24 Questions
What is the source of the first members of the cephalosporin class?
Cephalosporium acremonium
Which of the following bacteria produces peptidoglycan and is affected by natural penicillins?
Streptococcus pneumoniae
How are cephalosporins categorized?
By generation
What is the mechanism of resistance of some bacteria to natural penicillins?
All of the above
What is the nucleus of a cephalosporin composed of?
Two side chains
Which of the following bacteria is susceptible to natural penicillins?
Neisseria meningitidis
What is the characteristic of cephalosporins within the β-lactam group?
They are all β-lactam antibiotics
What is the characteristic of antistaphylococcal penicillins?
They have bulky residues on their R side chains that prevent binding by staphylococcal β-lactamases
What is the common feature of agents in each generation of cephalosporins?
They have similar spectra of activity
What is the term used to describe the categorization of cephalosporins?
Generation
Which of the following bacteria is resistant to antistaphylococcal penicillins?
Methicillin-resistant S. aureus (MRSA)
What is the significance of the generation categorization of cephalosporins?
It is helpful in remembering the properties of cephalosporins
What is the mechanism of action of natural penicillins?
Inhibition of cell wall formation
Which of the following bacteria produces β-lactamases that degrade natural penicillins?
Bacteroides fragilis
What is the benefit of understanding the properties of cephalosporins?
It is helpful in selecting the appropriate antibiotic for a particular infection
What is the limitation of natural penicillins?
They are limited by the production of β-lactamases, alteration of PBPs, and lack of peptidoglycan in some bacteria
Which type of penicillins is useful in treating infections caused by Staphylococcus aureus?
Antistaphylococcal penicillins
What is the primary mechanism of action of penicillins?
Binding to enzymes that assemble the bacterial cell wall
What is the effect of adding a β-lactamase inhibitor to an aminopenicillin?
Expanded spectrum of activity to include many enteric gram-negative bacilli and additional anaerobes
What is the primary difference between natural penicillins and aminopenicillins?
Aminopenicillins have improved activity against aerobic gram-negative bacteria
Which type of bacteria are natural penicillins most active against?
Aerobic gram-positive bacteria and anaerobic bacteria
What is the primary advantage of extended-spectrum penicillins over aminopenicillins?
Improved activity against aerobic gram-negative bacteria, including Pseudomonas aeruginosa
Which of the following is a characteristic of extended-spectrum penicillins?
Activity against enteric gram-negative rods and Pseudomonas aeruginosa
What is the effect of using extended-spectrum penicillins in combination with β-lactamase inhibitors?
These agents become among the most powerful antibacterial agents available
Study Notes
Penicillins
- Act by binding to PBPs, which are bacterial enzymes that function to assemble peptidoglycan.
- Natural penicillins have moderate activity against aerobic gram-positive bacteria and anaerobic bacteria, but poor activity against aerobic gram-negative bacteria and most atypical bacteria.
- Limitations of natural penicillins include:
- Producing penicillinases that degrade natural penicillins (e.g., some anaerobes, such as Bacteroides fragilis).
- Some bacteria produce PBPs that do not bind natural penicillins with high affinity (e.g., some strains of Streptococcus pneumoniae).
- Some bacteria do not make peptidoglycan and are not affected by natural penicillins (e.g., Mycoplasma and Chlamydia spp.).
Antistaphylococcal Penicillins
- Have bulky residues on their R side chains that prevent binding by staphylococcal β-lactamases.
- Useful in treating infections caused by S. aureus and Staphylococcus epidermidis, but not effective against methicillin-resistant S. aureus (MRSA) and methicillin-resistant S. epidermidis (MRSE).
Extended-Spectrum Penicillins
- Active against even more enteric gram-negative rods and importantly, Pseudomonas aeruginosa.
- Addition of a β-lactamase inhibitor to an extended-spectrum penicillin extends its activity to include most enteric gram-negative bacilli.
Cephalosporins
- Constitute a large extended family of antibiotics within the β-lactam group.
- Can be categorized by "generation", with each generation having similar spectra of activity.
- Each cephalosporin is composed of a nucleus with two side chains.
This quiz covers various bacteria species, their characteristics, and how they interact with antibiotics. Topics include Actinomyces israelii, Spirochetes, Treponema pallidum, Leptospira spp., and Bacteroides fragilis.
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