chapter 38 antibiotics part 1 copyright © 2014 by mosby, an imprint of elsevier inc

Chapter 38

Antibiotics Part 1

Copyright © 2014 by Mosby, an imprint of Elsevier Inc.

Community-associated infections An infection that is acquired by a person who has not

been hospitalized or had a medical procedure (such as dialysis, surgery, catheterization) within the past year

Infections: Sites of Origin

Copyright © 2014 by Mosby, an imprint of Elsevier Inc. 2

Health care–associated infections Contracted in a hospital or institutional setting Were not present or incubating in the patient on

admission to the facility More difficult to treat because causative

microorganisms are often drug resistant and the most virulent

Occur in 10% of hospitalized patients MRSA most common Previously known as nosocomial

Infections: Sites of Origin (cont’d)


Handwashing Antiseptics Disinfectants

Health Care–Associated Infections: Prevention


Disinfectant Kills organisms Used only on nonliving objects

Antiseptic Generally only inhibits the growth of microorganisms

but does not necessarily kill them Applied exclusively to living tissue

Health Care–Associated Infections: Prevention (cont’d)


Medications used to treat bacterial infections Ideally, before beginning antibiotic therapy, the

suspected areas of infection should be cultured to identify the causative organism and potential antibiotic susceptibilities

Antibiotics


Empiric therapy: treatment of an infection before specific culture information has been reported or obtained

Definitive therapy: antibiotic therapy tailored to treat organism identified with cultures

Prophylactic therapy: treatment with antibiotics to prevent an infection, as in intraabdominal surgery or after trauma

Antibiotic Therapy


Therapeutic response Decrease in specific signs and symptoms of infection

are noted (fever, elevated WBC, redness, inflammation, drainage, pain)

Subtherapeutic response Signs and symptoms of infection do not improve

Antibiotic Therapy (cont’d)


Superinfection Pseudomembranous colitis Secondary infection Resistance Food-drug interactions Host factors Allergic reactions

Antibiotic Therapy (cont’d)


Sulfonamides Penicillins Cephalosporins Macrolides Quinolones Aminoglycosides Tetracyclines

Antibiotics: Classes


Interference with cell wall synthesis Interference with protein synthesis Interference with DNA replication Acting as a metabolite to disrupt critical

metabolic reactions inside the bacterial cell

Antibiotic Therapy: Mechanism of Action


Bactericidal: kill bacteria Bacteriostatic: inhibit growth of susceptible

bacteria, rather than killing them immediately; will eventually lead to bacterial death

Actions of Antibiotics


One of the first groups of antibiotics Often combined with another antibiotic

Sulfamethoxazole combined with trimethoprim (a nonsulfonamide antibiotic), known as Bactrim, Septra, or co-trimoxazole and often abbreviated as SMX-TMP, is used commonly in clinical practice

Antibiotics: Sulfonamides


Bacteriostatic action Prevent synthesis of folic acid required for

synthesis of purines and nucleic acid Do not affect human cells or certain bacteria—

they can use preformed folic acid Only affect organisms that synthesize their own

folic acid

Sulfonamides: Mechanism of Action


Effective against both gram-positive and gram-negative bacteria

Treatment of UTIs caused by susceptible strains of: Enterobacter spp., Escherichia coli, Klebsiella spp.,

Proteus mirabilis, Proteus vulgaris, Staphylococcus aureus

Sulfonamides: Indications


Pneumocystis jirovecii pneumonia (PJP) Co-trimoxazole

Upper respiratory tract infections Sulfamethoxazole/trimethoprim is commonly

used for outpatient Staphylococcus infections, due to the high rate of community-acquired MRSA infections

Sulfonamides: Indications (cont’d)


