Antibiotics

1.) Use of broad-spectrum antibiotics may cause an overgrowth of

a) viruses

b) parasites

c) hair

d) fungi

a) viruses

b) parasites

c) hair

d) fungi

2.) Your patient Mr. Grace, reports taking isoniazid, rifampin, and pyrazinamide. Your patient is MOST likely being treated for which of the following conditions?

a) Endocarditis

b) Tuberculosis

c) HIV

d) Tonsillitis

a) Endocarditis

b) Tuberculosis

c) HIV

d) Tonsillitis

3.) An overgrowth of which of the following organisms is responsible for an antibiotic-associated diarrhea?

a) Clostridium difficile

b) Porphyromonas gingivalis

c) Staphylococcus aureus

d) Mucobacterium tuberculosis

a) Clostridium difficile

b) Porphyromonas gingivalis

c) Staphylococcus aureus

d) Mucobacterium tuberculosis

4.) A patient being treated for periodontal disease complains of a metallic taste. The drug that is causing the condition is:

a) Clindamycin

b) Metronidazole

c) Tetracycline

d) Augmentin

a) Clindamycin

b) Metronidazole

c) Tetracycline

d) Augmentin

5.) A two year old boy has an abscess related to tooth K and requires antibiotic therapy. With this information alone, which drug would be contraindicated?

a) Zithromycin

b) Penicillin

c) Tetracycline

d) Clindamycin

a) Zithromycin

b) Penicillin

c) Tetracycline

d) Clindamycin

6.) Patients may require antibiotic prophylaxis if they have which of the following conditions? CHOOSE 4

a) Prosthetic hip replacement

b) Congenital heart disease

c) Hypercholesterol

d) HBA1C below 8

e) Previous infective endocarditis

f) HBA1C above 8

g) Congestive heart failure

h) Cardiac arrhythmia

a) Prosthetic hip replacement

b) Congenital heart disease

c) Hypercholesterol

d) HBA1C below 8

e) Previous infective endocarditis

f) HBA1C above 8

g) Congestive heart failure

h) Cardiac arrhythmia

7.) Which of the following antiinfective agents is bacteriostatic, but may be bactericidal at higher dose levels?

a) Clindamycin

b) Metronidazole

c) Penicillin

d) Rifampin

a) Clindamycin

b) Metronidazole

c) Penicillin

d) Rifampin

8.) Which of the following medications can reduce the effectiveness of oral contraceptives?

a) Amoxicillin

b) Azithromycin

c) Erythromycin

d) Penicillin

e) All of the above

a) Amoxicillin

b) Azithromycin

c) Erythromycin

d) Penicillin

e) All of the above

9.) Mrs. Slocum presents with swelling and pain associated with an abscessed #6. She is being treated for rheumatoid arthritis with methotrexate. Which antibiotic would NOT be contraindicated?

a) Clindamycin

b) Amoxicillin

c) Penicillin

d) Augmentin

a) Clindamycin

b) Amoxicillin

c) Penicillin

d) Augmentin

10.) Which of the following antibiotics produces an exaggerated sunburn in a patient who has a brief exposure to sunlight while taking? CHOOSE 3

a) Tetracycline

b) Doxycycline

c) Levaquin

d) Vancomycin

e) Azithromycin

f) Metronidazole

a) Tetracycline

b) Doxycycline

c) Levaquin

d) Vancomycin

e) Azithromycin

f) Metronidazole

11.) When there are multiple species of bacteria causing an infection which type of antibiotic would be used?

a) Narrow spectrum

b) Broad spectrum

c) Narrow and broad spectrums together

d) Any antibiotic would do

a) Narrow spectrum

b) Broad spectrum

c) Narrow and broad spectrums together

d) Any antibiotic would do

12.) A bacteriostatic antibiotic and a bacteriocidal antibiotic can be taken together

a) True

b) False

a) True

b) False

13.) Mrs. Fleming has been taking penicillin for a large endodontic abscess on #5. After a few days she notices that she has developed a vaginal yeast infection. This is an example of:

a) An unrelated infection

b) A different infection due to the endodontic abscess

c) A secondary infection

d) A superinfection

a) An unrelated infection

b) A different infection due to the endodontic abscess

c) A secondary infection

d) A superinfection

14.) A patient is allergic to penicillin and requires antibiotic premedication to prevent infective endocarditis. Which one of the following antibiotics would be the drug of choice?

