Ppt chapter 39

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Chapter 39

Antibiotics Affecting the Bacterial Cell Wall

Chapter 39

Antibiotics Affecting the Bacterial Cell Wall


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.


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.


Cytoplasmic MembraneCytoplasmic Membrane


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.


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


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


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


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.


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.


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.


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.


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.


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


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.


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)


Cefazolin: Core Drug Knowledge Cefazolin: Core Drug Knowledge


– Treats many kinds of infections


– Administered: IM. Peak: 1.5 to 2 hours.


– Binds with PBPs, which disrupts bacterial cell wall synthesis


Cefazolin: Core Drug Knowledge (cont.)Cefazolin: Core Drug Knowledge (cont.)


– Known allergy to cephalosporins

• Adverse effects

– Maculopapular rash, GI symptoms, headache, dizziness, lethargy, paresthesias, and nephrotoxicity


– Aminoglycosides


Cefazolin: Core Patient Variables Cefazolin: Core Patient Variables

• Health status

– Assess history and allergies.


– Assess for pregnancy and lactation.

• Lifestyle, diet, and habits

– Assess lifestyle to ensure ability to comply with therapy.

• Environment



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.




Cefazolin: Planning and InterventionsCefazolin: Planning and Interventions


– Review culture and sensitivity tests to evaluate the efficacy of treatment.

– Oral suspensions should be kept in the refrigerator.


– Cefazolin may be taken with food or fluids to decrease GI distress.

– Evaluate the patient for CNS effects and use safety precautions.


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.


– Monitor the patient for any signs of superinfection and notify the prescriber immediately to arrange for treatment if superinfection does occur.


QuestionQuestion

• First-generation cephalosporins are effective at treating gram-negative infections.

– A. True

– B. False


AnswerAnswer

• B. False

• Rationale: The first-generation cephalosporins have little activity against gram-negative bacteria.


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.


Vancomycin: Core Drug Knowledge Vancomycin: Core Drug Knowledge


– Treating bacterial septicemia, endocarditis, bone and joint infections


– Administered: oral or IV. Excreted: kidneys and feces. Peak: 1 hour.


– Inhibits cell wall synthesis by altering the cell’s permeability


Vancomycin: Core Drug Knowledge (cont.)Vancomycin: Core Drug Knowledge (cont.)


– Hypersensitivity and pregnancy

• Adverse effects

– Ototoxicity and nephrotoxicity


– Antihyperlipidemic drugs and nondepolarizing muscle relaxants


Vancomycin: Core Patient Variables Vancomycin: Core Patient Variables

• Health status

– Assess for contraindications to therapy.


– Assess pregnancy and lactation status.

• Environment



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.


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.




Vancomycin: Planning and InterventionsVancomycin: Planning and Interventions


– Ensure that the patient receives the full course of vancomycin as prescribed.

– Culture and sensitivity results should be monitored.


– Administer vancomycin over at least 60 minutes.

– Assess the IV site frequently for signs of phlebitis.


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.


– Monitor for signs of ototoxicity.

– For patients receiving long-term or high-dose therapy, coordinate periodic audiometric testing and lab tests.


QuestionQuestion

• The oral form of vancomycin is used to treat

– A. Gastric ulcers

– B. Prostatitis

– C. Rupture of diverticulum

– D. Pseudomembranous colitis


AnswerAnswer

• D. Pseudomembranous colitis

• Rationale: Oral administration is used in treating some GI infections, such as pseudomembranous colitis.

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