Chapter 38
Antibiotics Part 1
Infections
Microorganisms invade body tissues
 Can be bacterial, viral, fungal, protozoan
 Community-associated infections

 An infection that is acquired by a person who has not
been hospitalized or had a medical procedure (e.g.,
dialysis, surgery, catheterization) within the past year
2
Health care–associated infections
 Contracted in a hospital or institutional setting
 Were not present or incubating in the pt on admit
 Occurs more than 48 hours after admission
 Difficult to treat because causative
microorganisms are often drug resistant and
the most virulent
 (
MRSA) is most common
 Previously known as nosocomial
 Top 10 leading causes of death in US
• 70% are preventable!!
 Costs us $$$9.8 billion annually
• UTI’s, surgical sites, pneumonia, IV lines, endless!!
3
Health Care–Associated Infections:
Prevention

Disinfectants
 Kills organisms
 Used only on nonliving objects
 Cidal agent: DESTROY

Antiseptics
 Generally only inhibits the growth of
microorganisms but does not necessarily kill them
 Applied exclusively to living tissue
 Static agents

HANDWASHING BEST WAY TO PREVENT
4
Antibiotics
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.
 Bacteria categorized and grouped based on
their shape and gram stain

 Help us guide antibiotic therapy!

Gram negatives generally harder to treat
5
Antibiotic Therapy Definitions

Empiric therapy:
 TX of an infection before specific culture info is known

Definitive therapy:
 antibiotics tailored to treat organism identified w/ cultures

Prophylactic therapy:
 TX w/ antibiotics to prevent an infection, as in surgery or
after trauma; SCIP

Therapeutic response:
 Decrease in specific s/s of infection are noted
(decreased fever, decreased WBC count and less
redness, inflammation, drainage: pus, phlegm, pain)

Subtherapeutic response
 Signs and symptoms of infection do not improve.
6
Antibiotic Therapy Definitions

Superinfection
 Normal bacteria flora are reduced; others flourish
 Yeast! & Clostridium difficile

Secondary infection
 Infection arises from another source; as opposed to
normal flora

Resistance
 Huge pressing public health concern
 Stop over treating for viruses, complete course of
therapy

Food–drug interactions
 Can affect absorption of antibiotic and effect efficacy
7
Antibiotic Therapy Considerations

Host factors to consider
 Age, pregnancy, genetics
 Kidney/liver function
 Site/source

Allergic reactions: penicillins and sulfonamides
are two broad classes of antibiotic to which many
people have allergic anaphylactic reactions
 Most common severe reactions: difficulty
breathing; significant rash, hives, or other
skin reaction; and severe gastrointestinal
(GI) intolerance
 remember n/v/d is not an allergic RXN
8
Actions of Antibiotics
Bactericidal: kill bacteria
 Bacteriostatic: inhibit growth of susceptible
bacteria rather than killing them immediately;
eventually leads to bacterial death

9
Antibiotic Classes:
Mechanism of Action:
Sulfonamides
 Penicillins
 Cephalosporins
 Macrolides
 Quinolones
 Aminoglycosides
 Tetracyclines
 Misc.


Interference with:
 cell wall synthesis
 protein synthesis
 DNA replication

Acting as a
metabolite to
disrupt critical
metabolic reactions
inside the bacterial
cell
10
Mechanisms for Combatting Bacteria
11
Antibiotics: Sulfonamides
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.
Bacteriostatic action
 MOA: Prevent synthesis of folic acid required for
synthesis of purines and nucleic acid (DNA/RNA)

 Only affect organisms that synthesize their own folic
acid; human cells not affected
Contraindications: SULFA allergy
 Interactions: sulfonylureas, warfarin, BC

12
Sulfonamides: Indications
Effective against gram-positive and gram negative
 Treatment of UTIs caused by susceptible strains
of:

 Enterobacter spp., Escherichia coli, Klebsiella spp.,
Proteus mirabilis, Proteus vulgaris, Staphylococcus
aureus

Pneumocystis carinii pneumonia
 Opportunistic HIV infection
Upper respiratory tract infections
 SMX-TMP is commonly used for outpatient
Staphylococcus infections because of the high
rate of community-acquired MRSA infections.

