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Rifamycins: Side Effects and Antimicrobial Activity
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Rifamycins: Side Effects and Antimicrobial Activity

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Questions and Answers

What is a common side effect of rifamycins?

  • Hypertension
  • Uveitis
  • Hepatitis
  • Nausea and vomiting (correct)

    • What is the primary use of rifamycins?

  • Combating viral infections
  • Treating gram-negative bacterial infections
  • Treating skin infections
  • Multidrug regimens for mycobacterial infections (correct)

    • What is a unique effect of rifampin?

  • It causes an orange-red discoloration of skin
  • It causes an orange-red discoloration of saliva
  • It causes an orange-red discoloration of urine
  • It causes an orange-red discoloration of tears (correct)

    • What is associated with rifabutin?

    <p>Uveitis</p> Signup and view all the answers

    What is the origin of the name 'rifamycin'?

    <p>From a French movie title</p> Signup and view all the answers

    What is the function of rifamycins in antibiotic treatment?

    <p>To add an accentuation effect to traditional treatment</p> Signup and view all the answers

    What is a potential consequence of rifampin use?

    <p>Staining of contact lenses</p> Signup and view all the answers

    What type of bacteria is susceptible to rifamycins?

    <p>Both gram-positive and gram-negative bacteria</p> Signup and view all the answers

    How do rifamycins contribute to antibacterial treatment?

    <p>By inhibiting bacterial transcription and translation</p> Signup and view all the answers

    What is the process by which mRNA is synthesized from DNA genes?

    <p>Transcription</p> Signup and view all the answers

    What is a possible hematologic abnormality associated with rifamycins?

    <p>Any of the above</p> Signup and view all the answers

    Why are rifamycins called 'accessory' antibiotics?

    <p>Because they are added to traditional treatment</p> Signup and view all the answers

    What is the outcome of inhibiting bacterial transcription and translation?

    <p>Inhibition of bacterial growth</p> Signup and view all the answers

    Which of the following is NOT a type of rifamycin?

    <p>Penicillin</p> Signup and view all the answers

    What is the process by which proteins are generated from mRNA templates?

    <p>Translation</p> Signup and view all the answers

    Why are antibiotics that inhibit bacterial transcription and translation effective against bacterial growth?

    <p>Because they inhibit protein synthesis</p> Signup and view all the answers

    What is the common structure of rifamycins?

    <p>An aromatic nucleus linked by an aliphatic handle on both ends</p> Signup and view all the answers

    What is the mechanism of action of rifamycins?

    <p>By inhibiting bacterial RNA polymerase</p> Signup and view all the answers

    How do rifamycins inhibit bacterial RNA polymerase?

    <p>By nestling deep into the DNA/RNA tunnel and steric blocking</p> Signup and view all the answers

    Why are rifamycins usually used in combination with other agents?

    <p>To prevent the emergence of resistant strains</p> Signup and view all the answers

    What is the effect of rifampin on the cytochrome P-450 system?

    <p>It induces the cytochrome P-450 system</p> Signup and view all the answers

    Why is rifabutin favored over rifampin in individuals with HIV infection?

    <p>Because it inhibits the cytochrome P-450 system to a lesser degree</p> Signup and view all the answers

    What is the advantage of using rifampin alone in prophylaxis?

    <p>It minimizes the chance that a rifampin-resistance mutation will spontaneously occur</p> Signup and view all the answers

    What is the common indication for rifamycins?

    <p>All of the above</p> Signup and view all the answers

    What is the purpose of rifamycins in antibacterial treatment?

    <p>To enhance the effectiveness of traditional treatment</p> Signup and view all the answers

    What is the significance of rifamycins in the context of bacterial growth?

    <p>They are targeting a crucial process for bacterial growth</p> Signup and view all the answers

    What is the role of rifamycins in relation to traditional antibiotics?

    <p>They are used in conjunction with traditional antibiotics</p> Signup and view all the answers

    What is the common feature of rifampin, rifabutin, rifapentine, and rifaximin?

    <p>They are all types of rifamycins</p> Signup and view all the answers

    What is the process that is targeted by rifamycins in order to inhibit bacterial growth?

    <p>Transcription and translation</p> Signup and view all the answers

    Why are rifamycins not typically used as a primary treatment?

    <p>They are usually used to enhance the effect of traditional antibiotics</p> Signup and view all the answers

    What is the relationship between rifamycins and bacterial growth?

    <p>Rifamycins inhibit bacterial growth</p> Signup and view all the answers

    What is the significance of rifamycins in antibacterial treatment?

    <p>They provide a minor enhancement to antibacterial treatment</p> Signup and view all the answers

    What is a characteristic of the antimicrobial activity of rifamycins?

    <p>They are effective against Gram-positive and Gram-negative bacteria, as well as Mycobacteria.</p> Signup and view all the answers

    What is a potential consequence of rifampin use on bodily fluids?

    <p>It results in an orange-red discoloration of tears, urine, and other body fluids.</p> Signup and view all the answers

    What is the primary use of rifabutin?

    <p>Treating mycobacterial infections</p> Signup and view all the answers

    What is a unique effect of rifampin on contact lenses?

    <p>It stains them.</p> Signup and view all the answers

    What is a common hematologic abnormality associated with rifamycins?

    <p>Neutropenia</p> Signup and view all the answers

    What is the origin of the name 'rifamycin'?

    <p>From the French movie Rififi</p> Signup and view all the answers

    What is a possible ocular effect of rifabutin?

    <p>Uveitis</p> Signup and view all the answers

    What is the common structural feature of rifamycins?

