Chapter 7 Study Guide

All of these antibiotics are typically administered topically except which of the following?

Clarithromycin Clarithromycin is a macrolide and is usually administered by mouth. Neomycin is combined with polymyxin and bacitracin in the topical ointment form Neosporin. Mupirocin (Bactroban) is a topical antibiotic that may be used to treat the streptococci or staphylococci that may be present with angular chilitis.

Which is the mechanism of action of the sulfonamide drug group?

Competitive inhibition of folic acid synthesis from paraaminobenzoic acid Sulfonamides, or "sulfa drugs," competitively inhibit the bacterial enzyme that converts paraaminobenzoic acid into folic acid. Bacteria are unable to synthesize folic acid for their growth; therefore, by inhibiting its synthesis, sulfonamides have a bacteriostatic action. Sulfonamides are used to treat otitis media, bronchitis, and urinary tract infections but are not commonly used to treat dental infections

Metronidazole is associated with this drug interaction and adverse drug effect with alcohol consumption.

Disulfiram-like reaction If alcohol is taken with metronidazole, a reaction such as that from disulfiram or Antabuse occurs. Disulfiram is a drug used to treat alcohol abuse and causes nausea, vomiting, abdominal cramps, and headache if alcohol is ingested. Because of this effect, alcohol and alcohol-containing mouth rinses should be avoided when the patient is taking metronidazole. Photosensitivity is an adverse drug effect associated with tetracycline. Clindamycin is associated with the serious adverse drug effect of pseudomembranous colitis (PMC), also known as antibiotic-associated colitis. Hepatoxicity is an adverse drug effect associated with the IV use of tetracyclines

Which group of antiinfectives is most likely to cause gastrointestinal upset?

Erythromycin Erythromycin has the highest incidence of gastrointestinal complaints of any of the antibiotics, although some degree of gastrointestinal upset is common with all of the antiinfectives

All statements are correct concerning antiinfective agents and localized dental infections except which of the following?

Even if adequate drainage can be obtained, antiinfective agents are indicated. If adequate drainage of a can be obtained, antiinfective agents are not indicated for most localized dental infections unless the patient is immunocompromised, because the body has been able to contain the infection to a small area, and drainage of the area will assist systemic defenses in overcoming the infection. If the patient is immunocompromised, antiinfective agents may be indicated for localized dental infection. Most localized dental infections arise from either periodontic- or endodontic-related sources, and the microorganisms present determine the antibiotic of choice.

All factors must be present for a microorganism to cause an infection except which of the following?

Exposure to cold and damp weather All of the factors except exposure to cold and damp can cause an infection, although these factors in an immunocompromised host could possibly increase the susceptibility to an infection. To cause an infection, the microorganism must have virulence or the ability to produce disease, be present in sufficient numbers, and meet with an insufficient immunologic response in the host.

What is the current American Heart Association prophylactic premedication dosage for the prevention of infective endocarditis in the patient who can take penicillin?

2 gram amoxicillin taken 30 to 60 minutes before treatment Two grams of amoxicillin, given 30 to 60 minutes before treatment, is the drug of choice for prophylaxis of infective endocarditis before a dental procedure in a patient who is not allergic to penicillin. Penicillin was formerly the drug of choice for prophylaxis of infective endocarditis before a dental procedure; however, amoxicillin's better absorption, higher plasma levels, and slightly broader spectrum of action have replaced penicillin in this role. Ampicillin, given parentally can be administered for the prevention of infective endocarditis in the patient who can take penicillin but is unable to take medication orally. Two grams cephalosporin may be taken 30 to 60 minutes before treatment in the patient who has a penicillin allergy, as long as the allergy did not produce severe adverse effects such as angioedema or anaphylaxis.

Please list the correct evolution of dental infections.(1) Gram-positive infection begins to include a variety of both gram-positive and gram-negative anaerobic microorganisms (mixed infection).(2) The infection consists of predominantly anaerobic microorganisms.(3) The anaerobic microorganisms coalesce into an abscess.(4) The organisms responsible for the dental infection are primarily gram-positive cocci.

4, 1, 2, 3 Dental infections start as primarily gram-positive cocci and rods and, if left undisturbed, grow in mass and complexity to include both gram-positive and gram-anaerobic microorganisms, becoming a mixed infection. The proportion of gram-anaerobic microorganisms increases as time passes, and they will eventually coalesce into an abscess

What is the primary advantage of penicillin V or penicillin VK over penicillin G?

