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106 Cards in this Set

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What is the goal of antimicrobial drugs?
The goal of antimicrobial drugs is either to disrupt the cell processes or structures of bactria, fungi and protozoa or inhibit the virus multiplication cycle.
What is selective toxicity?
Drugs should kill or inhibit growth of microbes without simultaneously damaging host tissues.
What are the primary basis of chemotheraphy?
To target infectious agent with chemical that irreversibly damages or inhibits it.
What are the fiver major components for useful drug targets?
Cell wall and membrane, the genetic material, protein synthesis and metabolic pathways.
What are the effects of drugs?
Inhibition of cell wall synthesis, Breakdown of cell membrane structure or function, inhibition of structure and functions of DNA and RNA, Inhibition of protein synthesis and Blocks on key metabolic pathways
Give me an example of drug's overlapping effect.
If DNA transcription is inhibite, then protein synthesis i inhibited as well.
What is drug's spectrum?
Drug's particular range of activity
What are the spectrum of antimicrobial drugs?
Narrow-spectrum, medium-spectrum and broad-spectrum
What is a narrow spectrum?
Effective on small range of cell types because they target a specific componet that is found only in certain bacteria.
Give me an example of narrow-spectrum drugs and how do they work?
Bacitracin - blocks the elongation of peptidoglycan in gram+ bacteria but has no effect on gram-
Polymysin breaks down the outer membrane on gram- cells but does not target gram+ ones
Give me an example of medium-spectrum drugs.
Ampicillin is effective on both gram+ and gram- bacteria, but not every type.
Give me an exampl of broad-spectrum drugs.
Tetracycline works on most gram- and gram + bacteria, rickettsisas, mycoplasmas and spirochetes. They usually have their effects on common cell components such as the ribosomes, which are found in all cells and mitochondria.
What is the purpose of peptidoglycan in bacterial cell?
It protects the cell against rupture from hypotonic environments and active cells must constantly synthesize new peptidoglycan and transprot it to its proper place.
How do penicillins and cephalosporins affect the bacteria cell wall?
Bind and block peptidases that cross-link the glycan molecules, thereby interrupting the completion of the cell wall.
Give me an example of drug that affects bacterial cell wall, and can also pass the cell walls of gram- species.
Penicillin (carbenicillin) and cephalosporins (ceftriaxone)
How do cycloserine affects the bacterial cell wall?
It inhibits the formation of the basic peptidoglycan subunits.
How do vancomysin affects the bacterial cell wall?
It hinders the elongation of the peptidoglycan.
What happens to a cell with a damaged membrane?
Dies from disruption in metabolism or lysis.
How do polymysins disrupt the cell membrane?
It interact with membrane phospholipids and cause leakage of protein nd nitrogen bases,particulary in gram- bacteria.
How do polyene antifungal antibiotics such as amphotericin B and nystatin disrupt cell membrane?
Form complexes with the sterols on fungal membranes, which cause abnormal openings and seepage of small ions.
How do chloroquine (antimalarial drug) affect the nucleic acid synthesis?
Binds and cross-links the double helix.
How do broad-spectrum quinolones affect nucleic acid synthesis?
Inhibit DNA unwindingenzymes or helicases, thereby stopping DNA replication and repair.
How do antiviral drugs affect nucleic acid synthesis ?
They are analogs of purine and pyrimidines which will insert the viral nucleic acid like a normal base.
What do most drugs that block protein synthesis do?
React with the ribosome mRNA complex.
What are the two possible targets of ribosomal inhibition?
30S subunit and 50S subunit
How do aminoglycosides such as streptomycin and gentamicin block protein synthesis?
Insert on sites on the 30S subunits and cause misreading of the mRNA, leading to abnormal proteins.
How do tetracylines block protein synthesis?
Blocks the attachment of tRNA on the A acceptor sites and effectively sstop further synthesis of that protein.
Give me examples of antibiotics that attach on 50S subunits and what do they do?
Chloramphenicol - prevents formation of peptide bonds
Erythromycin - inhibits translocation of the subunit during translation
What are oxazolidinones? How do they block protein synthesis?
