Basic Principles of Antimicrobial Therapy
A patient with pneumonia needs immediate antibiotic therapy, but culture results won't be available for 48 hours. What is the most appropriate approach?
a) Wait for culture results before starting any treatment
b) Start with the narrowest-spectrum antibiotic available
c) Give multiple antibiotics to cover all possible organisms
d) Start empiric therapy with a broad-spectrum antibiotic based on likely pathogens
Answer: d) Start empiric therapy with a broad-spectrum antibiotic based on likely pathogens
Rationale: When a patient has a severe infection, treatment must begin before laboratory test results are available. Drug selection should be based on clinical evaluation and knowledge of which microbes are most likely to cause infection at that particular site. A broad-spectrum agent can be used for initial treatment, then switched to a more selective antibiotic once the identity and drug sensitivity of the infecting organism have been determined. Samples for culture must be obtained before starting treatment, as antibiotics present during sampling can suppress microbial growth and confound identification.
How do penicillins cause bacterial cell death?
a) By inhibiting protein synthesis
b) By weakening the cell wall, causing bacteria to take up water and rupture
c) By damaging bacterial DNA
d) By inhibiting metabolic enzymes
Answer: b) By weakening the cell wall, causing bacteria to take up water and rupture
Rationale: Penicillins weaken the bacterial cell wall through two mechanisms: (1) inhibition of transpeptidases and (2) activation of autolysins. The bacterial cell wall is a rigid structure that prevents expansion against high internal osmotic pressure. When penicillins weaken this wall, bacteria take up excessive amounts of water and rupture, making penicillins bactericidal. The drugs simultaneously disrupt the synthesis of the cell wall and promote its active destruction, resulting in cell lysis and death.
A patient with a history of severe penicillin allergy is prescribed cefazolin. Which nursing action is most appropriate?
a) Hold the medication and notify the provider of the allergy history
b) Administer the medication and monitor for therapeutic effect
c) Administer diphenhydramine before giving the medication
d) Document the allergy but proceed with administration
Answer: a) Hold the medication and notify the provider of the allergy history
Rationale: Cephalosporins share a beta-lactam ring with penicillins, and cross-reactivity can occur. Notify the provider before administration.
How do tetracyclines suppress bacterial growth?
a) By destroying bacterial cell walls
b) By inhibiting protein synthesis through binding to the 30S ribosomal subunit
c) By preventing DNA replication
d) By disrupting the cell membrane
Answer: b) By inhibiting protein synthesis through binding to the 30S ribosomal subunit
Rationale: Tetracyclines suppress bacterial growth by inhibiting protein synthesis. These drugs bind to the 30S ribosomal subunit and thereby inhibit the binding of transfer RNA to the messenger RNA–ribosome complex. As a result, the addition of amino acids to the growing peptide chain is prevented. At the concentrations achieved clinically, the tetracyclines are bacteriostatic rather than bactericidal.
How do sulfonamides inhibit bacterial growth?
a) By blocking the combination of PABA with pteridine to form dihydropteroic acid, thereby inhibiting folate synthesis
b) By desintegrating the bacterial cell wall
c) By preventing bacterial DNA replication
d) By disrupting the bacterial cell membrane
Answer: a) By blocking the combination of PABA with pteridine to form dihydropteroic acid, thereby inhibiting folate synthesis
Rationale: Sulfonamides are structural analogs of para-aminobenzoic acid (PABA). They suppress bacterial growth by inhibiting synthesis of tetrahydrofolate, a derivative of folate. Folate is required by all cells to make DNA, RNA, and proteins. Sulfonamides block the step in which PABA is combined with pteridine to form dihydropteroic acid. Because of their structural similarity to PABA, sulfonamides act as competitive inhibitors of this reaction. Without adequate folate synthesis, bacteria are unable to synthesize DNA, RNA, and proteins needed for growth.
A patient with acute pyelonephritis requires hospitalization due to severe symptoms including high fever, chills, and severe flank pain. What is the initial treatment approach?
a) Oral antibiotics for 3 days
b) Administer a single-dose of IV antibiotic therapy
c) IV antibiotics initially, then switch to oral antibiotics within 24 to 48 hours once infection is controlled
d) Wait for culture results before starting any treatment
Answer: c) IV antibiotics initially, then switch to oral antibiotics within 24 to 48 hours once infection is controlled
Rationale: Severe pyelonephritis requires hospitalization and IV antibiotics. Options for IV therapy include ciprofloxacin, ceftriaxone, ceftazidime, ampicillin plus gentamicin, and ampicillin/sulbactam. After the infection has been controlled with IV antibiotics, a switch to oral antibiotics should be made, usually within 24 to 48 hours. Total treatment duration should be 7 to 14 days. This approach ensures rapid control of the severe infection while allowing for transition to oral therapy once the patient stabilizes, improving patient comfort and reducing healthcare costs
A 65-year-old patient taking glucocorticoids for arthritis is prescribed ciprofloxacin for a respiratory infection. What serious adverse effect should the nurse monitor for?
a) Hyperglycemia, especially after the morning meal
b) Tendon rupture, especially of the Achilles tendon
c) Seizures
d) Hypertension
Answer: b) Tendon rupture, especially of the Achilles tendon
Rationale: Ciprofloxacin and other fluoroquinolones have caused tendon rupture, usually of the Achilles tendon. People at highest risk are those 60 years of age and older, those taking glucocorticoids, and those who have undergone heart, lung, or kidney transplantation. Because tendon injury is reversible if diagnosed early, fluoroquinolones should be discontinued at the first sign of tendon pain, swelling, or inflammation. In addition, patients should refrain from exercise until tendinitis has been ruled out. Due to this risk, fluoroquinolones received a black box warning, and it is recommended that for treatment of UTIs and sinusitis, other drugs should be used first.