Better oral absorption The potassium salt of penicillin V or penicillin VK is more soluble than the free acid and is better absorbed when taken orally. Penicillin G is usually given parentally. Both agents have low cost, a narrow spectrum, and many resistant microorganisms.

A culture is a test that involves determining if an organism will respond to a specific antiinfective agent. Sensitivity testing involves growing the bacteria from a sample of infective exudate.

Both statements are false. A culture is a test that involves growing the bacteria from a sample of infective exudate. Sensitivity testing involves exposing an organism to test antiinfective agents to determine if the organism is sensitive or resistant to a specific antiinfective agent

Ciprofloxacin is bacteriostatic against a wide range of gram-positive organisms. A synergistic action may occur if ciprofloxacin is given with other antimicrobial agents.

Both statements are false. Ciprofloxacin is bactericidal against a wide range of gram-negative organisms. An additive action may occur if ciprofloxacin is given with other antimicrobial agents. Ciprofloxacin is indicated for infections of the lower respiratory tract, skin, bone and joint, and urinary tract infections.

Topical administration of antibiotics is the preferred route of administration. Topical administration of an antibiotic is less likely to result in an allergic reaction.

Both statements are false. Systemic administration of antibiotics is superior to topical administration and is preferred. Topical administration of a drug increases the possibility of an allergic reaction

All are common adverse effects of antiinfectives except which of the following?

Central nervous system depression Central nervous system depression is not a common adverse effect of antiinfective agents. Gastrointestinal upset, a decrease in the effectiveness of oral contraceptives, superinfection with Candida albicans, potentiation of oral anticoagulants, and potential to produce allergic reactions are all adverse drug effects seen in some degree with antiinfective agents.

The penicillins can be divided into all except which of the following major groups?

Cephalosporin The cephalosporins are closely related to the penicillins but are not in the penicillin family. Penicillin G and V, the penicillinase-resistant penicillins, amoxicillin/ampicillin, and the extended-spectrum penicillins are major groups of the penicillin family.

Which class of antibiotics is structurally related to the penicillins and has similar mechanisms of actions and indications as the penicillins?

Cephalosporins The bactericidal cephalosporins are a group of antibiotics that are structurally related to the penicillins. Their mechanism of action is also inhibition of cell wall synthesis, and they have a similar spectrum of bacterial activity. They have a lower incidence of allergic reactions than the penicillins.

Which situations would be an indication for use of an antiinfective agent?

Lesions associated with systemic dental infections with symptoms such as fever, malaise, and tachycardia should be drained. However, if drainage is not possible, antibiotics should be given. If adequate drainage can be obtained, antiinfective agents are not indicated for most localized dental infections unless the patient is immunocompromised.

What is the primary advantage of amoxicillin over penicillin?

Less frequent dosing Amoxicillin is a close relative of penicillin but has a few advantages over its older cousin, primarily less frequent dosing. Amoxicillin is taken three times a day rather than the four times a day needed for penicillin; thus, patient compliance is better. It is also better absorbed, reaches higher blood levels, and its absorption is not impaired by stomach contents. Amoxicillin and penicillin both have low toxicity, with relatively few adverse effects. Amoxicillin has a similar potency to penicillin, and has a slightly broader spectrum.

With a primarily anaerobic gram-negative infection, which antibiotic would be most effective?

Metronidazole Metronidazole is effective for treating primarily anaerobic gram-negative infections, such as those found in periodontal disease or deep pulpal infections. Erythromycin, penicillin/amoxicillin, and azithromycin are useful in treating infections resulting from gram-positive cocci

All are classified macrolides drugs except which of the following?

Minocycline Minocycline is a member of the tetracycline family; erythromycin, clarithromycin, and azithromycin are macrolides antiinfective agents

What antiinfective agent is most likely to produce an allergic reaction?

Penicillin Penicillin is the most common cause of drug allergies. All antiinfective agents, like all medications, have the potential to produce a variety of allergic reactions, from mild to life threatening.

Which drug or drugs are used most often in dentistry for beginning infections of primarily gram-positive cocci in patients with no allergies?

