Chapter 43
Antibiotics Part 1: Sulfonamides,
Penicillins, Cephalosporins,
Macrolides, and Tetracyclines
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Bacteria


Gram positive
Gram negative
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Infections

Community-acquired infection

An infection that is acquired by a person who has not
been hospitalized (within the past year) or had a
medical procedure (e.g., dialysis, surgery,
catheterization) within the past year
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Infections: Sites of Origin

Health care–associated infections







Contracted in a health care facility
Were not present or incubating in the patient on admission to the
facility
Occurs more than 48 hours after admission
One of the top 10 causes of death in Canada
More difficult to treat because causative microorganisms are often
drug resistant and the most virulent
Methicillin-resistant Staphylococcus aureus (MRSA) (most
common) and vancomycin-resistant Enterococcus (VRE)
Previously known as nosocomial infection
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Health Care–Associated Infections:
Prevention



Handwashing: single most important prevention
method
Antiseptics
Disinfectants
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Health Care–Associated Infections:
Prevention (cont.)

Disinfectant




Kills organisms
Used only on nonliving objects
Cidal agent
Antiseptic



Generally only inhibits the growth of microorganisms;
does not necessarily kill them
Applied exclusively to living tissue
Static agents
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Bacterial Morphology Shapes
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Gram-Positive and Gram-Negative
Bacteria
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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.
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Basic Sites of Antibiotic Activity
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Antibiotic Therapy



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 intra-abdominal
surgery or after trauma
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Antibiotic Therapy (cont.)

Therapeutic response


Decrease in specific signs and symptoms of infection
are noted (fever, elevated white blood cell count,
redness, inflammation, drainage, pain).
Subtherapeutic response

Signs and symptoms of infection do not improve.
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Antibiotic Therapy (cont.)







Superinfection
Pseudomembranous colitis: Clostridium difficile
Secondary infection
Resistance
Antimicrobial stewardship (Accreditation
Canada, 2014)
Food–drug interactions
Host factors
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Antibiotic Therapy (cont.)



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
Pregnancy-related host factors
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Antibiotic Therapy (cont.)


Host factors: age, allergies, kidney and liver
function, pregnancy status, genetic
characteristics, site of infection and host
defences
Glucose-6-phosphate dehydrogenase (G6PD)
deficiency and slow acetylation
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Antibiotics: Classes








Sulfonamides
Penicillins
Cephalosporins
Carbapenems
Macrolides
Quinolones
Aminoglycosides
Tetracyclines
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Antibiotic Therapy:
Describe Mechanism of Action

-
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List Actions of Antibiotics

-
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Antibiotics: Sulfonamides


One of the first groups of antibiotics
Often combined with another antibiotic

Sulfamethoxazole combined with trimethoprim (a
nonsulfonamide antibiotic) (Apo-Sulfratrim®, Protrim®,
Teva-Trimel®, Septra®) and often abbreviated as
SMX-TMP, is used commonly in clinical practice.
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Sulfonamides:
Describe Mechanism of Action

-
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Sulfonamides: List Indications

-
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Sulfonamides:
List Adverse Effects
Body System
Blood
Integumentary
Adverse Effects
-
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Sulfonamides:
List Adverse Effects (cont.)
Body System
GI
Other
Adverse Effects
-
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ß-Lactam Antibiotics




Penicillins
Cephalosporins
Carbapenems
Monobactams
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Penicillins




Natural penicillins
Penicillinase-resistant penicillins
Aminopenicillins
Extended-spectrum penicillins
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Penicillins (cont.)

Natural penicillins



penicillin G
penicillin V
Penicillinase-resistant drugs

cloxacillin sodium
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Penicillins (cont.)

Aminopenicillins



amoxicillin
ampicillin
Extended-spectrum drugs



piperacillin sodium
clavulanic potassium/ticarcillin disodium
piperacillin sodium/tazobactam sodium
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Penicillins: Describe Mechanism of
Action

-
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Chemical Structure of Penicillins
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Penicillins: List Indications

-
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Penicillins: List Contraindications
and Concerns

-
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Penicillins: List Adverse Effects

-
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Penicillins: List Interactions

-
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Cephalosporins





First generation
Second generation
Third generation
Fourth generation
Fifth generation (none available in Canada)
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Cephalosporins (cont.)





