CHAPTER 34
DRUGS FOR BACTERIAL INFECTIONS
LEARNING OUTCOME 1
Distinguish between the terms pathogenicity and virulence.
Concepts
1. Pathogens are organisms that can cause disease by bypassing the body’s defenses. Examples of some
pathogens are bacteria, viruses, fungi, intracellular organisms, and multicellular animals. Pathogens
generally cause disease by one of two basic mechanisms: invasiveness or toxin production.
Invasiveness is the ability of a pathogen to grow extremely rapidly and cause direct damage t o
surrounding tissues by their sheer numbers. The second mechanism is the production of toxins. Even
very small amounts of some bacterial toxins may disrupt normal cellular activity and, in extreme
cases, result in death.
2. Pathogenicity is the ability of an organism to cause infection. Virulence is the ability of a microbe to
produce disease when present in minute numbers.
LEARNING OUTCOME 2
Explain how bacteria are described and classified.
Concepts
Bacteria are described by their shape—bacilli (rod shape), cocci (spherical), or spirilla (spiral); their ability to
utilize oxygen—aerobic (with oxygen) or anaerobic (without), and by their staining characteristics—
LEARNING OUTCOME 3
Compare and contrast the terms bacteriostatic and bacteriocidal.
Concepts
1. Anti-infective drugs are known as antibacterial, antimicrobial, or antibiotic. They are classified by their
chemical structures (e.g., aminoglycoside, fluoroquinolone) or by their mechanism of action (e.g., cell-wall
inhibitor, folic-acid inhibitor). (See Table 34.1 for a look at bacterial pathogens and disorders.)
2. Anti-infective drugs act by affecting the target organism’s unique structure, metabolism, or life cycle.
The goal is to eliminate the pathogen by bactericidal properties (to kill bacteria) or bacter iostatic
properties (to slow the growth of bacteria). (See Figure 34.1 for Mechanisms of action of antimicrobial
drugs.)
LEARNING OUTCOME 4
Using a specific example, explain how resistance can develop to an anti-infective drug.
Concepts
1. Acquired resistance occurs when a pathogen acquires a gene for bacterial resistance, either through
mutation or from another microbe. Through mutation, the antibiotics destroy sensitive bacteria, and
insensitive (mutated) bacteria remain. Mutations are random and occur during cell division; mutated
bacteria multiply. It is important to remember that antibiotics do not create mutations. Acquired resistance
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can also be caused by another microbe when resistant bacteria are passed to others.
2. The widespread use of antibiotics has not caused resistance, but overprescribing of antibiotics has
worsened the problem because it results in loss of antibiotic effectiveness. Practitioners should only
prescribe when necessary. Long-time use increases resistant strains. Nosocomial infections are often
resistant. Prophylactic use is sometimes appropriate. The nurse should instruct the patient to take the full
dose. (See Figure 34.2 for an illustration of acquired resistance.)
LEARNING OUTCOME 5
Describe the nurse’s role in the pharmacologic management of bacterial infections.
Concepts
1. The role of the nurse in the pharmacologic management of bacterial infections involves careful
monitoring of a patient’s condition and providing education as it relates to the prescribed drug
treatment. Obtain baseline medical, surgical, and drug history; lifestyle and dietary habits, including
use of herbal or alternative therapies; and a detailed description of symptomology and current
therapies. Obtain specimens for culture and sensitivity prior to the start of antibiotic therapy. Monitor
for indications of response to therapy, including reduced fever, normal WBC count, improved
appetite, and absence of symptoms such as cough. After parenteral administration, observe the patient
for possible allergic reactions for 30 minutes, especially with the first dose. Monitor for
superinfections. Replacement of natural colon flora with probiotic supplements or cultured dairy
products such as yogurt or buttermilk may help to alleviate symptoms. Teach patients to wear medic
alert bracelets if allergic to antibiotics, to report any symptoms of an allergic reaction, and to not stop
taking the drug until the complete prescription has been taken.