Penicillin/amoxicillin In early infections consisting of gram-positive cocci, penicillin is the drug of choice, unless the patient has a penicillin allergy. Amoxicillin is most often used because it is less irritating to the stomach and can be taken with food or milk. Erythromycin or azithromycin would be indicated if the patient were allergic to penicillin. Metronidazole is used in combination with other medications for treatment of later infections with anaerobic microorganisms.

All are adverse effects that can occur with use of tetracycline except which of the following?

Permanent discoloration of teeth if taken after development No discoloration to teeth occurs if tetracycline is taken after tooth development is complete. Permanent discoloration of teeth and bones may occur if tetracycline is taken during odontogenesis. Minocycline can cause black pigmentation to the alveolar bones and the hard palate in all ages. Photosensitivity, gastrointestinal problems, including anorexia, nausea, vomiting, and diarrhea, and hepatotoxicity if given by intravenous administration, especially during pregnancy, are all adverse drug effects of tetracycline

Clindamycin is associated with the serious adverse drug effect of

Pseudomembranous colitis Clindamycin is associated with the serious adverse drug effect of pseudomembranous colitis (PMC), also known as antibiotic-associated colitis. PMC is characterized by severe, persistent, bloody diarrhea, and it can be fatal. Its etiology is the toxin produced by the bacterium Clostridium difficile and is associated with all antibiotics, not only clindamycin. Photosensitivity is an adverse drug effect associated with tetracycline. A disulfiram-like reaction is an adverse drug effect associated with the drug interaction between metronidazole and alcohol, which can produce nausea, vomiting, abdominal cramps, and headache. Hepatoxicity is an adverse drug effect associated with the intravenous (IV) use of tetracyclines.

Which adverse drug interactions could occur with antiinfectives?

Some antibiotics may decrease oral contraceptive efficacy by increasing their clearance from the body. Antiinfective agents may reduce the bacterial flora that produce vitamin K. Vitamin K is needed to for adequate blood clotting, so reduction may result in an increased effect of oral anticoagulant. Bacteriostatic agents may interfere with bactericidal agents

Broad-spectrum antiinfective agents taken over a long time period can lead to which adverse reactions?

Superinfection/suprainfection Broad-spectrum antibiotics taken for a long period can disturb the normal microflora of the body, allowing the emergence of organisms different from the original infecting organism and that are unaffected by or resistant to the antibiotic being used. This situation is termed a superinfection or suprainfection. Tolerance is a condition in which the patient no longer responds to the drug, and larger amounts of the drug are needed to produce the desired effect. Tolerance does not occur with antibiotics. Allergic reactions are not related to length of time a drug is taken; they can occur within minutes of the drug administration. Antibiotics do not produce dependence, or the physiologic or psychological need for a drug

Which antiinfective agent has reduced effectiveness if taken with dairy products, antacids, or calcium supplements?

Tetracycline Calcium divalent and trivalent cations reduce the absorption of tetracyclines in the intestine. Dairy products containing calcium, as well as antacids and mineral supplements containing these cations, should not be taken within 2 hours of ingesting tetracycline. The effectiveness of amoxicillin, clindamycin, and erythromycin are not affected by the intake of dairy products, antacids, or calcium supplements

Which antiinfective drug is contraindicated in a pregnant patient?

Tetracycline Tetracycline is contraindicated in pregnancy because of its staining effect on developing teeth. Tetracycline is rated as a Food and Drug Administration category D pregnancy drug. Amoxicillin, erythromycin, and penicillin VK are classified by the Food and Drug Administration as category B drugs, which are considered safe, due to lack of evidence of teratogenicity, although there are no controlled data on human pregnancy. Use of any medication should always weigh benefits against risks.

Which group of antiinfectives is commonly used to treat oral infections of periodontal origin?

Tetracyclines Tetracyclines are often used to treat certain periodontal conditions if conventional treatment with local measures has failed. Tetracyclines have the advantage in treatment of periodontal conditions of concentrating in the gingival crevicular fluid, and their broad spectrum of action is helpful in the primarily gram-negative environment of periodontal disease. Tetracyclines are usually not indicated for use of dental infections other than periodontal disease. The erythromycins, penicillins, and cephalosporins are not particularly useful in treatment of periodontal disease due to their action against the gram-positive spectrum of action, but they are very useful in treatment of oral infections caused by gram positive organisms

Antibiotic resistance is the natural or acquired ability of an organism to be immune to or to resist the effects of an antiinfective agent. An increase in the use of an antibiotic in a given population decreases the proportion of resistant organisms in that population.

