Anti-infective Drugs
Jan Bazner-Chandler
MSN, CNS, RN, CPNP
Bacteria
Bacteria
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Gram-positive bacterium has a thick layer of
peptioglycan.
Gram-negative bacterium has a thin
peptioglycan layer and an outer membrane.
Common Bacterial Pathogens
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Gram positive
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Staphylococcus aureus
Streptocci
Enterococci
Gram negative
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Escherichia coli or E-coli
Klebsiella
Proteus
Pseudomonas
Empiric Therapy
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Administration of antibiotics based on the
practitioner’s judgment of the pathogens most
likely to be causing the infection; it involves
the presumptive treatment of an infection to
avoid treatment delay before specific cuture
information has been obtained.
Prophylactic Antibiotic Therapy
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Antibiotics taken before anticipated exposure
to an infectious organism in an effort to
prevent the development of infection.
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IV antibiotics given prior to surgery
Superinfection
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An infection occurring during antimicrobial
treatment for another infection, resulting from
overgrowth of an organism not susceptible to
the antibiotic used.
A secondary infection that occurs due
weakening of the patients immune system by
the first infection.
Examples of Superinfections
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Fungal or yeast infection
Diarrhea due to diminished normal flora of
the gastrointestinal tract.
Laboratory Tests
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Gram stain – microscopic identification of
organism
Culture – identifies causative agent and
susceptibility to specific antibiotics
Serology – titers or antibodies measured
CBC – looking at WBC
Cultures
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Throat
Wound
Urine
Sputum
Blood
Clinical Pearl
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Always collect culture: urine, sputum, wound
drainage, or blood prior to starting antibiotic
therapy.
If technician is drawing blood make sure it
has been done before starting antibiotics.
Antimicrobials

Drugs used to prevent or treat infection
caused by pathogens
Two Classifications
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Bactericidal drugs kill bacteria directly.
Bacteriostatic drugs prevent bacteria from
dividing or inhibits their growth.
Two Types of Bacteria

Aerobic – grow and live in presence of
oxygen
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Staph & Strep
Anaerobic – cannot grow in presence of
oxygen
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Deep wounds
Characterized by abscess formation, foul-smelling
pus and tissue destruction
Community-Acquired Infection
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Less severe and easier to treat, although
drug resistant strains are increasing
Remember Staph is everywhere – it is normal
flora on skin and in the upper respiratory tract
MRSA: methicillin-resistant-Staphylococcus
aureus
Nosocomial Infections
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More severe and difficult to manage because
they often result from drug-resistant
microorganisms and occur in clients whose
resistance is impaired
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Pseudomonas
Proteus
Bacterial Resistance
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Bacteria develop the ability to produce
substances which block the action of
antibiotics or change their target or ability to
penetrate the cells.
What causes resistance?
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Widespread use of antimicrobial drug
Interrupted or inadequate antimicrobial
treatment of infection
Type of bacteria – gram-negative strains
have higher rates of resistance
Re-occurring infections
Condition of the host
Location – critical care areas
Opportunistic Host
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Compromised immune system
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Infants
Geriatric population
Cancer
HIV positive – low T-cell count
Burns
Skin breakdown
Client with total knee or hip replacement
Client History / Assessment
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Allergies
Previous drug reactions
Baseline renal and liver function
Review culture reports for appropriate
antibacterial drug choice
Patient response to antibiotics therapy
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Are they getting better?
Any side effects?
Antibiotics
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Sulfonamides
Penicillins
Cephalosporins
Macrolides
Fluoroquinolones
Aminoglycosides
Tetracyclines
Sulfonamides
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Action: inhibit the growth of bacteria
(bacteriostatic antibiotic) by inhibiting the
growth of susceptible bacteria by preventing
bacterial synthesis of folic acid.
Usually used in combination drugs.
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Trimethoprim / sulfamethoxazole: Trade name
Bactrim, Septra, TMP/SMX
Indications
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Broad spectrum: can be used against gram
negative and gram positive organisms
Very useful in treating kidney infections since
they achieve a high concentration in the
kidneys.
Susceptible organisms: Enterobacter, E.Coli,
Klebsiella, Proteus
Problem: organisms becoming more resistant
Specific Use of Sulfa Drugs
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HIV patients with pneumocystis carinii’
May be given Bactrim or Septra
prophylactically.
Contraindications
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Drug allergy to sulfa
Use of thiazide and loop diuretics
Pregnant women
Infants younger than 2 months of age
Adverse Effects
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Most common is cutaneous reactions – can
occur weeks after therapy started.
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Erythema multiforme (Stevens Johnson
Syndrome)
Toxic epidermal necrolysis
Photosensitivity reactions: exposure to
sunlight can result in severe sunburn
B-Lactam Antibiotics
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Includes 4 major drug classifications
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penicillins
cephalosporins
carbapenes
monobactams
Penicillin
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Derived from mold fungus
Penicillin
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First generation IM or IV
Newer penicillins have been developed that
increase gastric acid stability of penicillin
Good drug since it enters most bodily fluids:
joint, pleural, and pericardial.
