Podcast
Questions and Answers
Which generation of cephalosporins is generally considered to be more effective against Gram-positive bacteria, including methicillin-susceptible Staphylococcus aureus (MSSA)?
Which generation of cephalosporins is generally considered to be more effective against Gram-positive bacteria, including methicillin-susceptible Staphylococcus aureus (MSSA)?
- First Generation (correct)
- Fourth Generation
- Third Generation
- Fifth Generation
A patient with a known penicillin allergy requires antibiotic treatment for a Streptococcus pneumoniae infection. Which cephalosporin would be LEAST appropriate, considering potential cross-reactivity?
A patient with a known penicillin allergy requires antibiotic treatment for a Streptococcus pneumoniae infection. Which cephalosporin would be LEAST appropriate, considering potential cross-reactivity?
- Cefazolin (correct)
- Ceftriaxone
- Cefuroxime
- Aztreonam
A patient develops a Pseudomonas aeruginosa infection. Which cephalosporin would be most appropriate to target this specific bacteria?
A patient develops a Pseudomonas aeruginosa infection. Which cephalosporin would be most appropriate to target this specific bacteria?
- Ceftazidime (correct)
- Cephalexin
- Cefazolin
- Cefuroxime
Why is ceftriaxone contraindicated for co-administration with calcium-containing solutions?
Why is ceftriaxone contraindicated for co-administration with calcium-containing solutions?
Which of the following adverse effects is specifically associated with imipenem, especially at high doses or in patients with central nervous system (CNS) lesions or renal insufficiency?
Which of the following adverse effects is specifically associated with imipenem, especially at high doses or in patients with central nervous system (CNS) lesions or renal insufficiency?
A patient is prescribed imipenem, but the prescriber also includes cilastatin in the treatment regimen. What is the purpose of adding cilastatin to imipenem therapy?
A patient is prescribed imipenem, but the prescriber also includes cilastatin in the treatment regimen. What is the purpose of adding cilastatin to imipenem therapy?
Which of the following best describes the spectrum of activity of aztreonam?
Which of the following best describes the spectrum of activity of aztreonam?
A patient with a severe penicillin allergy requires treatment for a Gram-negative bacterial infection. Which of the following antibiotics would be MOST appropriate to use?
A patient with a severe penicillin allergy requires treatment for a Gram-negative bacterial infection. Which of the following antibiotics would be MOST appropriate to use?
Vancomycin is indicated for the treatment of which of the following infections?
Vancomycin is indicated for the treatment of which of the following infections?
What is the key mechanism of action of vancomycin?
What is the key mechanism of action of vancomycin?
A patient receiving vancomycin intravenously develops a rash, flushing, and fever shortly after the infusion begins. What is the MOST likely cause of these symptoms?
A patient receiving vancomycin intravenously develops a rash, flushing, and fever shortly after the infusion begins. What is the MOST likely cause of these symptoms?
How does the mechanism of action of cotrimoxazole (trimethoprim/sulfamethoxazole) lead to its antibacterial effects?
How does the mechanism of action of cotrimoxazole (trimethoprim/sulfamethoxazole) lead to its antibacterial effects?
Why is the use of sulfonamides avoided near term in pregnancy or in neonates?
Why is the use of sulfonamides avoided near term in pregnancy or in neonates?
Bacitracin is primarily used for:
Bacitracin is primarily used for:
Mupirocin is particularly effective against which bacteria:
Mupirocin is particularly effective against which bacteria:
Which of the following cephalosporins is LEAST likely to be effective against Pseudomonas aeruginosa?
Which of the following cephalosporins is LEAST likely to be effective against Pseudomonas aeruginosa?
A patient is prescribed cefuroxime for a respiratory tract infection. Which of the following statements regarding cefuroxime is most accurate?
A patient is prescribed cefuroxime for a respiratory tract infection. Which of the following statements regarding cefuroxime is most accurate?
Which of the following statements regarding the use of cephalosporins in patients with penicillin allergies is MOST accurate?
Which of the following statements regarding the use of cephalosporins in patients with penicillin allergies is MOST accurate?