    <p>Aromatic nucleus linked on both ends by an aliphatic “handle”</p> Signup and view all the answers

    How do rifamycins act on bacterial RNA polymerase?

    <p>They nestle deep into the DNA/RNA tunnel of the enzyme and sterically block elongation of the nascent mRNA molecule.</p> Signup and view all the answers

    Why do single mutations in the bacterial gene that encodes RNA polymerase lead to resistance to rifamycins?

    <p>Because they alter the binding site of rifamycins on RNA polymerase, preventing binding.</p> Signup and view all the answers

    Why are rifamycins usually used in combination with other agents?

    <p>To reduce the risk of resistance development.</p> Signup and view all the answers

    What is a unique characteristic of rifampin?

    <p>It is the most potent inducer of the cytochrome P-450 system.</p> Signup and view all the answers

    Why is rifabutin favored over rifampin in individuals with HIV infection?

    <p>It inhibits the cytochrome P-450 system to a lesser degree than rifampin.</p> Signup and view all the answers

    What is an advantage of using rifampin alone in prophylaxis?

    <p>It minimizes the chance that a rifampin-resistance mutation will spontaneously occur.</p> Signup and view all the answers

    Against which bacteria is rifampin effective as monotherapy for prophylaxis?

    <p>Neisseria meningitidis and Haemophilus influenzae</p> Signup and view all the answers

    What is the structural feature of aminoglycosides that includes amino sugars bound by glycosidic linkages?

    <p>A six-membered ring</p> Signup and view all the answers

    Which bacterial strains are aminoglycosides commonly used to treat?

    <p>Members of the Enterobacteriaceae and Pseudomonas aeruginosa</p> Signup and view all the answers

    Why are aminoglycosides usually used in combination with another active agent?

    <p>Because of disappointing results in animal studies</p> Signup and view all the answers

    What is the effect of antibiotics that inhibit bacterial cell wall synthesis on the uptake of aminoglycosides?

    <p>They enhance the uptake of aminoglycosides</p> Signup and view all the answers

    What is the effect of combining aminoglycosides with cell wall-active agents on aerobic gram-positive bacteria?

    <p>It has a synergistic effect</p> Signup and view all the answers

    Why are lower amounts of aminoglycosides used when combined with cell wall-active agents?

    <p>Because of their reduced dosage requirements</p> Signup and view all the answers

    What is the activity of aminoglycosides against aerobic gram-positive bacteria?

    <p>Lesser activity</p> Signup and view all the answers

    What is a characteristic of amikacin?

    <p>It is resistant to modification by some bacterial enzymes</p> Signup and view all the answers

    What is the main factor limiting the use of aminoglycosides?

    <p>Their toxicity</p> Signup and view all the answers

    What percentage of patients who receive aminoglycosides will develop nephrotoxicity or decreased renal function?

    <p>5% to 10%</p> Signup and view all the answers

    Which type of cells do aminoglycosides penetrate poorly, except for proximal renal tubule cells?

    <p>Human cells</p> Signup and view all the answers

    What is the typical time frame for renal toxicity to occur after starting aminoglycoside therapy?

    <p>4 to 5 days</p> Signup and view all the answers

    What is the usual outcome of aminoglycoside-induced nephrotoxicity?

    <p>Reversible kidney damage</p> Signup and view all the answers

    What is the most common type of ototoxicity associated with aminoglycosides?

    <p>Auditory impairment</p> Signup and view all the answers

    Which aminoglycoside is associated with especially high rates of vestibular toxicity?

    <p>Streptomycin</p> Signup and view all the answers

    What is the main advantage of using aminoglycosides in combination with cell wall-active agents?

    <p>Synergistic activity</p> Signup and view all the answers

    What is the primary reason aminoglycosides are effective against aerobic gram-negative bacteria?

    <p>Their positively charged nature allows them to bind to the negatively charged outer membrane</p> Signup and view all the answers

    How do aminoglycosides access the bacterial ribosomes?

    <p>Through an energy-dependent active bacterial transport mechanism that requires oxygen and an active proton motive force</p> Signup and view all the answers

    What is the target of aminoglycosides in bacterial cells?

    <p>The 30S subunit of the bacterial ribosome</p> Signup and view all the answers

    Why do aminoglycosides work poorly in anaerobic and acidic environments?

    <p>Because they require oxygen and an active proton motive force for their transport mechanism</p> Signup and view all the answers

    What is the result of aminoglycosides binding to the 30S subunit of the bacterial ribosome?

    <p>Protein mistranslation</p> Signup and view all the answers

    What is the characteristic of aminoglycosides that allows them to bind to the bacterial outer membrane?

    <p>Their positively charged nature</p> Signup and view all the answers

    Why is resistance to aminoglycoside antibiotics relatively rare?

    <p>For reasons that are unclear</p> Signup and view all the answers

    What is the structure of aminoglycoside molecules?

    <p>Two or more sugars bound by a glycosidic linkage to a central six-membered ring that contains amino group substituents</p> Signup and view all the answers

    Which of the following is an oral agent in the Macrolides class?

    <p>Clarithromycin</p> Signup and view all the answers

    What is a common feature of Erythromycin and Telithromycin?

    <p>They have similar chemical structures</p> Signup and view all the answers

    What is a characteristic of Azithromycin?

    <p>It is an oral agent</p> Signup and view all the answers

    What is Clarithromycin?

    <p>An oral agent in the Macrolides class</p> Signup and view all the answers

    What is a characteristic of Telithromycin?

    <p>It is a Ketolide</p> Signup and view all the answers

    What is a similarity between Macrolides and Ketolides?