13
Sulfonamides:
Adverse Effects
Body System
Blood
Integumentary
Adverse Effects
Hemolytic and aplastic
anemia, agranulocytosis,
thrombocytopenia
Photosensitivity, exfoliative
dermatitis, Stevens-Johnson
syndrome, epidermal
necrolysis
Copyright © 2017, Elsevier Inc. All rights reserved.
14
Sulfonamides:
Adverse Effects (Cont.)
Body System
GI
Other
Adverse Effects
Nausea, vomiting,
diarrhea, pancreatitis
Hepatotoxicity,
convulsions,
crystalluria,
toxic nephrosis,
headache, peripheral
neuritis, urticaria, cough
Copyright © 2017, Elsevier Inc. All rights reserved.
15
Nursing Implications: Sulfonamides
 Drug allergy to sulfa type drugs?
 Take with 2000 to 3000 mL of fluid/24 hr.
 Assess CBC count before beginning therapy
• Anemias, agranulocytosis
 Baseline kidney function
• Crystaluria
 Skin assessment: Stevens- Johnson
syndrome
 Take oral doses with food to minimize GI
upset.
16
Beta-Lactam Antibiotics (BLA):
Four Major Subclasses:
Penicillins, Cephalosporins, Carbapenems,
Monobactams
 Some bacteria have the capability to produce
enzymes (beta lactamases) that open the beta
lactam ring thereby
inactivating PCN;
 PCN will be combined
a beta lactamase
inhibitor to keep it active

with
 clavulanic acid
 tazobactam
 sulbactam
17
Copyright © 2017, Elsevier Inc. All rights reserved.
18
#1 BLA- Penicillins

Natural penicillins

 amoxicillin (peds)
 penicillin G
 ampicillin
 penicillin V

Penicillinaseresistant drugs
 nafcillin
 cloxacillin
 oxacillin
 dicloxacillin
Aminopenicillins (-)

Extended-spectrum
drugs (+/-/ANAB)
 carbenicillin
 piperacillin
 ticarcillin
 piperacillin/
tazobactam
(Zosyn)*- hospital
19
Penicillins: Mechanism of Action
bactericidal
 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; unstable membranes

 Result: Bacteria cells die from cell lysis.

Indications: Prevention and treatment of infections
caused by susceptible bacteria, such as:
 Gram-positive bacteria, including Streptococcus spp.,
Enterococcus spp., Staphylococcus spp.
 Extended spectrum PCNs have more coverage
20
Penicillins: Contraindications
Usually safe and well-tolerated medications
 Contraindicated: known drug allergy- inquire!
 Type of reaction that occurs in patients who
state they are allergic to penicillins
 Not all end in “cillin” (e.g., Zosyn, Augmentin)
 Many medication errors have occurred when a
penicillin drug called by its trade name is given
to a patient with a penicillin allergy.

21
Penicillins: Adverse Effects
Allergic reactions to the penicillins occur in 0.7%
to 4% of treatment courses.
 Urticaria, pruritus, angioedema, SOB
 Allergic to PCN = increased risk of allergy to
other beta-lactam antibiotics.

 Only patients with a history of throat swelling or hives
from penicillin should not receive cephalosporins.

Common adverse effects:
 Nausea, vomiting, diarrhea (BIG 3), abdominal pain

Other adverse effects are less common.
22
Penicillins: Interactions & NI

MANY interactions!
 NSAIDS
 Oral contraceptives
 Warfarin
 Others

Nursing IMPLICATIONS
 Take oral doses with water (not juices) because
acidic fluids may nullify the drug’s antibacterial action.
 Monitor patients taking penicillin for an allergic
reaction for at least 30 minutes after administration.
 Caution for cross allergies
23
#2 BLA: Cephalosporins– “C”
Semisynthetic antibiotics; Broad spectrum
 Structurally and pharmacologically related to PCNs
 Bactericidal action;
 MOA: interfere with bacterial cell wall synthesis
 Divided into groups according to their antimicrobial
activity (Broader spectrum of antibacterial activity &
gram – activity with each gen )