Semisynthetic antibiotics
Structurally and pharmacologically related
to penicillins
Bactericidal action
Broad spectrum
Divided into groups according to their
antimicrobial activity
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Cephalosporins:
First Generation




Good gram-positive coverage
Poor gram-negative coverage
Parenteral and oral forms
Example


cephalexin (Keflex®)
cefazolin
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Cephalosporins:
First Generation (cont.)

Used for surgical prophylaxis and for susceptible
staphylococcal infections

cefazolin: intravenous (IV) or intramuscular (IM)
 cephalexin (Keflex): oral dosage
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Cephalosporins:
Second Generation



Good gram-positive coverage
Better gram-negative coverage than firstgeneration cephalosporins
Examples




cefaclor
cefoxitin
cefuroxime
cefprozil
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Cephalosporins:
Second Generation (cont.)

cefoxitin (Mefoxin®): IV and IM

Used prophylactically for abdominal or colorectal
surgeries
 Also kills anaerobes

cefuroxime
cefuroxime axetil (Ceftin®) is oral form
 Surgical prophylaxis
 Does not kill anaerobes

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Cephalosporins:
Third Generation


Most potent group against gram-negative bacteria
Less active against gram-positive bacteria
Examples
 cefotaxime sodium
 cefixime
 cefpodoxime proxetil
 ceftizoxime
 ceftazidime
 ceftriaxone
40
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
Cephalosporins:
Third Generation (cont.)

ceftriaxone sodium



IV and IM, long half-life, once-a-day dosing
Elimination is primarily hepatic
Easily passes meninges and diffused into
cerebrospinal fluid to treat central nervous system
infections
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Cephalosporins:
Third Generation (cont.)

ceftazidime (Fortaz®)

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.
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Cephalosporins:
Fourth Generation


Broader spectrum of antibacterial activity than
third-generation cephalosporins, especially
against gram-positive bacteria
Uncomplicated and complicated urinary tract
infection

cefepime hydrochloride (Maxipime®)
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Cephalosporins:
List Adverse Effects

-
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Carbapenems




Broadest antibacterial action of any antibiotics to
date
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.
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Carbapenems (cont.)

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®)
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Monobactams

aztreonam (Cayston®)
Synthetic ß-lactam antibiotic
 Primarily active against aerobic gram-negative
bacteria (E. coli, Klebsiella spp., Pseudomonas spp.)
 Bactericidal
 Parenteral use only
 Used for management of cystic fibrosis patients with
chronic pulmonary Pseudomonas aeruginosa
infections

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Macrolides




erythromycin (E-Mycin®, many others)
azithromycin (Zithromax®)
clarithromycin (Biaxin®)
fidaxomicin (Dificid®)
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Macrolides:
Describe Mechanism of Action

-
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Macrolides: List Indications

-
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Macrolides: List Adverse Effects

-
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Tetracyclines



doxycycline hyclate (Doxycin®, Vibramycin®,
others)
minocycline hydrochloride (Minocin®)
tigecycline (Tygacil®)
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Tetracyclines (cont.)





Natural and semisynthetic
Obtained from cultures of Streptomyces
Bacteriostatic: inhibit bacterial growth
Inhibit protein synthesis
Stop many essential functions of the bacteria
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Tetracyclines (cont.)



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 younger than 8
years of age or in pregnant or lactating women
because tooth discoloration will occur if the drug
binds to the calcium in the teeth
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Tetracyclines: List Indications

Wide spectrum

-
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Tetracyclines: List Adverse Effects

-
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List Nursing Implications

-
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List Nursing Implications (cont.)

Sulfonamides

-
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Nursing Implications (cont.)

Penicillins

-
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Nursing Implications (cont.)

Cephalosporins

-
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Nursing Implications (cont.)

Macrolides

-
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Nursing Implications (cont.)

Tetracyclines

-
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Nursing Implications (cont.)

Monitor therapeutic effects.

-
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