a) Amoxicillin

b) Erythromycin

c) Clindamycin

d) Tetracycline

a) Amoxicillin

b) Erythromycin

c) Clindamycin

d) Tetracycline

15.) Arestin belongs to which class of antibiotics?

a) Tetracyclines

b) Penicillins

c) Quinolones

d) Macrolides

a) Tetracyclines

b) Penicillins

c) Quinolones

d) Macrolides

16.) Which of the following antibiotics are not recommended for use in dentistry? (CHOOSE 3)

a) Vancomycin

b) Tetracyclines

c) Macrolides

d) Aminoglycosides

e) Penicillins

f) Sulfonamides

a) Vancomycin

b) Tetracyclines

c) Macrolides

d) Aminoglycosides

e) Penicillins

f) Sulfonamides

17.) An antibiotic-associated severe gastrointestinal problem is referred to as:

a) gastritis

b) fungal infection

c) antibiotic resistance

d) pseudomembranous colitis

a) gastritis

b) fungal infection

c) antibiotic resistance

d) pseudomembranous colitis

18.) From the following list, select the drugs associated with intrinsic tooth staining in children younger than 8 years of age

a) erythromycin

b) minocycline

c) metronidazole

d) doxycycline

e) clindamycin

f) tetracycline

a) erythromycin

b) minocycline

c) metronidazole

d) doxycycline

e) clindamycin

f) tetracycline

Name five potential adverse effects that may result from antibiotic therapy:

a.

b.

c.

d.

e.

Name five potential adverse effects that may result from antibiotic therapy:

a. bacterial resistance

b. GI effects (nausea, vomiting, diarrhea)

c. Allergic reactions

d. Superinfections

e. photosensitivity

A bactericidal antibiotic is one that _______ bacteria whereas a bacteriostatic antibiotic __________ bacteria.

A bactericidal antibiotic is one that kills bacteria whereas a bacteriostatic antibiotic inhibits bacteria.

______________ is an enzyme that breaks down the ___________ ring on penicillin and can be produced by the bacteria ____________________. Amoxicillin is combined with ___________ acid to form the drug Augmentin which is resistant to the effects of the enzyme.

Beta-lactamase is an enzyme that breaks down the beta-lactam ring on penicillin and can be produced by the bacteria Staphylococcus aureus. Amoxicillin is combined with clavulanic acid to form the drug Augmentin which is resistant to the effects of the enzyme.

Pseudomembranous colitis is caused by the bacteria ___________________ and is associated with all antibiotics, especially _____________ and can possibly be prevented by taking _____________________ along with the antibiotic.

Pseudomembranous colitis is caused by the bacteria Clostridium difficile and is associated with all antibiotics, especially Clindamycin and can possibly be prevented by taking Lactobacillus acidophilus (a probiotic) along with the antibiotic.

Allergies to penicillin are seen in about ___ % of the population and there is a cross-hypersensitivity between penicillin and ______________.

Allergies to penicillin are seen in about 10% of the population and there is a cross-hypersensitivity between penicillin and cephalosporins.

TRUE or FALSE: Clindamycin (Cleocin) is safe for patients with gastrointestinal issues.

FALSE

Name two precautions/directions with tetracyclines:

a.

b.

Name two precautions/directions with tetracyclines:

a. do not take with milk, dairy products, iron, magnesium-containing products, or antacids

b. wait ≥ 2 hours before/after taking lipid-lowering drugs to take tetracyclines

Who must not be prescribed tetracyclines?

• pregnant women

• children ≤ 8 yrs

Name two precautions with metronidazole (Flagyl):

a.

b.

Name two precautions with metronidazole (Flagyl):

a. NO alcohol

b. NO anticoagulants (e.g. Warfarin)

List the four antibiotics that treat TB disease:

a.

b.

c.

d.