 First generation
 Second generation
 Third generation
 Fourth generation
 Fifth generation
24
Cephalosporins: First Generation
Good gram-positive coverage
 Poor gram-negative coverage
 IV, IM & PO forms
 Examples
 cefadroxil (Duricef, Ultracef)
 cephradine (Velosef)
 cefazolin (Ancef)
 cephalexin (Keflex)
• Used for surgical prophylaxis and for
susceptible staphylococcal infections
(cellulitis)

25
Cephalosporins: Second Generation
Good gram-positive coverage
 Better gram-negative coverage than first generation
 Only generation with some drugs ability to cover
anaerobes
 Examples
 cefaclor (Ceclor)
 cefprozil (Cefzil)
 cefoxitin (Mefoxin)
 cefuroxime (Zinacef IV, Ceftin PO) - Surgical
prophylaxis
 cefotetan (Cefotan)

26
Cephalosporins: Third Generation
Most potent group against gram-negative bacteria
 Less active against gram-positive bacteria
 Majority IV
 Examples
 cefotaxime (Claforan)
 ceftazidime (Fortaz)–

• Used for difficult-to-treat organisms such Pseudomonas
 cefdinir (Omnicef)
 ceftizoxime (Cefizox)
 ceftriaxone (Rocephin)- IM or IV
 cefpodoxime
 ceftibuten (Cedax)
27
Cephalosporins: 4th 5th Generation

Fourth: Broader spectrum of antibacterial activity than third
generation, especially against gram positive bacteria &
Enterobacter
 Uncomplicated and complicated UTI, skin infections &
pneumonia
• cefepime (Maxipime)

Fifth: newest & even broader spectrum of antibacterial
activity
• ceftaroline (Teflaro)
• Effective against a wide variety of organisms
 Only cephalosporin that treats MRSA
 Skin infections & pneumonia
28
Cephalosporins: Adverse Effects & NI

Adverse Effects:
 Similar to penicillins
 Mild diarrhea, abdominal cramps, rash, pruritus, redness,
edema
 Potential cross-sensitivity with penicillins if allergies exist

Nursing Implications:
 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.
 Monitor renal & hepatic Function
29
#3 BLA: CarbaPENEMS
Broadest antibacterial action of any antibiotics to
date
 Bacterialcidal & inhibit cell wall synthesis
 Reserved for complicated body cavity and
connective tissue infections in acutely ill hospitalized
patients
 Must be infused over 60
minutes
 May cause drug-induced
seizure activity

 This risk can be reduced
with proper dosage.
30
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)

Copyright © 2017, Elsevier Inc. All rights reserved.
31
4th BLA: Monobactams

aztreonam (Azactam)
 Only; Synthetic beta-lactam antibiotic
 Primarily active against aerobic gram-
negative bacteria (E. coli, Klebsiella spp.,
Pseudomonas spp.)
 Bactericidal, inhibits bacterial cell wall
synthesis
 Parenteral use only
 Used for moderately severe systemic
infections and UTIs
32
Macrolides

erythromycin (E-mycin, E.E.S, others)
 Older; speeds up GI motility (gastroporesis)
azithromycin (Zithromax)
 clarithromycin (Biaxin)
 fidaxomicin (Dificid, Dificlir)

 New only for tx of Cdiff
MOA: Prevent protein synthesis within bacterial
cells by binding to their 50S ribosomes
 Considered bacteriostatic (bacteria will eventually
die); In high enough concentrations, may also be
bactericidal

33
Macrolides: Indications
Strep infections- Streptococcus pyogenes (group A
beta-hemolytic streptococci)
 Mild to moderate upper & lower respiratory tract
infections- Haemophilus influenzae
 Spirochetal infections

 Syphilis and Lyme disease
Gonorrhea, Chlamydia, Mycoplasma
 clarithromycin (Biaxin)- H. pylori & mycobacterium
avium-intracellulare
 Drugs of choice for the TX of many gram-positive
organisms in penicillin allergic patients, pneumonia
caused by Mycobacterium and Legionella.

