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Questions and Answers
Antimicrobial drugs have the ability to injure or kill an invading microorganism without harming the cells of the __________.
Antimicrobial drugs have the ability to injure or kill an invading microorganism without harming the cells of the __________.
host
Selection of the most appropriate antimicrobial agent requires knowing the organism’s __________.
Selection of the most appropriate antimicrobial agent requires knowing the organism’s __________.
identity
A rapid assessment of the nature of the pathogen can sometimes be made on the basis of the __________ stain.
A rapid assessment of the nature of the pathogen can sometimes be made on the basis of the __________ stain.
Gram
Patients require __________ therapy when immediate treatment is necessary.
Patients require __________ therapy when immediate treatment is necessary.
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Identifying the __________ of the infection is essential to choosing the correct antimicrobial agent.
Identifying the __________ of the infection is essential to choosing the correct antimicrobial agent.
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Characterizing the organism is central to the selection of the proper __________.
Characterizing the organism is central to the selection of the proper __________.
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It is generally necessary to __________ the infective organism for a conclusive diagnosis.
It is generally necessary to __________ the infective organism for a conclusive diagnosis.
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Factors such as patient __________ and cost of therapy are important in the selection of an antimicrobial agent.
Factors such as patient __________ and cost of therapy are important in the selection of an antimicrobial agent.
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Some β-lactam antibiotics can enter the ______.
Some β-lactam antibiotics can enter the ______.
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A compound with a ______ molecular weight has an enhanced ability to cross the blood–brain barrier.
A compound with a ______ molecular weight has an enhanced ability to cross the blood–brain barrier.
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Compounds with a high molecular weight penetrate poorly, even in the presence of ______ inflammation.
Compounds with a high molecular weight penetrate poorly, even in the presence of ______ inflammation.
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A high degree of ______ binding of a drug restricts its entry into the CSF.
A high degree of ______ binding of a drug restricts its entry into the CSF.
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The amount of ______ drug in serum is important for CSF penetration.
The amount of ______ drug in serum is important for CSF penetration.
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Multidrug-resistant organisms (MDROs) have developed resistance to multiple classes of ______.
Multidrug-resistant organisms (MDROs) have developed resistance to multiple classes of ______.
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Elimination of infecting organisms from the body depends on an intact ______ system.
Elimination of infecting organisms from the body depends on an intact ______ system.
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Poor ______ function may cause accumulation of certain antibiotics.
Poor ______ function may cause accumulation of certain antibiotics.
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Serum creatinine levels are used as an index of ______ function for adjustment of drug regimens.
Serum creatinine levels are used as an index of ______ function for adjustment of drug regimens.
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Direct monitoring of serum levels is preferred for identifying ______ toxicities.
Direct monitoring of serum levels is preferred for identifying ______ toxicities.
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Certain combinations of antibiotics show ______, meaning the combination is more effective than either of the drugs used separately.
Certain combinations of antibiotics show ______, meaning the combination is more effective than either of the drugs used separately.
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Drug A activity 30% + Drug B activity 20% = ______ for the addition effect.
Drug A activity 30% + Drug B activity 20% = ______ for the addition effect.
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Drug A activity 30% + Drug B activity 20% = ______ for the synergistic effect.
Drug A activity 30% + Drug B activity 20% = ______ for the synergistic effect.
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A bacteriostatic agent may interfere with the action of a ______ agent.
A bacteriostatic agent may interfere with the action of a ______ agent.
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Most gram-negative organisms are inherently resistant to ______.
Most gram-negative organisms are inherently resistant to ______.
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Acquired antibiotic resistance often involves the gain or alteration of bacterial ______ information.
Acquired antibiotic resistance often involves the gain or alteration of bacterial ______ information.
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Resistance can develop from DNA undergoing spontaneous ______ or through movement between organisms.
Resistance can develop from DNA undergoing spontaneous ______ or through movement between organisms.
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Other antimicrobial agents, such as ______, have less specificity and are reserved for life-threatening infections.
Other antimicrobial agents, such as ______, have less specificity and are reserved for life-threatening infections.
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The choice of therapy usually centers on the site of infection, severity of the illness, and ______ to take oral medications.
The choice of therapy usually centers on the site of infection, severity of the illness, and ______ to take oral medications.
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Treatment of methicillin-resistant ______ aureus (MRSA) generally includes drugs like vancomycin and linezolid.