List the four antibiotics that treat TB disease:

a. Isoniazid (INH)

b. Rifampin (RIF)

c. Pyrazinamide (PZA)

d. Ethambutol (EMB)

What is pyridoxine and why must it be taken with isoniazid?

Pyridoxine is Vitamin B6. It must be taken with isoniazid to prevent a pyridoxine deficiency which can cause peripheral neuropathy.

List four issues that have helped create antibiotic resistance:

a.

b.

c.

d.

List four issues that have helped create antibiotic resistance:

a. delayed tx (diagnosis wasn’t made early enough, inadequate doses of antibiotic were initially given, wrong antibiotic)

b. pt discontinued the drug early

c. pt took leftover antibiotics

d. pt missed doses

What are the potential issues with the drug methotrexate and antibiotics? Why?

Concurrent use of methotrexate and penicillins can lead to a potentially fatal interaction. Penicillin competes with methotrexate in the kidneys for excretion, leading to toxic levels of methotrexate (it has a narrow therapeutic index).

Which antibiotics cause photosensitivity/phototoxicity?

• tetracyclines (doxycycline, minocycline, tetracycline)

• fluoroquinolones (ciprofloxacin, levofloxacin, ofloxacin)

• sulfonamides (sulfamethoxazole-trimethoprim (Bactrim))

Clindamycin is bacteriostatic at _____ mg and _____________ at 300 mg.

Clindamycin is bacteriostatic at 150 mg and bactericidal at 300 mg.

Antiinfective Agents Definitions

• Antiinfective Agents: substances that act against or destroy infections; can come from ANY SOURCE (made by a microorganism OR developed in a chemistry laboratory) and can inhibit or kill a VARIETY of organisms such as bacteria, protozoa, and viruses

• Antibacterial Agents: substances that destroy or suppress the growth or multiplication of bacteria; can come from any source (made by a microorganism OR developed in a chemistry laboratory); only affects BACTERIA

  • Antibiotic Agents: chemical substances produced by MICROORGANISMS that have the capacity, in diluted solutions, to destroy or suppress the growth or multiplication of organisms or prevent their action

    • Bactericidal: the ability to KILL bacteria; IRREVERSIBLE effect

    • Bacteriostatic: the ability to INHIBIT or RETARD the multiplication or growth of bacteria; REVERSIBLE effect (remove contact with agent → bacteria are still able to grow and multiply)

• Antimicrobial Agents: substances that destroy or suppress the growth or multiplication of microorganisms

• Antifungal Agents: substances that destroy or suppress the growth or multiplication of fungi

• Antiviral Agents: substances that destroy or suppress the growth or multiplication of viruses

Antibiotics

Antibiotic Agents: chemical substances produced by MICROORGANISMS that have the capacity, in diluted solutions, to destroy or suppress the growth or multiplication of organisms or prevent their action

.

Types:

• Bactericidal: the ability to KILL bacteria; IRREVERSIBLE effect

• Bacteriostatic: the ability to INHIBIT or RETARD the multiplication or growth of bacteria; REVERSIBLE effect (remove contact with agent → bacteria are still able to grow and multiply)

Spectrum of Activity:

• Narrow spectrum

• Broad spectrum

• Extended spectrum

.

Adverse Effects:

• bacterial resistance to the antibiotic: bacteria will continue to multiply, grow, and survive in the presence of concentrations of an antibiotic that are usually lethal to organisms

  • inherent antibiotic resistance: bacteria are naturally resistant

  • acquired antibiotic resistance: bacteria have adapted and evolved resistance

    • Spontaneous Mutation

    • Genetic Exchange: bacteria share genetic information with each other via transduction, transformation, or bacterial conjugation

    • Active Efflux: efflux pumps allow microorganisms to regulate their internal environment by pumping toxic substances out of the cell; key mechanism of gram (-) bacteria

    • Epigenetics: external modifications to DNA that turn genes on/off; affects how the cell reads genes but does not change the DNA sequence itself; means “above” or “on top of” genetics