    <p>They are both antibiotics with similar chemical structures</p> Signup and view all the answers

    What is a common use of Macrolides and Ketolides?

    <p>Treating bacterial infections</p> Signup and view all the answers

    What is a characteristic of Macrolides?

    <p>They are only effective against staphylococci and streptococci</p> Signup and view all the answers

    What is the common structure of macrolides?

    <p>A large cyclic core with sugar residues</p> Signup and view all the answers

    How do macrolides function?

    <p>By blocking the exit of newly synthesized peptides</p> Signup and view all the answers

    What is a common mechanism of resistance to macrolides?

    <p>All of the above</p> Signup and view all the answers

    What is the effect of methylation of the ribosome in bacteria?

    <p>Increased resistance to macrolides</p> Signup and view all the answers

    What is the result of resistance to one macrolide?

    <p>Resistance to all macrolides</p> Signup and view all the answers

    What is the mechanism of action of aminoglycosides?

    <p>Inhibition of protein synthesis by binding to the 50S subunit of the ribosome</p> Signup and view all the answers

    What is a common feature of macrolides and aminoglycosides?

    <p>Targeting of ribosomes and prevention of protein production</p> Signup and view all the answers

    What is the significance of macrolides and aminoglycosides in antibacterial treatment?

    <p>They are used in combination with other agents to enhance efficacy</p> Signup and view all the answers

    What is the main characteristic of macrolide antibiotics?

    <p>They are active against some gram-positive bacteria, some gram-negative bacteria, and some atypical bacteria.</p> Signup and view all the answers

    Which of the following is a ketolide?

    <p>Telithromycin</p> Signup and view all the answers

    What is the common use of macrolide antibiotics?

    <p>Treatment of respiratory infections</p> Signup and view all the answers

    Which of the following is not a macrolide antibiotic?

    <p>Telithromycin</p> Signup and view all the answers

    What is the characteristic of macrolide antibiotics in terms of their effectiveness?

    <p>They are not reliably effective against most bacteria in any one group</p> Signup and view all the answers

    Which of the following macrolide antibiotics is effective against mycobacteria?

    <p>All of the above</p> Signup and view all the answers

    What is the main advantage of using macrolide antibiotics?

    <p>They are very useful agents for the treatment of specific types of infections</p> Signup and view all the answers

    Which of the following is a common feature of macrolide antibiotics?

    <p>They are active against a wide range of bacteria</p> Signup and view all the answers

    What type of bacteria are tetracyclines active against?

    <p>Aerobic gram-positive and gram-negative bacteria</p> Signup and view all the answers

    Which of the following is an advantage of doxycycline over tetracycline?

    <p>Longer half-life allowing for twice daily dosing</p> Signup and view all the answers

    What is the spectrum of activity of doxycycline?

    <p>Essentially the same as tetracycline</p> Signup and view all the answers

    What is the strength of tetracyclines?

    <p>Activity against atypical bacteria</p> Signup and view all the answers

    What is the common feature of tetracycline and doxycycline?

    <p>Similar spectrum of activity</p> Signup and view all the answers

    What type of bacteria are tetracyclines active against, in addition to aerobic gram-positive bacteria?

    <p>Aerobic gram-negative bacteria</p> Signup and view all the answers

    What is the common indication for tetracyclines?

    <p>Infections caused by atypical bacteria</p> Signup and view all the answers

    What is the structural feature of tetracycline?

    <p>A tetracyclic structure</p> Signup and view all the answers

    What is a unique feature of tigecycline compared to other tetracyclines?

    <p>It has a glycyl amide group that prevents recognition by efflux pumps</p> Signup and view all the answers

    What is minocycline often used to treat?

    <p>Methicillin-resistant staphylococcal infections</p> Signup and view all the answers

    What is the mechanism by which tigecycline is resistant to bacterial efflux pumps?

    <p>It has a glycyl amide group that prevents recognition</p> Signup and view all the answers

    Which of the following bacteria is typically resistant to tigecycline?

    <p>Pseudomonas aeruginosa</p> Signup and view all the answers

    What is the class of antibiotics that tigecycline belongs to?

    <p>Glycylcyclines</p> Signup and view all the answers

    What is the spectrum of activity of minocycline similar to?

    <p>Other tetracyclines</p> Signup and view all the answers

    What is the mechanism of resistance to tetracyclines?

    <p>Efflux pumps and modifications of the 30S ribosomal subunit</p> Signup and view all the answers

    Which of the following is a characteristic of tigecycline's antimicrobial spectrum?

    <p>It is effective against most aerobic gram-negative bacteria</p> Signup and view all the answers

    What is a potential consequence of tetracycline use in pregnant women?

    <p>Discoloration of actively forming teeth and deposition in growing bone</p> Signup and view all the answers

    What is a common side effect associated with minocycline use?

    <p>Blue-black hyperpigmentation of skin and mucous membranes</p> Signup and view all the answers

    Why are tetracyclines contraindicated in children younger than 8 years?

    <p>They may cause discoloration of actively forming teeth and deposition in growing bone</p> Signup and view all the answers

    What is a characteristic of tigecycline, a glycylcycline?

    <p>It has excellent activity against atypical bacteria</p> Signup and view all the answers

    What is a potential consequence of tetracycline use?

    <p>All of the above</p> Signup and view all the answers

    What is a common feature of tetracyclines?

    <p>One of their core rings is a potent chelator of metal ions</p> Signup and view all the answers

    What is the general mechanism of action of clindamycin?

    <p>It inhibits bacterial translation by binding to the 50S ribosomal subunit.</p> Signup and view all the answers

    Which type of bacteria is NOT typically susceptible to clindamycin?

