32 Questions
What is the primary mechanism of action of bacteriostatic antibacterial agents?
Inhibiting protein synthesis
Which of the following is a characteristic of ideal antimicrobial agents?
Long half-life
What is the primary mechanism of resistance to antibiotics in bacterial biofilms?
Formation of a polysaccharide matrix
Which of the following is NOT a mechanism of antimicrobial resistance?
Increased uptake
What is the unit of measurement for minimum inhibitory concentration (MIC) in antibiotic sensitivity testing?
mg/L
What is the primary reason for considering patient's medical history when selecting an antibiotic?
To identify potential allergies
Which of the following antibacterial agents is classified as a broad-spectrum agent?
Tetracyclines
What is the term for the ability of an antibiotic to selectively target bacterial cells while sparing host cells?
Selectivity
What is the primary goal of empirical therapy in antibiotic treatment?
To provide broad-spectrum coverage until the organism is identified
Which of the following antibiotics is NOT effective against anaerobes?
Cephalosporins
What is the primary advantage of using a beta-lactamase inhibitor combination?
It allows the beta-lactam antibiotic to continue working despite the presence of beta-lactamase
Which of the following antibiotics is associated with an increased risk of C. difficile infection?
Cephalosporins
What is the primary indication for using vancomycin?
Gram-positive bacterial infections, including MRSA and VRE
Which of the following antibiotics is not typically used to treat multidrug-resistant Gram-negative infections?
Amoxicillin + clavulanate
What is the primary advantage of using teicoplanin over vancomycin?
It is easier to administer
Which of the following antibiotics is used to treat acute Gram-positive skin infections?
Dalbavancin
Which of the following mechanisms of antibiotic resistance is characterized by the production of enzymes that destroy or inactivate the antibiotic?
Drug inactivating enzymes
What is the primary consideration when selecting an antibiotic for a patient with a severe infection?
The severity of the infection
What is the primary advantage of using combination therapy in antibiotic treatment?
To increase the spectrum of activity against different types of bacteria
Which of the following types of antibacterial agents is classified based on its mechanism of action?
Bactericidal
Which of the following antibiotics is active against most gram positives but not gram negatives?
Vancomycin
What is the unit of measurement used to express the results of antibiotic sensitivity testing using the Etest method?
mg/L
What is the primary indication for using piperacillin/tazobactam?
To treat gram-negative infections, including Pseudomonas species
Which of the following antibiotics requires therapeutic drug monitoring (TDM)?
Vancomycin
Which of the following is a characteristic of an ideal antimicrobial agent?
Selectively toxic
What is the primary mechanism of antibiotic resistance in bacterial biofilms?
Biofilm mode of growth
What is the primary advantage of using teicoplanin over vancomycin?
It is easier to administer
Which of the following types of antibacterial agents is classified based on its spectrum of activity?
Broad-spectrum
Which of the following antibiotics is used to treat complicated gram-negative urinary tract infections?
Meropenem + vaborbactam
What is the primary goal of disc sensitivity testing?
To predict the clinical response to antibiotic therapy
What is the primary mechanism of action of beta-lactam antibiotics?
Interference with bacterial cell wall formation
Which of the following antibiotics is active against most gram negatives, including anaerobes?
Carbapenems
Study Notes
Classification of Antimicrobial Agents
- Antibacterial, antifungal, antiviral, and antiprotozoal agents
- Antibacterial agents can be classified by:
- Mechanism of action (bactericidal or bacteriostatic)
- Spectrum (broad or narrow)
- Target site
- Chemical structure (antibacterial class)
Ideal Features of Antimicrobial Agents
- Selectively toxic
- Few adverse effects
- Reach site of infection
- Oral or IV formulation
- Long half-life (infrequent dosing)
- No interference with other drugs
Mechanisms of Resistance
- Drug inactivating enzymes (e.g. beta-lactamases, aminoglycoside enzymes)
- Altered target (e.g. resistance to methicillin, macrolides, and trimethoprim)
- Altered uptake (decreased permeability or increased efflux)
- Biofilm mode of growth (made of polysaccharides)
Genetic Mechanisms of Resistance
- None mentioned
Measuring Antibiotic Activity
- Disc sensitivity testing (sensitive, intermediate, or resistant)
- Antibiotic sensitivity by Etest (minimum inhibitory concentration (MIC) as mg/L)
- Automated antibiotic sensitivity testing (MIC as mg/L)
Considerations for Antibiotic Therapy
- Severity/cause of infection
- Patient's medical history, other drugs, and allergy to antibiotics