What is the mechanism of action of amphotericin B?
a) It inhibits fungal cell wall synthesis
b) It inhibits fungal protein synthesis
c) It prevents fungal DNA replication
d) It binds to ergosterol in the fungal cell membrane, increasing permeability and causing leakage of intracellular contents
Answer: d) It binds to ergosterol in the fungal cell membrane, increasing permeability and causing leakage of intracellular contents
Rationale: Amphotericin B binds to components of the fungal cell membrane, increasing permeability. The resultant leakage of intracellular cations (especially potassium) reduces viability. The component of the fungal membrane to which amphotericin B binds is ergosterol, a member of the sterol family. This binding disrupts membrane integrity, leading to cell death. Depending on the concentration of amphotericin B and the susceptibility of the fungus, the drug may be fungistatic or fungicidal. Bacteria are not affected because bacterial membranes lack sterols.
What is the primary mechanism of action of acyclovir?
a) It inhibits viral protein synthesis
b) It prevents viral entry into host cells
c) It is converted to acyclovir triphosphate, which inhibits viral DNA polymerase and terminates the growing DNA chain
d) It disrupts viral cell membranes from developing and reverses the DNA replication process
Answer: c) It is converted to acyclovir triphosphate, which inhibits viral DNA polymerase and terminates the growing DNA chain
Rationale: Acyclovir is inactive in its original form and must undergo conversion to acyclovir triphosphate to be effective. This activation occurs through a series of phosphorylation reactions. The final active form, acyclovir triphosphate, has two actions: (1) it inhibits viral DNA polymerase, and (2) it becomes incorporated into the growing viral DNA chain, where it acts as a chain terminator, thereby preventing further DNA synthesis. Acyclovir is highly selective for viral DNA polymerase over human DNA polymerase, which contributes to its safety profile.
Why is rifampin always given in combination with at least one other anti-TB drug?
a) To reduce the cost of treatment
b) To prevent adverse effects
c) Because resistance can develop rapidly when rifampin is used alone
d) To improve drug absorption and to decrease GI upset symptoms
Answer: c) Because resistance can develop rapidly when rifampin is used alone
Rationale: Rifampin is one of the most effective anti-TB drugs and is bactericidal to Mycobacterium tuberculosis at both extracellular and intracellular sites. It is a drug of choice for treating pulmonary TB and disseminated disease. However, because resistance can develop rapidly when rifampin is used alone, the drug is always given in combination with at least one other anti-TB agent. Multiple-drug regimens kill or suppress the growth of organisms as quickly as possible and reduce the emergence of drug-resistant organisms. This is crucial in preventing the development of multidrug-resistant TB (MDR TB).
Why is matching the antimicrobial spectrum to the specific pathogen important?
a) It reduces healthcare costs only
b) It prevents all side effects
c) The drug should be active against the pathogen but no broader than required
d) Broad-spectrum antibiotics are always more effective
Answer: c) The drug should be active against the pathogen, but no broader than required
Rationale: A prime rule of antimicrobial therapy is to match the drug with the bug. The antimicrobial should be active against known or suspected pathogens, but its spectrum should be no broader than required. Using unnecessarily broad-spectrum agents when narrower-spectrum drugs would suffice can lead to resistance development and disruption of normal flora. The drug should be selected based on its effectiveness against the specific causative pathogen.
Why are penicillins active only against bacteria that are undergoing growth and division?
a) Penicillin-binding proteins (PBPs) are expressed only during bacterial cell growth
b) Dormant bacteria are naturally resistant to all antibiotics
c) The cell wall is thicker in dormant bacteria
d) Penicillins cannot penetrate non-dividing cells
Answer: a) Penicillin-binding proteins (PBPs) are expressed only during bacterial growth
Rationale: The molecular targets of penicillins are called penicillin-binding proteins (PBPs), which include transpeptidases, autolysins, and other bacterial enzymes. These PBPs are located on the outer surface of the cytoplasmic membrane. Bacteria express PBPs only during growth and division. Because PBPs must be present for penicillins to work, these drugs are active only when bacteria are growing and dividing.
A nurse is teaching a patient about oral cephalexin. Which statement indicates the patient needs further teaching?
a) “I should take the medication with food if it upsets my stomach.”
b) “I will complete the entire prescription even if I feel better.”
c) “If I develop diarrhea, I should stop the medication immediately.”
d) “I should report any rash or difficulty breathing to my provider.”
Answer: c) “If I develop diarrhea, I should stop the medication immediately.”
Rationale: Mild diarrhea is common, but stopping abruptly is inappropriate. Severe diarrhea may indicate C. difficile infection and should be reported.
What is the mechanism of selective toxicity for tetracyclines?
a) Tetracyclines only bind to bacterial ribosomes
b) Tetracyclines cannot enter any mammalian cells
c) Bacteria actively accumulate tetracyclines via an energy-dependent transport system that mammalian cells lack
d) Mammalian ribosomes are completely different from bacterial ribosomes
Answer: c) Bacteria actively accumulate tetracyclines via an energy-dependent transport system that mammalian cells lack
Rationale: Selective toxicity of the tetracyclines results from their poor ability to cross mammalian cell membranes. To influence protein synthesis, tetracyclines must first gain access to the cell interior. These drugs enter bacteria by way of an energy-dependent transport system. Mammalian cells lack this transport system and hence do not actively accumulate the drug. Consequently, although tetracyclines are inherently capable of inhibiting protein synthesis in mammalian cells, their levels within host cells remain too low to be harmful.