Treatment of methicillin-resistant ______ aureus (MRSA) generally includes drugs like vancomycin and linezolid.
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Parenteral administration is used for drugs that are poorly absorbed from the ______ tract.
Parenteral administration is used for drugs that are poorly absorbed from the ______ tract.
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Rational dosing of antimicrobial agents is based on their pharmacodynamics and ______ properties.
Rational dosing of antimicrobial agents is based on their pharmacodynamics and ______ properties.
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Three important properties that influence the frequency of dosing are concentration dependent killing, time-dependent killing, and ______ effect.
Three important properties that influence the frequency of dosing are concentration dependent killing, time-dependent killing, and ______ effect.
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The oral route of administration is appropriate for ______ infections that can be treated on an outpatient basis.
The oral route of administration is appropriate for ______ infections that can be treated on an outpatient basis.
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Some antibiotics, such as ______ and aminoglycosides, are poorly absorbed from the gastrointestinal tract.
Some antibiotics, such as ______ and aminoglycosides, are poorly absorbed from the gastrointestinal tract.
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The cost of therapy can vary widely among drugs that show similar ______ in treating an infection.
The cost of therapy can vary widely among drugs that show similar ______ in treating an infection.
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Safety is related not only to the inherent nature of the drug but also to ______ factors that can predispose to toxicity.
Safety is related not only to the inherent nature of the drug but also to ______ factors that can predispose to toxicity.
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Certain antimicrobial agents, including aminoglycosides and daptomycin, show a significant increase in the rate of bacterial killing as the concentration of antibiotic increases from 4- to 64-fold the ______ of the drug for the infecting organism.
Certain antimicrobial agents, including aminoglycosides and daptomycin, show a significant increase in the rate of bacterial killing as the concentration of antibiotic increases from 4- to 64-fold the ______ of the drug for the infecting organism.
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In contrast, β-lactams, glycopeptides, macrolides, clindamycin, and linezolid do not exhibit ______-dependent killing.
In contrast, β-lactams, glycopeptides, macrolides, clindamycin, and linezolid do not exhibit ______-dependent killing.
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The clinical efficacy of these antimicrobials is best predicted by the percentage of time that blood concentrations of a drug remain above the ______.
The clinical efficacy of these antimicrobials is best predicted by the percentage of time that blood concentrations of a drug remain above the ______.
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The PAE is a persistent suppression of microbial growth that occurs after levels of antibiotic have fallen below the ______.
The PAE is a persistent suppression of microbial growth that occurs after levels of antibiotic have fallen below the ______.
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Antimicrobial drugs exhibiting a long PAE often require only one dose per day, particularly against ______ negative bacteria.
Antimicrobial drugs exhibiting a long PAE often require only one dose per day, particularly against ______ negative bacteria.
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Chemotherapeutic agents acting only on a single or a limited group of microorganisms are said to have a ______ spectrum.
Chemotherapeutic agents acting only on a single or a limited group of microorganisms are said to have a ______ spectrum.
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Extended spectrum is the term applied to antibiotics that are modified to be effective against gram-positive organisms and also against a significant number of ______ negative bacteria.
Extended spectrum is the term applied to antibiotics that are modified to be effective against gram-positive organisms and also against a significant number of ______ negative bacteria.
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Drugs such as tetracycline, fluoroquinolones, and carbapenems affect a wide variety of microbial species and are referred to as ______-spectrum antibiotics.
Drugs such as tetracycline, fluoroquinolones, and carbapenems affect a wide variety of microbial species and are referred to as ______-spectrum antibiotics.
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It is therapeutically advisable to treat patients with a single agent that is most specific to the ______ organism.
It is therapeutically advisable to treat patients with a single agent that is most specific to the ______ organism.
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This strategy reduces the possibility of ______ infections.
This strategy reduces the possibility of ______ infections.
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Study Notes
Antimicrobial Drugs
- Antimicrobial drugs work by selectively targeting invading microorganisms without harming host cells.
- Antimicrobial drugs are effective because of their selective toxicity.
- They can injure or kill invading microorganisms.
Selection of Antimicrobial Agents
- Choosing the right antimicrobial agent depends on the organism's identity, its susceptibility to different agents, the site of the infection, patient factors, safety, and cost.
- Identifying the infecting organism is crucial for selecting the appropriate drug.