    <p>Aerobic gram-negative bacteria</p> Signup and view all the answers

    What is the structure of clindamycin shown in Figure 6-8?

    <p>A lincosamide antibiotic</p> Signup and view all the answers

    What is the primary use of clindamycin?

    <p>Treatment of infections caused by aerobic gram-positive and anaerobic bacteria</p> Signup and view all the answers

    Which of the following bacteria is susceptible to clindamycin?

    <p>Staphylococcus aureus</p> Signup and view all the answers

    What is the advantage of using clindamycin?

    <p>It is effective against aerobic gram-positive and anaerobic bacteria</p> Signup and view all the answers

    What is the mechanism of action of clindamycin on bacterial protein synthesis?

    <p>It inhibits the elongation of protein synthesis</p> Signup and view all the answers

    Which of the following is NOT a common feature of clindamycin's antimicrobial activity?

    <p>It is effective against aerobic gram-negative bacteria</p> Signup and view all the answers

    What is the mechanism of action of chloramphenicol?

    <p>Binding to bacterial ribosomes</p> Signup and view all the answers

    What is a common side effect of chloramphenicol?

    <p>Reversible suppression and irreversible aplastic anemia</p> Signup and view all the answers

    What is clindamycin derived from?

    <p>Lincomycin</p> Signup and view all the answers

    What type of bacteria is clindamycin active against?

    <p>Community-acquired methicillin-resistant bacteria</p> Signup and view all the answers

    How do bacteria acquire resistance to chloramphenicol?

    <p>By increasing the production of enzymes that inactivate the drug</p> Signup and view all the answers

    What is the common structure of lincosamide antibiotics?

    <p>Amino acid linked to an amino sugar</p> Signup and view all the answers

    What is the purpose of chloramphenicol in antibacterial treatment?

    <p>To inhibit bacterial protein synthesis</p> Signup and view all the answers

    What is the significance of clindamycin in antibacterial treatment?

    <p>It is active against many strains of community-acquired methicillin-resistant bacteria</p> Signup and view all the answers

    What is the mechanism of action of clindamycin?

    <p>Inhibiting protein synthesis by binding to the 50S subunit of the bacterial ribosome</p> Signup and view all the answers

    What type of bacteria is clindamycin active against?

    <p>Gram-positive aerobic bacteria and anaerobic bacteria</p> Signup and view all the answers

    What is a major toxicity of clindamycin?

    <p>Clostridium difficile colitis</p> Signup and view all the answers

    Why is clindamycin not useful against?

    <p>Aerobic gram-negative bacteria</p> Signup and view all the answers

    What is the result of clindamycin killing many components of the normal bacterial flora in the bowel?

    <p>Overgrowth by Clostridium difficile</p> Signup and view all the answers

    What is the name of the serious form of Clostridium difficile colitis?

    <p>Pseudomembranous colitis</p> Signup and view all the answers

    Which of the following bacteria are susceptible to clindamycin?

    <p>Staphylococci and streptococci</p> Signup and view all the answers

    Why is clindamycin often used as adjunctive therapy?

    <p>To prevent the production of bacterial toxins</p> Signup and view all the answers

    What is the mechanism of action of linezolid?

    <p>It prevents the formation of the first peptide bond of the nascent peptide</p> Signup and view all the answers

    What is a characteristic of oxazolidinones?

    <p>They are completely synthetic compounds</p> Signup and view all the answers

    Why are some aerobic gram-negative bacilli intrinsically resistant to linezolid?

    <p>They produce efflux pumps active against linezolid</p> Signup and view all the answers

    What is the consequence of a single amino acid mutation within the gene encoding a portion of the ribosome?

    <p>Resistance to linezolid</p> Signup and view all the answers

    What do streptogramins consist of?

    <p>Two different macrocyclic compounds</p> Signup and view all the answers

    What type of bacteria is linezolid active against?

    <p>Most aerobic gram-positive bacteria</p> Signup and view all the answers

    Where do streptogramins bind to inhibit protein synthesis?

    <p>The 50S subunit of the bacterial ribosome</p> Signup and view all the answers

    What is the structure of linezolid?

    <p>An oxazolidinone core with modifications</p> Signup and view all the answers

    What is the mechanism of synergy between quinupristin and dalfopristin?

    <p>Dalfopristin enhances the binding of quinupristin to the ribosome</p> Signup and view all the answers

    Why is linezolid effective against methicillin-resistant staphylococci?

    <p>It targets a different site on the bacterial ribosome</p> Signup and view all the answers

    How many mechanisms of resistance to streptogramins are described?

    <p>Three</p> Signup and view all the answers

    What is the significance of linezolid being a synthetic compound?

    <p>It has a unique mechanism of action</p> Signup and view all the answers

    When was the first streptogramin, pristinamycin, marketed in Europe?

    <p>1968</p> Signup and view all the answers

    What is the only streptogramin available in the United States?

    <p>Quinupristin/dalfopristin</p> Signup and view all the answers

    What type of bacteria is susceptible to quinupristin/dalfopristin?

    <p>Aerobic gram-positive bacteria</p> Signup and view all the answers

    What is a common side effect of quinupristin/dalfopristin when given through a peripheral intravenous catheter?

    <p>Pain, inflammation, and thrombophlebitis</p> Signup and view all the answers

    What is quinupristin/dalfopristin effective against?

    <p>Most aerobic gram-positive bacteria</p> Signup and view all the answers

    What is the significance of quinupristin/dalfopristin's in vitro activity against some aerobic gram-negative bacteria and some anaerobic bacteria?