What is the primary reason meropenem is considered to have a lower risk of seizures compared to imipenem?
What is the primary reason meropenem is considered to have a lower risk of seizures compared to imipenem?
Why is aztreonam a suitable option for patients with penicillin allergies?
Why is aztreonam a suitable option for patients with penicillin allergies?
Which of the following statements is MOST accurate regarding the administration of vancomycin?
Which of the following statements is MOST accurate regarding the administration of vancomycin?
What is the most likely mechanism behind 'Red man syndrome,' a common adverse effect associated with rapid vancomycin infusion?
What is the most likely mechanism behind 'Red man syndrome,' a common adverse effect associated with rapid vancomycin infusion?
What is the rationale for using trimethoprim in combination with sulfamethoxazole?
What is the rationale for using trimethoprim in combination with sulfamethoxazole?
What is the primary mechanism by which sulfonamides can cause kernicterus in neonates?
What is the primary mechanism by which sulfonamides can cause kernicterus in neonates?
Which of the following best describes the clinical use of bacitracin, considering its mechanism of action and potential toxicities?
Which of the following best describes the clinical use of bacitracin, considering its mechanism of action and potential toxicities?
Mupirocin is commonly used to treat impetigo. What is the MOST likely mechanism of action that makes it effective for this condition?
Mupirocin is commonly used to treat impetigo. What is the MOST likely mechanism of action that makes it effective for this condition?
A patient is diagnosed with a mixed aerobic and anaerobic intra-abdominal infection following surgery. Which of the following cephalosporins would offer the broadest spectrum of activity against both types of bacteria?
A patient is diagnosed with a mixed aerobic and anaerobic intra-abdominal infection following surgery. Which of the following cephalosporins would offer the broadest spectrum of activity against both types of bacteria?
While most cephalosporins are renally excreted, which of the following is primarily eliminated via the biliary route, a consideration in patients with renal impairment?
While most cephalosporins are renally excreted, which of the following is primarily eliminated via the biliary route, a consideration in patients with renal impairment?
A patient is prescribed cotrimoxazole. Which of the following findings indicates a potential adverse drug reaction that warrants immediate attention?
A patient is prescribed cotrimoxazole. Which of the following findings indicates a potential adverse drug reaction that warrants immediate attention?
A patient with a history of renal insufficiency is prescribed an aminoglycoside antibiotic in conjunction with a cephalosporin. Which cephalosporin adverse effect should be MOST closely monitored?
A patient with a history of renal insufficiency is prescribed an aminoglycoside antibiotic in conjunction with a cephalosporin. Which cephalosporin adverse effect should be MOST closely monitored?
Flashcards
Cephalosporins
Cephalosporins
Inhibits bacterial cell wall synthesis; similar to penicillin, many generations exist.
Carbapenems
Carbapenems
A group of antibiotics that inhibit the cell wall synthesis. Effective against bacteria that are resistant to beta-lactam antibiotics.
Monobactams
Monobactams
An antibiotic that is effective against narrow range of Gram-negative bacteria, including Pseudomonas aeruginosa. It can be used on patients allergic to penicillins or cephalosporins.
Vancomycin
Vancomycin
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Folate Metabolism Inhibitors
Folate Metabolism Inhibitors
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Mupirocin
Mupirocin
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Polymyxin B
Polymyxin B
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Cilastatin
Cilastatin
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Bacitracin
Bacitracin
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Kernicterus
Kernicterus
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Beta-lactamases
Beta-lactamases
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Cephalosporin Generations
Cephalosporin Generations
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Cephalosporins Uses
Cephalosporins Uses
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Cephalosporins: Diarrhea
Cephalosporins: Diarrhea
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Cephalosporins: Injection Pain
Cephalosporins: Injection Pain
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Ceftriaxone Precaution
Ceftriaxone Precaution
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Sulfamethoxazole Action
Sulfamethoxazole Action
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Trimethoprim Action
Trimethoprim Action
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Sulfa Drug Side Effects
Sulfa Drug Side Effects
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Steven-Johnson Syndrome
Steven-Johnson Syndrome
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Crystalluria & Nephropathy
Crystalluria & Nephropathy
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Study Notes
Cell Wall Inhibitors
- Includes Cephalosporins
- Mechanism of action is similar to Penicillin
Cephalosporins
- Classified into 5 generations: 1st, 2nd, 3rd, 4th, and 5th Generation
- Cephalosporins are generally resistant to beta-lactamases, except for the 1st and 2nd generations, which are sensitive
1st Generation Cephalosporins
- Cefazolin, Cephalexin (PO), Cefadoxil (PO)
- Highly active on Gram-positive bacteria (including MSSA) and some activity against Gram-negative bacteria
2nd Generation Cephalosporins
- Cefuroxime (IV/PO), Cefoxitin, Cefaclor (PO)
- More active on Gram-negative than 1st generation, weaker on Gram-positive.
