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Copyright © 2012 Wolters Kluwer Health | Lippincott Williams & Wilkins
Chapter 39
Antibiotics Affecting the Bacterial Cell Wall
Chapter 39
Antibiotics Affecting the Bacterial Cell Wall
Copyright © 2012 Wolters Kluwer Health | Lippincott Williams & Wilkins
Physiology Physiology
• Bacteria are surrounded by a rigid cell wall that is responsible for maintaining the integrity of the internal cellular environment.
• The interior of the cell has a high osmotic pressure.
• If the bacterial cell wall is not intact, the internal osmotic pressure draws fluid into the cell until it bursts.
• Even when the cell wall is breached by an antibiotic, bacterial death may not occur because of bacterial resistance.
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Physiology (cont.)Physiology (cont.)
• Drugs that affect the bacterial cell wall must be able to penetrate the cell wall to bind to molecular targets on the cell.
• Beta-lactamases are enzymes that disrupt the beta-lactam ring.
• This mechanism inactivates beta-lactam drugs.
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Cytoplasmic MembraneCytoplasmic Membrane
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Pathophysiology Pathophysiology
• Bacteria may cause infections in any body organ, structure, or fluid.
• In addition to the original bacterial infection, the loss of certain “good” bacteria may result in a superinfection.
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Penicillins Penicillins • Penicillins were the first antibiotics introduced for clinical
use.
• Alexander Fleming derived them from Penicillium molds in 1929.
• Subsequent versions of penicillin have been developed to decrease the adverse effects of the drug and to modify its ability to act on resistant bacteria.
• Penicillins are also called beta-lactam antibiotics because their chemical structure contains a beta-lactam ring that is essential for antibacterial activity.
• Penicillins are classified as narrow spectrum.
• Prototype drug: penicillin G
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Penicillin G: Core Drug Knowledge Penicillin G: Core Drug Knowledge
• Pharmacotherapeutics
– Infections caused by susceptible gram-positive bacteria
• Pharmacokinetics
– Administered: IM or IV. Highly protein bound. Excreted: kidneys.
• Pharmacodynamics
– Inhibits the third and final stage of bacterial cell wall synthesis
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Penicillin G: Core Drug Knowledge (cont.)Penicillin G: Core Drug Knowledge (cont.)
• Contraindications and precautions
– Known allergies to penicillin, cephalosporins, or imipenem
• Adverse effects
– GI upset, rash, fever, wheezing, possibly anaphylaxis and death
• Drug interactions
– Tetracyclines, aminoglycosides, and probenecid
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Penicillin G: Core Patient Variables Penicillin G: Core Patient Variables
• Health status
– Assess health history and allergies.
• Life span and gender
– The drug counteracts the effects of an oral contraceptive.
• Lifestyle, diet, and habits
– Administer the drug around the clock.
• Environment
– Assess the environment where the drug will be given.
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Penicillin G: Nursing Diagnoses and Outcomes Penicillin G: Nursing Diagnoses and Outcomes • Risk for Injury related to drug-related allergic reactions
– Desired outcome: The patient will recognize symptoms of allergy and contact the prescriber immediately to minimize ill effects.
• Imbalanced Nutrition: Less than Body Requirements related to drug-induced GI effects, such as diarrhea, GI upset, altered taste sensation, or superinfection
– Desired outcome: The patient will maintain consistent body weight and consult the prescriber about persistent adverse effects that affect nutritional status.
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Penicillin G: Nursing Diagnoses and Outcomes (cont.)Penicillin G: Nursing Diagnoses and Outcomes (cont.)
• Diarrhea related to drug therapy
– Desired outcome: The patient will avoid dehydration, maintain fluid intake, and contact the prescriber about persistent diarrhea.
• Risk for Infection related to overgrowth of nonsusceptible organisms
– Desired outcome: The patient will report signs of superinfection to the prescriber.