    <p>Its clinical efficacy in treating these infections is currently unclear</p> Signup and view all the answers

    What bacteria are included in the 'who’s who list' of troublesome aerobic gram-positive bacteria?

    <p>Methicillin-resistant staphylococci, penicillin-resistant S.pneumoniae, and some vancomycin-resistant enterococci</p> Signup and view all the answers

    How does quinupristin/dalfopristin inhibit bacterial protein production?

    <p>By inhibiting the peptidyltransferase activity of the ribosome</p> Signup and view all the answers

    What is the significance of quinupristin/dalfopristin's mechanism of action?

    <p>It leads to cross-resistance with macrolides and clindamycin</p> Signup and view all the answers

    What is the clinical significance of quinupristin/dalfopristin's activity against methicillin-resistant staphylococci, penicillin-resistant S.pneumoniae, and some vancomycin-resistant enterococci?

    <p>It is significant for treating infections caused by these bacteria</p> Signup and view all the answers

    What type of bacteria is susceptible to rifamycins?

    <p>Both a and b</p> Signup and view all the answers

    What is a common side effect of rifamycins?

    <p>All of the above</p> Signup and view all the answers

    What is unique about rifampin?

    <p>It causes orange-red discoloration of tears and urine.</p> Signup and view all the answers

    What is the primary use of rifamycins?

    <p>Treatment of mycobacterial infections</p> Signup and view all the answers

    What is associated with rifabutin?

    <p>Uveitis</p> Signup and view all the answers

    What is the origin of the name 'rifamycin'?

    <p>From the French movie Rififi</p> Signup and view all the answers

    What is a common effect of rifampin on bodily fluids?

    <p>It turns them orange-red</p> Signup and view all the answers

    What is a possible hematologic abnormality associated with rifamycins?

    <p>All of the above</p> Signup and view all the answers

    What is the common structural feature of rifamycins?

    <p>An aromatic nucleus linked by an aliphatic &quot;handle&quot;</p> Signup and view all the answers

    How do rifamycins act on bacterial RNA polymerase?

    <p>They block the tunnel of the enzyme</p> Signup and view all the answers

    What is the primary mechanism of resistance to rifamycins?

    <p>Mutations in the bacterial gene that encodes RNA polymerase</p> Signup and view all the answers

    Why are rifamycins usually used in combination with other agents?

    <p>To prevent the emergence of resistant strains</p> Signup and view all the answers

    What is a unique characteristic of rifampin?

    <p>It is the most potent inducer of the cytochrome P-450 system</p> Signup and view all the answers

    Why is rifabutin favored over rifampin in individuals with HIV infection?

    <p>It inhibits the cytochrome P-450 system to a lesser degree</p> Signup and view all the answers

    Against which bacteria is rifampin effective as monotherapy for prophylaxis?

    <p>Neisseria meningitidis</p> Signup and view all the answers

    What is an advantage of using rifampin alone in prophylaxis?

    <p>It reduces the chance of resistance development</p> Signup and view all the answers

    What is a characteristic of rifapentine?

    <p>It has a long serum half-life, leading to its use in once-weekly regimens.</p> Signup and view all the answers

    What is a unique feature of rifaximin?

    <p>It is poorly absorbed and has limited activity against invasive bacteria.</p> Signup and view all the answers

    What is a potential effect of rifamycins on the body?

    <p>They can induce the cytochrome P-450 system.</p> Signup and view all the answers

    What is a characteristic of rifampin?

    <p>No correct answer</p> Signup and view all the answers

    What is a common feature of rifamycins?

    <p>They have varying serum half-lives.</p> Signup and view all the answers

    What is a use of rifamycins?

    <p>Treating bacterial infections.</p> Signup and view all the answers

    What is a characteristic of rifabutin?

    <p>It is favored over rifampin in individuals with HIV infection.</p> Signup and view all the answers

    What is a feature of rifamycins?

    <p>They inhibit bacterial protein production.</p> Signup and view all the answers

    What is the function of the ε subunit of DNA polymerase III?

    <p>3′ to 5′ exonuclease activity</p> Signup and view all the answers

    What is the purpose of proofreading in DNA replication?

    <p>To remove mismatched bases</p> Signup and view all the answers

    What is the role of DNA polymerase III in DNA replication?

    <p>To synthesize new DNA strands</p> Signup and view all the answers

    What is the result of the ε subunit's 3′ to 5′ exonuclease activity?

    <p>The removal of mismatched bases</p> Signup and view all the answers

    What is the relationship between DNA polymerase III and proofreading?

    <p>DNA polymerase III is involved in proofreading</p> Signup and view all the answers

    What is the significance of the ε subunit in DNA polymerase III?

    <p>It is responsible for proofreading</p> Signup and view all the answers

    What is the benefit of proofreading in DNA replication?

    <p>It increases the accuracy of DNA replication</p> Signup and view all the answers

    What is the purpose of the proofreading activity of DNA polymerase III?

    <p>To ensure the fidelity of DNA replication</p> Signup and view all the answers

    What was the result of blending the E. coli infected with a T2 phage containing 35S protein?

    <p>Most of the radioactivity remained in the supernatant</p> Signup and view all the answers

    What is the location of the radioactive DNA in the experiment where a T2 phage containing 32P DNA was mixed with the host bacterium?

    <p>In the pellet</p> Signup and view all the answers

    What is the purpose of the centrifugation step in the experiment?

    <p>To separate the phage particles from the host cells</p> Signup and view all the answers

    What is the role of the 35S protein in the experiment?