Why don't sulfonamides harm human cells even though all cells require folate?
a) Humans produce a different type of folate
b) Human cells have thicker inner and outer membranse that block sulfonamides
c) Humans have enzymes that inactivate sulfonamides
d) Mammalian cells obtain folate from dietary sources using a specialized transport system, rather than synthesizing it
Answer: d) Mammalian cells obtain folate from dietary sources using a specialized transport system rather than synthesizing it
Rationale: Bacteria are unable to take up folate from their environment, so they must synthesize it from precursors. In contrast, mammalian cells do not manufacture their own folate. Instead, they simply take up folate obtained from the diet using a specialized transport system for uptake. Because mammalian cells use preformed folate rather than synthesizing it, sulfonamides are harmless to us. This selective toxicity makes sulfonamides safe for human use while remaining effective against bacteria.
A 28-year-old woman experiences her fourth urinary tract infection in the past year, all occurring within 2 days after sexual intercourse. What prophylactic approach is most appropriate?
a) Continuous daily antibiotics for life for the partner
b) Double strength antibiotics taken before intercourse
c) Avoiding all sexual activity for 3-6 months
d) Single-dose antibiotic therapy taken after intercourse
Answer: d) Single-dose antibiotic therapy taken after intercourse
Rationale: More than 80% of recurrent UTIs in females result from reinfection, which may be related to sexual intercourse. If reinfection is associated with sexual intercourse, the risk can be decreased by voiding after intercourse and by single-dose prophylaxis (e.g., TMP/SMX taken after intercourse). The three most common drug treatment regimens for postcoital prophylaxis are: (1) one low-dose tablet of trimethoprim, (2) sulfamethoxazole/trimethoprim, or (3) nitrofurantoin. This targeted approach prevents infection without requiring continuous antibiotic use.
A patient on ciprofloxacin therapy plans to spend the day at the beach. What essential patient education should the nurse provide?
a) Expose as much skin as possible to sunlight to enhance the absorbtion and effectiveness of the medication
b) Take an extra dose of the medication before each sun exposure
c) Avoid sunlight and sunlamps; wear protective clothing and apply sunscreen; discontinue at first sign of phototoxic reaction
d) Sunlight exposure has no effect on fluoroquinolone therapy
Answer: c) Avoid sunlight and sunlamps; wear protective clothing and apply sunscreen; discontinue at first sign of phototoxic reaction
Rationale: Ciprofloxacin and other fluoroquinolones pose a risk of phototoxicity (severe sunburn), characterized by burning, erythema, exudation, vesicles, blistering, and edema. These reactions can occur after exposure to direct sunlight, indirect sunlight, and sunlamps even if a sunscreen has been applied. Patients should be warned about phototoxicity and advised to avoid sunlight and sunlamps. People who must go outdoors should wear protective clothing and apply sunscreen. Ciprofloxacin should be withdrawn at the first sign of a phototoxic reaction (e.g., burning sensation, redness, rash).
A patient receiving IV amphotericin B develops fever, chills, rigors, nausea, and headache 2 hours after the infusion begins. What is the best explanation for these symptoms?
a) The patient is experiencing an allergic reaction
b) These are infusion reactions caused by the release of proinflammatory cytokines from monocytes and macrophages
c) The patient has developed sepsis
d) The amphotericin B is contaminated
Answer: b) These are infusion reactions caused by the release of proinflammatory cytokines from monocytes and macrophages
Rationale: Intravenous amphotericin frequently produces fever, chills, rigors, nausea, and headache. These reactions are caused by the release of proinflammatory cytokines (tumor necrosis factor, interleukin-1, interleukin-6) from monocytes and macrophages. Symptoms begin 1 to 3 hours after starting the infusion and persist about 1 hour. Mild reactions can be reduced by pretreatment with diphenhydramine plus acetaminophen. Intravenous meperidine or dantrolene can be given if rigors occur. Infusion reactions are less intense with lipid-based amphotericin formulations than with the conventional formulation.
A patient with renal impairment is prescribed acyclovir. Why must the dosage be adjusted?
a) Renal impairment increases drug absorption
b) Acyclovir is eliminated primarily by the kidneys; renal impairment prolongs the half-life from 2.5 hours to 20 hours in anuric patients
c) Renal disease increases the risk of allergic reactions
d) The drug is more toxic when metabolized by the kidneys
Answer: b) Acyclovir is eliminated primarily by the kidneys; renal impairment prolongs the half-life from 2.5 hours to 20 hours in anuric patients
Rationale: Elimination of acyclovir is renal, primarily as the unchanged drug. In patients with normal kidney function, acyclovir has a half-life of 2.5 hours. The half-life is prolonged by renal impairment, reaching 20 hours in anuric patients. Accordingly, dosages should be reduced in patients with kidney disease. This dosage adjustment is critical to prevent drug accumulation and potential toxicity. Similar considerations apply to other antiviral agents that are renally eliminated.
A patient with HIV infection and active tuberculosis is being started on rifampin. What important drug interaction should the nurse discuss?
a) Rifampin enhances the effects of all HIV medications
b) Rifampin can accelerate the metabolism of most protease inhibitors and NNRTIs, decreasing their effectiveness
c) HIV medications increase rifampin toxicity
d) There are no significant interactions between TB and HIV drugs
Answer: b) Rifampin can accelerate the metabolism of most protease inhibitors and NNRTIs, decreasing their effectiveness
Rationale: Drug interactions between drugs for TB infection and drugs for HIV infection are a common problem, especially for patients taking rifampin. Rifampin, a cornerstone of TB therapy, can accelerate the metabolism of most protease inhibitors and most nonnucleoside reverse transcriptase inhibitors (NNRTIs) used to treat HIV and can thereby decrease their effects. This creates a therapeutic dilemma: if patients take rifampin to treat TB, they will be unable to take most protease inhibitors or NNRTIs for HIV. Rifabutin is an alternative that causes less acceleration of antiretroviral drug metabolism, allowing many antiretroviral drugs to still be used effectively.
