Chapter 22: Antiinfective Agents

Review for exam on antiinfective agents in dentistry.

What is considered one of the most important problems in the dental office?

The control of infection

According to the text, what can an oral infection rapidly do?

Spread and produce severe illness or become fatal

What two techniques are required for the prevention of postoperative dental infections?

Aseptic technique and sterilization techniques

What three things are required for the successful treatment of infection?

Knowledge of the patient's medical history, characteristics of infection, and pharmacology of antimicrobial agents

How is 'antiinfective agents' defined?

Substances that act against or tend to destroy infections

How is 'antimicrobial agents' defined?

Substances that kill or suppress the growth or multiplication or prevent the action of microorganisms

How is 'antibacterial agents' defined?

Substances that destroy or suppress the growth or multiplication of bacteria

How is 'antibiotic agents' defined?

Chemical substances produced by microorganisms that can destroy or suppress the growth or prevent the action of organisms in dilute solutions

What is the primary difference between the terms 'antibiotic' and 'synthetic antibacterial agents'?

Antibiotics are produced by microorganisms; antibacterial agents are made in a laboratory

How is 'antiviral agents' defined?

Substances that destroy or suppress the growth or multiplication of viruses

How is 'antifungal agents' defined?

Substances that destroy or suppress the growth or multiplication of fungi

How is 'spectrum' defined in the context of drugs?

The range of activity of a drug

Compare narrow-spectrum and broad-spectrum antibacterial agents.

Narrow-spectrum acts against primarily gram-positive or gram-negative; broad-spectrum acts against a wide variety, including both gram positive & gram negative and some viruses

How is 'resistance' defined regarding microorganisms?

Microorganisms that are unaffected by an antimicrobial agent

What is 'natural resistance'?

When an organism has always been resistant to an antimicrobial agent

What is 'acquired resistance'?

When an organism previously sensitive to an antimicrobial agent develops resistance

How can acquired resistance occur naturally?

By natural selection of a spontaneous mutation or they undergo genetic changes in order to survive against drugs or immune response

Identify three processes of genetic recombination that result in passing on resistance from one bacterial strain to another:

Conjugation, transformation, and transduction

How is 'bactericidal' defined?

The ability to kill bacteria

Is the effect of a bactericidal agent reversible or irreversible?

Irreversible, because when the drug or agent is removed from that particular bacteria is stop or dead

How is 'bacteriostatic' defined?

The ability to inhibit or retard the multiplication or growth of bacteria

Why is the bacteriostatic process considered reversible?

Because bacteria can grow and multiply once the agent is removed

On what variables does the label 'bactericidal' or 'bacteriostatic' depend?

Dose used, serum concentration attainable, and the organism being treated

With low concentrations a certain drug may be bacteriostatic; TRUE/FALSE

TRUE

With high concentrations, a certain drug may be ____________.

Bactericidal

Why is a bactericidal agent preferred in patients with severely impaired defense mechanisms?

Because the body’s ability to fight infection is compromised

Can the agent for a nonimmunocompromised patient be chosen without regard to bactericidal/bacteriostatic status?

Yes

Which antiinfective agents are listed only as bactericidal in Table 22-1?

Penicillins, Cephalosporins, Metronidazole, Aminoglycosides, Bacitracin, Vancomycin, Polymyxin

Which antiinfective agents are listed as bacteriostatic in Table 22-1?

Tetracyclines, Chloramphenicol, Spectinomycin, Sulfonamides

Which drug is noted as potentially bactericidal at higher blood levels against some organisms in Table 22-1?

Erythromycin and Clindamycin

How is 'blood level' defined?

Concentration of antiinfective agent present in the blood or serum

What is the 'minimum inhibitory concentration (MIC)'?

The lowest concentration needed to inhibit visible growth of an organism on media after $18$ to $24$ hours of incubation

Why is the MIC test preferred over disc tests?

It is more reliable and quantitative

How is 'synergism' defined in antibiotic therapy?

A combination of two antibiotics more rapidly bactericidal than either drug used alone

Give an example of a synergistic combination for treating Pseudomonas aeruginosa septicemia.

Carbenicillin-like penicillins and an aminoglycoside

How is 'antagonism' defined in drug combinations?

The bactericidal rate for the combination of two drugs is less than for either drug used alone

When is antagonism often exhibited?

When bacteriostatic and bactericidal agents are used in combination

How is 'superinfection' (or suprainfection) defined?

Infection caused by the proliferation of microorganisms different from those causing the original infection

What often causes superinfection?

Broad-spectrum antibiotics like tetracycline

Overgrowth of which fungus is common when gram-positive and gram-negative bacteria are reduced?

$$Candida\,albicans$$

How is 'infection' defined according to the text?

Invasion of the body by pathogenic microorganisms and the reaction of the tissues to their presence and toxins

What are the three principal factors determining the likelihood of a microorganism causing infection?

(1) Virulence, (2) Number of organisms, (3) Resistance of the host

What are local components of host resistance?

Tissue trauma, inadequate wound closure, and lack of blood clot retention

Which conditions decrease systemic resistance to infection according to Table 22-2?

Addison’s disease, ARC, AIDS, Alcoholism, Blood dyscrasias, Diabetes mellitus, Immunoglobulin deficiency, Leukemia, Malnutrition

Which drug types decrease systemic resistance to infection according to Table 22-2?

Immunosuppressive drugs, Cytotoxic drugs, Adrenal corticosteroids (Antineoplastic agents)

What did Gerhard Domagk observe in $1932$?

That the azo dye Prontosil protected mice against streptococci

Who observed that a mold produced a substance inhibiting bacteria in $1928$?

Fleming (England)

What was the naturally occurring substance named by Fleming in $1928$?

