20 Questions
What is the primary mechanism of resistance to β-lactam antibiotics in bacteria such as Escherichia coli and Haemophilus influenzae?
production of β-lactamase enzyme
What is the purpose of combining a β-lactamase inhibitor with a β-lactam antibiotic?
to protect the antibiotic from enzymatic hydrolysis
Which of the following bacteria is NOT susceptible to piperacillin?
Klebsiella pneumoniae
What is the primary indication for the use of antipseudomonal penicillins such as piperacillin and ticarcillin?
Infections caused by Pseudomonas aeruginosa
Which of the following infections is NOT typically treated with β-lactam antibiotics?
Fungal infections
What is the effect of combining a β-lactamase inhibitor with a β-lactam antibiotic on its antimicrobial spectrum?
broadening of the antimicrobial spectrum
What is the primary function of beta-lactamase inhibitors in antibiotic therapy?
To protect hydrolyzable penicillins from inactivation
Which of the following is a mechanism of penicillin resistance in bacteria?
Alterations in the target enzyme, transpeptidase
What is the primary concern regarding the use of beta-lactam antibiotics in patients with impaired renal function?
Accumulation of the drug leading to increased toxicity
Which of the following drug interactions is a concern when using beta-lactam antibiotics?
Increased risk of bleeding when combined with warfarin
What is the primary target of beta-lactam antibiotics in bacterial cells?
The peptidoglycan cell wall
In which stage of bacterial growth are bacteria most susceptible to the action of beta-lactam antibiotics?
Log phase
What is the mechanism by which high doses of bacteriostatic drugs can act as bactericidal agents?
By preventing the growth of bacteria
Which of the following bacteria is intrinsically resistant to β-Lactam antibiotics?
Mycoplasma
What is the postantibiotic effect (PAE) of β-Lactam antibiotics?
The delay in bacterial growth after antibiotic treatment
What is the common mechanism of action of Penicillins, Cephalosporins, Carbapenems, and Monobactams?
Inhibition of cell wall synthesis
What is the reason for the limited use of Penicillins despite being the most widely effective antibiotics?
Increased resistance
What is the function of Penicillin Binding Proteins (PBPs) in bacterial cell membrane?
To synthesize cell wall
What is the effect of β-Lactam antibiotics on susceptible bacteria?
Death due to imbibition of water
What is the structural characteristic of β-Lactam antibiotics?
Heteroatomic ring structure with 3 carbon and 1 nitrogen atom
Study Notes
Antibiotic Classification
- Bacteriocidal: kill bacteria
- Bacteriostatic: prevent growth of bacteria
- High doses of bacteriostatic drugs may act as bacteriocidal agents
β-Lactams
- All β-lactam antibiotics are bactericidal in nature
- Mechanism of action: bind to specific receptors on bacterial cell membrane (Penicillin Binding Proteins, PBPs) → inhibit transpeptidase enzyme → prevent cross-linking of peptidoglycan chains
- Bacteria formed in the presence of β-lactams lack cell-wall, causing imbibition of water and leading to cell death
- Bacteria like Mycoplasma are intrinsically resistant to β-lactams and vancomycin due to lack of cell-wall
β-Lactam Subclasses
- Penicillins
- Cephalosporins
- Carbapenems
- Monobactams
Penicillins
- Most widely effective antibiotics and also the least toxic drugs known
- Members of this family differ from one another in the R substituent attached to the 6-aminopenicillanic acid residue
- The nature of this side chain affects the antimicrobial spectrum, stability to stomach acid, and susceptibility to bacterial degradative enzymes (β-lactamases)
- Mechanism of action:
- Penicillin (or other cell wall synthesis inhibitor) is added to the growth medium
- The cell begins to grow, but is unable to synthesize new cell wall
Definitions
- Beta-lactamases: bacterial enzymes that hydrolyze the beta-lactam ring of certain penicillins and cephalosporins
- Beta-lactam inhibitors: potent inhibitors of some bacterial beta-lactamases used in combinations to protect hydrolyzable penicillins from inactivation
- Penicillin-binding proteins (PBPs): bacterial cytoplasmic membrane proteins that act as the initial receptors for penicillins and other beta-lactam antibiotics
- Peptidoglycan: chains of polysaccharides and polypeptides that are cross-linked to form the bacterial cell wall
- Transpeptidases: bacterial enzymes involved in the cross-linking of linear peptidoglycan chains, the final step in cell wall synthesis
- Selective toxicity: more toxic to the invader than to the host
Clinical Uses
- Urinary tract infections
- Respiratory tract infections
- Meningitis
- To treat Gonorrhea, Syphilis, typhoid, bacillary dysentery
- Sub acute bacterial endocarditis
- Bone and joint infections
- Bronchitis, Pneumonia
- Skin and Soft tissue infections
This quiz covers the basics of antibiotics, their types and mechanisms of action. It includes bacteriocidal and bacteriostatic drugs, and the properties of β-LACTAMS antibiotics.
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