What are cephalosporins derived from?
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An antibiotic produced by the fungus Cephalosporium acremonium.
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What are cephalosporins derived from?
An antibiotic produced by the fungus Cephalosporium acremonium.
What is the chemical structure of cephalosporins based on?
Derivatives of 7-amino-cephalosporanic acid fused to a six-member dihydrothiazine ring.
How are cephalosporins classified?
They are grouped into 'generations' based on their spectrum of antimicrobial activity.
What is a key characteristic of newer generations of cephalosporins compared to older ones?
Newer generations have significantly greater gram-negative antimicrobial properties but often decreased activity against Gram-positive organisms.
What advantage do newer cephalosporins have regarding dosing frequency?
They have much longer half-lives, resulting in a decrease of dosing frequency.
What type of bacteria do 1st generation cephalosporins primarily cover?
Mostly Gram-positive bacteria.
Name two examples of 1st generation cephalosporins.
Cefazolin and Cephalexin.
Which generation of cephalosporins includes Cefaclor and Cefuroxime?
2nd Generation.
What is the primary coverage of 4th generation cephalosporins?
Mostly Gram-negative bacteria.
What is Ceftaroline classified as?
5th generation or advanced generation cephalosporin.
How does the Gram-negative coverage change from 1st to 4th generation cephalosporins?
There is increasing Gram-negative coverage from the 1st to the 4th generation.
What additional coverage does Ceftaroline provide compared to the 3rd generation?
Added MRSA coverage.
What are the most commonly used first generation cephalosporins?
Cephalexin, cefadroxil, and cefazolin.
What types of bacteria are first generation cephalosporins effective against?
Gram positive bacteria (Streptococcus, Staphylococcus) and limited Gram-negative bacteria (E.coli, Klebsiella, Proteus).
What is a poor coverage characteristic of first generation cephalosporins?
They have poor coverage against anaerobes, intracellular bacteria, and spirochetes.
What is the parenteral use of cefazolin?
Surgical wound prophylaxis and treatment of Streptococcal Pharyngitis.
What type of bacteria do 2nd generation cephalosporins retain some activity against?
Gram positive bacteria.
What type of bacteria do 2nd generation cephalosporins have greater activity against?
Gram-negative bacteria.
What is a characteristic of true cephalosporins regarding beta-lactamase?
They are more resistant to beta-lactamase.
What infections are true cephalosporins used for?
Community-acquired infections of the upper and lower respiratory tract.
What increased coverage do cephamycins provide?
Increased coverage to anaerobes, specifically Bacteroides fragilis.
Name two examples of cephamycins.
Cefotetan and cefoxitin.
What are the third generation cephalosporins mentioned?
Ceftriaxone, Cefotaxime, Ceftazidime.
How does the activity of third generation cephalosporins compare to second generation agents against Gram-positive cocci?
They are less active than second generation agents against Gram-positive cocci, but much more active against the Enterobacteriaceae.
What is a notable ability of third generation cephalosporins regarding the blood-brain barrier?
They can cross the blood-brain barrier.
What type of bacteria are third generation cephalosporins active against?
They are active against anaerobes.
What are the two cephalosporins mentioned that have adequate drug levels in CSF for empiric therapy for bacterial meningitis?
Cefotaxime and ceftriaxone.
Which cephalosporin is active against Pseudomonas aeruginosa?
Ceftazidime.
What is a limitation of ceftazidime regarding CNS penetration?
It has poor CNS penetration and should not be used for meningitis.
How does the antipseudomonal activity of ceftazidime compare to piperacillin/tazobactam?
The antipseudomonal activity of ceftazidime is similar to piperacillin/tazobactam.
What are the two main drugs classified as 4th generation cephalosporins?
Cefepime and Cefpirome.
What is a key characteristic of 4th generation cephalosporins regarding their activity against gram-positive organisms?
They have similar activity against gram-positive organisms as first generation cephalosporins.
What type of bacteria do 4th generation cephalosporins show excellent activity against?
Enterobacteriaceae and Pseudomonas aeruginosa.