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Penicillin G: Planning and InterventionsPenicillin G: Planning and Interventions
• Maximizing therapeutic effects
– Review culture and sensitivity reports to make sure that penicillin G is appropriate for the patient.
– Optimally, drug therapy should continue for at least 7 to 10 days.
• Minimizing adverse effects
– Provide small, frequent meals; mouth care; and ice chips.
– Notify the prescriber if a substantial change develops in the intake-to-output ratio.
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Penicillin G: Teaching, Assessment, and EvaluationsPenicillin G: Teaching, Assessment, and Evaluations
• Patient and family education
– Stress the importance of completing the full course of antibiotics.
– Emphasize the need to take penicillin G exactly as prescribed at evenly spaced intervals.
• Ongoing assessment and evaluation
– Monitor for signs of allergic reaction and for resolution of the presenting symptoms of infection.
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QuestionQuestion
• Penicillin G is given via which of the following route(s)?
– A. Oral
– B. IM
– C. IV
– D. Both B and C
– E. All of the above
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AnswerAnswer
• D. Both B and C
• Rationale: Penicillin G is absorbed rapidly from the gastrointestinal (GI) tract but is unstable in gastric acid. Because of this instability, penicillin G is not given orally.
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Cephalosporins Cephalosporins • The cephalosporins were first introduced in the 1960s.
• They are similar to the penicillins in structure and in activity and are also considered beta-lactam antibiotics.
• Four generations of cephalosporins have been introduced, each group with its own spectrum of activity.
• Selecting an antibiotic from this class depends on the sensitivity of the involved organism.
• The major differences between the generations include their activity against gram-negative bacteria, their resistance to beta-lactamases, and their ability to distribute into cerebrospinal fluid.
• Prototype drug: cefazolin (Ancef, Kefzol)
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Cefazolin: Core Drug Knowledge Cefazolin: Core Drug Knowledge
• Pharmacotherapeutics
– Treats many kinds of infections
• Pharmacokinetics
– Administered: IM. Peak: 1.5 to 2 hours.
• Pharmacodynamics
– Binds with PBPs, which disrupts bacterial cell wall synthesis
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Cefazolin: Core Drug Knowledge (cont.)Cefazolin: Core Drug Knowledge (cont.)
• Contraindications and precautions
– Known allergy to cephalosporins
• Adverse effects
– Maculopapular rash, GI symptoms, headache, dizziness, lethargy, paresthesias, and nephrotoxicity
• Drug interactions
– Aminoglycosides
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Cefazolin: Core Patient Variables Cefazolin: Core Patient Variables
• Health status
– Assess history and allergies.
• Life span and gender
– Assess for pregnancy and lactation.
• Lifestyle, diet, and habits
– Assess lifestyle to ensure ability to comply with therapy.
• Environment
– Assess the environment where the drug will be given.
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Cefazolin: Nursing Diagnoses and Outcomes Cefazolin: Nursing Diagnoses and Outcomes
• Diarrhea related to drug effects
– Desired outcome: The patient will avoid dehydration, maintain fluid intake, and contact the prescriber if diarrhea persists.
• Imbalanced Nutrition: More or Less than Body Requirements related to GI effects, alteration in taste, superinfections
– Desired outcome: The patient will maintain body weight and contact the prescriber if persistent adverse effects alter nutritional status.
• Risk for Infection related to overgrowth of nonsusceptible organisms
– Desired outcome: The patient will report signs of superinfection to the prescriber.
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Cefazolin: Planning and InterventionsCefazolin: Planning and Interventions
• Maximizing therapeutic effects
– Review culture and sensitivity tests to evaluate the efficacy of treatment.
– Oral suspensions should be kept in the refrigerator.
• Minimizing adverse effects
– Cefazolin may be taken with food or fluids to decrease GI distress.
– Evaluate the patient for CNS effects and use safety precautions.