    <p>To carry the phage genetic information</p> Signup and view all the answers

    What is the result of the blender treatment on the phage infection process?

    <p>It has no effect on the infection process</p> Signup and view all the answers

    What is the purpose of using the 32P DNA in the experiment?

    <p>To label the phage DNA</p> Signup and view all the answers

    What is the location of the phage particles after the blender treatment?

    <p>In the supernatant</p> Signup and view all the answers

    What is the significance of the experiment?

    <p>It shows that the blender treatment has no effect on the infection process</p> Signup and view all the answers

    What is the role of the phage particles in the experiment described?

    <p>To carry genetic information into the bacterial cells</p> Signup and view all the answers

    What is the result of the experiment using 35S-labeled T2?

    <p>The majority of the radioactive protein was in the supernatant</p> Signup and view all the answers

    What is the significance of the experiment using 32P-labeled T2?

    <p>It indicates that the phage DNA carries the genetic information needed to complete the infection process</p> Signup and view all the answers

    What is the feature of informational molecules such as DNA, RNA, and proteins?

    <p>They are built from a sequence of monomers</p> Signup and view all the answers

    What is the result of the blender treatment in the experiment?

    <p>It had no effect on the infection process</p> Signup and view all the answers

    What is the purpose of the centrifugation step in the experiment?

    <p>To separate the phage particles from the bacterial cells</p> Signup and view all the answers

    What is the conclusion drawn from the experiment?

    <p>The phage DNA carries the genetic information needed to complete the infection process</p> Signup and view all the answers

    What is the relationship between the sequence of monomers and the information in informational molecules?

    <p>The sequence of monomers determines the function of the molecule</p> Signup and view all the answers

    Study Notes

    Rifamycins

    • Rifamycins can affect the levels of other drugs metabolized by the same system.
    • They can cause gastrointestinal complaints like nausea, vomiting, and diarrhea, and may also be associated with hepatitis.
    • Skin rashes and hematologic abnormalities may occur.
    • Rifampin causes an orange-red discoloration of tears, urine, and other body fluids.

    Antimicrobial Activity of Rifamycins

    • Rifamycins are effective against:
      • Gram-positive bacteria
      • Staphylococci
      • Gram-negative bacteria
      • Haemophilus influenzae
      • Neisseria meningitidis
      • Mycobacteria
      • Mycobacterium tuberculosis
      • Mycobacterium avium complex
      • Mycobacterium leprae

    History of Rifamycins

    • The name "rifamycin" was derived from the French movie "Rififi".
    • Rifamycins are used primarily as components of multidrug regimens for mycobacterial infections and some staphylococcal infections.

    Mechanism of Action

    • Rifamycins act by inhibiting bacterial RNA polymerase.
    • They nestle deep into the DNA/RNA tunnel of this enzyme and sterically block elongation of the nascent mRNA molecule.
    • Resistance develops relatively easily and can result from single mutations in the bacterial gene that encodes RNA polymerase.

    Rifampin

    • Rifampin is the oldest and most widely used of the rifamycins.
    • It is also the most potent inducer of the cytochrome P-450 system.
    • Rifampin is effective against staphylococcal infections and is used for prophylaxis against Neisseria meningitidis and Haemophilus influenzae.

    Rifabutin

    • Rifabutin is favored over rifampin in individuals who are simultaneously being treated for tuberculosis and HIV infection.
    • It inhibits the cytochrome P-450 system to a lesser degree than rifampin or rifapentine and can be more easily administered along with antiretroviral agents.

    Rifamycins

    • Rifamycins can affect the levels of other drugs metabolized by the same system.
    • They can cause gastrointestinal complaints such as nausea, vomiting, and diarrhea.
    • They have been associated with hepatitis and can cause skin rashes and hematologic abnormalities.
    • Rifampin causes an orange-red discoloration of tears, urine, and other body fluids.
    • Rifabutin has been associated with uveitis.

    Antimicrobial Activity of Rifamycins

    • Rifamycins are effective against Gram-positive bacteria, including Staphylococci.
    • They are effective against Gram-negative bacteria, including Haemophilus influenzae and Neisseria meningitidis.
    • They are effective against Mycobacteria, including Mycobacterium tuberculosis, Mycobacterium avium complex, and Mycobacterium leprae.

    History of Rifamycins

    • The name "rifamycin" was derived from the French movie "Rififi," which was popular at the time of their discovery.

    Mechanism of Action

    • Rifamycins act by inhibiting bacterial RNA polymerase.
    • They nestle deep into the DNA/RNA tunnel of this enzyme and sterically block elongation of the nascent mRNA molecule.

    Resistance and Use

    • Resistance to rifamycins can develop relatively easily and can result from single mutations in the bacterial gene that encodes RNA polymerase.
    • Rifamycins are usually used in combination with other agents to prevent the emergence of resistant strains.
    • They are used primarily as components of multidrug regimens for mycobacterial infections and some staphylococcal infections.
    • Rifampin is effective as monotherapy for prophylaxis against Neisseria meningitidis and Haemophilus influenzae.

    Structure of Aminoglycosides

    • Aminoglycosides consist of amino sugars bound by glycosidic linkages to a six-membered ring that contains amino group substituents.
    • The six-membered ring is relatively conserved.

    Antibacterial Activity

    • Aminoglycosides have excellent activity against aerobic gram-negative bacteria, including Enterobacteriaceae and Pseudomonas aeruginosa.
    • They are active to a lesser degree against aerobic gram-positive bacteria.
    • Uptake of aminoglycosides is enhanced by antibiotics that inhibit bacterial cell wall synthesis, such as β-lactams and vancomycin.
    • Synergistic efficacy is observed when used with cell wall-active agents against aerobic gram-positive bacteria.