Newer drug class that affect the assembly of the completed ribosome by blocking the attachment site for the 50S and 30S subunits.
Give me and example of drugs that exibits ompetitive inhibition.
Sulfonamides and trimethoprim - drugs that act by mimicking the normal substrate of an enzyme by a process called competitive inhibition.
Why do sulfonamides and trimethoprim given to the cell in high concentration?
To ensure that a needed enzyme is constantly occupied by the metabolic analog rather than the true substrate of the enzyme. As the enzyme is no longer to produce products, cellular metabolism slows or stops.
How do sulfonamides and trimethoprim affect the metabolic pathway?
Interfere wih folate metabolism by blcoking enzyms required for synthesis of tetrahydrofolate, which is needed in bacterial cells for the synthesis of folic acid and eventual production of DNA and RNA and amino acids.
Why do sulfonamides and trimethoprim given simultaneously?
To achieve synergistic effect so that a lower dosage of each drug can be used.
How do sulfonamides and trimethoprim exibits selective toxicity?
Mammal derive folic acid from diet and so do not process this ezyme system, while bacteria and protozoan parasite must synthesize folic acid.
What are first-generation cephalosporins?
Cephalothin and cefazolin - most effective against gram+ cocci and a few gram - bacteria
What are second-generation cephalosporins?
cefaclor and cefonacid - are more effective than the first generation froms in treating infections by gram- bacteria such as Enterobacter, Proteus and Haemophilus
What are third-generation cephalosporins?
cephalexin (Keflex) and ceftriaxone (Rocephin) are broad spectrum with especially well-developed activity against enteric bacteria that produce beta-lactamases
What are fourth generation cephalosporins?
cefepime and are effective with both gram - and gram + bacterial infections and are rapidly microbicidal.
What are other beta-lactam drugs?
Imipenem and aztreonam
What is imipenem?
Imipenem are broad-spectrum carbapenem used for infections with aerobic and anaerobic pathogens, active in very low concetrations and can be taken by mouth with very few side effects except allergies
What is aztreonam-monobactam?
Narrow-spectrum antibiotic for treating pneumonia, septicemia and urinary tract infections by gram - aerobic bacilli. Useful when treating person who are allergic to penicilin.
What is vancomysin?
narrow-spectrum antibiotic most effective in treating staphylococcal infections in cases of penicillin and methicillin resistance or in patients with an allergy to penicillins.
What drug treat clostridium infections in children and endocarditis caused by Enterococcus faecalis?
Vancomysin
What is bacitracin claim to fame?
Major component of neosporin for combating superficial skin infections by streptococci and staphylococci
Bacitracin is produced by what bacteria?
Bacillus subtilis
How does isoniazid (INH) works?
Works by interfering with the synthesis of mycolic acid, a necessary component of cell wall of acid-fast organisms.
What is indicated with isoniazid (INH) for both active tuberculosis and prophylazis in case of positive TB test?
Oral doses
What is aureomycin?
First antibiotic of tetracycline and was used to synthesized terramycin, tetracyline and several semisynthetic derivatives of tetracyclines.
Doxycycline and minocycline are treatment for what?
Sexually transmitted diseases, Rocky Mountain spotted fever, Lyme disease, typhus, Mycoplasma pneumonia, cholera, leptospirosis, acne and some protozoan infections.
Administration of chloramphenicol is limited to what?
typhoid fever, brain abscesses, rickettsial and chlamydial infections for which an alternative therapy is not an alternative.
What are fosfomycin trimethamine?
Phosphoric acid agent effective as alternative treatment for urinary tract infections caused by enteric bacteria. It works by inhibiting an enzyme necessary for cell wall synthesis.
What are synercid?
It is an antibiotic from the streptogamin group of drugs that contains two active chemicals. Effective against Staphylococcus and Enterococcus species that cause endocarditis and surgical infections, and against resistant strains of Streptococcus.
How does synercid works?
Works by binding to sites ont he 50S ribosome, inhibiting petpide transfer and elongation.
What is daptomycin?
Lipopeptide directed mainly against gram+ bacteria, acting to disrupt multiple aspcts of membrane function.