34
Macrolides: Adverse Effects

GI effects, >with erythromycin
 N/v/d, hepatotoxicity, flatulence, jaundice, anorexia

azithromycin and clarithromycin:
 fewer GI adverse effects, longer duration of action,
better efficacy, better tissue penetration
 Watch QT interval
 These drugs are highly protein bound and metabolized
in the liver


will cause severe interactions with other protein-bound drugs
and other drugs hepatically metabolized
Drug absorption is enhanced when taken on an empty
stomach
 because of the high incidence of GI upset, many drugs
are taken after a meal or snack.
35
TetraCYCLINES
demeclocycline (Declomycin)
 oxytetracycline (Terramycin)
 doxycycline (Doryx, Vibramycin)
 minocycline (Minocin)
 tigecycline (Tygacil)
 tetracycline

Bacteriostatic: inhibit bacterial growth
 MOA: Inhibit protein synthesis

 Stop many essential functions of the bacteria
37
Tetracyclines: Indications

Wide spectrum
 Gram-negative and gram-positive organisms,
protozoans,
 Drugs of choice for: Mycoplasma spp.,
Rickettsia spp., Chlamydia,
 syphilis, Lyme disease, acne, H. pylori,
syphilis, others
Copyright © 2017, Elsevier Inc. All rights reserved.
38
Tetracyclines: Adverse Effects:

Strong affinity for calcium
 Discoloration of permanent teeth and tooth
enamel in fetuses and children < 8 or nursing infants
 May retard fetal skeletal development if taken during
pregnancy

Alteration in intestinal flora may result in:
 Superinfection (overgrowth of nonsusceptible organisms
such as Candida spp- Vaginal candidiasis)
 Diarrhea & Pseudomembranous colitis

May also cause:
 Gastric upset
 Enterocolitis
 Maculopapular rash
39
Nursing Implications: Tetracyclines
 Avoid milk products, iron preparations, antacids, and
other dairy products because of the chelation and
drug- binding that occur.– drug interactions
 Potentiate effects of birth control & warfarin
 Take all medications with 6 to 8 oz of fluid, preferably water.
 Because of photosensitivity, avoid sunlight and
tanning beds.
Copyright © 2017, Elsevier Inc. All rights reserved.
40
Chapter 39: Antibiotics Part 2
Treating Resistant bugs!
Copyright © 2017, Elsevier Inc. All rights reserved.
Multidrug-Resistant Organisms
Organisms that are resistant to one
or more classes of antimicrobial drugs
 Methicillin-resistant Staphylococcus aureus (MRSA)

 No longer seen just in hospitals; approximately 50% of staph
infections contracted in the community involve MRSA

Vancomycin-resistant Enterococcus (VRE)
 usually seen in urinary tract infections (UTIs)

Organisms producing extended-spectrum betalactamases (ESBLs)
 resistant to all beta-lactam antibiotics
 treated only quinolones or some others

Carbapenem-resistant Enterobacteriaceae (CRE)
 tigecycline and colistimethate used to treat CRE
42
*Aminoglycosides
Potent; drugs of choice for virulent infection
 Poor oral absorption; no oral forms (exception:
neomycin) all are IV or IM route
 MOA: Bactericidal; prevent protein synthesis
 Kill mostly gram-negative bacteria; some
gram-positive bacteria
 gentamicin
 neomycin (Neo-fradin)- PO
 tobramycin (TOBI)
 streptomycin
 amikacin- last hoorah! (Gent & tobi resistant)

43
Aminoglycosides: Indications
Used to kill serious gram-negative bacteria, such
as Pseudomonas spp., Escherichia coli, Proteus
spp., Klebsiella spp., Serratia spp.
 Used for certain gram + infections that are resistant

 Enterococcus; endocarditis w/ strep
Often used in combination with other antibiotics for
synergistic effects (beta-lactams or vancomycin)
 neomycin PO