    Resistance

    • Resistance is not always class-wide, with some aminoglycosides (e.g., amikacin) being resistant to modification by certain bacterial enzymes.
    • Resistance to aminoglycosides remains relatively rare.

    Toxicity

    • Aminoglycosides are associated with nephrotoxicity and ototoxicity.
    • Nephrotoxicity occurs in approximately 5% to 10% of patients, but can be as high as 50% in patients with specific risk factors.
    • Renal toxicity is usually reversible, and renal function often returns to normal after discontinuation of the drug.
    • Ototoxicity consists of two types: auditory impairment (which may lead to irreversible hearing loss) and vestibular toxicity (which results in disturbances in balance).

    Pharmacology

    • Aminoglycosides are positively charged molecules that are relatively large, but still only one-third the size of vancomycin.
    • They have excellent activity against aerobic gram-negative bacteria due to their size and positively charged nature.
    • Aminoglycosides require an energy-dependent active bacterial transport mechanism to penetrate the bacterial cytoplasmic membrane.
    • They work poorly in anaerobic and acidic environments, such as abscesses, and have no activity against anaerobic bacteria.

    Mechanism of Action

    • Aminoglycosides act by binding to the 30S subunit of the bacterial ribosome.
    • This causes mismatching between the mRNA codon and the charged aminoacyl-tRNA, promoting protein mistranslation.

    Macrolides and Ketolides

    • Macrolide antibiotics are effective against some gram-positive bacteria, some gram-negative bacteria, some atypical bacteria, some mycobacteria, and even some spirochetes.
    • They are not reliably effective against most bacteria in any one group.
    • Macrolides are useful for treating specific types of infections, such as respiratory infections, and for targeting specific organisms.

    Structure and Mechanism of Action

    • Macrolides consist of a large cyclic core called a macrocyclic lactone ring, decorated with sugar residues.
    • They bind tightly to the 50S subunit of the bacterial ribosome, blocking the exit of the newly synthesized peptide.
    • Macrolides function similarly to aminoglycosides, targeting ribosomes and preventing protein production.

    Resistance Mechanisms

    • Inhibition of drug entry and accumulation: macrolides have difficulty penetrating the outer membrane of most aerobic gram-negative bacilli and are actively pumped out of some resistant bacteria.
    • Enzyme-mediated ribosome binding site alteration: some bacteria acquire resistance by methylating the portion of the 50S ribosome normally bound by macrolides.
    • Mutation of the ribosome binding site: rare mutations occur that affect the portion of the bacterial ribosome bound by macrolides.
    • Resistance to one macrolide implies resistance to all members of the group.

    Types of Macrolides

    • Erythromycin, clarithromycin, and azithromycin are members of the macrolide group.
    • Telithromycin is a recently approved member of the structurally related class of antibiotics called the ketolides.

    Spectrum of Activity

    • Macrolides are active against various bacteria, including some staphylococci and streptococci.

    Tetracycline Antibiotics

    • Active against some aerobic gram-positive bacteria (e.g., S. pneumoniae) and gram-negative bacteria (e.g., H. influenzae, N. meningitidis)
    • Also active against some anaerobic bacteria and spirochetes (e.g., Borrelia burgdorferi, Treponema pallidum)
    • Strong activity against atypical bacteria (e.g., rickettsiae, chlamydiae, mycoplasmas)

    Tetracycline

    • Discovered in 1953, still used today
    • Available in oral formulation

    Doxycycline

    • Similar spectrum of activity to tetracycline
    • Longer half-life, allows for twice-daily dosing
    • More commonly used than tetracycline

    Minocycline

    • Similar spectrum of activity to tetracycline
    • Preferable for treating methicillin-resistant staphylococcal infections
    • Occasionally used for leprosy (Mycobacterium leprae infections)

    Tigecycline

    • Structurally related to tetracyclines, but not a true tetracycline
    • Member of the glycylcyclines class
    • Addition of glycyl amide group makes it insensitive to bacterial efflux pumps and ribosomal modifications that confer resistance to tetracyclines
    • Broad antimicrobial spectrum, active against most aerobic gram-negative bacteria, including multidrug-resistant Acinetobacter spp.
    • Exceptions include P. aeruginosa and Proteus spp., which produce efflux pumps that recognize tigecycline

    Toxicity and Contraindications

    • Tetracyclines are relatively safe, but have contraindications
    • Chelate metal ions (e.g., calcium), leading to tooth discoloration and bone deposition
    • Should not be given to pregnant women, and given cautiously to children <8 years old
    • Hypersensitivity reactions (e.g., rashes, anaphylaxis) occur, but are rare
    • Minocycline use may cause blue-black hyperpigmentation of skin and mucous membranes
    • Tetracyclines are associated with phototoxicity, gastrointestinal side effects, and hepatotoxicity

    Chloramphenicol

    • Binds to bacterial ribosomes, inhibiting protein synthesis and bacterial growth
    • Effective against aerobic gram-positive and gram-negative bacteria
    • Resistance occurs when bacteria acquire the ability to inactivate the drug or prevent its accumulation
    • Major factor limiting its use is its toxicity, which includes reversible and irreversible aplastic anemia

    Clindamycin

    Structure and Mechanism

    • Synthetic derivative of lincomycin, part of the lincosamide antibiotic group
    • Characterized by an amino acid linked to an amino sugar
    • Binds to the 50S subunit of the bacterial ribosome, inhibiting protein synthesis