A patient with severe immunocompromise develops a bacterial infection. What is the primary goal of antibiotic therapy in this patient?
a) To completely eliminate all bacteria without help from the immune system
b) To use rapidly bactericidal drugs since host defenses cannot adequately assist
c) To use only narrow-spectrum antibiotics
d) To wait for the immune system to recover before treating
Answer: b) To use rapidly bactericidal drugs since host defenses cannot adequately assist
Rationale: Host defenses (immune system and phagocytic cells) are critical for successful antimicrobial therapy. In most cases, drugs work in concert with the host's defense systems to subdue infections—the usual objective is to suppress microbial growth to the point where the balance tips in favor of the host. When treating immunocompromised patients (such as those with AIDS or undergoing cancer chemotherapy), the only hope lies with rapidly bactericidal drugs, as these patients' impaired defenses cannot adequately assist in fighting infection. Even bactericidal drugs may prove inadequate in severely immunocompromised hosts.
What is the primary mechanism by which bacteria develop resistance to penicillins?
a) Altered ribosomes
b) Thickening of the cell wall
c) Production of beta-lactamases (penicillinases) that cleave the beta-lactam ring
d) Increased efflux pumps
Answer: c) Production of beta-lactamases (penicillinases) that cleave the beta-lactam ring
Rationale: Beta-lactamases are enzymes that cleave the beta-lactam ring and thereby render penicillins inactive. Penicillinases are beta-lactamases that act selectively on penicillins. These enzymes are produced by both gram-positive and gram-negative bacteria. Gram-positive organisms produce large amounts and export them into the surrounding medium, while gram-negative bacteria produce smaller amounts and secrete them into the periplasmic space. The genes for beta-lactamases can be transferred between bacteria via plasmids, promoting the spread of resistance.
Which nursing consideration is most important when administering ceftriaxone to a neonate?
a) Monitor for nephrotoxicity
b) Avoid concurrent administration with calcium-containing IV solutions
c) Administer with food to reduce GI upset
d) Monitor for ototoxicity
Answer: b)
Rationale: Ceftriaxone can precipitate with calcium in neonates, leading to fatal reactions. Avoid concurrent administration
A 6-year-old child with a bacterial infection is prescribed an antibiotic. Why should tetracyclines be avoided in this patient?
a) Children cannot swallow tetracycline tablets
b) Children are allergic to all tetracyclines
c) Tetracyclines are ineffective in children
d) Tetracyclines cause permanent discoloration of teeth when given to children younger than 8 years
Answer: d) Tetracyclines cause permanent discoloration of teeth when given to children younger than 8 years
Rationale: Tetracyclines bind to calcium in developing teeth, resulting in yellow or brown discoloration; hypoplasia of the enamel may also occur. Discoloration of permanent teeth occurs when tetracyclines are taken by patients age 4 months to 8 years, the interval during which tooth enamel is being formed. Accordingly, these drugs should be avoided by children younger than 8 years. The intensity of tooth discoloration is related to the total cumulative dose, with staining becoming darker with prolonged and repeated treatment.
A patient develops a rash after starting sulfonamide therapy. What is the most appropriate nursing action?
a) Discontinue the sulfonamide immediately to minimize risk of severe reactions
b) Apply topical corticisteroid cream and continue the medication
c) Reduce the dose by half
d) Reassure the patient that rashes are normal and harmless
Answer: a) Discontinue the sulfonamide immediately to minimize risk of severe reactions
Rationale: Sulfonamides can induce various hypersensitivity reactions in about 3% of patients. While mild reactions like rash are relatively common, there is a risk of progression to Stevens-Johnson syndrome, a rare but severe reaction with a mortality rate of about 25%. Symptoms include widespread lesions of the skin and mucous membranes, combined with fever, malaise, and toxemia. To minimize the risk for severe reactions, sulfonamides should be discontinued immediately if skin rash of any sort is observed. Early recognition and prompt discontinuation are essential safety measures.
A male patient with benign prostatic hypertrophy develops a complicated UTI with severe symptoms. Why must the causative organism be identified before selecting antibiotic therapy?
a) The microbiology of complicated UTIs is less predictable, involving various organisms beyond E. coli
b) All antibiotics are equally effective for complicated UTIs
c) Males cannot be treated empirically under any circumstances because they generally refuse to comply with long term treatments
d) Complicated UTIs are always fungal infections
Answer: a) The microbiology of complicated UTIs is less predictable, involving various organisms beyond E. coli
Rationale: Complicated UTIs occur in patients with structural or functional abnormalities of the urinary tract that predispose them to infection (such as prostatic hypertrophy, renal calculi, or indwelling catheters). The microbiology of complicated UTIs is less predictable than uncomplicated UTIs. Although E. coli is common, other possibilities include Klebsiella species, Proteus species, Pseudomonas species, Staphylococcus aureus, Enterobacter species, Serratia species, and even Candida species. For treatment to succeed, the identity and drug sensitivity of the causative organism must be determined. Urine for microbiologic testing should be obtained before giving antibiotics.