2. Drug therapy with penicillins: Assess previous drug reactions to penicillin. If the patient has a history of
a severe penicillin allergic reaction, also avoid cephalosporins. Monitor for hyperkalemia and
hypernatremia. Monitor cardiac status, including ECG changes.
3. Cephalosporin therapy: Assess for the presence or history of bleeding disorders because cephalosporins
may reduce prothrombin levels through interference with vitamin K metabolism. Assess renal and hepatic
function. Avoid alcohol; some cephalosporins cause a disulfiram (Antabuse)–like reaction when alcoholic
beverages are consumed.
4. Tetracycline therapy: This is contraindicated for use with patients who are pregnant and lactating
because of the drug’s effect on linear skeletal growth of the fetus and child. Tetracycline therapy is
also contraindicated in children less than 8 years of age because of the drug’s ability to cause
permanent mottling and discoloration of the teeth. Tetracyclines decrease the effectiveness of oral
contraceptives, so advise female patients to use an alternate method of birth control while taking the
medication. Use with caution in patients with impaired kidney or liver function. Tetracyclines cause
photosensitivity. Do not take these medications with milk products, iron supplements, magnesium containing laxatives, or antacids.
5. Macrolide therapy: Assess for the presence of respiratory infection. Examine the patient for history of
cardiac disorders, because macrolides may exacerbate existing heart disease. Monitor hepatic enzymes
with certain macrolides, such as erythromycin estolate. Multiple drug–drug interactions occur with
macrolides.
6. Aminoglycoside therapy: Monitor for ototoxicity and nephrotoxicity during the course of therapy.
Hearing loss may occur after therapy has been completed. Neuromuscular function may also be impaired.
Increase fluid intake, unless otherwise contraindicated, to promote excretion.
7. Fluoroquinolone therapy: Because these agents may decrease leukocytes, monitor the WBC count.
Carefully monitor patients with liver and renal dysfunction, because the drug is metabolized by the liver
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and excreted by the kidneys. Inform the patient that these drugs may cause dizziness and lightheadedness
and advise against driving or performing hazardous tasks during drug therapy. Inform patients receiving
norfloxacin (Noroxin) that photophobia is possible. Some fluoroquinolones, such as ciprofloxacin (Cipro),
may affect tendons, especially in children.
8. Sulfonamide therapy: Assess for anemia or other hematological disorders, because sulfonamides may
cause hemolytic anemia and blood dyscrasias. Assess renal function, because sulfonamides may increase
the risk for crystalluria. Avoid administering these agents in patients with a history of hypersensitivity to
sulfonamides, because this can induce a skin abnormality called Stevens–Johnson syndrome. Avoid
exposure to direct sunlight; use sunscreen and protective clothing to decrease the effects of
photosensitivity.
9. Antituberculosis therapy: Assess the patient for a history of alcohol abuse, AIDS, liver disease, or kidney
disease, because many antituberculosis drugs are contraindicated in those conditions. Use caution in
patients with renal dysfunction, those who are pregnant or lactating, or those with a history of convulsive
disorders. Assess for gouty arthritis. Because some antituberculosis drugs interact with oral contraceptives
and decrease their effectiveness, female patients with childbearing potential should use an alternate form of
birth control while using these medications. If taking isoniazid, avoid foods containing tyramine, such as
aged cheese, smoked and pickled fish, beer and red wine, bananas, and chocolate.
LEARNING OUTCOME 6
Explain the importance of culture and sensitivity testing to anti-infective chemotherapy.
Concepts
1. Careful selection of the correct antibiotic, through the use of culture and sensitivity testing, is essential for
effective pharmacotherapy and to limit adverse effects. Broad-spectrum antibiotics are effective for a wide
variety of bacteria. Narrow-spectrum antibiotics are effective for a narrow group of bacteria.
2. Culture and sensitivity testing is examination of a specimen for microorganisms. The specimen is grown in
the lab and identified. It is tested for sensitivity to different antibiotics. Bacteria may take several days to
identify. Viruses may take several weeks to identify. Broad-spectrum antibiotics may be started before the
lab culture is completed.
LEARNING OUTCOME 7
Identify the mechanism of development and symptoms of superinfections caused by anti-infective
therapy.
