antimicrobial agents chapter 7. copyright 2007 thomson delmar learning, a division of thomson...
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Antimicrobial Agents
Chapter 7
Copyright 2007 Thomson Delmar Learning, a division of Thomson Learning Inc. All rights reserved.
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Anti-infective Therapy
Modern age Discovery of sulfanilamide in 1936 Commercial introduction of penicillin in 1941
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Antimicrobial Therapy
Original antimicrobials: derived from microorganisms
Newer agents: chemically synthesized
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Factors Leading to Infection
Age: young and elderly Increased exposure to pathogenic
organisms Disruption of the normal barriers Inadequate immunological defenses Impaired circulation Poor nutritional status
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Sources of Infection
Bacteria Fungi Viruses
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Administering Antimicrobial Agents
Consider the following: Location of the infecting organism in the
body Status of the client’s organ function
(continues)
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Administering Antimicrobial Agents
Consider the following: Age of the client Pregnancy and/or lactation Likelihood of developing organisms resistant
to the antimicrobial agent
(continued)
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Overuse
Overuse of antimicrobial agents can lead to the development of severely resistant organisms.
Promoted the development of organisms that are not affected by any of the available therapies
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Resistant Organisms
MRSA/VRSA: methicillin/vancomycin-resistant Staphylococcus aureus
VRE: vancomycin-resistant Enterococcus
ORSA: oxacillin-resistant Staphylococcus aureus
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Antimicrobial Therapy
Prevent infections. Use Universal Precautions.
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Classifications
Antimicrobial agents are classified based on the following factors:
Bactericidal or bacteriostatic Site of action Narrow or broad spectrum Adverse effects
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Antimicrobial Classes
Sulfonamides Penicillins Cephalosporins Tetracyclines Macrolides
Aminoglycosides Fluoroquinolones Carbapenem Ketolides
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Sulfonimides
First group of antibiotics General action
Bacteriostatic effect Inhibit para-aminobenzoic acid (PABA)
• PABA is essential for bacterial growth
Broad spectrum
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Sulfonamides: Therapeutic Uses
Treatment of urinary tract infections Otitis media Certain vaginal infections Some respiratory infections
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Sulfonamides: Adverse Effects
Hypersensitivity Renal dysfunction Hematological changes
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Sulfonamides: Nursing Implications
Consume at least 1 liter of fluid/day Avoid sunlight and tanning beds Reduce the effectiveness of oral
contraceptives
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Sulfonamide Combinations
Sulfonamides also combined with: Antimicrobials, diuretics, oral
hypoglycemics, and carbonic anhydrase inhibitors
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Penicillins
Part of a large group of chemically related antibiotics
Derived from fungus or mold Cephalosporins currently used instead of
the penicillins
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Penicillins: Action
Inhibit synthesis of the bacterial cell wall Most effective on newly forming and actively
growing cell walls Some of the penicillins are rapidly destroyed
in the stomach. Given IM or IV
(continues)
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Action of penicillin on bacteria (from Medicines and You, U.S. Department of Health and Human Services)
(continued)
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Resistance to Penicillins
Frequent early use of penicillin caused: Penicillinase
The bacteria to produce penicillin-destroying enzymes
Potassium clavulanate inhibits penicillinase: combined with penicillin
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Penicillins: Therapeutic Uses
Prevention and treatment of gram (+) bacterial infections:
Enterococcus, Streptococcus, and Staphylococcus bacteria
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Penicillins: Adverse Effects
Hypersensitivity Gastrointestinal symptoms Neurotoxicity Renal dysfunction
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Cephalosporins
Chemically and pharmacologically related to penicillins
Action: prevent bacterial cell wall synthesis
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Cephalosporins: Action
Either bactericidal or bacteriostatic; depends on:
Susceptibility of organism Dose of drug Tissue concentration Rate of bacteria multiplication
