Chapter 11 Objectives Flashcards
Objective 1 Defining the terms antibacterials, antifungals, antivirals, etc. In what ways, if any, is an “antibiotic” different from an “antibacterial?”
Antibacterials are antiseptics that only act against bacteria.
Antifungals: agents for treating fungal infections
Antivirals: for viral infections
Antibiotic~’Anti-infective’: is a chemotherapeutic agent that inhibits or abolishes the growth of micro-organisms, such as bacteria, fungi, or protozoans. The term originally referred to any agent with biological activity against living organisms; however, “antibiotic” now is used to refer to substances with anti-bacterial, anti-fungal, or anti-parasitical activity.
Objective 2
Describe the historical milestones in the development of the earliest antibacterial agents to the later antiviral drugs.
- 1880–Pasteur develops effective immunizations for anthrax and rabies; determines that certain microorganisms inhibit the replication of others, even from different kingdoms (i.e. pen–>strep)
- 20th Century–Ehrlich found ‘magic bullet’ arsenic compound–606 ‘Salvarsan’–for syphilis and trypanosmiasis
- 1930s Germany–Domagk succesfully tested sulfanilamide for his daughter’s sepsis–became first sulfa antibacterial ‘Prontosil’
- Doctors used to have to inject mercury compounds intraurethrally–“cure worse than the disease”
- Even earlier remedies include: herbs, garlic, maggots, salts and spices
- 1982–Alexander Flemming isolates active antibaceterial substance from mold “Penicillin”
- Florey & Chain developed the drug for use by the allies in WWII; All 3 shared the Nobel Prize
- Penicillins continue to be developed: pen G –> pen V–>ampicillin & amoxicillin–>ticarcillin-3/4th generation, (and later Augmentin)
Objective 6
Name the other major groups of antibacterial
agents that have emerged since the sulfa drugs and penicillins.
Be prepared to discuss the drug mechanisms by which the different categories of antibiotic drugs kill bacteria.
Make note of the major infections they are used to treat, and the toxicities they may produce
AMINOGLYCOSIDES–(streptomycin, gentamicin) 1943 from studying soil bacteria; have to be used parenterally or topically and monitored because of toxicity potential; inhibit bacterial protein synthesis
CEPHALOSPORINS–from family of beta-lactams (penicillin-like), secreted from mold, interfere with bacterial cell wall synthesis
CARBAPENEMS & MONOBACTAMS–also beta-lactams–cell wall inhibitors, newer than pen and ceph, used for complicated infections who’ve developed resistance to other drugs; not available in oral form (Aztreonam or Azactam is best known)
Objective 5
Discuss the prevalence of penicillin allergy, and its association with the beta-lactam ring common between the penicillins and cephalosporins. Name two antibacterial agents that can be given in place of penicillin for those who
are allergic.
Determined by skin tests; raised, red rash of hives–serious;
More prevalent in older generation when first developed because they were so widely used or ‘over-used’
Other options: Flouroquinolones, Macrolides, Tetracyclines
Objective 3
Define gram negative and gram positive as a
means of identifying types of bacteria.
Explain the significance of the beta-lactam ring in certain antibiotics and the enzyme penicillinase secreted by many gram positive species.
Describe how environmental, consumer, and medical factors contribute to produce antibiotic-resistant bacteria.
A method to classify 2 distinct types of bacteria based on structural differences in their bacterial cell wall;
In gram-staining protocol, Gram (+) retain the crystal violet dye color and gram (-) do not;
Gram (-) are more resistant to antibiotics because they have an additional lipid membrane that is basically impermeable
Bacteria began to develop enzymes (penicillinase) that could cleave the B-lactam ring in the drug and render it ineffective
Antibiotic resistance began to occur because:
we over-used antibiotics and broad-spectrum became narrower so certain drugs are no longer as widely effective;
patients/consumers take too often in too low dosages so weak species are bred out, strong remain and they become smarter/more resistant
Objective 4
Describe what is meant by an antibiotic “spectrum” of coverage.
Explain the differences between “Broad Spectrum” antibiotics and “Narrow Spectrum” antibiotics. Categorize the major groups of antibacterial agents into either broad or narrow spectrum, then explain how this nomenclature fails to fully describe the realities of fighting microbes in the 21st century.
How widely effective a drug is against different types of infectious agents
‘Broad’–equally effective against a variety of gram- & gram+ organisms (i.e. tetracyclines, flouraquinolones, 2,3,4 generation cephalosporins, carbapenems and monobactams)
‘Narrow’–only effective agains one or the other (i.e. sulfa drugs, penicillins, aminoglycosides and glycopeptides)
Many drugs’ effectiveness had been changed by bacterial resistance so we need new ways to categorize them–like what bugs they specifically kill
Objective 7
Describe the historical milestones in the
development of the earliest antiviral agents.
Objective 8
List major groups of antiviral drugs and diseases they treat
- Began to develop just 35 years ago
- 1960s–2 drugs for opthalmic herpes infections and complications of smallpox vaccine but had not good side effects
- 1970s–better antivirals (acylclovir-types) made the previous ones obsolete
- 1976–FDA approved amantadine (Symmetrel) for influenza in adults & children;
- 1980s–AIDS pandemic occured AND good antivirals began to be developed
- 1980–Virazole (ribavirin) inhalant for RSV; also for hemmorraghic fevers, Hanta virus, and Hep C (in combo with interferons)
- 1977–Zovirax (acyclovir) was tested
- 1982–it became available to doctors–1st blockbuster antiviral; first released as a topical cream for Herpes and then a 5/day pill (more effective but less convenient), and then discovered effective for genital herpes as well
- Drugs for HSV I & II are effective against other herpes viruses as well
- Other acyclovir drugs include: Valtrex (valcyclovir) and Famvir (famciclovir)
- 1999–neuroaminidase inihibitors: oseltamivir (Tamiflu) and zanamivir (Relenza) have now replaced Symmetrel and TIV- Trivalent Influenza vaccine (the flu shot)
(Objective 7)
More milestones of antiviral drug development
- AIDS–at first only palliative care but now drugs to suppress the virus and prevent replication-20 drugs that inhibit reverse transcriptase, viral protease or block virus entry but no actual cure
- NARTIs or ‘nukes’–(AZT) prevent HIV from replicating by blocking reverse transcriptase
- NNRTIs or “non-nukes”–directly bind reverse transcriptase enzyme (separate from the nucleoside binding site)
- 1995–PIs or ‘Protease Inhibitors’, most potent class of HIV antiviral drugs, targeting the viral protease enzyme
- HAART–combing 3-4 drugs–now preferred
- 2006–FDA approved ‘Atripla’ the first 3-drug combo
- Alpha, Beta & Gamma Interferons–modulate the immune response to viruses and cancer; each has individual effects but there is some overlap
- Antiviral resistance–from even minimal noncompliance; pathogens mutate and become less susceptible over time
- Only 5 antiviral drugs in 1990
- Over 60 available today