- Rapid assessment can sometimes be made based on a Gram stain, but culture and susceptibility testing are often necessary for definitive diagnosis
- Empiric therapy may be needed immediately for critically ill patients before the infecting organism or its susceptibility is identified.
Bacteriostatic versus Bactericidal Drugs
- Bacteriostatic drugs inhibit the growth and replication of bacteria, allowing the immune system to eliminate them.
- Bactericidal drugs kill the bacteria at the achievable serum levels within the patient.
- Bactericidal agents are usually the drugs of choice in seriously ill or immunocompromised patients.
Minimum Inhibitory Concentration (MIC)
- MIC is the lowest concentration of an antimicrobial agent that prevents visible growth of an organism after 24 hours.
- It is used to evaluate the susceptibility of microorganisms to antimicrobials in vitro.
- MIC helps in choosing the appropriate antibiotic therapy.
Minimum Bactericidal Concentration (MBC)
- MBC is the lowest concentration of an antimicrobial agent that results in a 99.9% decline in colony counts after overnight broth dilution incubations.
- MBC determines the minimum amount of drug needed to effectively kill most of the bacteria.
Effect of Site of Infection on Therapy: The Blood-Brain Barrier
- Adequate antibiotic levels at the infection site are crucial for effective treatment.
- Factors such as lipid solubility, molecular weight, and protein binding influence the penetration of antimicrobials into various tissues, including the central nervous system (CNS).
Patient Factors
- Patient factors, such as immune system status, kidney function, liver function, age, and pregnancy, influence antimicrobial selection and dosing.
- Chronic conditions like alcoholism and diabetes can compromise the immune response.
- Age, kidney, and liver function can affect drug metabolism, necessitating dosage adjustments.
Safety of the Agent
- Certain antibiotics, like penicillin, have low toxicity and are effective for diverse infections.
- Others, like chloramphenicol, are more toxic and should be reserved for life-threatening conditions.
- Safety considerations must encompass both the drug's inherent toxicity and patient-specific factors.
Cost of Therapy
- Antimicrobial drug costs vary significantly based on several factors including the agent and the duration of the course.
Route of Administration
- Oral administration is suitable for mild infections treated as outpatients..
- Intravenous administration is initially used in hospitalized patients, but oral treatment can often be used afterward if possible.
- Certain antibiotics are poorly absorbed from the GI tract, necessitating parenteral administration
Determining Rational Dosing
- Rational antibiotic dosing is influenced by the relationship between drug concentrations and antimicrobial effect, and drug pharmacokinetics (absorption, distribution, metabolism, and elimination).
- Factors to consider:
- Concentration-dependent killing – higher concentrations are more effective
- Time-dependent killing – maintaining above a specific concentration for extended durations is key
- Post-antibiotic effect – some drugs continue suppressing growth even after concentration falls below the MIC
Prophylactic Use of Antibiotics
- Prophylactic use of antibiotics is necessary in certain situations (surgical procedures, dental work).
- Prophylaxis should be carefully calculated to prevent resistance.
Complications of Antimicrobial Therapy
- Some drugs cause hypersensitivity (allergic reactions).
- Some produce direct toxicity unrelated to antimicrobial activity.
Superinfections
- Broad-spectrum antibiotics can disrupt the normal flora, leading to an overgrowth of other microorganisms.
- This can cause superinfections, sometimes needing additional treatments.
Combinations of Antimicrobial Drugs
- Often, a combination of antimicrobials is more efficient than a singular agent
- Combinations, especially in severe cases, can reduce infection time and limit the development of antibiotic resistance.
- Some combinations interfere with each other's mechanisms.
Drug Resistance
- Bacteria can develop resistance, reducing the effectiveness of antibiotics.
- Resistance arises from genetic changes within the bacterial organisms; these can appear naturally or be acquired.
Narrow, Extended, and Broad-Spectrum Antibiotics
- Narrow-spectrum antimicrobials combat a limited group of microorganisms.
- Extended-spectrum antimicrobials target a wider range, encompassing gram-positive and diverse gram-negative bacteria.
- Broad-spectrum antimicrobials target a wide variety of bacterial types, but overuse can contribute to antimicrobial resistance.
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Description
This quiz covers the fundamental concepts of antimicrobial drugs, including their selective toxicity and the criteria for selecting appropriate agents. It highlights the importance of identifying the infecting organism and discusses the differences between bacteriostatic and bactericidal drugs. Test your knowledge on these critical aspects of antimicrobial therapy.