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Cefazolin: Teaching, Assessment, and EvaluationsCefazolin: Teaching, Assessment, and Evaluations
• Patient and family education
– Because cefazolin and the other cephalosporins are similar to penicillins, follow the same guidelines for providing patient and family education to a patient receiving penicillin.
• Ongoing assessment and evaluation
– Monitor the patient for any signs of superinfection and notify the prescriber immediately to arrange for treatment if superinfection does occur.
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QuestionQuestion
• First-generation cephalosporins are effective at treating gram-negative infections.
– A. True
– B. False
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AnswerAnswer
• B. False
• Rationale: The first-generation cephalosporins have little activity against gram-negative bacteria.
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Vancomycin Vancomycin
• Vancomycin (Vancocin) is a complex and unusual tricyclic glycopeptide antibiotic.
• It is the only drug in its class.
• The use of vancomycin is limited by its ability to produce toxic effects.
• Vancomycin is used only when other antibiotics fail to resolve an infection.
• It has been touted as being able to eradicate most gram-positive pathogens.
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Vancomycin: Core Drug Knowledge Vancomycin: Core Drug Knowledge
• Pharmacotherapeutics
– Treating bacterial septicemia, endocarditis, bone and joint infections
• Pharmacokinetics
– Administered: oral or IV. Excreted: kidneys and feces. Peak: 1 hour.
• Pharmacodynamics
– Inhibits cell wall synthesis by altering the cell’s permeability
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Vancomycin: Core Drug Knowledge (cont.)Vancomycin: Core Drug Knowledge (cont.)
• Contraindications and precautions
– Hypersensitivity and pregnancy
• Adverse effects
– Ototoxicity and nephrotoxicity
• Drug interactions
– Antihyperlipidemic drugs and nondepolarizing muscle relaxants
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Vancomycin: Core Patient Variables Vancomycin: Core Patient Variables
• Health status
– Assess for contraindications to therapy.
• Life span and gender
– Assess pregnancy and lactation status.
• Environment
– Assess the environment where the drug will be given.
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Vancomycin: Nursing Diagnoses and Outcomes Vancomycin: Nursing Diagnoses and Outcomes
• Risk for Injury related to drug-induced histamine-release reactions
– Desired outcome: The patient will experience no preventable reaction related to vancomycin.
• Disturbed Sensory Perception (auditory) related to drug-induced ototoxicity
– Desired outcome: The patient will report any unusual auditory sensations and have periodic audiograms to detect early ototoxicity.
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Vancomycin: Nursing Diagnoses and Outcomes (cont.)Vancomycin: Nursing Diagnoses and Outcomes (cont.)
• Excess Fluid Volume related to nephrotoxicity from drug therapy
– Desired outcome: The patient will remain normovolemic throughout therapy.
• Risk for Infection related to overgrowth of nonsusceptible organisms
– Desired outcome: The patient will report signs of superinfection to the prescriber.
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Vancomycin: Planning and InterventionsVancomycin: Planning and Interventions
• Maximizing therapeutic effects
– Ensure that the patient receives the full course of vancomycin as prescribed.
– Culture and sensitivity results should be monitored.
• Minimizing adverse effects
– Administer vancomycin over at least 60 minutes.
– Assess the IV site frequently for signs of phlebitis.
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Vancomycin: Teaching, Assessment, and EvaluationsVancomycin: Teaching, Assessment, and Evaluations• Patient and family education
– Advise the patient of the importance of completing therapy.
– Explain the potential adverse effects and need for periodic blood monitoring.
• Ongoing assessment and evaluation
– Monitor for signs of ototoxicity.
– For patients receiving long-term or high-dose therapy, coordinate periodic audiometric testing and lab tests.
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QuestionQuestion
• The oral form of vancomycin is used to treat
– A. Gastric ulcers
– B. Prostatitis
– C. Rupture of diverticulum
– D. Pseudomembranous colitis
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AnswerAnswer
• D. Pseudomembranous colitis
• Rationale: Oral administration is used in treating some GI infections, such as pseudomembranous colitis.