Not effective against intraocular (eye) or
cerebral spinal fluid infection (CSF)
Penicillin
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Bactericidal action against sensitive bacteria
Action: binds to bacterial wall, resulting in cell
death
Susceptible Bacteria
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Gram-positive organisms
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Streptococcus
Enterococcus
Staphylococcus
Adverse Reactions
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Most common reaction is GI (diarrhea) when
administered orally.
Urticaria (rash), pruritus (itching), and
angioedema (swelling of the throat)
Severe reaction: Steven’s Johns Syndrome
Note: when giving IV or IM observe for ½ to 1
hour after giving for adverse reactions.
Hives
Anaphylaxis
Combination Penicillin / B-lactamases
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Unasyn
Augmentin
Timentin
Zosyn
Ampicillin – Synthetic Penicillin
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Broad spectrum effective against several
gram-positive and gram-negative bacteria
E-coli, proteus, Salmonella, Shigella
Not effective against staphylococci on
gonococci
Bronchitis, sinusitis, and otitis media
Ampicillin
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Bactericidal action – spectrum is broader
than penicillin
Binds to bacterial wall resulting in cell death
Nursing Implications
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Same as penicillin
Ask client about oral contraceptive use – drug
may cause transient decrease in
effectiveness
Advise to use additional BC – barrier
protection during antibiotic therapy
Amoxicillin
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Trade name: Amoxil, Trimox, Wymox
Classification: aminopenicillins
Indications: skin infections, otitis media (ear
infection), sinusitis, respiratory infections.
Inexpensive in generic form but required
frequent dosing (q 8 hours)
Amoxicillin
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Oral equivalent of Ampicillin
Readily absorbed and reaches therapeutic
levels rapidly
Drug of choice in prevention of bacterial
endocarditis
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Clients with total knee or hip replacement, heart
valve replacement need to take prior to any dental
work, endoscopy exams
Dosing for Amoxicillin
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Adults: 250 to 500 mg q8h
Infants and children less than 20 kg:
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20 – 40 mg / kg / day divided into doses q 8 hours
Cephalosporins
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Widely used drug derived from fungus
Used against gram–negative bacteria
Widely absorbed and distributed in most
bodily fluids – placenta and breast milk
Cephalosporin
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First generation Cephalosporin drugs do not
reach therapeutic levels in CSF (cerebral
spinal fluid) but 2nd, and 3rd generation drugs
do – especially important in treating
meningitis.
Meningitis
First Generation Cephalosporins
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Bactericidal action – binds to bacterial cell
wall, causing cell death
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Keflex (PO) still used extensively in treatment of
skin infections
Ancef – often ordered preoperatively
Impetigo
First Generation Cephalosporins
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Bactericidal action – binds to bacterial cell
wall, causing cell death
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Keflex (PO) still used extensively in treatment of
skin infections
Ancef – often ordered preoperatively in clients
undergoing orthopedic procedures
Keflex
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First generation cephalosporin
Action: binds to bacterial cell wall membrane,
causing cell death
Therapeutic effect: bactericidal action against
susceptible bacteria
Active against many gram-positive cocci –
step and staph
Client teaching
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May be taken with or without food but food
may minimize the GI irritation
Distribution: may cross placenta or enter
breast milk in low concentrations.
Excreted entirely by the kidneys.
Keflex Dosing
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Adults: 250 – 500 mg q 6 hours
Children: 25 – 50 mg / kg / day in divided
doses q 6 h
Cefazolin or Ancef
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Cefazolin – first generation cephalosporin
Well absorbed following IM or IV
administration
Crosses to placenta and breast milk in small
concentrations
Minimal CSF penetration
Excreted by kidneys
Knee or hip replacement
Ancef Dosing
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IV
Used for UTI, bone and skin infections,
endocarditis
Not suitable for treatment of meningitis
Perioperative prophylaxis
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1 gram within 60 minutes of incision
Post operatively every 8 hours for 24 hours (3 doses)
Second-Generation Cephalosporins
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More active against some gram-negative
organisms and anaerobic organisms than the
first generation drugs.
May be effective in infections resistant to
other antibiotics
Penetration into CSF is poor but adequate to
be used in meningitis
Action: bactericidal – binds to cell wall
Third Generation Cephalosporin Drugs
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Similar to the second generation but has
increased activity against gram-negative
pathogens even for drug resistant pathogens.
CSF penetration is better than the first two
generation cephalosporin drugs.
Drug / Drug Allergies
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If a client is allergic to penicillin there is a 1 to
18% chance they will be allergic to
cephalosporin drugs.
Carbapenems
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Has very broad antibacterial action
Are often used for complicated body cavity
and connective tissue infections in the
hospitalized patient.
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imipenem-cilastatin (Primaxin)
meropenen (Merrem): only drug in this class used
in the treatment of bacterial meningitis.
Macrolides
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Macrolides first developed in the 1950s with
the drug: erythromycin.
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Four main drugs
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azithromycin * Zithromax
Clarithromcin * Biaxin
dirithromycin
erythromycin
Macrolides
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Two of the new drugs in the macrolide
classification: azithromycin and clarithromycin
have longer duration and improved
resistance to acid degradation in the
stomach.