Question 3
Why is rifaximin (Xifaxan) an appropriate choice for traveler's diarrhea caused by E. coli?
a) It is absorbed systemically and treats all types of infections
b) It is the only known antibiotic to be effective against E. coli
c) It can be given intravenously for faster action
d) It is a nonabsorbable oral antibiotic that achieves high concentrations in the intestinal tract.
Answer: d) It is a nonabsorbable oral antibiotic that achieves high concentrations in the intestinal tract
Rationale: Rifaximin is an oral nonabsorbable analog of rifampin used to kill bacteria in the gut. It inhibits bacterial DNA-dependent RNA polymerase, resulting in inhibition of protein synthesis and bacterial death. Rifaximin is administered by mouth, and very little (less than 0.4%) is absorbed. As a result, the drug achieves high concentrations in the intestinal tract and is excreted unchanged in the stool. This makes it ideal for treating intestinal infections like traveler's diarrhea. However, rifaximin is not effective against severe diarrhea associated with fever or bloody stools and should not be used if these are present.
A patient with vulvovaginal candidiasis asks about treatment options. Which statement about treatment is correct?
a) Just 1 or 3 days of topical therapy can be curative, or a single 150-mg dose of oral fluconazole
b) Treatment requires at least 2 weeks of therapy and 3 months of prophylactic antibiotics
c) Oral medications are always more effective than topical agents
d) Antibiotics are the preferred treatment
Answer: a) Just 1 or 3 days of topical therapy can be curative, or a single 150-mg dose of oral fluconazole
Rationale: Vulvovaginal candidiasis is very common, occurring in 75% of women at least once in their lives. With current drugs, just 1 or 3 days of topical therapy can be curative. In addition, oral therapy may be used: A single 150-mg dose of fluconazole can be curative, but it causes more side effects (headache, rash, GI disturbance) than topical agents. Major drugs for uncomplicated vulvovaginal candidiasis appear equally effective, so drug selection is based largely on patient preference. Longer regimens have no demonstrated advantage over shorter ones.
What is the optimal timing for initiating zanamivir or oseltamivir treatment for influenza?
a) Within 12 hours of symptom onset for maximum benefit; no later than 2 days after onset
b) Within 7 days of symptom onset and no later than 14 days after onset
c) Treatment can begin at any time during the illness
d) Only after laboratory confirmation of influenza
Answer: a) Within 12 hours of symptom onset for maximum benefit; no later than 2 days after onset
Rationale: Dosing must begin early—preferably no later than 2 days after symptom onset and ideally much sooner. This is important because benefits decline greatly when treatment is delayed. When treatment is started within 12 hours of symptom onset, symptom duration is reduced by more than 3 days; when started within 24 hours, symptom duration is reduced by less than 2 days; and when started within 36 hours, symptom duration is reduced by only 29 hours. Unfortunately, in the real world, patients may be unable to obtain and fill a prescription soon enough for the drug to be of significant benefit.
A patient on pyrazinamide therapy develops malaise, anorexia, nausea, vomiting, and jaundice. What is the priority nursing action?
a) Encourage the patient to continue taking the medication until they finish the prescribed course
b) Advise taking the medication with food every morning
c) Inform the prescriber immediately as these are signs of hepatotoxicity; pyrazinamide should be discontinued
d) Reduce the dose by half
Answer: c) Inform the prescriber immediately as these are signs of hepatotoxicity; pyrazinamide should be discontinued
Rationale: Pyrazinamide is the most hepatotoxic of all the first-line TB drugs. High-dose therapy has caused hepatitis and, rarely, fatal hepatic necrosis. The earliest manifestations of liver damage are elevations in serum levels of transaminases (AST and ALT). Patients should be informed about signs of hepatitis (e.g., malaise, anorexia, nausea, vomiting, jaundice) and instructed to notify the prescriber if they develop. Pyrazinamide should be discontinued if significant injury to the liver occurs. The drug should not be used by patients with preexisting liver disease. The risk for liver injury is increased by concurrent therapy with isoniazid or rifampin.
When would an alternative antimicrobial agent be chosen instead of the drug of first choice?
a) When the first-choice drug is more expensive
b) When the patient is allergic to the drug of choice
c) When the patient prefers oral medication
d) When the pharmacy doesn't stock the first-choice drug
Answer: b) When the patient is allergic to the drug of choice
Rationale: For most infections, there is usually one drug that is superior to alternatives—the drug of first choice. This drug may be preferred for greater efficacy, lower toxicity, or more narrow spectrum. Whenever possible, the drug of first choice should be employed. Alternative agents should be used only when the first-choice drug is inappropriate. Conditions that rule out a first-choice agent include: (1) allergy to the drug of choice, (2) inability of the drug to penetrate to the site of infection, and (3) heightened susceptibility of the patient to toxicity of the first-choice drug.
Why are penicillinase-resistant penicillins considered to have a narrow antimicrobial spectrum?
a) They only work against viral infections
b) They are less effective than penicillin G against all bacteria
c) They cannot penetrate any bacterial cell walls
d) They are used specifically against penicillinase-producing staphylococci
Answer: d) They are used specifically against penicillinase-producing staphylococci
Rationale: Penicillinase-resistant penicillins (nafcillin, oxacillin, and dicloxacillin) have a very narrow antimicrobial spectrum and are used only against penicillinase-producing strains of staphylococci (S. aureus and S. epidermidis). Because most strains of staphylococci produce penicillinase, these drugs are the drugs of choice for the majority of staphylococcal infections. However, they should not be used against infections caused by non-penicillinase-producing staphylococci because they are less active than penicillin G against these bacteria.