Concepts
1. Multidrug therapy may be affected by antagonism, which occurs when combining two drugs decreases
the efficacy of each of the drugs. Use of multiple antibiotics increases the risk of resistance. Multidrug
therapy can be used when multiorganisms cause the infection, for the treatment of tuberculosis, for the
treatment of HIV.
2. Superinfections are secondary infections that may occur during antibiotic therapy if too many host flora
are killed by an antibiotic. Host flora prevent the growth of pathogenic organisms. Pathogenic
microorganisms have a chance to multiply when they can opportunistically take advantage of a suppressed
immune system. Signs and symptoms include diarrhea, bladder pain, painful urination, or abnormal vaginal
discharge.
3. Host factors such as immune-system status, local conditions at the infection site, allergic reactions, age,
pregnancy status, and genetics influence the choice of antibiotic.
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LEARNING OUTCOME 8
For each of the drug classes listed in Drugs at a Glance, know representative drug examples, and explain
their mechanism of action, primary actions, and important adverse effects.
Concepts
1. Penicillin. Prototype drug: penicillin G (Pentids).
Mechanism of action: to kill bacteria by disrupting their cell walls. Primary use: as the drug of choice
against streptococci, pneumococci, and staphylococci organisms that do not produce penicillinase; also a
medication of choice for gonorrhea and syphilis. Adverse effects: diarrhea, nausea, and vomiting;
superinfections; and anaphylaxis. (See Table 34.2.)
2. Cephalosporin. Prototype drug: cefotaxime (Claforan).
Mechanism of action: to act as a third-generation cephalosporin with a broad spectrum of activity against
gram-negative organisms. Primary use: to be effective against many bacterial species that have developed
resistance to earlier-generation cephalosporins—serious infections of the lower respiratory tract, central
nervous system, genitourinary system, bones, blood, and joints. Adverse effects: hypersensitivity,
anaphylaxis, diarrhea, vomiting, nausea, and pain at the injection site. (See Table 34.3.)
3. Tetracycline. Prototype drug: tetracycline HCL (Achromycin, others).
Mechanism of action: to be effective against a broad range of gram- positive and gram-negative organisms.
Primary use: for chlamydiae, rickettsiae, and mycoplasma. Adverse effects: superinfections. Tetracycline
irritates the GI mucosa and may cause nausea, vomiting, epigastric burning, diarrhea, discoloration of the
teeth, and photosensitivity. (See Table 34.4.)
4. Macrolide. Prototype drug: erythromycin (E-Mycin, Erythrocin).
Mechanism of action: to act as a spectrum similar to that of the penicillins and to be effective against most
gram-positive bacteria. Primary use: as the preferred drug for infections of Bordetella pertussis (whooping
cough), Corynebacterium diphtheriae, and most gram-positive bacteria. Adverse effects: nausea,
abdominal cramping, and vomiting. The most severe adverse effect is hepatotoxicity. (See Table 34.5.)
5. Aminoglycoside. Prototype drug: gentamicin (Garamycin).
Mechanism of action: to act as a broad-spectrum, bacteriocidal antibiotic. Primary use: for serious urinary,
respiratory, nervous, or GI infections when less-toxic antibiotics are contraindicated. It is often used in
combination with other antibiotics or when drugs from other classes have proven ineffective. It is used
parenterally, or as drops (Genoptic), for eye infections. Adverse effects: ototoxicity and nephrotoxicity.
(See Table 34.6.)
6. Fluoroquinolone. Prototype drug: ciprofloxacin (Cipro).
Mechanism of action: to inhibit bacterial DNA gyrase, thus affecting bacterial replication and DNA repair.
Primary use: to be more effective against gram-negative than gram-positive organisms. It is prescribed for
respiratory infections, bone and joint infections, GI infections, ophthalmic infections, sinusitis, and
prostatitis. Adverse effects: nausea, vomiting, diarrhea, phototoxicity, headache, and dizziness. (See Table
34.7.)
