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Questions and Answers
Some β-lactam antibiotic can enter the ______
Some β-lactam antibiotic can enter the ______
CSF
A compound with a low molecular weight has an enhanced ability to cross the ______ barrier
A compound with a low molecular weight has an enhanced ability to cross the ______ barrier
blood–brain
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
meningeal
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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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 kidney function may cause accumulation of certain ______
Poor kidney function may cause accumulation of certain ______
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Serum creatinine levels are frequently used as an index of ______ function
Serum creatinine levels are frequently used as an index of ______ function
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The site of ______ influences drug choice in the absence of susceptibility data.
The site of ______ influences drug choice in the absence of susceptibility data.
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Previous infections, age, and recent travel history should be considered in the patient's ______.
Previous infections, age, and recent travel history should be considered in the patient's ______.
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Broad-spectrum therapy may be indicated when the organism is ______ or when polymicrobial infections are likely.
Broad-spectrum therapy may be indicated when the organism is ______ or when polymicrobial infections are likely.
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Bacteriostatic drugs limit the spread of infection until the immune system ______ the pathogen.
Bacteriostatic drugs limit the spread of infection until the immune system ______ the pathogen.
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Bactericidal drugs are the drugs of choice for seriously ill and ______ patients.
Bactericidal drugs are the drugs of choice for seriously ill and ______ patients.
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The minimum inhibitory concentration (MIC) is the lowest antimicrobial concentration that prevents visible ______ of an organism.
The minimum inhibitory concentration (MIC) is the lowest antimicrobial concentration that prevents visible ______ of an organism.
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The MIC serves as a quantitative measure of in vitro ______ and is commonly used in practice.
The MIC serves as a quantitative measure of in vitro ______ and is commonly used in practice.
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Bactericidal drugs kill bacteria at serum levels ______ in the patient.
Bactericidal drugs kill bacteria at serum levels ______ in the patient.
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Certain combinations of antibiotics, such as β-lactams and __________, show synergism.
Certain combinations of antibiotics, such as β-lactams and __________, show synergism.
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The addition effect is calculated as Drug A activity 30% + Drug B activity 20% = __________.
The addition effect is calculated as Drug A activity 30% + Drug B activity 20% = __________.
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The synergistic effect is calculated as Drug A activity 30% + Drug B activity 20% = __________.
The synergistic effect is calculated as Drug A activity 30% + Drug B activity 20% = __________.
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A number of antibiotics act only when organisms are __________.
A number of antibiotics act only when organisms are __________.
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Coadministration of a bacteriostatic agent like __________ with a bactericidal agent may lead to interference.
Coadministration of a bacteriostatic agent like __________ with a bactericidal agent may lead to interference.
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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 requires the gain or alteration of bacterial __________.
Acquired antibiotic resistance requires the gain or alteration of bacterial __________.
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Resistance develops due to the ability of __________ to undergo spontaneous mutation.
Resistance develops due to the ability of __________ to undergo spontaneous mutation.
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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 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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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 ______ 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 ______ 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 ______ to the infecting organism.
It is therapeutically advisable to treat patients with a single agent that is most ______ to the infecting organism.
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This strategy reduces the possibility of ______, decreases the emergence of resistant organisms, and minimizes toxicity.
This strategy reduces the possibility of ______, decreases the emergence of resistant organisms, and minimizes toxicity.
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Alteration in an antibiotic ______ site is one mechanism of drug resistance.
Alteration in an antibiotic ______ site is one mechanism of drug resistance.
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Decreased penetrability of the drug is due to decreased ______.
Decreased penetrability of the drug is due to decreased ______.
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Increased ______ of the drug can contribute to antibiotic resistance.
Increased ______ of the drug can contribute to antibiotic resistance.
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Antibiotic-inactivating ______ can also confer resistance on microorganisms.
Antibiotic-inactivating ______ can also confer resistance on microorganisms.
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S.pneumoniae resistance to β-lactam antibiotics involves alterations in penicillin-binding ______.
S.pneumoniae resistance to β-lactam antibiotics involves alterations in penicillin-binding ______.
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Gram-negative organisms can limit the penetration of certain agents due to alterations in the structure of ______.
Gram-negative organisms can limit the penetration of certain agents due to alterations in the structure of ______.
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Prophylactic use of antibiotics is common in clinical situations such as dental procedures and ______.
Prophylactic use of antibiotics is common in clinical situations such as dental procedures and ______.
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The duration of antibiotic ______ should be closely monitored to prevent resistance.
The duration of antibiotic ______ should be closely monitored to prevent resistance.
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The drug may produce an allergic response or may be toxic in ways unrelated to the antimicrobial ______.
The drug may produce an allergic response or may be toxic in ways unrelated to the antimicrobial ______.
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Hypersensitivity reactions can range from urticaria (hives) to ______ shock.
Hypersensitivity reactions can range from urticaria (hives) to ______ shock.
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High serum levels of certain antibiotics may cause toxicity by directly affecting cellular processes in the ______.
High serum levels of certain antibiotics may cause toxicity by directly affecting cellular processes in the ______.
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Drug therapy with broad-spectrum antimicrobials can lead to alterations of the normal microbial flora of the upper respiratory, oral, intestinal, and genitourinary ______.