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Classes of Cephalosporin
Include several generations: First: good gram-positive coverage Second: good gram-positive coverage;
some gram-negative coverage Third: less gram-positive coverage; more
gram-negative coverage Fourth: good gram-negative coverage
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Treatment with Cephalosporins
Treat infections of: Skin Bone Heart Blood Respiratory tract Gastrointestinal tract Urinary tract
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Cephalosporins: Adverse Effects
Hypersensitivity Cross-sensitivity reaction to penicillin Thrombophlebitis (when given IV) Sterile abscess (when given IM) Nephrotoxicity
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7 - 29
Tetracyclines
Action: inhibit protein synthesis in the bacterial cell; bacteriostatic
Broad spectrum Bacteria: gram – and gram +
Effective against: protozoa, Mycoplasma, Rickettsia, Chlamydia, syphilis, Lyme disease
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7 - 30
Tetracyclines: Nursing Implications
Bind to Ca2+, Mg2+, and Al3+ ions and form insoluble complexes
Do not give tetracycline with: Dairy products, antacids, or iron salts
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Tetracyclines: Toxic Effects
Do not give to children. Affects tooth development from:
Fourth month of fetal development to 8 years old
Temporary and permanent discoloration of developing teeth
Photosensitivity Superinfection
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7 - 32
Macrolides
Action Bacteriostatic: inhibits protein synthesis in
the bacterial cell Primarily used for respiratory,
gastrointestinal, urinary, skin, and soft tissue infections
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Treatment with Macrolides
Treat both gram + and some gram – organisms
Erythromycin: preferred (pertussis) Primarily metabolized by the liver and
excreted in the urine
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Macrolides: Adverse Effects
Hypersensitivity Gastrointestinal effects Hepatotoxicity Jaundice
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Aminoglycosides
Poor oral absorption Given intravenously, not orally
Action Bactericidal: inhibit cell wall protein
synthesis Effective: gram – and some gram + Narrow therapeutic range
Potent antibiotics with serious toxicities!
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Aminoglycosides: Toxicities
Serious toxicities: caution Nephrotoxicity Ototoxicity Block neuromuscular action, which can
lead to respiratory paralysis Monitor drug levels, both peak and
trough
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Fluoroquinolones
First oral antibiotics effective against gram-negative bacteria
Excellent oral absorption
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Fluoroquinolones: Action
Bactericidal: alter DNA Broad spectrum: effective against gram-
negative organisms and some gram-positive organisms
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Treatment with Fluoroquinolones
Treat infections of: Lower respiratory tract Bone and joint Infectious diarrhea Urinary tract Skin Sexually transmitted diseases
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Fluoroquinolones: Nursing Implications
Consume at least 1 liter of fluid/day
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Carbapenems
Action: Inhibit synthesis of the bacterial cell wall
Broad spectrum Effective:
Gram negative Gram positive
Treat community acquired pneumonia
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Carbapenems: Nursing Considerations
Given intravenously and intramuscularly Cross-sensitivity to penicillins Advantage
Given once every 24 hours
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Carbapenems: Adverse Effects
Hypersensitivity Diarrhea Local reactions at intramuscular and
intravenous sites
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Ketolides
FDA approved in 2004 New class
Developed from macrolides Semisynthetic Treat macrolide-resistant strep pneumonia
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Ketolides: Adverse Effects
Hypersensitivity Headache Diarrhea
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Urinary Tract Anti-infectives
Trimethoprim Most common Blocks the synthesis of folate in bacteria,
thus inhibiting formation of nucleic acid and protein
(continues)
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7 - 47
Urinary Tract Anti-infectives
Others Methenamine products: produces local
bactericidal effect Nitrofurantoin: stops CHO metabolism
Produces yellow-brown urine
(continued)
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7 - 48
Antimicrobial Therapy
General nursing implications Instructions take as prescribed:
Length of time: do not stop before antimicrobials are gone
Assess for signs and symptoms of returning infection
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Antimicrobials: Nursing Implications
Obtain cultures from appropriate sites before beginning therapy.