How do cephalosporins compare to penicillins in terms of beta-lactamase resistance across generations?
a) All cephalosporins are equally susceptible to beta-lactamases
b) First-generation are destroyed; second-generation less sensitive; third-, fourth-, and fifth-generation are highly resistant
c) Only fifth-generation cephalosporins are susceptible
d) Cephalosporins are completely immune to all beta-lactamases
Answer: b) First-generation are destroyed; second-generation less sensitive; third-, fourth-, and fifth-generation are highly resistant
Rationale: Not all cephalosporins are equally susceptible to beta-lactamases. Most first-generation cephalosporins are destroyed by beta-lactamases; second-generation cephalosporins are less sensitive to destruction; and third-, fourth-, and fifth-generation cephalosporins are highly resistant. Some beta-lactamases that act on cephalosporins (called cephalosporinases) can also cleave the beta-lactam ring of penicillins. This progressive resistance to beta-lactamases is a key advantage of newer generation cephalosporins.
A patient with significant renal impairment needs tetracycline therapy. Which tetracycline would be the safest choice?
a) Tetracycline
b) Demeclocycline
c) Doxycycline
d) All tetracyclines are equally safe in renal impairment
Answer: c) Doxycycline
Rationale: Tetracycline and demeclocycline are eliminated primarily in the urine and hence accumulate to toxic levels in patients with kidney disease. Accordingly, patients with kidney disease should not use these drugs. Long-acting tetracyclines (doxycycline and minocycline) are eliminated by the liver, primarily as metabolites. Because these agents are excreted by the liver, their half-lives are unaffected by kidney dysfunction. Accordingly, the long-acting agents are drugs of choice for tetracycline-responsive infections in patients with renal impairment.
Why should sulfonamides not be administered to infants younger than 2 months of age?
a) Their kidneys cannot excrete the drug
b) They lack the enzymes to metabolize sulfonamides
c) Sulfonamides displace bilirubin from plasma proteins, increasing the risk of kernicterus
d) Infants are always allergic to sulfonamides
Answer: c) Sulfonamides displace bilirubin from plasma proteins, increasing the risk of kernicterus
Rationale: Kernicterus is a disorder in newborns caused by the deposition of bilirubin in the brain. Bilirubin is neurotoxic and can cause severe neurologic deficits and even death. Under normal conditions, infants are not vulnerable to kernicterus because bilirubin in their blood is tightly bound to plasma proteins and therefore is not free to enter the central nervous system (CNS). Sulfonamides promote kernicterus by displacing bilirubin from plasma proteins. Because the blood-brain barriers of infants are poorly developed, the newly freed bilirubin has easy access to sites within the brain. Therefore, sulfonamides should not be administered to infants younger than 2 months of age, pregnant patients after 32 weeks of gestation, or those who are breastfeeding.
A 35-year-old woman has experienced six urinary tract infections over the past year. What long-term management strategy is most appropriate?
a) No treatment unless symptoms occur
b) Low-dose prophylactic antibiotics (such as TMP/SMX, trimethoprim, or nitrofurantoin) for at least 6 months with periodic urine cultures
c) High-dose antibiotics taken weekly
d) Immediate referral for surgical intervention
Answer: b) Low-dose prophylactic antibiotics (such as TMP/SMX, trimethoprim, or nitrofurantoin) for at least 6 months with periodic urine cultures
Rationale: When reinfections are frequent (three or more per year), long-term prophylaxis may be indicated. Prophylaxis can be achieved with low daily doses of several agents, including trimethoprim (100 mg), nitrofurantoin (50 or 100 mg), or TMP/SMX (40 mg/200 mg). Prophylaxis should continue for at least 6 months. During this time, periodic urine cultures should be obtained to monitor effectiveness. If a symptomatic episode occurs during prophylaxis, standard therapy for acute cystitis should be given. This approach significantly reduces the frequency of recurrent infections and improves quality of life.
A patient with chronic liver disease and hepatic encephalopathy is prescribed rifaximin. What is the rationale for this treatment?
a) Rifaximin kills intestinal bacteria that produce ammonia, preventing brain injury
b) Rifaximin treats the underlying liver disease and stimulates brain cell production
c) Rifaximin increases liver enzyme production in the first 3 days of treatment
d) Rifaximin enhances protein absorption
Answer: a) Rifaximin kills intestinal bacteria that produce ammonia, preventing brain injury
Rationale: Rifaximin was approved for the prevention of hepatic encephalopathy (brain injury) in patients with chronic liver disease. In all of us, intestinal bacteria produce ammonia, a toxic substance normally cleared by the liver. However, in patients with liver disease, the liver cannot remove much ammonia, and it can accumulate to levels that harm the brain. Rifaximin helps prevent encephalopathy by killing the intestinal bacteria that produce ammonia. For this indication, the dosage is 550 mg twice daily for as long as needed.
A patient taking oral terbinafine for a toenail fungal infection reports persistent nausea, fatigue, dark urine, and right upper abdominal pain. What should the nurse do?
a) Reassure the patient these are normal side effects
b) Advise the patient to take the medication with food
c) Instruct the patient to discontinue terbinafine immediately and undergo evaluation of liver function
d) Tell the patient to reduce the dose by half
Answer: c) Instruct the patient to discontinue terbinafine immediately and undergo evaluation of liver function
Rationale: Oral terbinafine may pose a risk of liver failure. Some terbinafine users have died of liver failure, and others have required a liver transplant. Patients should be informed about signs of liver dysfunction (persistent nausea, anorexia, fatigue, vomiting, jaundice, right upper abdominal pain, dark urine, pale stools), and if they appear, patients should discontinue terbinafine immediately and undergo evaluation of liver function. Baseline tests for serum alanine and aspartate aminotransferases are recommended. Terbinafine is not recommended for patients with preexisting liver disease.