  • possible causes:

    • 1. treatment resistance: “doctor-induced resistance” causing a delay in tx bc the diagnosis wasn’t made early enough, inadequate doses were initially given, the wrong antibiotic was given

    • 2. misuse resistance: pt did not take as directed, pt did not take on prescribed schedule, pt missed doses, pt discontinued the drug early, pt took left-over antibiotics

    • 3. overuse/overprescription of antibiotics

• Superinfections: the overgrowth of an organism that was not present when the treatment of an infection began; infection imposed upon another infection due to the overgrowth of normal flora (GI tract, oral cavity, respiratory tract, vaginal area) or the eradication of microorganisms that are part of the normal flora, usually associated with prolonged antibiotic use and broad-spectrum antibiotics; can cause overgrowth of candidiasis and can cause stomatitis or glossitis

• GI issues: direct/indirect irritation caused by an imbalance in the normal GI flora, resulting in nausea, vomiting, and/or diarrhea; may be avoided by taking probiotics such as Lactobacillus acidophilus (ex: antibiotic-associated pseudomembranous colitis caused by overgrowth of Clostridium difficile)

• allergic reactions

• photosensitivity: certain antibiotics (and diuretics, retinoids, and BC pills) can make the skin sensitive to the sunlight by interacting with UV light to create toxic or inflammatory reactions in skin cells; symptoms: severe sunburn, blistering, rashes

  • tetracyclines: doxycycline, minocycline, tetracycline

  • fluoroquinolones: ciprofloxacin, levofloxacin, ofloxacin

  • sulfonamides: sulfamethoxazole-trimethoprim (Bactrim)

• drug interactions

Indications for Antibiotics

• acute odontogenic/orofacial infections

• prophylaxis against IE

• prophylaxis for pts at risk for infection because of immunocompromise (DM with HbA1C >8, immunosuppressant drugs, transplant pts)

• periodontal therapy:

  • systemic antibiotics are used in conjunction with periodontal debridement and/or surgery (e.g. Grade C periodontitis, NPDs)

  • topical antimicrobial agents (e.g. Arestin, aka minocycline HCl) used for localized periodontitis

• endodontic therapy:

  • endodontic lesion WITH soft tissue swelling AND systemic involvement (fever, lymphadenopathy, cellulitis) or spread of infection (NOT indicated in an uncomplicated endodontic infection / well-localized soft tissue swelling WITHOUT systemic signs of infection)

• prophylaxis for postsurgical infection

• peri-implantitis:

  • infections associated with bone loss and/or suppuration (NOT indicated in peri-implant mucositis → use chlorhexidine gluconate instead)

Antibiotic Families

• Penicillins

• Cephalosporins

• Nitroimidazoles

• Quinolones (Fluoroquinolones)

• Macrolides

• Lincomycins

• Tetracyclines

• Sulfonamides

• Vancomycin

• Aminoglycosides

Beta-Lacam and Penicillin Resistance

Penicillins & Cephalosporins are potent bactericidal agents that contain a beta-lactam ring. The beta-lactam ring interferes with bacterial cell wall synthesis.

method of action: inhibits one or more of the penicillin-binding proteins (PBPs) (the enzymes involved in the synthesis of the bacterial cell wall and in maintaining its integrity via cross-linkages/transpeptidases) → no cell wall → internal part of bacterial cell is vulnerable to outside environment → lysis (cell rupture) → death

---

Beta-Lactamase (penicillinase): bacterial enzymes that cleave the beta-lactam ring, rendering penicillin ineffective and causing penicillin resistance

• 95% of Staphylococcus aureus produce beta-lactamase

• Augmentin: Amoxicillin + clavulanic acid → prevents the penicillin beta-lactam ring from being destroyed by the beta-lactamase enzyme

Penicillins

• method of action: bactericidal (cell wall synthesis inhibitors via beta-lactam ring)

• discovered by Sir Alexander Fleming

• administration: oral or parenterally (NEVER topical due to allergic reaction)