 Given orally to decontaminate the GI tract before surgical
procedures
 Also used as an enema for this purpose
 Used to treat hepatic encephalopathy: helps reduce
44
the number of ammonia producing bacteria in GI tract
Aminoglycosides:
Adverse Effects

Therapeutic drug monitoring: serious toxicities
 Ototoxicity and nephrotoxicity are the most significant
Headache
 Paresthesia
 Fever
 Superinfections
 Vertigo
 Skin rash
 Dizziness
 n/v/d

45
Aminoglycosides: Monitoring

Serum levels measured to prevent toxicity
 Peak: highest drug levels for once-daily regimens
 Trough: lowest to ensure adequate renal clearance of
the drug and avoid toxicity; drawn just before next dose
• Trough level high= >risk nephrotoxicity & ototoxicity
 Aminoglycocydes are concentration-dependent killing
 MIC: Lowest concentration of drug needed to kill
bacteria
 Serum level needs to be at least eight times higher than
the MIC for most effective bacterial kill
 Time-dependent killing (beta-lactams)
 Amt of time above MIC is critical for max bacterial kill
46
Copyright © 2017, Elsevier Inc. All rights reserved.
47
Aminoglycosides:
Therapeutic Drug Monitoring

Postantibiotic effects
 Continued bacterial growth suppression that
occurs after antibiotic exposure

Resistance
 Emerging…

Drug interactions:
 Other nephrotoxic drugs
 Concurrent use with loop diuretics increases
ototoxicity risk
 warfarin
48
Quinolones AKA fluoroquinolones

excellent oral absorption
 Comparable to IV route
Absorption reduced by antacids
 Effective against gram-negative organisms and
some gram-positive organisms

 ciprofloxacin (Cipro)
 norfloxacin (Noroxin)
 levofloxacin (Levaquin)
 moxifloxacin (Avelox)
 gemifloxacin (Factive)
49
Quinolones: Mechanism of Action
MOA: interferes w/ DNA replicationbactericidal
 Indications:
 Used to treat S. aureus, Serratia
marcescens, and Mycobacterium
fortuitum
 Gram-negative bacteria
such as Pseudomonas
 Complicated urinary tract, respiratory,
bone and joint, GI, skin, and STDs
 Treats anthrax (ciprofloxacin)

50
Quinolones: Interactions

Oral quinolones: antacids, calcium, magnesium,
iron, zinc preparations, or sucralfate
 Patients need to take the interacting drugs at least
1 hour before or after taking quinolones.
Dairy products
 Enteral tube feedings
 Probenecid
 Nitrofurantoin
 Oral anticoagulants
 Amiodarone

Copyright © 2017, Elsevier Inc. All rights reserved.
51
Quinolones: Adverse Effects
Body System
CNS
GI
Cardiac
Adverse Effects
Headache, dizziness,
insomnia, depression,
restlessness, convulsions
Nausea, vomiting, diarrhea,
constipation, thrush, increased
liver function study results,
others
Prolonged QT interval
52
Quinolones: Adverse Effects
Body System
Integumentary
Other
Adverse Effects
Rash, pruritus, urticaria,
flushing
Ruptured tendons,*
tendonitis,* fever, chills,
blurred vision, tinnitus
Black box warning: increased risk of
tendonitis and tendon rupture.
**Not recom for kids < 8 because may affect
cartilage development
*
53
Miscellaneous Antibiotics
clindamycin (Cleocin)
 linezolid (Zyvox)
 metronidazole (Flagyl)
 nitrofurantoin (Macrodantin, Furadantin)
 quinupristin–dalfopristin (Synercid)
 daptomycin (Cubicin)
 vancomycin (Vancocin, Vancoled)
 colistimethate (Coly-Mycin)
 telavancin (Vibativ)

