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Questions and Answers
Which class of antibiotics works by inhibiting bacterial growth rather than killing bacteria immediately?
Which class of antibiotics works by inhibiting bacterial growth rather than killing bacteria immediately?
What is the main purpose of clavulanic acid in the context of antibiotics?
What is the main purpose of clavulanic acid in the context of antibiotics?
Which antibiotic is highlighted as being effective against Pseudomonas aeruginosa?
Which antibiotic is highlighted as being effective against Pseudomonas aeruginosa?
What characteristic is unique to aminoglycosides compared to other classes of antibiotics?
What characteristic is unique to aminoglycosides compared to other classes of antibiotics?
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Which of the following antibiotics is specifically resistant to penicillinase?
Which of the following antibiotics is specifically resistant to penicillinase?
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What is the primary mode of action of sulfonamides?
What is the primary mode of action of sulfonamides?
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Which antibiotic is used primarily as a topical agent?
Which antibiotic is used primarily as a topical agent?
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What type of bacterial infections can Gentamicin treat?
What type of bacterial infections can Gentamicin treat?
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What is the primary action of antibiotics that inhibit RNA polymerase?
What is the primary action of antibiotics that inhibit RNA polymerase?
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What is the reason for combining β lactams in treatment?
What is the reason for combining β lactams in treatment?
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Which of the following is NOT a result of misusing antibiotics?
Which of the following is NOT a result of misusing antibiotics?
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What is a characteristic of live, nonpathogenic bacteria in medical treatment?
What is a characteristic of live, nonpathogenic bacteria in medical treatment?
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Which of the following factors contributes to the unresponsiveness of microorganisms to antibiotics?
Which of the following factors contributes to the unresponsiveness of microorganisms to antibiotics?
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Which condition could potentially lead to serious complications when using probiotics?
Which condition could potentially lead to serious complications when using probiotics?
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Which of the following is a method by which bacteria develop resistance to antibiotics?
Which of the following is a method by which bacteria develop resistance to antibiotics?
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What type of infection is more likely to occur due to the emergence of multidrug-resistant bacteria?
What type of infection is more likely to occur due to the emergence of multidrug-resistant bacteria?
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What is a primary reason for the use of combinations of antibiotics in treating polymicrobial infections?
What is a primary reason for the use of combinations of antibiotics in treating polymicrobial infections?
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What is a potential consequence of incorrect antibiotic combinations in treatment?
What is a potential consequence of incorrect antibiotic combinations in treatment?
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Which of the following mechanisms is NOT associated with the unresponsiveness of microorganisms to antibiotics?
Which of the following mechanisms is NOT associated with the unresponsiveness of microorganisms to antibiotics?
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What characteristic allows penicillins to have selective toxicity against bacteria?
What characteristic allows penicillins to have selective toxicity against bacteria?
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What describes the effect of live, nonpathogenic bacteria in treating diseases?
What describes the effect of live, nonpathogenic bacteria in treating diseases?
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Which of the following classes of antibiotics includes compounds effective against MRSA?
Which of the following classes of antibiotics includes compounds effective against MRSA?
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What is the outcome of the phenomenon of '1 + 1 = 0' in antibiotic therapy?
What is the outcome of the phenomenon of '1 + 1 = 0' in antibiotic therapy?
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Which of the following is a common cause of multidrug resistance in bacteria?
Which of the following is a common cause of multidrug resistance in bacteria?
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Which antibiotic can be described as both bactericidal and effective against Gram-positive bacteria?
Which antibiotic can be described as both bactericidal and effective against Gram-positive bacteria?
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Which type of patients are particularly at risk of serious complications from probiotic use?
Which type of patients are particularly at risk of serious complications from probiotic use?
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What is the primary role of beta-lactamases in bacterial resistance?
What is the primary role of beta-lactamases in bacterial resistance?
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Which of the following antibiotics specifically targets DNA gyrase?
Which of the following antibiotics specifically targets DNA gyrase?
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What is the term used to describe bacteria's ability to decrease antibiotic accumulation internally?
What is the term used to describe bacteria's ability to decrease antibiotic accumulation internally?
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What type of bacteria is resistant to natural penicillins, necessitating the use of penicillinase-resistant alternatives?
What type of bacteria is resistant to natural penicillins, necessitating the use of penicillinase-resistant alternatives?
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Which antibiotic example is primarily used in the treatment of urinary tract infections (UTIs)?
Which antibiotic example is primarily used in the treatment of urinary tract infections (UTIs)?
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What is the function of compounds like clavulanic acid in antibiotic therapy?
What is the function of compounds like clavulanic acid in antibiotic therapy?
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Study Notes
Antimicrobial Definitions
- Antimicrobials: Naturally occurring or synthetically derived compounds that inhibit or destroy bacteria.
- Ideal Antibiotic: Shows selective toxicity, does not develop bacterial resistance, is non-allergenic, water-soluble, and stable with good tissue distribution.