Body System Adverse Effects

Blood Hemolytic and aplastic anemia, agranulocytosis,thrombocytopenia

Integumentary Photosensitivity, exfoliative dermatitis, Stevens-

Johnson syndrome, epidermal necrolysis

Sulfonamides: Adverse Effects


Body System Adverse Effects

GI Nausea, vomiting, diarrhea, pancreatitis

Other Hepatotoxicity, convulsions, crystalluria,

toxic nephrosis, headache, peripheral neuritis, urticaria, cough

Sulfonamides: Adverse Effects (cont’d)


Penicillins Cephalosporins Carbapenems Monobactams

Beta-Lactam Antibiotics


Natural penicillins Penicillinase-resistant penicillins Aminopenicillins Extended-spectrum penicillins

Penicillins


Natural penicillins penicillin G penicillin V

Penicillinase-resistant drugs nafcillin cloxacillin oxacillin dicloxacillin

Penicillins (cont’d)


Aminopenicillins amoxicillin (Amoxil), ampicillin (generic only)

Extended-spectrum drugs carbenicillin piperacillin ticarcillin

Penicillins (cont’d)


Penicillins enter the bacteria via the cell wall Inside the cell they bind to penicillin-binding

protein Once bound, normal cell wall synthesis is

disrupted Result: bacteria cells die from cell lysis Penicillins do not kill other cells in the body

Penicillins: Mechanism of Action


Prevention and treatment of infections caused by susceptible bacteria, such as: Gram-positive bacteria, including Streptococcus spp.,

Enterococcus spp., Staphylococcus spp.

Penicillins: Indications


Allergic reactions to the penicillins occur in 0.7% to 4% of treatment courses Urticaria, pruritus, angioedema

Those allergic to penicillins have an increased risk of allergy to other beta-lactam antibiotics

Only those patients with a history of throat swelling or hives from penicillin should not receive cephalosporins

Penicillins: Adverse Effects


Common adverse effects Nausea, vomiting, diarrhea, abdominal pain

Other adverse effects are less common

Penicillins: Adverse Effects (cont’d)


MANY interactions! NSAIDs Oral contraceptives Warfarin Others

Penicillins: Interactions


Classroom Response Question

A patient is receiving Augmentin (amoxicillin and clavulanic acid) liquid solution through a PEG tube. What is the purpose of the clavulanic acid?A.It works synergistically with the antibiotic to improve potency.

B.It inhibits the action of the enzymes produced by beta-lactamase–producing bacteria.

C.It protects the antibiotic from the harmful gastric acid secretions in the stomach.

D.It enhances the absorption of the antibiotic in the small intestine.


First generation Second generation Third generation Fourth generation Fifth generation

Cephalosporins


Semisynthetic antibiotics Structurally and pharmacologically related

to penicillins Bactericidal action Broad spectrum Divided into groups according to their

antimicrobial activity

Cephalosporins (cont’d)


Good gram-positive coverage Poor gram-negative coverage Parenteral and PO forms Examples

cefadroxil (Duricef, Ultracef) cephradine (Velosef) cefazolin (Ancef) cephalexin (Keflex)

Cephalosporins: First Generation


Used for surgical prophylaxis, and for susceptible staphylococcal infections cefazolin (Ancef and Kefzol): IV or IM cephalexin (Keflex): PO

Cephalosporins: First Generation (cont’d)


Good gram-positive coverage Better gram-negative coverage than first

generation Examples: cefaclor (Ceclor) cefprozil (Cefzil) cefoxitin (Mefoxin) cefuroxime (Zinacef) cefotetan (Cefotan)

Cephalosporins: Second Generation


cefoxitin (Mefoxin): IV and IM Used prophylactically for abdominal or colorectal

surgeries Also kills anaerobes

cefuroxime Zinacef is parenteral form; Ceftin is PO Surgical prophylaxis Does not kill anaerobes

Cephalosporins: Second Generation (cont’d)


Most potent group against gram-negative bacteria

Less active against gram-positive bacteria Examples cefotaxime (Claforan) ceftazidime (Fortaz) cefdinir (Omnicef) ceftizoxime (Cefizox) ceftriaxone (Rocephin)