7. Sulfonamide. Prototype drug: trimethoprim-sulfamethoxazole (Bactrim, Septra).
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Mechanism of action: to kill bacteria by inhibiting bacterial metabolism of folic acid, or folate. Primary
use: for urinary tract infections. It is also approved for the treatment of Pneumocystis carinii pneumonia,
for shigella infections of the small bowel, and for acute episodes of chronic bronchitis. Adverse effects:
skin rashes, nausea, vomiting, agranulocytosis, or thrombocytopenia. (See Table 34.8.).
8. Miscellaneous. Examples of miscellaneous antibiotics are clindamycin (Cleocin)—used for oral
infections caused by bacteriocides. An adverse effect associated with clindamycin is
pseudomembranous colitis.
Metronidazole (Flagyl) is used to treat H. pylori infections of the stomach;
vancomycin (Vancocin)—effective for MRSA infections; adverse effects include ototoxicity,
nephrotoxicity, and red man syndrome.
Some of the new miscellaneous antibiotics are: Oxazolidinones— linezolid (Zyvox) is as effective as
vancomycin against MRSA; Cyclic lipopeptides—daptomycin (Cubicin) is used to treat serious skin
infections; Carbapenems—imipenem (Primaxin) has some of the broadest spectrums; Ketolides—
telithromycin (Ketek) is used for respiratory infections; Glycylcyclines—tigecycline (Tygacil) is used
for drug-resistant abdominal infections and complicated skin infections. (See Table 34.9.)
ANIMATIONS AND VIDEOS
 Mechanism in Action: Penicillin (Pentids)
 Mechanism in Action: Ciprofloxacin (Cipro)
LEARNING OUTCOME 9
Explain how the pharmacotherapy of tuberculosis differs from that of other infections.
Concepts
1. Tuberculosis is caused by Mycobacterium tuberculosis. Its cell wall is resistant to anti-infectives, so the
body’s immune response attempts to isolate the pathogen by walling it off. Tuberculosis may remain
dormant in walled-off areas called tubercles, but a decreased immune system can give tuberculosis the
opportunity to become active.
2. Therapy is long term. Six to twelve months of drug therapy is needed to reach isolated pathogens in the
tubercles, and the therapy must be continued for the full course even if there are no symptoms. Patients
with multidrug-resistant infections require therapy for 24 months. Multidrug therapy consists of two to
four antibiotics that are administered concurrently. Multiple-drug therapies are needed in the treatment
of tuberculosis because the complex microbes are slow growing and commonly develop drug
resistance. Therapy is initiated with first-choice drugs, and then when resistance develops, secondchoice drugs are used. The second-choice drugs are more toxic and less effective than first-choice
drugs.
3. Chemoprophylaxis means that antituberculosis drugs are used prophylactically in high-risk populations.
Close contacts and family members of recently infected tuberculosis patients begin therapy immediately
after a patient has a positive tuberculin test. Patients with AIDS, those who are HIV-positive, or those who
are receiving immunosuppressant drugs also receive therapy.
LEARNING OUTCOME 10
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Use the nursing process to care for patients who are receiving drug therapy for bacterial infections.
Concepts
1. Patients Receiving Antibacterial Therapy—Assessment: Obtain a complete health history
including allergies, drug history, and possible drug interactions. Assess signs and symptoms of
current infection noting location, characteristics, presence or absence of drainage and character of
drainage, duration, presence or absence of fever or pain. Evaluate appropriate laboratory findings
(e.g., CBC, culture and sensitivity, hepatic and renal function studies). Report immediately severe
diarrhea, especially containing mucus, blood, or pus, yellowing of sclera or skin decreased urine
output or darkened urine. Assess for possibility of pregnancy or breast -feeding in patients prescribed
tetracycline antibiotics.
2. Patients Receiving Antibacterial Therapy—Nursing diagnoses: Infection; Pain, related to infection;
Hyperthermia; Deficient Knowledge (drug therapy); Risk for Injury, related to adverse drug effects; Risk for
Deficient Fluid Volume, related to fever, diarrhea caused by adverse drug effects; Risk for Noncompliance,
related to adverse drug effects, deficient knowledge, or cost of medication.