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Antitubercular Agents
Tuberculosis (TB) Mycobacterium tuberculosis
An aerobic bacillus Requires oxygen to survive
Antitubercular agents treat all forms of Mycobacterium
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Tuberculosis
TB close to eradication; new resistant strain developed in immunocompromised individuals and immigrants to the U.S.
Drug therapy is given in two forms: Preventive therapy Active therapy
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TB: Preventive Therapy
Preferred agent INH (Isoniazid) Known as chemoprophylaxis
Safest Low cost Action: tuberculostatic and tuberculocidal Treatment: 18 months to 2 years
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Isoniazid
INH Action: inhibits the synthesis of mycolic acid
Adverse effects of INH Hepatotoxicity: jaundice Peripheral neuritis Nausea Skin rashes
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Multiple Drug Therapy
Required: combination of two or three agents
Helps prevent development of resistant strains
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Antitubercular Therapy
Effectiveness depends on: Where Strain Effective drug combination Sufficient duration Effective drug compliance
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Antitubercular Agents: Nursing Implications
Client education is critical. Therapy may last for up to 24 months. Take medications exactly as ordered. Emphasize the importance of strict
compliance.
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Antitubercular Agents: Nursing Implications
Do not consume alcohol. Diabetic: monitor blood glucose levels INH and rifampin:
Oral contraceptives ineffective
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7 - 58
Lyme Disease
Spirochete Borrelia burgdorferi Transmitted from a deer tick
Symptoms Rash Flulike symptoms, followed by arthritis and
fatigue
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Treatment for Lyme Disease
Oral doxycycline Adults: 100 mg b.i.d Length: 10 to 14 days
Adverse effect Photosensitivity
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7 - 60
Fungi
Contracted Air Skin to skin
Due to normal flora being killed off: Antibiotics Corticosteroid therapy Antineoplastic agents Suppressed immune system
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Mycotic Infections
Three general types Cutaneous Subcutaneous Systemic (can be life threatening)
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Antifungal Agents
Treatment Antibiotic therapy will not work. Requires prolonged treatment
Human cell structure resembles fungi cell structure.
Action Antifungal agents take advantage of the
slight differences of the cell structures.
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Antifungal Agents: General Adverse Effects
Topical: irritation and redness Oral: nausea, vomiting, and diarrhea May potentiate antihistamines
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Antifungal Agents: Adverse Effects
IV: hepatotoxicity, renal toxicity, and phlebitis
IV drugs must be diluted and administered slowly: amphotericin B
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Antifungal Agents: Nursing Implications
IV Monitor vital signs every 15 to 30 minutes. Monitor input and output. Monitor urinalysis findings.
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Antiviral Agents
Viruses cause many infectious disorders: Acute: common cold Chronic: herpes Slow growing: AIDS
Available vaccines Polio, rabies, and smallpox
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Viral Replication
A virus cannot replicate on its own. It must attach to and enter a host cell.
Uses the host cell’s energy to synthesize protein: DNA and RNA
(continues)
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7 - 68
Life cycle of a virus
(continued)
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Interferons
Normally, interferons protect the cells from infecting viruses.
Interferon: continuous research Recent antifungal agents end in “vir”
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7 - 70
Antiviral Agents: Key Characteristics
Inhibit viral replication by interfering with: Viral nucleic acid synthesis and/or regulation Ability of virus to bind to cells
Interferon: stimulates immune system
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Treatment with Antiviral Agents
Antiviral agents treat: Influenzae A Herpes simplex RSV AIDS, HIV
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Antiviral Agents: Adverse Effects
Bone marrow suppression Nephrotoxicity Hepatotoxicity Gastrointestinal effects Central nervous system effects
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7 - 73
Antiviral Agents: Nursing Implications
Be sure to teach proper application: Ointments Aerosol powders
Emphasize handwashing. Wear gloves for topical application.
(continues)
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Antiviral Agents: Nursing Implications
Usually not a cure Replications cease: remain in nerve fibers
Therapeutic effects vary Range from delayed progression of AIDS
and ARC to decrease in flulike symptoms Frequency of herpes-like flare-ups decrease
(continued)
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