Cephalosporins: Third Generation


ceftriaxone (Rocephin) IV and IM, long half-life, once-a-day dosing Elimination is primarily hepatic Easily passes meninges and diffused into CSF to

treat CNS infections

Cephalosporins: Third Generation (cont’d)


ceftazidime (Ceptaz, Fortaz, Tazidime) IV and IM forms Excellent gram-negative coverage Used for difficult-to-treat organisms such as

Pseudomonas spp. Excellent spectrum of coverage Resistance is limiting usefulness

Cephalosporins: Third Generation (cont’d)


Broader spectrum of antibacterial activity than third generation, especially against gram-positive bacteria

Uncomplicated and complicated UTI cefepime (Maxipime)

Cephalosporins: Fourth Generation


ceftaroline (Teflaro) Broader spectrum of antibacterial activity Effective against a wide variety of organisms

• MRSA

Cephalosporins: Fifth Generation


Similar to penicillins Mild diarrhea, abdominal cramps, rash, pruritus,

redness, edema Potential cross-sensitivity with penicillins if

allergies exist

Cephalosporins: Adverse Effects


Broadest antibacterial action of any antibiotics to date

Reserved for complicated body cavity and connective tissue infections in acutely ill hospitalized patients

May cause drug-induced seizure activity This risk can be reduced with proper dosage

Carbapenems


imipenem/cilastatin (Primaxin) Used for treatment of bone, joint, skin, and soft-tissue

infections; many other uses Cilastatin inhibits an enzyme that breaks down

imipenem meropenem (Merrem) ertapenem (Invanz) doripenem (Doribax)

Carbapenems


aztreonam (Azactam) Synthetic beta-lactam antibiotic Primarily active against aerobic gram-negative

bacteria (E. coli, Klebsiella spp., Pseudomonas spp.) Bactericidal Parenteral use only Used for moderately severe systemic infections and

UTIs

Monobactams


erythromycin (E-mycin, E.E.S, others) azithromycin (Zithromax) clarithromycin (Biaxin)

Macrolides


Prevent protein synthesis within bacterial cells Considered bacteriostatic Bacteria will eventually die In high enough concentrations, may also be

bactericidal

Macrolides:Mechanism of Action


Strep infections Streptococcus pyogenes (group A beta-hemolytic

streptococci) Mild to moderate URI and LRI

Haemophilus influenzae Spirochetal infections

Syphilis and Lyme disease Gonorrhea, Chlamydia, Mycoplasma

Macrolides: Indications


azithromycin and clarithromycin Approved for Mycobacterium avium-intracellulare

complex infection (opportunistic infection associated with HIV/AIDS)

clarithromycin Recently approved for use in combination with

omeprazole for treatment of active ulcer disease associated with Helicobacter pylori infection

Macrolides: Indications (cont’d)


GI effects, primarily with erythromycin Nausea, vomiting, diarrhea, hepatotoxicity, flatulence,

jaundice, anorexia Azithromycin and clarithromycin: fewer GI

adverse effects, longer duration of action, better efficacy, better tissue penetration

Macrolides: Adverse Effects


telithromycin (Ketek) Only drug in this class Better antibacterial coverage than macrolides Associated with severe liver disease Use is limited

Ketolide


demeclocycline (Declomycin) oxytetracycline (Terramycin) tetracycline doxycycline (Doryx, Vibramycin) minocycline (Minocin) tigecycline (Tygacil)

Tetracyclines


Natural and semisynthetic Obtained from cultures of Streptomyces Bacteriostatic—inhibit bacterial growth Inhibit protein synthesis Stop many essential functions of the bacteria

Tetracyclines (cont’d)


Bind (chelate) to Ca+++ and Mg++ and Al+++ ions to form insoluble complexes

Dairy products, antacids, and iron salts reduce oral absorption of tetracyclines

Should not be used in children under age 8 or in pregnant/lactating women because tooth discoloration will occur if the drug binds to the calcium in the teeth

