram-negative aerobes
c. Gram-positive anaerobes
d. Gram-negative anaerobes

Answer 22

b. Gram-negative aerobes

Although aminoglycosides (such as gentamicin) are somtimes used synergistically against gram-positive aerobes, this is not their most common use. They are typiclaly used for their activity against gram-negative aerobes. Aminoglycosides to not have good anaerobic activity.

Question 23

A 77 yo F was started on abx for pna tx. After 3 days of antibiotic therapy, the Scr doubled. Which of the following abx is most likely responsible for this increase om Scr?
a. Doxycycline
b. Clarithromycin
c. Tobramycin
d. Lineaolid

Answer 23

c. Tobramycin

Aminoglycosides such as tobramycin accumulate in the proximal tubular cells of the kidney and disrupt calcium-mediated transport processes. This results in kidney damage ranging from mild, reversible renal impairment to severe, potentially irreversible acute tubular necrosis.

Nephrotoxicity is not commonly associated with tetracyclines (doxycycline), macrolides (clarithromycin), or oxazolidinones (linezolid).

Question 24

A 24 yo pregnant F was dx’d with community-acquired pna and will be managed in an outpt setting. Which of the following abx is a safe option for this pt to treat her pna?
a. Azithromycin
b. Doxycycline
c. Fidaxomicin
d. Gentimicin

Answer 24

a. Azithromycin

Azithromycin is available PO and considered safe in pregnancy.

Doxycycline should not be used in pregnancy due to its ability to cross the placenta and affect bone and skeletal development in the fetus.

Fidaxomicin does not reach therapeutic concentrations in serum or at this site of infection. It concentrates in the gut.

Gentimicin crosses the placental barrier and may accumulate in fetal plasma and amniotic fluid. It would also not be used clincially in this outpt scenario.

Question 25

A pt is dx’d with C. diff-associated diarrhea. Which of the following abx is the best choice for this infection?
a. Azithromicycin
b. Clindamycin
c. Fidaxomicin
d. Tobramycin

Answer 25

c. Fidaxomicin

Fidaxomicin is the only protein synthesis inhibitor abx that is effective against C. diff diarrhea.

Question 26

Linezolid would be a good choice for abx tx in which of the following scenarios?
a. Bacteremia caused by S. aureus
b. UTI caused by E. coli
c. pna caused by drug-resistant Streptococcus pneumoniae
d. Diabetic foot infection caused by Pseudomonas aeruginosa

Answer 26

c. pna caused by drug-resistant Streptococcus pneumoniae

Linezolid does have coverage against resistant S. pneumoniae.

It is not an optimal choice for bacteremia.

Linezolid does not have coverage against gram-negative E. coli and P. aeruginosa.

Question 27

A pt has an infection with culture results showing growth of MRSA, VRE, and extended-spectrum B-lactamase-producing E. coli. Which fo the following abx would be effective against all 3 bacteria?
a. Clarithromycin
b. Linezolid
c. Quinupristin/dalfopristin
d. Tigecycline

Answer 27

d. Tigecycline

Tigecycline is active against MRSA, VRE, and ESBL-producing bacteria.

Clarithromycin is not active against MRSA.

Linezolid and quinupristin/dalfopristin are only active agaisnt gram-positive bacteria.

Question 28

A pt has pna that is requiring tx. They are receiving a SSRI for tx of depression. Which of the following abx is contraindicated in this pt?
a. Doxycycline
b. Gentamicin
c. Linezolid
d. Azithromycin

Answer 28

c. Linezolid

Due to risk of serotonin syndrome, linezolid use is contraindicated in pts taking SSRIs.

Question 29

Which of the following abx is contraindicated in a pt who is currently receiving a strong CYP3A4 inhibitor?
a. Minocycline
b. Lefamulin
c. Plazomicin
d. Fidaxomicin

Answer 29

b. Lefamulin

Due to being metabolized by CYP3A4, concomitant use of lefamulin and strong CYP3A4 inhibitors or inducers are contraindicated.

Question 30

A 32 yo M presents to an outpt clinic with a 5-day hx of productive cough, purulent sputum, and SOB. He is dx’d with community-acquired pna (CAP). It is noted that this pt has a severe ampicillin allergy (anaphylaxis). Which of the following is an acceptable tx for this pt?
a. Levofloxacin
b. Ciprofloxacin
c. Pencillin VK
d. Nitrofurantoin

Answer 30

a. Levofloxacin

S. pneumoniae is a common cause of CAP, and the respiratory fluoroquinolones levofloxacin and moxifloxacin provide good coverage.

Ciprofloxacin does not cover S. pneumoniae well ad is a poor choice for the tx of CAP.

Penicillin would be a poor choice due to allergy.

Nitrofurantoin has no clincial utility for RTI.

Question 31

Which of the following drugs is correctly matched with the appropriate adverse effect?

Answer 31

c.