Penicillin

In which year did Chain and coworkers report the low toxicity and systemic antibacterial effectiveness of penicillin?

In $1940$

What is the only way to reasonably ensure an antibiotic will kill an infecting microorganism?

Culture and sensitivity tests

What is a limitation of in vitro culture and sensitivity tests?

They do not differentiate between bactericidal and bacteriostatic effects or show in vivo potency

In the case of an abscess, what is the preferred collection method for a culture?

Aspiration with a needle after mucosa is wiped with antiseptic

How can a sample be collected from a draining lesion for culture?

Using a swab from an anaerobic pack or prereduced tube

How long is required before antibiotic sensitivity test results are available?

$1$ to $2$ days

What are the two divisions for the use of antiinfective agents in dentistry?

Prophylactic and Therapeutic

What are the three therapeutic situations for oral cavity infections?

Caries, acute oral infections, and periodontal infections

What is the organism responsible for the most common dental infection, caries?

$$Streptococcus\,mutans$$

What is the treatment of choice for caries?

Local physical removal of microbial plaque (good oral hygiene)

How does fluoride act as an anticaries agent?

It acts on the tooth structure and probably affects surrounding microorganisms

Which topical antibiotics have been shown to control plaque?

Vancomycin and Kanamycin

Which antibiotic not approved in the U.S. has been used elsewhere for its antiplaque effect?

Spiramycin

What factors are needed in clinical trials to determine antibiotic contribution to periodontal outcomes?

Positive controls, double-blinding, sufficient patient numbers, long follow-up, and categorization of patients

What organisms are primarily found in the healthy gingival sulcus?

Gram-positive organisms such as Streptococcus and Actinomyces

Which gram-negative organisms increase in number during the development of gingivitis?

$Bacteriodes\,intermedius$, Haemophilus species, and $Fusobacterium\,nucleatum$

What is the percentage of gram-negative anaerobic rods in advanced adult periodontitis?

$75\%$ (three fourths)

Which organism is present in ANUG lesions and is sensitive to most antibiotics except erythromycin?

$$Bacteroides\,gingivalis$$

Veillonella parvula strains are sensitive to which three antibiotics?

Penicillin, clindamycin, and tetracycline

What percentage of organisms in LJP are gram-negative?

$$65\%$$

Which bacteria are prominent in LJP and insulin-dependent juvenile diabetics with periodontitis?

$Actinobacillus\,actinomycetem-comitans$ and Capnocytophaga species

What are the drugs of choice for LJP based on Table 22-3?

Tetracycline and minocycline

Is antibiotic treatment indicated for soft tissue infections and abscesses without systemic symptoms?

No

What is often sufficient treatment for abscesses if systemic symptoms are absent?

Incision and drainage

Which gram-positive cocci are often involved in osteomyelitis and abscesses?

Aerobic streptococci

What is the drug of choice for oral abscesses, osteomyelitis, and soft tissue infections?

Penicillin V

What basic question should a clinician ask before starting antimicrobial therapy?

Does this particular patient need the assistance of antimicrobial agents to resolve this particular infection?

Are local symptoms like pain, edema, and purulence indications for antibiotic treatment in a healthy patient?

No

Which systemic manifestations indicate the need for antimicrobial therapy?

Fever, malaise, and lymphadenopathy

When should an infection be aggressively treated with antimicrobial agents?

When it is acute, severe, and rapidly spreading

Identify three clear-cut indications for prophylactic antibiotic coverage.

History of rheumatic heart disease, congenital heart disease, or presence of a prosthetic heart valve

What is the drug of choice for oral prophylaxis in low-risk patients?

Oral penicillin

What antibiotic is recommended for endocarditis prophylaxis if the patient is allergic to penicillin?

Erythromycin

For high-risk patients with prosthetic valves, what parenteral combination is recommended for prophylaxis?

Ampicillin plus gentamicin

What intravenous antibiotic is recommended for high-risk patients with a penicillin allergy?

Vancomycin

What organism is most frequently isolated from infected hip prostheses?

$$Staphylococcus\,aureus$$

According to Jacobsen and Murray, what antibiotics should be used for hip prosthesis prophylaxis if bacteria are penicillin-resistant?

Penicillinase-resistant penicillins, erythromycin, or clindamycin

Which patients require antibiotic coverage before procedures that produce bacteremias, based on shunts?

Renal dialysis patients with arteriovenous shunts and patients with ventriculo-atrial shunts for hydrocephaly

Do patients with indwelling transvenous pacemakers require prophylactic antibiotics?

Yes

In which cardiac case is prophylaxis specifically not recommended after healing?

Coronary bypass surgery and surgically closed defects without Dacron patches

Does mitral valve prolapse without insufficiency require prophylaxis?

No

How much antiinfective agent should be given to a patient after symptom resolution?

Sufficient amount to last for $2$ days after resolution

What is the typical duration of treatment for dental infections without complications in a nonimmunocompromised host?

$5$ to $7$ days

How long should therapy continue if an infection is produced by beta-hemolytic streptococci?

At least $10\,days$

What is the typical treatment duration for an immunocompromised host's dental infection?

$$2\,weeks$$

How can the chance of superinfection be minimized?

Use the most specific agent, shortest effective course, and adequate doses

Which antibiotic group is noted as 'more allergenic' than others in the text?

Penicillins

Antiinfective agents interfere with which component of birth control pills?

The estrogenic component

Which antituberculosis agent has the most reported pregnancies associated with antibiotic-pill interaction?

Rifampin

What is the second most implicated drug group in oral contraceptive failure due to antibiotics?

Tetracyclines

What serious gastrointestinal complaint is historically associated with clindamycin?

Pseudomembranous colitis (PMC)

Which agent causing PMC is now known to occur with amoxicillin, cephalosporins, and erythromycin?

$$Clostridium\,difficile$$