How do 4th generation cephalosporins compare to 3rd generation cephalosporins in terms of resistance to beta-lactamases?
They have greater resistance to beta-lactamases than third generation cephalosporins.
What significant ability do 4th generation cephalosporins have regarding the blood-brain barrier?
They can cross the blood-brain barrier and are effective in meningitis.
In what context is Cefepime commonly used?
As empiric therapy of infection.
What is the role of 4th generation cephalosporins in treating serious infections?
They are considered drugs of last resort for serious infections.
How does the anti-pseudomonal activity of Cefepime compare to other antibiotics for ventilator-associated pneumonia?
It is similar to that of ceftazidime and Piperacillin/tazobactam.
What is the primary use of 5th generation cephalosporins?
They are used for their extended spectrum, particularly against MRSA and enterococci.
Which two 5th generation cephalosporins are mentioned?
Ceftobiprole and Ceftaroline (Teflaro).
What is the activity of 5th generation cephalosporins against Pseudomonas aeruginosa?
They are active against Pseudomonas aeruginosa but have no antipseudomonal activity.
What type of bacteria are 5th generation cephalosporins active against?
They are active against anaerobic Gram-positive bacteria.
How do 5th generation cephalosporins compare to vancomycin and ceftazidime?
They have comparable activity to vancomycin and ceftazidime.
What are the rare immediate hypersensitivity reactions caused by cephalosporins?
Rash, urticaria, or anaphylaxis.
What percentage of individuals allergic to penicillin may also react to cephalosporins?
Approximately 5% to 10%.
What are the names of the four carbapenems mentioned?
Imipenem, Meropenem, Doripenem, Ertapenem.
What makes carbapenems resistant to certain enzymes?
They are resistant to beta-lactamases.
What is the role of carbapenems in antimicrobial therapy?
They are the last line of defense against many organisms that are resistant to other antimicrobial agents.
What type of bacteria do carbapenems have excellent activity against?
Aerobic Gram-positive, aerobic Gram-negative, and anaerobic bacteria.
Do carbapenems have activity against MRSA?
No, they have no activity against MRSA.
What is Imipenem combined with to enhance its effectiveness?
Cilastatin.
What is the role of Cilastatin in relation to Imipenem?
It is a dehydropeptidase inhibitor.
How is Imipenem metabolized in the body?
It is hydrolyzed in the mammalian kidney by the dihydropeptidase enzyme.
What is the final product of the combination of Imipenem and Cilastatin?
Tienam.
What is Imipenem used to treat?
Certain serious infections including endocarditis, respiratory tract infections (including pneumonia), urinary tract infections, abdominal infections, blood infections, skin infections, bone infections, and joint infections.
What are the two carbapenems mentioned in the text?
Meropenem and Ertapenem.
Does Ertapenem need to be administered with cilastatin?
No, it does not need to be administered in conjunction with cilastatin.
How does Ertapenem's activity against aerobic Gram-positive bacteria compare to other carbapenems?
Ertapenem is less active against aerobic Gram-positive bacteria than the other carbapenems.
What is a significant adverse effect of imipenem at high doses?
High incidence of seizures.
Is the incidence of seizures associated with meropenem?
No, it is not associated with meropenem.
What type of bacteria is Aztreonam effective against?
Only against Gram-negative bacteria, including Enterobacteriaceae and Pseudomonas.
Does Aztreonam have activity against Gram-positive bacteria?
No, it has no activity against Gram-positive and anaerobic bacteria.
What is the mechanism of action of Vancomycin?
Vancomycin binds to the d-alanyl-d-alanine portion of the peptide side chain of precursor peptidoglycan subunits, preventing access of PBPs and inhibiting peptidoglycan synthesis.
What is the primary route of administration for Vancomycin to treat systemic infections?
Intravenous (IV).
What type of bacteria is Vancomycin active against?
Gram positive cocci, including MRSA.
What is the absorption characteristic of Vancomycin from the gastrointestinal tract?
Poor absorption from GIT.