The first statement is true; the second statement is false. An increase in the use of an antibiotic in a given population increases the proportion of resistant organisms in that population

Caries is an important dental infection produced by Streptococcus mutans. Traditional antiinfective agents have been useful for this problem in the general population.

The first statement is true; the second statement is false. Caries is an important communicable dental infection, but traditional antiinfective agents have not been effective in treating caries. This is largely due to the constant presence of bacterial biofilm that is the etiologic agent of caries, and the location of caries, which is in a nonvascular structure, the enamel. The treatment of choice is ingestion of appropriately fluoridated water, regular physical disruption of bacterial biofilm, a diet low in refined carbohydrates, regular preventive dental visits, and appropriately placed sealants

Mr. Garza indicates on his medical history that he is taking isoniazid, pyrazinamide, and rifampin. What is the most likely reason he is taking these medicines?

Tuberculosis Tuberculosis (TB) is difficult to treat due to the ability of the tubercle bacilli to develop resistant strains easily, the bacteriostatic nature of the medications, and lack of appropriate medication compliance. Because of the danger of resistance, at least three drugs are used in combination concurrently in treatment of active tuberculosis. Isoniazid (INH), rifampin, ethambutol, and pyrazinamide are combined for treatment of pulmonary TB. INH and rifampin are given every day for 9 to 12 months. Pyrazinamide and ethambutol are used only in the first two months of treatment

The terms antibiotic, antiinfective, antimicrobial, and antibacterial are often used interchangeably. However, only an __ is exclusively produced by microorganisms.

Antibiotic By definition, only antibiotics are produced exclusively by microorganisms, whereas the other agents may be produced in a laboratory from nonliving sources. Penicillin, cephalosporin, and tetracyclines are true antibiotic agents. Antiinfective agents are substances that act against or destroy infections. An antibacterial substance destroys or suppresses the growth or multiplication of bacteria, and an antimicrobial agent is a substance that destroys or suppresses the growth of microorganisms

Antibiotic resistance can occur in all except which of the following ways?

Transfer of DNA genetic material from one nonresistant organism to another very different resistant organism via transduction, transformation, or bacterial conjugation Natural selection of spontaneous mutation and sharing of genetic material confers resistance from one resistant microorganism to another nonresistant microorganism via transduction, transformation, or bacterial conjugation.

__ is the antiinfective drug of choice for prophylactic premedication for a patient with artificial heart valves if the patient is not allergic to penicillin.

Amoxicillin Amoxicillin is the drug of choice for prophylaxis of bacterial endocarditis before a dental procedure in the patient who is not allergic to penicillin. Penicillin VK was originally the drug of choice for this indication, but the slightly broader antimicrobial spectrum and fewer gastrointestinal adverse effects of amoxicillin have resulted in its substitution for penicillin VK. Erythromycin was formerly the drug of choice prophylaxis of bacterial endocarditis before a dental procedure in the patient who is not allergic to penicillin; however, it has been replaced by clindamycin due to the severe gastrointestinal adverse effects of erythromycin. Clindamycin is the drug of choice for prophylaxis of bacterial endocarditis before a dental procedure in the patient who is allergic to penicillin.

Which statement about erythromycin is incorrect?

Allergic reactions are common with erythromycin. Allergic reactions to erythromycin are uncommon, making erythromycin the drug of choice against aerobic microorganisms in penicillin-allergic patients. Erythromycin is bacteriostatic and interferes with protein synthesis, and the spectrum of action closely resembles that of penicillin against gram-positive bacteria. Adverse effects include severe gastrointestinal distress. Erythromycin can increase the serum concentrations of many drugs through inhibition of the hepatic metabolism of these drugs.

The ability of an antiinfective agent to slow or stop the growth of an organism is tested by use of a(n)

The most effective treatment of infections would require that the organism be cultured and sensitivity tests would be performed. Culturing involves growing the bacteria from a sample of infective exudate, and sensitivity testing involves exposing the organism to certain test antibiotics and determining whether the organism is sensitive or resistant. An antibody assay is a test to determine if the body has produced antibodies in response to exposure to a specific antigen. Minimum inhibitory concentration (MIC) is the lowest concentration of an antimicrobial agent that inhibits the visible growth of a microorganism after overnight incubation.