A patient with asthma is prescribed zanamivir for influenza. What serious adverse effect should the nurse monitor for?
a) Liver failure
b) Cardiac arrhythmias and high risk for developing right-sided congestive heart failure
c) Renal toxicity
d) Severe bronchospasm and respiratory decline
Answer: d) Severe bronchospasm and respiratory decline
Rationale: In patients with preexisting lung disorders (e.g., asthma, chronic obstructive pulmonary disease), zanamivir may cause severe bronchospasm and respiratory decline. Some patients have required immediate treatment or hospitalization. Deaths have occurred. Nevertheless, given the effect of influenza itself on lung function, it is not clear that zanamivir was the cause. Nonetheless, because of the potential risk, zanamivir is not recommended for patients with underlying airway disease. Because zanamivir is administered as an inhaled powder, even patients with healthy lung function may experience cough or throat irritation.
What is the most critical nursing intervention to prevent the development of multidrug-resistant tuberculosis (MDR TB)?
a) Ensuring strict adherence to the prescribed drug regimen for the full duration of treatment
b) Administering high doses of antibiotics to destroy the infection earlyand prevent spreading
c) Isolating the patient permanently
d) Using only one antibiotic at a time until clear signs of improvement are noted
Answer: a) Ensuring strict adherence to the prescribed drug regimen for the full duration of treatment
Rationale: Strict adherence to the prescribed drug regimen is crucial for suppressing TB disease. Adherence is difficult because of the long duration of treatment (6 to 9 months for traditional regimens, or 4 months for newer shortened regimens). The most common cause of MDR TB and XDR TB is misuse or mismanagement of drug therapy, either from inappropriate selection or use of antibiotics. Not taking the drugs as prescribed could lead to a drug-resistant infection. Nursing interventions focus on patient teaching for drug adherence, providing accurate information in multiple formats, and emphasizing that failure to adhere could result in treatment failure and drug resistance.
A patient with bacterial meningitis requires antibiotic therapy. What special consideration must be made regarding the site of infection?
a) Oral antibiotics are preffered for meningitis
b) Lower doses are needed because the brain is small
c) Any antibiotic will work since bacteria are present
d) The antibiotic must be able to cross the blood-brain barrier to reach the therapeutic concentrations
Answer: d) The antibiotic must be able to cross the blood-brain barrier to reach therapeutic concentrations
Rationale: To be effective, an antibiotic must be present at the site of infection in a concentration greater than the minimum inhibitory concentration (MIC). At some sites, drug penetration may be hampered, making it difficult to achieve the MIC. In meningitis, the blood-brain barrier impedes drug access. Two approaches can be used: (1) select a drug that readily crosses the blood-brain barrier, or (2) inject an antibiotic directly into the subarachnoid space. The site of infection significantly impacts drug selection and route of administration to ensure adequate drug concentrations reach the infected area.
Why are penicillins generally more effective against gram-positive bacteria than gram-negative bacteria?
a) Gram-positive bacteria have no defense mechanisms
b) The gram-positive cell wall is easily penetrated, giving penicillins easy access to PBPs
c) Gram-negative bacteria are viruses
d) Penicillins only bind to gram-positive cell walls
Answer: b) The gram-positive cell wall is easily penetrated, giving penicillins easy access to PBPs
Rationale: The gram-positive cell envelope has only two layers: the cytoplasmic membrane plus a relatively thick cell wall. Despite its thickness, the cell wall can be readily penetrated by penicillins, giving them easy access to PBPs on the cytoplasmic membrane. In contrast, the gram-negative cell envelope has three layers, including an additional outer membrane that is difficult to penetrate. As a result, only certain penicillins (e.g., ampicillin) can cross the outer membrane and reach PBPs on the cytoplasmic membrane.
What is special about ceftaroline (a fifth-generation cephalosporin) compared to most other cephalosporins?
a) It has demonstrated activity against MRSA
b) It is the only oral cephalosporin
c) It has no side effects
d) It works against viral infections
Answer: a) It has demonstrated activity against MRSA
Rationale: Methicillin-resistant staphylococci produce altered PBPs that have a low affinity for cephalosporins, making most cephalosporins ineffective against MRSA. However, ceftaroline, a fifth-generation cephalosporin, has demonstrated activity against methicillin-resistant Staphylococcus aureus (MRSA). This makes ceftaroline unique among cephalosporins and provides an important treatment option for MRSA infections beyond vancomycin.
What is the proper administration instruction for oral tetracyclines?
a) Take with milk to reduce stomach upset
b) Take on an empty stomach with a full glass of water, at least 2 hours before or after dairy products or antacids
c) Take with calcium supplements to prevent bone loss
d) Take with meals for better absorption
Answer: b) Take on an empty stomach with a full glass of water, at least 2 hours before or after dairy products or antacids
Rationale: Oral tetracyclines should be taken on an empty stomach (1 hour before meals or 2 hours after) and with a full glass of water. An interval of at least 2 hours should separate tetracycline ingestion and the ingestion of products that can chelate these drugs (e.g., milk, calcium or iron supplements, antacids). Chelation—the binding of tetracyclines to these substances—significantly reduces drug absorption and effectiveness, making proper timing of administration essential for therapeutic success.