Which anaerobic bacteria is Vancomycin particularly effective against?
C. difficile.
What does the flow chart indicate about the antimicrobial activity of Glycopeptides against Gram negative bacteria?
They are not effective (indicated by a STOP sign).
What does the flow chart indicate about the antimicrobial activity of Glycopeptides against anaerobes?
They have some activity (indicated by a CAUTION sign).
What is the significance of the blue circle with a plus sign in the flow chart?
It indicates activity against Gram positive bacteria.
What does the blue rounded shape with a minus sign in the flow chart represent?
It indicates no activity against Gram negative bacteria.
What does the image of Vancomycin boxes and vials represent?
Different formulations of Vancomycin for injection.
What can rapid infusion of Vancomycin lead to?
Red man syndrome, characterized by pruritus and an erythematous rash on the face, neck, and upper torso.
How can red man syndrome be prevented during Vancomycin infusion?
By slowing the rate of infusion to 1-2 hours.
What type of bacteria is Bacitracin effective against?
Only Gram-positive bacteria.
What is the mechanism of action of Bacitracin?
It inhibits cell wall biosynthesis by interfering with the transport of peptidoglycan precursors across the cytoplasmic membrane.
Why is Bacitracin used only topically?
Due to its toxicity.
What is the mechanism of action of Fosfomycin?
It inhibits the synthesis of peptidoglycan precursor by binding to the phosphoenolpyruvate transferase enzyme (MurA).
What does Fosfomycin inhibit in bacterial cell wall synthesis?
It inhibits the first step in cell wall synthesis.
How is Fosfomycin excreted from the body?
Unchanged in urine, achieving high concentrations for a prolonged period.
What is the primary use of Fosfomycin?
In prophylaxis and treatment of UTIs.
What type of pathogens does Fosfomycin have broad antibacterial activity against?
Both Gram-positive and Gram-negative pathogens.
What type of antibiotic is Daptomycin?
Cyclic lipopeptide antibiotic (glycopeptide).
What is the mechanism of action of Daptomycin?
It inserts into the bacterial cytoplasmic membrane and forms an ion-conducting channel, allowing ions to escape and resulting in bacterial death.
What type of bacteria is daptomycin active against?
Gram-positive bacteria, including highly resistant strains such as MRSA.
Is daptomycin effective against Gram-negative pathogens?
No, daptomycin is not active against Gram-negative pathogens.
In what type of infections is daptomycin used?
In the treatment of systemic and life-threatening infections.
Why should daptomycin not be used to treat pneumonia?
Because it has poor activity in the lungs.
What are two specific infections that daptomycin is used to treat?
S. aureus bacteremia and S. aureus endocarditis.
What type of bacteria is Colistin effective against?
Gram-negative bacteria.
What is the chemical structure of Colistin?
A cationic cyclic decapeptide with a fatty acid side chain.
How does Colistin alter membrane permeability?
By binding to negatively charged lipopolysaccharide molecules in the bacterial outer membrane, displacing Ca+2 and Mg+2 ions, and increasing permeability.
What role does the fatty acid tail of Colistin play?
It facilitates further insertion of Colistin into the outer membrane, leading to increased permeability and lysis of the bacterium.
What type of bacteria is Colistin active against?
Many aerobic Gram-negative bacteria.
What types of bacteria does Colistin lack activity against?
Gram-positive bacteria and anaerobic bacteria.
What serious infections is Colistin used to treat?
Infections with multidrug-resistant Gram-negative bacteria, such as UTI, skin infection, and meningitis.
What are the main toxicities associated with Colistin?
Nephrotoxicity and neurotoxicity.
Which specific bacteria are mentioned as being treated with Colistin?
P. aeruginosa, E. coli, Klebsiella spp.
What are the two main categories of cell wall synthesis inhibitors?
Beta-lactams and Non-beta-lactam antibiotics.
What are the subcategories of Beta-lactams?
Penicillins, Cephalosporins, Carbapenem, and Monobactams.
What are the examples of Non-beta-lactam antibiotics?
Vancomycin and Bacitracin.