    Antimicrobial Activity

    • Active against aerobic gram-positive bacteria, including some strains of Staphylococcus aureus and Streptococcus pneumoniae
    • Active against anaerobic bacteria, including some Bacteroides fragilis and Clostridium spp.
    • Not active against aerobic gram-negative bacteria

    Toxicity

    • Major toxicity is the occurrence of Clostridium difficile colitis (0.01% to 10% of individuals)
    • Kills normal bacterial flora in the bowel, allowing for overgrowth by C. difficile
    • Can cause diarrhea not caused by C. difficile and rash

    Linezolid

    • A synthetic antibiotic belonging to the oxazolidinones class
    • Inhibits protein synthesis by binding to the 50S subunit of the bacterial ribosome
    • Prevents association of the 50S subunit with the 30S subunit, thus preventing ribosome assembly
    • Also inhibits protein synthesis by preventing formation of the first peptide bond of the nascent peptide
    • Resistance has been detected due to a single amino acid mutation within the gene encoding a portion of the ribosome
    • Some aerobic gram-negative bacilli, such as E. coli, are intrinsically resistant to linezolid due to efflux pumps active against this compound
    • Has excellent activity against most aerobic gram-positive bacteria, including methicillin-resistant staphylococci, penicillin-resistant S. pneumoniae, and vancomycin-resistant enterococci

    Streptogramins

    • Consist of two different macrocyclic compounds that work together to kill bacteria
    • Each component binds to the 50S subunit of the bacterial ribosome to inhibit protein synthesis
    • Synergy occurs because each component alone inhibits a different step in protein elongation, and dalfopristin induces a conformational change in the ribosome that enhances quinupristin binding
    • Resistance to streptogramins occurs through three mechanisms: modification of the 50S ribosomal subunit, enzymatic inactivation of streptogramins, and production of efflux pumps
    • Quinupristin/dalfopristin has activity against aerobic gram-positive bacteria, including methicillin-resistant staphylococci, penicillin-resistant S. pneumoniae, and some vancomycin-resistant enterococci
    • Has in vitro activity against some aerobic gram-negative bacteria and some anaerobic bacteria, but clinical efficacy is unclear

    Quinupristin/Dalfopristin

    • Available in the United States as an intravenous formulation
    • Has antimicrobial activity against a range of aerobic gram-positive bacteria (Table 6-13)
    • Adverse effects related to the site of infusion are common, including pain, inflammation, and thrombophlebitis

    Rifamycins

    • Rifamycins are a class of antibiotics that block protein production.
    • Examples of rifamycins include rifampin, rifabutin, rifapentine, and rifaximin.

    Structure and Mechanism of Action

    • Rifamycins have a similar structure, with an aromatic nucleus linked by an aliphatic "handle" on both ends.
    • They act by inhibiting bacterial RNA polymerase, nestling deep into the DNA/RNA tunnel and sterically blocking elongation of the nascent mRNA molecule.

    Resistance

    • Resistance to rifamycins develops relatively easily due to single mutations in the bacterial gene that encodes RNA polymerase.
    • These mutations change only a single amino acid at the site where the rifamycins bind to RNA polymerase, preventing binding.

    Uses

    • Rifamycins are used primarily as components of multidrug regimens for mycobacterial infections and some staphylococcal infections.
    • Rifampin is used in combination with other antibiotics to treat staphylococcal infections and as monotherapy for prophylaxis against Neisseria meningitidis and Haemophilus influenzae.

    Rifampin

    • Rifampin is the oldest and most widely used of the rifamycins.
    • It is the most potent inducer of the cytochrome P-450 system.
    • It causes an orange-red discoloration of tears, urine, and other body fluids, which can lead to patient anxiety and the staining of contact lenses.

    Rifabutin

    • Rifabutin is favored over rifampin in individuals who are simultaneously being treated for tuberculosis and HIV infection.
    • It inhibits the cytochrome P-450 system to a lesser degree than rifampin or rifapentine, making it easier to administer with antiretroviral agents.

    Rifapentine

    • Rifapentine has a long serum half-life, which has led to its use in once-weekly regimens for immunocompetent patients with tuberculosis.

    Rifaximin

    • Rifaximin is a poorly absorbed rifamycin that is used for the treatment of travelers' diarrhea.
    • It has limited activity against invasive bacteria, such as Salmonella and Campylobacter spp. due to its poor systemic absorption.

    Nucleic Acid and Protein Structure

    • After centrifugation, the radioactivity in the supernatant (where phage particles remained) and in bacterial cells in the pellet was determined to understand the infection process.
    • The experiment showed that blender treatment did not disrupt the infection process, as progeny phages were produced.
    • When 35S-labeled T2 was used, the majority of the radioactive protein was in the supernatant, whereas when 32P-labeled T2 was used, the radioactive DNA was in the bacterial cells that formed the pellet.

    Characteristics of DNA, RNA, and Amino Acids

    • DNA, RNA, and proteins are informational molecules, and their structure is critical to their function.
    • The sequence of monomers (nucleotides or amino acids) determines the information encoded in these molecules.
    • DNA and RNA are composed of nucleotides linked together by covalent bonds.
    • Amino acids are linked together to form a polypeptide.

    DNA Replication and Proofreading

    • DNA polymerase III has an additional function of proofreading, which is the removal of a mismatched base immediately after it has been added.
    • The ε subunit of DNA polymerase III has 3′ to 5′ exonuclease activity, which is essential for proofreading.

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    This quiz covers the side effects and antimicrobial activity of rifamycins, including gastrointestinal complaints, skin rashes, and hematologic abnormalities.

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