What patient education should the nurse provide to minimize the risk of renal damage from sulfonamides?
a) Take the medication with antacids
b) Maintain daily urine output of at least 1200 mL by drinking 8 to 10 glasses of water each day
c) Restrict fluid intake to concentrate the urine
d) Take the medication only with meals
Answer: b) Maintain daily urine output of at least 1200 mL by drinking 8 to 10 glasses of water each day
Rationale: Because of their low solubility, older sulfonamides tended to come out of solution in the urine, forming crystalline aggregates in the kidneys, ureters, and bladder. These aggregates cause irritation and obstruction, sometimes resulting in anuria and even death. Renal damage is less common with today's sulfonamides, but there is still a risk. To minimize the risk for renal damage and crystalluria, adults should maintain a daily urine output of at least 1200 mL. This can be accomplished by consuming at least 8 to 10 glasses of water each day. High urine flow helps prevent crystal formation and keeps the urinary tract flushed.
A 22-year-old female college student presents with dysuria, urinary frequency, and suprapubic discomfort that began 2 days ago. She has no fever or flank pain. What is the most appropriate first-line antibiotic therapy?
a) Ciprofloxacin for 14 days
b) Trimethoprim/sulfamethoxazole (TMP/SMX) or nitrofurantoin for 3 days
c) Ampicillin/sulbactam IV
d) Fosfomycin single dose followed by 7 days of cephalexin
Answer: b) Trimethoprim/sulfamethoxazole (TMP/SMX) or nitrofurantoin for 3 days
Rationale: This patient has acute uncomplicated cystitis. Guidelines for uncomplicated cystitis recommend nitrofurantoin, trimethoprim/sulfamethoxazole, or fosfomycin as first-line therapy for patients at low risk of antimicrobial resistance. Short-course therapy (3 days) is generally more effective than single-dose therapy and is preferred for uncomplicated, community-associated infections in non-pregnant women whose symptoms began less than 7 days before treatment. Short-course therapy offers advantages including lower cost, greater adherence, fewer side effects, and less potential for promoting bacterial resistance compared to conventional 5-7 day therapy.
A patient is prescribed fidaxomicin (Dificid) for Clostridioides difficile infection (CDI). What advantage does fidaxomicin have over vancomycin for this indication?
a) It can be given intravenously
b) It is less expensive and prevents the patient for harmful side effects
c) It has a higher cure rate and lower recurrence rate
d) It works faster with symptom relief in 24 hours
Answer: c) It has a higher cure rate and lower recurrence rate
Rationale: Fidaxomicin is a narrow-spectrum bactericidal antibiotic indicated only for diarrhea associated with Clostridioides difficile infection (CDI). In one trial, fidaxomicin was compared with vancomycin, a standard treatment for CDI. The cure rate with fidaxomicin was higher than with vancomycin, and the recurrence rate was lower. Like rifaximin, fidaxomicin inhibits DNA-dependent RNA polymerase, causing inhibition of protein synthesis and bacterial death. It is administered orally with low systemic absorption, achieving high concentrations in the intestine where it kills C. difficile. The dosage is 200 mg twice daily with or without food.
An HIV-positive patient develops oral candidiasis (thrush). What is the recommended first-line treatment approach?
a) IV amphotericin B
b) Topical therapy with clotrimazole troches or miconazole mucoadhesive buccal tablets
c) Surgical debridement
d) No treatment is needed as it will resolve spontaneously
Answer: b) Topical therapy with clotrimazole troches or miconazole mucoadhesive buccal tablets
Rationale: Patients infected with HIV frequently develop infection with Candida species, usually Candida albicans. Up to 75% of patients experience oral candidiasis (thrush), which often responds to topical therapy, such as clotrimazole troches, which are allowed to dissolve in the mouth, or miconazole mucoadhesive buccal tablets, which are applied to the mucosal surface over the canine fossa. Systemic therapy with the oral azole fluconazole is an alternative for oral candidiasis. Oral azoles are more convenient than topical therapy and probably more effective; however, they are also more expensive.
A patient on zidovudine therapy requires blood count monitoring. What hematologic adverse effect is of greatest concern?
a) Elevated white blood cell count
b) Bone marrow suppression resulting in granulocytopenia and thrombocytopenia
c) Polycythemia
d) Elevated platelet count
Answer: b) Bone marrow suppression resulting in granulocytopenia and thrombocytopenia
Rationale: The adverse effect of greatest concern with zidovudine is bone marrow suppression, which can result in granulocytopenia and thrombocytopenia. These effects, which are usually reversible, are more likely with IV therapy than with oral therapy. Because of the risk for adverse hematologic effects, blood cell counts must be monitored. Treatment should be interrupted if the absolute neutrophil count falls below 500/mm³ or if the platelet count falls below 25,000/mm³. Cell counts usually begin to recover within 3 to 5 days. Zidovudine should be used with caution in patients with preexisting cytopenias.
A patient with latent tuberculosis infection (LTBI) who is HIV-positive and taking antiretroviral drugs asks about treatment options. Which drug might be most appropriate?
a) Rifampin only
b) Rifapentine only
c) Isoniazid, which may be the treatment of choice due to significant interactions between rifapentine/rifampin and antiretroviral drugs
d) No treatment is needed for latent TB
Answer: c) Isoniazid, which may be the treatment of choice due to significant interactions between rifapentine/rifampin and antiretroviral drugs
Rationale: For more than 30 years, daily or twice-weekly isoniazid has been the standard treatment for patients with latent tuberculosis infection (LTBI). While isoniazid is no longer recommended as the sole agent for all patients with LTBI, it still has a place in therapy and may be the treatment of choice for patients who have HIV infection and who are taking antiretroviral drugs that have significant interaction with rifapentine and rifampin. This is because rifamycin drugs (rifampin and rifapentine) can significantly reduce the effectiveness of many antiretroviral medications by accelerating their metabolism, creating a therapeutic challenge in co-infected patients.