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Dosing is less frequent
GI effects decreased
Better absorption than erythromycin
Macrolides
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Action: work by inhibiting protein synthesis in
susceptible bacteria.
Contraindications: drug allergy
Adverse effect: new drugs have lower GI
effects and are used in patients allergic to
penicillin / cephalosporin drugs.
Ketaloids
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Only one drug in this drug classification
Generic: telithromycin
Trade: Ketek
Available for oral use only.
Better acid stability and antibacterial
coverage than macrolides.
Tetracyclines
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Action: binds to divalent (Ca2 + mg2) and Al3
mettalic ions to form insoluble complexes.
Why do you need to know this?
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When given with milk, antacids or iron there is a
reduction in oral absorption.
Contraindicated in children under 8 years of age
because it can result in tooth discoloration.
Tetracyclines
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When used? Syphilis and Lyme disease
Antibiotics Used to Treat Serious
Infections
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IM or IV administration
Have more toxic side effects
Blood levels may need to be monitored to
determine therapeutic versus toxic levels of
mediation in the blood.
Serious Adverse Effects
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Nephrotoxicity: Toxicity to kidneys, often drug
induced and manifesting in compromised
kidney function.
Ototoxicity: Toxicity to the ears, often druginduced and manifested by varying degrees
of hearing loss than is likely to be permanent.
Pseudomembranous colitis: a necrotizing,
inflammatory bowel condition associated with
antibiotic therapy.
Aminoglycosides
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Pharmacologic classification: Bactericidal
drugs
Therapeutic classification: anti-infective
Action: inhibits protein synthesis at the level
of the 30s ribosome
Work primarily on dosing due to
concentration dependent killing of bacteria
Concentration Dependent
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A property of some antibiotics, especially
aminoglycosides and vancomycin, of
achieving a relatively, high plasma drug
concentration, results in the most effective
bacterial kill.
Blood Plasma Levels
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Peak levels: refers to amount of drug present in
blood plasma within
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15 to 30 minutes of IV drug administration
30 to 90 minutes of IM drug administration
Trough levels: refers to lowest level of drug
present in the blood plasma.
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Since the drugs can cause severe adverse effects the
excretion of the drug needs to be monitored.
Blood drawn just before the next dose given.
Adverse Effects Aminoglycosides
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Nephrotoxicity occurs in 5 to 25% and
ototoxicity (damage to VIII cranial nerve)
occurs in 3 to 14%.
Aminoglycosides
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gentamicin (Garamycin)
tobramycin (Nobcin, TOBI)
neomycin (Neo-Fradin)
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used to irrigate bowel before major bowel surgery
Topical applied to eye and skin infections
Floroquinolones
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Action: destroys bacteria by altering their
DNA.
Two most common drugs:
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ciproflxcin (Cipro)
clindamycin (Cleocin)
Used in treatment of chronic infections or
deep (anaerobic) abdominal infections and
MRSA.
Major Adverse Side Effect
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Clindamycin or Cleocin can cause
pseudomembranous colitis
Signs and symptoms: abdominal pain and
diarrhea
MRSA Infections
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MRSA infection is caused by Staphylococcus
aureus bacteria — often called "staph."
MRSA stands for methicillin-resistant
Staphylococcus aureus. It's a strain of staph
that's resistant to the broad-spectrum
antibiotics commonly used to treat it. MRSA
can be fatal.
MRSA
Vancomycin
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Action: destroys bacteria by binding to the
bacterial cell wall, producing immediate
inhibition of cell wall synthesis and death.
One of the drugs used in MRSA infections
that are resistant to floroquinolones (cleocin).
Adverse Effect
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Red man syndrome has often been
associated with rapid infusion of the first dose
of the drug and was initially attributed to
impurities found in vancomycin preparations.
Even after improvement in vancomycin's
purity, however, reports of the syndrome
persist.
Flushing on upper chest, neck and face
Intervention: slow the IV infusion rate.
Drugs to help with the Flu
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Tamiflu and Relenza
Uses: active against influenza virus types A
and B.
Shown to reduce the duration of influenza
infection by a few days.
Anti-viral Drugs
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Kill or suppress viruses by either destroying
virons or inhibiting their ability to replicate.
Does not irradicate the virus but helps the
immune system to eliminate the virus.
Herpes Zoster
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Herpes simplex virus type 1: cold sore
Herpes simplex virus type 2: genital herpes
Human herpesvirus type 3: chicken pox or
shingles
Human herpesvirus type 4: Espstein Barr
Virus
Human herpesvirus type 5: CMV or
cytomegalovirus
Cold Sore
Herpes Zoster - Shingles
Herpes Drugs
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Generic: acyclovir
Trade: Zovirax
Action: interferes with DNA synthesis.
Therapeutic effects: Inhibition of viral
replication, decreased viral shedding and
reduced time for healing of lesions.
acyclovir
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Comes in topical, po and IV preparations
Should be started within 24 hours of
outbreak.