Tetracyclines (cont’d)


Wide spectrum Gram-negative and gram-positive organisms,

protozoa, Mycoplasma, Rickettsia, Chlamydia, syphilis, Lyme disease, acne, others

Demeclocycline is also used to treat SIADH by inhibiting the action of ADH

Tetracyclines: Indications


Strong affinity for calcium Discoloration of permanent teeth and tooth

enamel in fetuses and children, or nursing infants if taken by the mother

May retard fetal skeletal development if taken during pregnancy

Tetracyclines: Adverse Effects


Alteration in intestinal flora may result in: Superinfection (overgrowth of nonsusceptible

organisms such as Candida) Diarrhea Pseudomembranous colitis

Tetracyclines: Adverse Effects (cont’d)


May also cause: Vaginal candidiasis Gastric upset Enterocolitis Maculopapular rash Other effects

Tetracyclines: Adverse Effects (cont’d)


Before beginning therapy, assess drug allergies; renal, liver, and cardiac function; and other lab studies

Be sure to obtain thorough patient health history, including immune status

Assess for conditions that may be contraindications to antibiotic use or that may indicate cautious use

Assess for potential drug interactions

Nursing Implications


It is ESSENTIAL to obtain cultures from appropriate sites BEFORE beginning antibiotic therapy

Nursing Implications (cont’d)


Instruct patients to take antibiotics exactly as prescribed and for the length of time prescribed; they should not stop taking the medication early when they feel better

Assess for signs and symptoms of superinfection: fever, perineal itching, cough, lethargy, or any unusual discharge



For safety reasons, check the name of the medication carefully because there are many drugs that sound alike or have similar spellings




When completing an admission assessment, the patient states that she is allergic to sulfa drugs. What will the nurse do next?A. Mark the allergy on her medical record.B. Place an “allergy” armband on the patient.C. Ask the patient for more information about the allergic reaction she had.D. Notify the physician about the patient’s allergy.


Each class of antibiotics has specific adverse effects and drug interactions that must be carefully assessed and monitored

The most common adverse effects of antibiotics are nausea, vomiting, and diarrhea

All oral antibiotics are absorbed better if taken with at least 6 to 8 ounces of water




A patient has a prescription for a sulfa drug as treatment for a urinary tract infection. She is also taking an oral contraceptive, an oral sulfonylurea antidiabetic drug, and phenytoin for a history of seizures. Which drug may pose a potential serious interaction with the sulfa drug?

A.The oral contraceptive

B.The oral antidiabetic drug

C.The phenytoin

D.All of these


Sulfonamides Take with 2000 to 3000 mL of fluid/24 hr Assess RBCs prior to beginning therapy Take oral doses with food



Penicillins Take oral doses with water (not juices) as acidic fluids

may nullify drug’s antibacterial action Monitor patients taking penicillin for an allergic

reaction for at least 30 minutes after administration



Cephalosporins Assess for penicillin allergy; may have cross allergy Give orally administered forms with food to decrease

GI upset, even though this will delay absorption Some of these drugs may cause a disulfiram

(Antabuse)-like reaction when taken with alcohol



Macrolides These drugs are highly protein-bound and will cause

severe interactions with other protein-bound drugs The absorption of oral erythromycin is enhanced

when taken on an empty stomach, but because of the high incidence of GI upset, many drugs are taken after a meal or snack



Tetracyclines Avoid milk products, iron preparations, antacids, and

other dairy products because of the chelation and drug-binding that occurs

Take all medications with 6 to 8 ounces of fluid, preferably water

Because of photosensitivity, avoid sunlight and tanning beds



Monitor for therapeutic effects Improvement of signs and symptoms of infection Return to normal vital signs Negative culture and sensitivity tests Disappearance of fever, lethargy, drainage, and

redness Monitor for adverse reactions



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