- Active against anaerobes
3rd Generation Cephalosporins
- Cefotaxime, Ceftriaxone, Cefixime (po), Cefoperazone, Ceftazidime (Antipseudomons)
- Activity against Gram-negative bacteria and variable activity against Gram-positive bacteria
4th Generation Cephalosporins
- Cefepime
- Activity against Gram-positive, Gram-negative, and Pseudomonas
5th Generation Cephalosporins
- Ceftaroline (Anti-MRSA)
- Activity against Gram-positive, Gram-negative, and MRSA
Cephalosporin Uses
- Commonly used antibiotic
- Alternatives to penicillins for ENT, upper respiratory tract, and skin infections, particularly when 1st generation cephalosporins can be used
- Treatment of penicillinase-producing staphylococcal infections
- Treatment of respiratory, urinary, and soft tissue infections
- Treatment of Septicemia, combined with aminoglycosides
- Surgical prophylaxis: Cefazolin is used
- Treatment and prophylaxis of Meningitis: Ceftriaxone is used
- Treatment of Gonorrhoea
- Treatment of Typhoid: Ceftriaxone and Cefoperazone are excreted mainly in bile
- Treatment of Pseudomonal infections using anti-pseudomonal cephalosporins
- Treatment of Mixed aerobic/anaerobic infections like Peritonitis & Pelvic Inflammatory Disease (PID) using Cefuroxime, cefotaxime, and ceftriaxone
Cephalosporin Adverse Effects
- Hypersensitivity reactions: similar to penicillin but less common
- 10% of patients allergic to penicillin show cross-reactivity with cephalosporins
- Patients with an immediate-type reaction to penicillin should not be given cephalosporins
- Diarrhea: due to alteration of gut flora, more common with oral agents
- Pain after IM injection
- Thrombophlebitis after IV injection
- Hypoprothrombinaemia (bleeding) with cefoperazone and ceftriaxone
- Low-grade nephrotoxicity with preexisting renal disease and concurrent use of aminoglycosides
Cephalosporin Precaution
- Ceftriaxone should not be mixed or co-administered with calcium-containing solutions due to the risk of precipitation of ceftriaxone-calcium salt and should not be administered within 48 hours of each other
Carbapenems and Monobactams
- Both are types of cell wall inhibitors
Carbapenems
- Imipenem, Meropenem
- Similar mechanism to penicillin (binds to specific PBP)
- Administered via IV or IM injection
- Broad spectrum: Effective against Gram-positive, Gram-negative, Pseudomonas, and anaerobic bacteria
- Resistant to most beta-lactamases
- May cause cross-sensitivity in patients allergic to other beta-lactam antibiotics.