- Taking samples before start of antibiotic therapy
- Broad spectrum antibiotics for unidentified causative organisms
- Route of administration (oral or IV)
- Dose of antibiotics
- Longevity of therapy
- Combination therapy
- Prophylaxis
Selection of Antibiotics for Treatment
- Empirical therapy initially
- Isolate and identify the organism
- Determine its sensitivity
- Treat with an appropriate antibiotic
Beta-lactams
- Penicillins:
- Penicillin (mainly active against streptococci)
- Amoxicillin (active against streptococci and some gram-negatives)
- Flucloxacillin (active against staphylococci and streptococci)
- Beta-lactamase inhibitor combinations (e.g. amoxicillin/clavulanate, piperacillin/tazobactam)
- Cephalosporins:
- Broad-spectrum but no anaerobe activity
- Cetriaxone (good activity in the CSF)
- Concern over association with C.difficile
- Ceftazidime + avibactam and ceftlozane + tazobactam (used for multidrug resistant Gram negative infections)
- Carbapenems:
- Imipenem, meropenem, and ertapenem (broad spectrum, including anaerobes)
- Active against most gram negatives
- Generally safe in penicillin allergy
- Imipenem + relebactam (used for serious gram negative infections)
- Meropenem + vaborbactam (used for complicated gram negative UTI)
Glycopeptides
- Vancomycin:
- Active against most gram positive (not gram negative)
- Some enterococci resistant (VRE)
- Resistance in staphs rare
- Not absorbed (oral for C.difficile only)
- Therapeutic drug monitoring (TDM) required (narrow therapeutic window)
- Teicoplanin:
- Similar activity to vancomycin
- Easier to administer
- Dalbavancin and telavancin:
- Used for acute gram positive skin infections
- Used for MRSA pneumonia
Tetracyclines
- Tetracycline and doxycycline:
- Similar spectrum, both oral only
Classification of Antimicrobial Agents
- Antibacterial, antifungal, antiviral, and antiprotozoal agents
- Antibacterial agents can be classified by:
- Mechanism of action (bactericidal or bacteriostatic)
- Spectrum (broad or narrow)
- Target site
- Chemical structure (antibacterial class)
Ideal Features of Antimicrobial Agents
- Selectively toxic
- Few adverse effects
- Reach site of infection
- Oral or IV formulation
- Long half-life (infrequent dosing)
- No interference with other drugs
Mechanisms of Resistance
- Drug inactivating enzymes (e.g. beta-lactamases, aminoglycoside enzymes)
- Altered target (e.g. resistance to methicillin, macrolides, and trimethoprim)
- Altered uptake (decreased permeability or increased efflux)
- Biofilm mode of growth (made of polysaccharides)
Genetic Mechanisms of Resistance
- None mentioned
Measuring Antibiotic Activity
- Disc sensitivity testing (sensitive, intermediate, or resistant)
- Antibiotic sensitivity by Etest (minimum inhibitory concentration (MIC) as mg/L)
- Automated antibiotic sensitivity testing (MIC as mg/L)
Considerations for Antibiotic Therapy
- Severity/cause of infection
- Patient's medical history, other drugs, and allergy to antibiotics
- Taking samples before start of antibiotic therapy
- Broad spectrum antibiotics for unidentified causative organisms
- Route of administration (oral or IV)
- Dose of antibiotics
- Longevity of therapy
- Combination therapy
- Prophylaxis
Selection of Antibiotics for Treatment
- Empirical therapy initially
- Isolate and identify the organism
- Determine its sensitivity
- Treat with an appropriate antibiotic
Beta-lactams
- Penicillins:
- Penicillin (mainly active against streptococci)
- Amoxicillin (active against streptococci and some gram-negatives)
- Flucloxacillin (active against staphylococci and streptococci)
- Beta-lactamase inhibitor combinations (e.g. amoxicillin/clavulanate, piperacillin/tazobactam)
- Cephalosporins:
- Broad-spectrum but no anaerobe activity
- Cetriaxone (good activity in the CSF)
- Concern over association with C.difficile
- Ceftazidime + avibactam and ceftlozane + tazobactam (used for multidrug resistant Gram negative infections)
- Carbapenems:
- Imipenem, meropenem, and ertapenem (broad spectrum, including anaerobes)
- Active against most gram negatives
- Generally safe in penicillin allergy
- Imipenem + relebactam (used for serious gram negative infections)
- Meropenem + vaborbactam (used for complicated gram negative UTI)
Glycopeptides
- Vancomycin:
- Active against most gram positive (not gram negative)
- Some enterococci resistant (VRE)
- Resistance in staphs rare
- Not absorbed (oral for C.difficile only)
- Therapeutic drug monitoring (TDM) required (narrow therapeutic window)
- Teicoplanin:
- Similar activity to vancomycin
- Easier to administer
- Dalbavancin and telavancin:
- Used for acute gram positive skin infections
- Used for MRSA pneumonia
Tetracyclines
- Tetracycline and doxycycline:
- Similar spectrum, both oral only
Quiz on the classification of antibacterial, antifungal, antiviral, and antiprotozoal agents based on their mechanism of action, spectrum, target site, and chemical structure.
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