Drug therapy with broad-spectrum antimicrobials can lead to alterations of the normal microbial flora of the upper respiratory, oral, intestinal, and genitourinary ______.
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The overgrowth of opportunistic organisms, especially fungi or resistant ______, may occur due to superinfections.
The overgrowth of opportunistic organisms, especially fungi or resistant ______, may occur due to superinfections.
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Antimicrobial drugs can be classified by their chemical structure, mechanism of ______, or activity against particular types of organisms.
Antimicrobial drugs can be classified by their chemical structure, mechanism of ______, or activity against particular types of organisms.
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Examples of antifungal infections include those caused by various species of ______.
Examples of antifungal infections include those caused by various species of ______.
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Antimicrobials can be specifically designed to target ______ infections.
Antimicrobials can be specifically designed to target ______ infections.
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Study Notes
Antimicrobial Drugs
- Antimicrobial drugs treat infections by selectively targeting invading microorganisms without harming host cells.
- Selective toxicity is a key characteristic of effective antimicrobial drugs.
Selection of Antimicrobial Agents
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Choosing the right antimicrobial agent involves several factors:
- Identifying the infecting organism.
- Assessing the organism's susceptibility to particular agents.
- Determining the site of infection, and patient factors.
- Evaluating the safety and cost of therapy.
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Identifying the infecting organism is crucial for proper drug selection.
- Gram staining can sometimes provide a rapid assessment.
- Culturing the organism is often necessary for a conclusive diagnosis.
- Susceptibility testing determines the effectiveness of different antimicrobial agents.
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Empiric therapy might be necessary in critically ill patients to quickly start treatment based on symptoms.
- Ideally, empiric therapy is used only when the bacteria is unknown or when there is insufficient time to complete detailed identification of the infection.
Timing of Antimicrobial Treatment
- Acutely ill patients needing immediate treatment:
- Neutropenic patients.
- Patients with meningitis
- Infections of unknown origin
- Treatment should ideally start after specimens for laboratory analysis have been obtained.
Selecting a drug
- Drug selection in the absence of complete susceptibility data is based on:
- Site of infection.
- Patient history, including previous infections, immune status, and recent antibiotic use.
- Potential for polymicrobial infections.
Determining Antimicrobial Susceptibility
- After isolating the pathogen, determining its susceptibility to various antimicrobials is used to guide treatment choices.
- Minimum inhibitory concentration (MIC) is a measure of the lowest drug concentration that stops bacterial growth.
- Minimum bactericidal concentration (MBC) measures the lowest drug concentration that kills 99.9% of the bacteria.
Effect of Infection Site on Therapy
- Antibiotic must reach the site of infection at sufficient levels to eliminate the infection successfully.
- Permeability of tissues affects how drugs reach the site of infection.
- The blood-brain barrier, for instance, limits access for certain drugs.
- Factors like the drug's lipid solubility, molecular weight, and protein binding affect drug penetration.
Patient Factors
- The patient's overall health affects the choice of antimicrobial treatment.
- Factors:
- Immune system function
- Renal and hepatic function
- Age
- Pregnancy and lactation.
- Allergies.
Types of Antimicrobial Drugs
- Bacteriostatic drugs inhibit bacterial growth.
- Bactericidal drugs kill bacteria.
Minimum Inhibitory Concentration (MIC)
- The lowest concentration of an antimicrobial that prevents the visible growth of an organism.
- Quantitative measure for in vitro susceptibility testing.
Minimum Bactericidal Concentration (MBC)
- The lowest concentration of an antimicrobial that results in a 99.9% decrease in bacterial colony count.
- Assesses the drug's ability to kill bacteria.
Drug Combinations
- Combining drugs can offer several advantages:
- Synergistic effects: combination > sum of individual effects.
- Disadvantages:
- Interference between drugs' mechanisms of actions.
- Potential for drug resistance.
Drug Resistance
- Bacteria can develop resistance to antimicrobials.
- Mechanisms include genetic mutations and acquiring antibiotic resistance-genes.
Prophylactic Use of Antibiotics
- Use of antibiotics to prevent infections in specific situations (e.g., surgeries, dental procedures)
- Prophylactic use duration should be cautiously observed.
Complications of Antimicrobial Therapy
- Antibiotic treatment can cause various unintended effects:
- Hypersensitivity reactions (allergic reactions).
- Direct toxicity affecting host cells.
- Superinfections (drug-induced infections): opportunistic infections occur when broad-spectrum antibiotics disrupt the normal bacteria in the body.
Bacterial Resistance
- Bacteria can tolerate the maximum tolerated level of an antimicrobial agent, without preventing their growth.
- Resistance can be inherent (present from the beginning) or acquired (develop subsequently).
Classification of Antimicrobial Drugs
- Classified by chemical structure, mechanism of action, and target organism.
Bacterial Target Sites
- Cell wall synthesis
- Protein synthesis
- Nucleic acid synthesis
- Metabolic pathways
Fungal Infections
- Treatment is often targeted at specific fungal metabolic pathways.
Viral Infections
- Antivirals targeting viral replication cycles are used for treatment.
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Description
Test your knowledge on antimicrobial drugs and the selection process for appropriate therapies. This quiz covers the principles of selective toxicity, identification of infecting organisms, and factors influencing the choice of antimicrobial agents. Ensure you understand the critical importance of susceptibility testing and empiric therapy.