54
*metronidazole (Flagyl)
 MOA: inhibits microbial DNA synthesis
 Used for anaerobic organisms
 Widely used to treat intraabdominal
and gynecologic infections
• CDiff
 Protozoal infections
 can also be classified as
antiprotazoan
 Several drug interactions
• Avoid alcohol
an
55
**vancomycin (Vancocin)**
 Bactericidal & treatment of choice for MRSA because it’s
the most effective and other gram-positive infections
 Class: Glycopeptide
 MOA: binds to bacterial cell walls inhibiting synthesis
 Oral vancomycin is indicated for (C. difficile) and for the
treatment of staphylococcal enterocolitis.
 Monitor blood levels to ensure therapeutic & prevent toxicity
 May cause ototoxicity and nephrotoxicity
 Red man syndrome may occur
• Flushing or itching of head, neck, face,
upper trunk
• Antihistamine may be ordered
to
reduce these effects
• Should be infused over 60 minutes
56
• Rapid infusions may cause hypotension.
clindamycin (Cleocin)
Class: lincosamide
 MOA: inhibits protein synthesis
 Used for chronic bone, GU & intraabd. Infections

 reserved for serious infections and/or resistant infections
 May cause C. difficile infection!

linezolid (Zyvox)
 New class: oxazolidinones
 MOA: inhibits protein synthesis
 Used to treat VRE & skin structure infections, MRSA and
penicillin resistant pneumococcal infections.
 May cause hypotension, serotonin syndrome if taken with
SSRIs & reactions if taken with tyramine-containing foods57
nitrofurantoin (Macrodantin)
 Primarily used for UTIs because drug concentrates in
the urine (E. coli, S. aureus, Klebsiella spp.,
Enterobacter spp.)
 Use carefully if renal function is impaired, may cause fatal
hepatotoxicity
 daptomycin (Cubicin)
 new class known as lipopeptides
 MOA: unknown
 Treats complicated skin & soft tissue infections caused by
susceptible gram-positive bacteria, including MRSA and
VRE
 It is not to be used in pneumonia, because the drug is
inactivated by the surfactant that is secreted by lung tissue.58
**Nursing Implications: Antibiotic Therapy

Assess drug allergies; renal, liver, and cardiac
function & other lab studies (toxicities?)
 Monitor your peak/trough levels; draw serum levels
as ordered by pharmacist
Be sure to obtain thorough patient health history,
including immune status; baseline head to toe
 Assess for conditions that may be
contraindications or that may indicate cautious
use & potential drug interactions.
 It is ESSENTIAL to obtain cultures from
appropriate sites BEFORE beginning
antibiotic therapy.

 Know your source (or suspected) of infection
**Nursing Implications

Assess for signs and symptoms of
superinfection: fever, perineal itching, cough,
lethargy, or any unusual discharge, mucous
membranes, mouth sores, watery diarrhea
 Encourage consumption of probiotics to prevent
superinfection (yogurt, buttermilk, lactobicillis)
 Teach s/s of superinfection to report

Assess for signs of allergic RXN
 Wheezing, swelling, SOB, rashes, itching
 What to do???

Assess for signs of TOXICITY
 Ringing in the ears, dizziness/vertigo
64
Nursing Implications
Check IV compatibility &
reconstitute appropriately
prior to administration
 Watch your IV site: extravasation? Infiltration?
 For safety reasons, check the name of the
medication carefully because there are many
antibiotics that sound alike or have similar
spellings.
 Verify concentration
 Each class of antibiotics has specific adverse
effects and drug interactions that must be
carefully assessed and monitored.

65
Patient Education
Instruct pts to take antibiotics exactly as
prescribed and for the length of time
prescribed; (don’t stop even if they feel better)
 The most common adverse effects of
antibiotics are nausea, vomiting, and diarrhea– 
Ensure adequate hydration & snack
All oral antibiotics are absorbed better if taken
with at least 6 to 8 oz of water.
 Reliable back up method for birth control!!
 HANDWASHING!
 Caution with exposure to sunlight
 Encourage not to take antibiotics excessively

66
Nursing Implications:

Monitor for therapeutic
effects:
 Improvement of S/S of infection
• Return to normal vital signs
• Negative culture and sensitivity tests
 WBC trends
• Disappearance of fever, lethargy, drainage,
and redness
67