- Bactericidal: Kill bacteria; examples include aminoglycosides, beta-lactams, vancomycin, quinolones, rifampin, and metronidazole.
- Bacteriostatic: Inhibit bacterial growth; examples include chloramphenicol, clindamycin, erythromycin, sulfonamides, trimethoprim, and tetracyclines.
- Antifungal: Targets fungi.
- Antiviral: Targets viruses.
- Antiprotozoal: Targets protozoa.
- Antihelminth: Targets parasitic worms.
Mechanisms of Action of Antibiotics
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Cell Wall Synthesis Inhibitors: Prevent the synthesis of peptidoglycans needed for the bacterial cell wall.
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Penicillins: Interfere with the synthesis of bacterial cell walls.
- Natural penicillins are effective against gram-positive cocci except Staphylococcus aureus.
- Penicillinase-resistant penicillins are effective against Staphylococci aureus.
- Extended-spectrum penicillins work against many gram-negative bacteria.
- Cephalosporins: Broad-spectrum antibiotics that work similarly to penicillins.
- Glycopeptides (Vancomycin): Important in treating methicillin-resistant Staphylococcus aureus (MRSA).
- Monobactam (Aztreonam): Specifically works on Pseudomonas aeruginosa.
- Carbapenems (Imipenem): Powerful drugs that are generally effective against gram-negative organisms, including Pseudomonas.
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Penicillins: Interfere with the synthesis of bacterial cell walls.
Inhibitors of Protein Synthesis
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30S Inhibitors: Bind to the bacterial 30S ribosomal subunit, disrupting protein synthesis.
- Examples: Aminoglycosides (gentamicin, amikacin), Tetracyclines (oxytetracycline).
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50S Inhibitors: Bind to the 50S ribosomal subunit, also disrupting protein synthesis.
- Examples: Macrolides (erythromycin), Chloramphenicol, Streptogramins (retapamulin).
Alteration of Cell Membrane Function
- Polymyxins: Topical antibiotics that disrupt the bacterial membrane.
- Daptomycin: Active against gram-positive bacteria, including MRSA and VRSA.
Inhibitors of Nucleic Acid Synthesis
- Co-trimoxazole: Treatment for urinary tract infections (UTIs). Combines sulphamethoxazole and trimethoprim.
- Quinolones (Ciprofloxacin, Levofloxacin): Inhibit DNA gyrase.
- Rifampicin: Inhibits RNA polymerase, inhibiting mRNA synthesis, and is used to treat tuberculosis.
Antimicrobial Combinations (Synergistic/Antagonistic)
- Additive Effects: Results in a sum of individual antimicrobial effects.
- Synergistic Effects: A combination of antimicrobials that produce a result better than that of the individual acting alone.
- Antagonistic Effects: A combination of antimicrobials that produce a result worse than that of the individual effect alone
Probiotics
- Live, nonpathogenic bacteria and/or yeasts used to treat or prevent diseases.
- Mechanisms: Exclude pathogens by colonizing the mucosa, enhance immune response, reduce inflammation, and treat antibiotic-associated diarrhea. Examples of probiotic foods: Yogurt, tempeh, sourdough, kimchi, kombucha, and sauerkraut.
Bacterial Resistance to Antibiotics & Failure of Treatment
- Misuse of Antibiotics Leading to emergence of multidrug-resistant bacteria including the following: MRSA, VRSA, and Pan-resistant Gram-negative bacteria.
- Causes for failure: Choice of antibiotic, inadequate dosage, or duration of treatment, route of antibiotic administration, or using antagonistic antibiotic combination.
- Bacterial resistance mechanisms: Reduction in intracellular antibiotic accumulation (decreasing permeability) or active efflux (efflux pumps) of the antibiotic. Enzymatic inactivation (inactivating enzymes) of antibiotics or alteration or inactivation of the target receptors of the antibiotic.
- Failure of antibiotic treatment can result from viral or mixed bacterial infection, inappropriate antibiotic choice, inadequate dosage, or treatment duration, incorrect administration route, or antagonistic antibiotic combinations.
- Misuse of antibiotics leads to the development of resistant strains, including multidrug-resistant (MDR) bacteria, which can cause life-threatening infections.
Clinical Case and Questions (Page 8)
- Clinical Case: A 45-year old female presenting with fever, burning urination, frequency, and dysuria; microbiological tests revealed gram-negative bacilli, Nitrofurantoin was prescribed.
- Inhibitors of protein synthesis: Tetracyclines, Aminoglycosides, Macrolides, Chloramphenicol
- Mechanisms of Antibiotic Resistance:
- Decreased permeability of the cell wall to the antibiotic.
- Active efflux pumps remove the antibiotic from the bacterial cell.
- Enzymatic inactivation of the antibiotic (e.g., inactivation of penicillins by β-lactamases).
- Modification of the bacterial target site (e.g., alteration of the ribosome preventing antibiotic binding).
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