Ch 7 pharm exam 2

What are antibiotics?

drugs targeting processes that are essential for bacterial growth and survival; can do it by:

What does bactericidal mean?

antibiotic kills bacteria

• stops growth/reproduction AND cell killing

What does bacteriostatic mean?

antibiotic stops their growth

•stops growth/reproduction with no cell killing

What does bacteriolytic mean?

stops growth/reproduction AND cell killing/destruction

What is antibiotic prophylaxis?

the use of antibiotics to prevent infection rather than treat it

What is an antibiotic's spectrum of activity?

the range of microorganisms it can kill or inhibit

• narrow-spectrum: can only target certain groups

• broad-spectrum: targets wider range of bacteria; designates antibiotics that are effective against both gram - and gram +

What is antibiotic resistance?

bacteria resistant to multiple antibiotics → superbugs

• all microbial resistance patterns are local, based on use of antibiotics in a particular community

What is virulence?

microorganism's ability to infect the host

• multi-factorial

• have no control over this

What are aerobic bacteria?

they survive and grow in an oxygenated environment

What are anaerobic bacteria?

they do not require oxygen for growth

• some anaerobes react negatively or even die if oxygen is present → obligate anaerobes

What does immunodeficient mean?

An impairment of the immune system that prevents it from working properly

What does immunocompromised mean?

A broad term for someone with a weakened immune system

What are the 5 mechanisms of action of antibiotics?

1. Inhibition of cell wall synthesis

2. Alteration in cell membrane integrity

3. Inhibition of ribosome

4. Inhibition of nucleic acid (DNA) synthesis

5. Inhibition of folic acid (vitamin B9) synthesis

How are penicillins named?

end in -cillin

If a patient is allergic to penicillin, the patient is also likely to be allergic to which class of drugs?

cephalosporins

• structurally related to penicillins

Which classes of antibiotics are relatively "safe" in pregnant women?

• penicillin

• erythromycin

Which antibiotics are contraindicated in pregnancy?

• metronidazole

• chloramphenicol

• aminoglycosides

• tetracyclines

What is penicillinase and how does it provide resistance to penicillin to bacteria?

beta-lactamase

• destroys the beta-lactam ring of penicillin, rendering it inactive

• breaks down penicillin and other compounds that are susceptible to penicillinase, making them inactive

What does it mean for a drug to have "penicillinase-resistance"?

resistant to bacterial enzymes that cause penicillin to be inactivated

How do penicillins work?

bind to penicillin-binding proteins (PBPs)

• inhibits the formation of cross-linkages (peptidoglycans)

• destroys cell wall and leads to lysis

Why are penicillins widely used in dentistry?

• Bactericidal potency

• Lack of toxicity

• Spectrum of activity - penicillin is very effective against many aerobic and anaerobic bacteria

What does it mean for an antibiotic to have a narrow spectrum?

only targets specific class of antibiotics

What does it mean for an antibiotic to have a broad spectrum?

targets both gram negative AND gram positive bacteria

What are the most common side effects of antibiotics?

• GI distress - most common

• superinfection

• allergic reaction

What are two major drug interactions common in antibiotics?

• Oral contraceptives: decreases efficacy of oral contraceptives by increasing their clearance from body

• Oral anticoagulants: some anticoagulants act through inhibition of vitamin K-dependent blood coagulation proteins. Since the gut bacterial flora produce a majority of vitamin K, when one takes an antibiotic, you could further decrease vitamin K production

Which classes of drugs inhibit bacterial ribosome subunits?

• Erythromycin - macrolide - 50S subunit

• Clindamycin - lincomycin - 50S subunit

• Tetracyclines - 30S subunit

• Aminoglycosides - 30S subunit

Which classes of antibiotics are known to accumulate in gingival crevicular fluid?

• Tetracyclines

• Metronidazole

What are the uses of tetracyclines?

used in certain periodontal situations because of the ability to concentrate in the GCF

What are the adverse reactions of tetracyclines?

not very common, but still possible

• GI distress: anorexia, nausea, vomiting, etc.

• GI local irritation from alteration of flora

• if they are used during the period of enamel calcification, they can produce permanent discoloration of the teeth and enamel hypoplasia

• hepatotoxicity, nephrotoxicity, hematologic effects, superinfection, photosensitivity, CNS, and allergies are all possible

What are drug interactions of tetracyclines?

• oral contraceptives

• barbiturates and phenytoin can reduce effect of doxycycline

• enhances effects of other drugs leading to toxicity

Which patient population is recommended to receive prophylactic antibiotics prior to their dental treatments involving tissue damage & bleeding?

patients at high risk for bacterial endocarditis:

• prosthetic cardiac valve

• previous infective endocarditis

• congenital heart disease

*to prevent prosthetic joint infection -- no longer recommended by ADA

What are two topical antibiotic agents we discussed?

Neosporin & Mupirocin

neomycin: OTC, neosporin
mupircon: treats impetigo; infections with staphylococcus or streptococcus

What is neosporin?

Neomycin + Polymyxin B + Bacitracin

• often used topically for wounds

• OTC

What is mupirocin?

"Bactroban"

• inhibits protein synthesis by binding to bacterial isoleucyl transfer-RNA synthetase

• topical treatment of impetigo

• used to treat bacterial infection with streptococci or staphylococci that is occasionally present with angular cheilitis

• prescription needed

What factors contribute to failure in anti-infective therapy?

• Patient adherence

• Ineffective or wrong antibiotic

• Poor debridement

• Failure of antibiotic to reach site of infection

• Inadequate host defense

• Resistance to antibiotics

What are the different mechanisms by which bacteria develop antibiotic resistance?

• Enzymatic inactivation

• Alteration of target sites

How does antibiotic resistance occur through enzymatic activation?

very common mechanism of resistance

• beta-lactamase (penicillinase) hydrolyzes penicillins and cephalosporins → drug inactive

• acetyltransferases inactivate chloramphenicol, aminoglycosides, and tetracyclines

How does antibiotic resistance occur through alteration of target sites?

• ribosomal point mutations (tetracyclines, macrolides, and clindamycin)

• altered DNA gyrase and topoisomerase (fluoroquinolones)

• modified penicillin-binding proteins (PBPs) in viridans group streptococci (VGS) and pneumococci (beta-lactam antibiotics)