Antimicrobial Agents Chapter 7. Copyright 2007 Thomson Delmar Learning, a division of Thomson Learning Inc. All rights reserved. 7 - 2 Anti-infective

Antimicrobial Agents

Chapter 7

Copyright 2007 Thomson Delmar Learning, a division of Thomson Learning Inc. All rights reserved.

7 - 2

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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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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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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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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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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Urinary Tract Anti-infectives

Others Methenamine products: produces local

bactericidal effect Nitrofurantoin: stops CHO metabolism

Produces yellow-brown urine

(continued)


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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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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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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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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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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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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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Antimicrobial Agents Chapter 7. Copyright 2007 Thomson Delmar Learning, a division of Thomson Learning Inc. All rights reserved. 7 - 2 Anti-infective