3. Patients Receiving Antibacterial Therapy—Planning: The patient will report diminished signs and
symptoms of infection, decreased fever; be free from or experience minimal adverse effects. Verbalize an
understanding of the drug’s use, adverse effects, and required precautions. Demonstrate proper selfadministration of the medication (e.g., dose, timing, when to notify provider).
4. Patients Receiving Antibacterial Therapy—Implementation: Monitor vital signs and symptoms of
infection to determine antibacterial effectiveness. Monitor for hypersensitivity and allergic reaction.
Monitor for severe diarrhea. Monitor periodic lab work: hepatic and renal function tests, CBC, urinalysis,
culture and sensitivity, peak and trough drug levels. Administer drug around the clock. Monitor for
superinfection. Monitor intake of OTC products such as antacids, calcium supplements, iron products, and
laxatives containing magnesium. Monitor for photosensitivity. Monitor for hepatic, renal, and/or ototoxicity
(e.g., jaundice, RUQ pain, darkened urine, diminished urine output, tinnitus, vertigo). Determine the
interactions of the prescribed antibiotics with various foods and beverages. Monitor IV site for signs and
symptoms of tissue irritation, severe pain, and extravasation. Monitor for side effects, renal function,
symptoms of ototoxicity, and compliance with antibiotic therapy. Monitor for development of “Red Man”
syndrome in patients receiving vancomycin.
5. Patients Receiving Antibacterial Therapy—Evaluation: Planning: The patient will report diminished
signs and symptoms of infection, decreased fever; be free from or experience minimal adverse effects.
Verbalize an understanding of the drug’s use, adverse effects, and required precautions. Demonstrate proper
self-administration of the medication (e.g., dose, timing, when to notify provider).
6. Patients Receiving Antituberculosis Agents—Assessment: Obtain a complete health history including
allergies, drug history, and possible drug interactions. Assess signs and symptoms of current infection
noting symptoms, duration, or any recent changes. Assess for concurrent infections, particularly HIV.
Assess for presence or history of tuberculosis, immunosuppressant status, and kidney or liver disease.
Assess cognitive ability to comply with long-term therapy. Evaluate appropriate laboratory findings (e.g.,
CBC, AFB culture and sensitivity, hepatic and renal function studies).
7. Patients Receiving Antituberculosis Agents—Nursing diagnoses: Infection; Fatigue; Imbalanced
Nutrition, Less than Body Requirements, related to fatigue, adverse drug effects; Deficient Knowledge (drug
therapy, infection control measures); Risk for Noncompliance, related to adverse drug effects, deficient
knowledge, length of treatment required, or cost of medication; Risk for Social Isolation, related to disease,
length of treatment.
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8. Patients Receiving Antituberculosis Agents—Planning: The patient will report diminished signs and
symptoms of infection, decreased fever and fatigue, increased appetite). Be free from or experience minimal
adverse effects. Verbalize an understanding of the drug’s use, adverse effects and required precautions.
Demonstrate proper self-administration of the medication (e.g., dose, timing, when to notify provider).
9. Patients Receiving Antituberculosis Agents—Implementation: Monitor for hepatic side effects. Monitor
for neurologic side effects. Collect sputum specimens. Monitor for dietary compliance when patient is
taking isoniazid. Monitor for side effects specific to various antituberculosis drugs. Monitor for hepatic,
renal, and/or ototoxicity (e.g., jaundice, RUQ pain, darkened urine, diminished urine output, tinnitus,
vertigo). Establish infection-control measures. Establish therapeutic environment to ensure adequate rest,
nutrition, hydration, and relaxation. Monitor patient’s ability and motivation to comply with therapeutic
regimen.
10. Patients Receiving Antituberculosis Agents—Evaluation: The patient reports diminished signs and
symptoms of infection, decreased fever and fatigue, increased appetite). Is free from or experiences minimal
adverse effects. Verbalizes an understanding of the drug’s use, adverse effects, and required precautions.
Demonstrates proper self-administration of the medication (e.g., dose, timing, when to notify provider).
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