- Used for severe infections due to multi-resistant organisms, and serious mixed infections (pulmonary, intra-abdominal & soft-tissue)
- Common side effects nausea and vomiting
- Seizures (especially with imipenem) may occur with high doses, CNS lesions, or renal insufficiency
- Imipenem is combined with cilastatin to inhibit its metabolism and prolong its activity
- Imipenem decreases the metabolism of Imipenem which in turn, it prolings drug activity and prevent formation of nephrotoxic metabolites
- Meropenem is not combined with cilastatin since it's not sensitive to renal dipeptidase
Monobactams
- Aztreonam
- Similar mechanism to penicillin (binds to specific PBP)
- Administered via IV or IM injection
- Narrow spectrum: Effective against Gram-negative bacteria including Pseudomonas aeruginosa
- Resistant to narrow-spectrum beta-lactamases
- No cross-sensitivity: can be used in patients allergic to penicillins or cephalosporins
- Used for hospital-acquired infections (urinary, biliary, GI & female genital tracts)
- May cause hepatotoxicity, especially in infants and young children
Vancomycin
- Spectrum: Gram-positive bacteria, including MRSA, Enterococcus, and Clostridium difficile
- Mechanism of Action: Inhibits cell wall synthesis by preventing the assembly of peptidoglycan units and cross-linking.
- Route of Administration: Injection (not absorbed orally)
- Can be administered Orally (in specific indications)
- Systemic use targets MRSA infections (skin and soft tissue infections, pneumonia, osteomyelitis, septicemia, endocarditis, meningitis, surgical prophylaxis if MRSA areas) and as a penicillin substitute for allergic patients.
- Oral use treats pseudomembranous colitis (second-line to metronidazole) and staphylococcal enterocolitis.
- Adverse effects include ototoxicity (potentially permanent nerve damage), nephrotoxicity, and red man syndrome (rash, fever, and flushing due to rapid histamine release).
Folate Metabolism Inhibitors
- Cotrimoxazole (Sulfamethoxazole + Trimethoprim)
Mechanism of Action
- Cotrimoxazole (sulfamethoxazole/trimethoprim)
- Bactericidal
- Sulfamethoxazole inhibits dihydrofolate synthase
- Prevents conversion of PAPA to DHFA (folic acid)
- Trimethoprim: Inhibits dihydrofolate reductase, which prevents conversion of DHFA (folic acid) to THFA (folinic acid)
- This process is essential for nucleic acid and protein synthesis
Folate Synthesis
- THFA is needed for bacterial protein, DNA, and RNA synthesis
- PABA is para-amino-benzoic acid
- DHFA is di-hydro-folic acid
- THFA is tetra-hydro-folic acid
Spectrum
- Broad spectrum
- Effective against Gram-positive and Gram-negative bacteria
- Effective against Pneumocystis jiroveci (fungus) and malarial parasite
Uses
- Upper Respiratory Tract Infections
- Urinary Tract Infections (UTI)
- Pneumocystis jiroveci pneumonia (PJP)
- Bronchitis
- Prostatitis and vaginitis
- Malaria
Side Effects
- Sulfamethoxazole causes hypersensitivity reactions, including fever, rash, and Steven-Johnson syndrome (rare but potentially fatal)
- Crysalluria and nephropathy: due to insoluble metabolite
- Jaundice and Kernicterus in neonates: If sulfonamide is used near term (last 2 weeks) during pregnancy or in neonates, it causes bilirubin encephalopathy
- BCZ displaces bilirubin from plasma protein binding sites and bilirubin crosses BBB
- Trimethoprim can cause megaloblastic anemia or neural tube defects in babies of pregnant women
Bacitracin
- Mechanism of Action: Inhibits cell wall synthesis
- Spectrum: Gram-positive bacteria
- Only topical application (toxic if systemic)
- Uses: Available in ophthalmic and dermatologic ointments
Polymyxin B
- Mechanism of Action: Disrupts the structure of the bacterial cell membrane.
- Works against Gram-negative bacteria
- There are topical preparations of bacitracin that may include polymyxin and/or neomycin
Mupirocin
- Mechanism of Action: Inhibits bacterial protein synthesis.
- Spectrum: Gram-positive bacteria, with good activity against S. pyogenes, MSSA, and MRSA.
- Administered topically only
- Available as cream and ointment for dermatologic use and as an ointment for intranasal use
- Indicated for the treatment of traumatic skin lesions and impetigo secondarily infected with S. aureus or S. pyogenes.
- Side effects include irritation at the site of application and eye irritation (if there is eye contact)
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