• spectrum of activity: primarily effective against gram (+) cocci and bacilli bacteria (Streptococcus pneumoniae) and some gram (-) bacteria

  • Narrow-spectrum: natural penicillins

    • Penicillin V & Penicillin G

    • not very effective against gram (-) bacteria because penicillin can’t penetrate their thick lipopolysaccharide coat

  • Broad-spectrum

    • Aminopenicillins (amoxicillin and ampicillin) & antipseudomonal penicillins (piperacillin, ticarcillin)

    • more effective against gram (-) bacteria

• Pharmacokinetics:

  • Absorption: primarily absorbed from duodenum, but depends on acid stability in the stomach; absorption is greatest when taken on an empty stomach (exception: amoxicillin which can be taken with food); all penicillins must be taken with a full glass of water to increase absorption from the GI tract

    • Penicillin VK: absorbed orally (acid stable)

    • Piperacillin & Ticarcillin: injected to bypass the stomach (not acid stable)

  • Elimination: excretion by kidneys (note: dosage must be reduced in those with renal failure)

• Indications:

  • Penicillin VK & Amoxicillin: the only 2 penicillins used in dentistry for mild-mod odontogenic infections

    • Penicillin VK: mild-mod endodontic, periodontic, and odontogenic infections

    • Amoxicillin: more serious infections (broad-spectrum); effective against Peptostreptococcus (found in perio sites)

      • Augmentin (amoxicillin + clavulanic acid): used for resistant strains of bacteria, especially for perio pts that are refractory to tx, NPDs, and some surgeries (especially sinus lifts)

Penicillin Adverse Effects and Drug Interactions

Adverse Effects:

• allergic reactions occur in <10% of the population

• pseudomembranous colitis

• GI upset (most common adverse effect causing nausea, vomiting, diarrhea; oral penicillins may be taken with a probiotic like Lactobacillus acidophilus)

• superinfection

Drug Interactions

• Penicillin + bacteriostatic antibiotic (i.e. tetracyclines, erythromycins) → space the two antibiotics so they are not given concurrently

• Oral contraceptives → may render oral contraceptives ineffective (estrogen undergoes enterohepatic circulation and needs bacteria in the gut to break it down before it reabsorbs; penicillin prevents this causing poor absorption of estrogen and rendering the oral contraceptive ineffective)

• Food → increases breakdown of penicillin in the stomach

• Probenecid (gout tx) → decreases renal elimination of penicillins

• Pregnancy/Nursing (Category B)

• Methotrexate → potentially fatal interaction due to toxic levels of methotrexate (low TI); penicillin and methotrexate compete in the kidneys for excretion, leading to a buildup of methotrexate and toxicity

Cephalosporins

• method of action: bactericidal (cell wall synthesis inhibitors via beta-lactam ring)

• similar beta-lactam ring as penicillins

• Indications:

  • NOT used for dental infections due to high $

  • skin, bone, genitourinary, and respiratory tract infections; otitis media, acute prostatitis

  • great for bone penetration

• Adverse Effects: similar to penicillins

  • NOTE: There is a 10% cross-hypersensitivity reaction with peniciliins (aka: 10% of people allergic to penicillin will also be allergic to cephalosporins). → BOARD QUESTION

Nitroimidazoles: Metronidazole (Flagyl)

• method of action: bactericidal

• spectrum of activity: affective against obligate or strict anaerobes (like subgingival bacteria)

• Indications:

  • Metronidazole + amoxicillin → useful against Aa and Pg in rapidly progressing (grade C) periodontitis, NPDs, and nonresponding periodontitis

  • found in GCF

• Adverse Effects:

  • GI upset (okay with food)

  • metallic taste

  • dry mouth

  • dark urine

    • okay in renal disease; dark urine does not indicate any effects on the kidneys

• Drug Interactions:

  • alcohol → disulfiram-like reaction causing headache, nausea, vomiting

    • NO alcohol, including alcohol mouth rinse!

  • lithium → causes toxicity

  • anticoagulants (warfarin) → increased bleeding

    • okay with antiplatelets

Quinolones (Fluoroquinolones)