40 Questions
Which type of bacteria is this antibiotic effective against?
Aerobic gram-negative organisms
What is the name of the combinations used to manage complicated infections?
Beta-lactam and beta-lactamase inhibitor combinations
What is the main function of peptidoglycan in bacterial cells?
Provides mechanical stability to the cell wall
What is the structure of peptidoglycan in gram-positive bacteria?
Thick and made of multiple layers
What is the action of beta-lactam antibiotics on peptidoglycan synthesis?
They inhibit the synthesis of peptidoglycan
What are the targets of beta-lactam antibiotics?
Penicillin-binding proteins
What is the effect of food on the oral absorption of antibiotics?
Food can affect oral absorption of antibiotics
What is the consequence of beta-lactam antibiotics binding to penicillin-binding proteins?
Inhibition of peptidoglycan synthesis
What is a unique feature of the structure of sulfonamide antibiotics?
N4 amine group
What is the mode of action of sulfonamides?
They competitively inhibit the synthesis of folic acid
What is the classification of sulfonamides based on?
Their half-life
What happens to a cell when the process of tetracyclines is halted?
It can no longer maintain proper functioning and will be unable to grow or further replicate
What is the primary use of sulfonamides?
Preventing UTIs
What is the term used to describe the effect of tetracyclines on bacterial cells?
Bacteriostatic
Why are human cells unaffected by sulfonamides?
They utilize preformed folic acid from the diet
What is the sensitivity pattern of sulfonamides among microbes?
Time-dependent and place-dependent
What is a growing concern regarding tetracycline antibiotics?
The emergence of bacterial strains resistant to them
Where are bacterial genes that are resistant to tetracyclines often encoded?
On plasmids or transferable elements
What is a consequence of bacterial resistance to sulfonamides?
Decreased susceptibility to other antibiotics
What is one mechanism of resistance to tetracyclines?
Altering ribosomal protection proteins
What is the nature of sulfonamides?
Bacteriostatic
What is the primary site of oral tetracycline absorption?
All of the above
What decreases the absorption of tetracyclines when administered?
Multivalent cations
Where do tetracyclines have poor penetration?
Cerebral spinal fluid
What is the drug of choice for respiratory infections caused by pneumocystis jiroveci and Nocardia asteroides?
Cotrimoxazole
What is the pregnancy category of chloramphenicol?
Category C
What is a common side effect of sulfonamide and cotrimoxazole?
All of the above
Why should cotrimoxazole be avoided during pregnancy?
All of the above
Why should plasma concentrations of chloramphenicol be monitored?
Especially in the elderly, children, and those with hepatic impairment
What is the therapeutic range of chloramphenicol?
15 to 25 mg/L
What is the primary mechanism of action of beta-lactam antibiotics?
Inhibition of cell wall formation
Why should female patients have pregnancy tests before starting chloramphenicol?
To ensure they are not pregnant
What is the estimated percentage of the total antibiotic market accounted for by beta-lactam antibiotics?
60%
What is the name of the ring structure found in beta-lactam antibiotics?
4-membered cyclic amide
What is a common symptom of aplastic anemia?
Excessive tiredness
What is the most common route of administration associated with fatal overdoses of chloramphenicol?
Intravenous administration
What is the name of the group of antibiotics that includes penicillin, cephalosporins, and monobactams?
Beta-lactam antibiotics
Why should the dose of cotrimoxazole be reduced in patients with renal disease?
To prevent ureamia
What is the condition caused by chloramphenicol toxicity in infants?
Grey baby syndrome
Why are preterm neonates more likely to be affected by chloramphenicol toxicity?
Because their liver is immature
Study Notes
Sulfonamide Antibiotics
- Sulfonamide antibiotics have an N4 amine group in their structure, which contributes to their higher incidence of allergic-type reactions.
- They are bacteriostatic in nature, acting as antimetabolites, and were the first antimicrobial agents used against pyrogenic bacteria.
Classification of Sulfonamides
- Sulfonamides are classified based on their half-life:
- Short-acting (4-8 hours): e.g., Sulfadiazine
- Intermediate-acting (8-12 hours): e.g., Sulfamethoxazole, Sulfamoxazole
- Long-acting (7 days): e.g., Sulfadoxine, Sulfamethapyrazine
- Special-purpose sulfonamides: e.g., Sulfacetamide, Sulfasalazine, Silver sulfadiazine
Mode of Action of Sulfonamides
- Sulfonamides inhibit bacterial folate synthase, which leads to the inhibition of folate formation.
- They competitively inhibit the synthesis of dihydrofolic acid, which is essential for bacterial growth.
- Human cells, which require preformed folic acid, are unaffected by sulfonamides.
Antibacterial Spectrum of Sulfonamides
- Sulfonamides are primarily bacteriostatic against many gram-positive and gram-negative bacteria.
- In higher concentrations, they may act as bactericidal.
- They are sensitive to Streptococcus pyogenes, Haemophilus influenza, and Vibrio cholerae.
- They are primarily used to prevent urinary tract infections (UTIs).
Resistance to Sulfonamides
- Most bacteria can develop resistance to sulfonamides.
- Resistance is common in upper and lower respiratory tract infections (RTIs), Haemophilus influenza, and chronic bronchitis.
Adverse Effects of Sulfonamides
- All adverse effects of sulfonamides can be produced by cotrimoxazole.
- Folate deficiency (megaloblastic anemia) and blood dyscrasias can occur.
- Caution should be taken when administering sulfonamides to pregnant women, elderly people, and patients with renal disease.
Beta-Lactam Antibiotics
- Beta-lactam antibiotics contain a 4-membered cyclic amide (β-lactam ring).
- They include penicillins, cephalosporins, thienamycins, clavulanic acid, nocardicins, and monobactams.
Mechanism of Action of Beta-Lactam Antibiotics
- Beta-lactam antibiotics inhibit the last step in peptidoglycan synthesis by acylating the transpeptidase involved in cross-linking peptides to form peptidoglycan.
- They target penicillin-binding proteins (PBPs), leading to the loss of viability and lysis of bacterial cells.
Administration of Beta-Lactam Antibiotics
- Oral administration can be affected by food, and oral absorption occurs primarily in the stomach, duodenum, and small intestine.
- Topical, intramuscular (IM), and intravenous (IV) forms of the medication are also available.
Resistance to Beta-Lactam Antibiotics
- Bacterial resistance to beta-lactam antibiotics is a growing concern.
- Mechanisms of resistance include alteration in ribosomal protection proteins, efflux pumps, and tetracycline modification.
Learn about sulfonamide antibiotics, their structure, and mechanism of action. Understand their classification based on half-life and examples of short-acting and intermediate-acting sulfonamides.
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