What is Telithromycin (Ketek) used for?
Respiratoy tract infections caused by macrolide resistant bacteria
What is used to treat infections from MRSA and VRE?
Linezolid (Zyvox)
How does primaquine work with Plasmodium?
Eliminates the liver phase of infection. Administered to patients with relapsing cases of malaria.
How does chloroquine works?
Suppresses acute attacks associated with infection of red blood cells. Taken alone for prophylaxis and suppression of acute forms of malaria.
What is mefloquine?
semisynthetic analogs of quinine used to treat infctionsaused by chloroquine-resistant strains.
What is the drug effective in treating mild and severe intestinal infections and hepatic disease caused by Entamoeba histolytica?
Amoebecide, metronidazole (Flagyl)
What is a most effective drug for antihelminth?
The most effective drugs immobilize, disintegrate, or ihibit the metabolism of all stages of the life cycle.
What are Mebendazole and thiabendazole for?
Used for infections of roundworms. Works locally in the intestine to inhibit the function of their glucose utilization and disables them.
What do pyrantel and piperaine do?
Paralyze the muscles of intestinal roundworms.
What do niclosamide do?
destroys the scolex and the adjoining proglottids of tapworms, theeby lossening the worm's holdfast.
What is the treatment for various tapeworms and fluke infections?
Praziquantel
What is the veterinary drug now used for strongyloidiasis and oncocercosis in humans?
Ivermectin
What are the major modes of actions for antiviral agents?
Barring penetration of the virus into the host cell. Blocking replication, transcription, and/or translation of viral genetic material. Preventing the normal maturation of viral particles.
What are amantadine and rimantidine?
Restricted to treating influenza A. Blocks he hemagglutinin receptors - prevent fusion of the virus with the cell membranes and consequently interfere with entry, uncoating and releas of virus.
What are relenza and tamiflu?
Blocks neurominidase enzymes of Influenza A and influenza B
What are the drugs for herpes virus infections?
Acyclovir (Zovirax), valcyclovir (Valtrex), famciclovir (Famvir), peniciclovir (Denavir)
What are Ganciclovir (Cytovene)
Used parentally to treat cytomegalovirus infection in patients with compromised immune system.
What is the name of the enzyme used by the virus to incorporate viral DNA?
Thymidine kinase
How come valacyclovir and famciclovir only active on virally effective cells?
When the inactive drug enters into the virally infected cell, the virus's own thymidine kinase converts it to a working antiviral agent.
What are the two types of targets for anti-HIV drugs?
Nucleoside revrse transcriptase analogs(NRTIs) and Nonnucleoside reverse transcriptase inhibitors (NNRTIs)
How does NRTIs works?
Directly stop DNA synthesis
How does NNRTIs works?
interfere with the function of RT enzyme itself and prevent its reactive site from synthesizing DNA
Examples of NRTIs
epivir, abacavir, didanosine, stavudine and zidovudine (retrovir, AZT)
What can be used at all stages of HIV infection, ncluding as prophylaxis for accidental exposure?
Retrovir
Examples of NNRTIs
nevirapine, efavirenz, delaviridine
What is HIV protease?
Enzyme essential for the virus's release, which involes in cutting elongate protein strands of teh virus before they are assembled into the finished virion.
What is protease inhibitor?
Blocks HIV protease and causing viruse to be defective and not infective.
Examples of Protease inhibitor.
indinavir, crixivan and saquinavir
What are Maravoc?
Keeps HIV out of cells by covering up CD4 receptors on the white blood cells that HIV usually infects, preventing the virus from adhering into the cell.
What is Fuzeon?
Prevents HIV infection when it stops the envelope of the virus from fusing with the host cell after it has attached.
What is integrase inhibitor - raltegravir?
Effective in preventing the HIV DNA, once its formed from being incorporated or integrated into the host's chromosome - since this step is required for viral multiplication, virus replication cannot proceed.
What is the therapeutic approach for HIV?
Combine theraphy
Examples of Recombinant DNA Interferons.
Betaseron and Roferon
What are the therapeutic effects of interferon?
Reducing the time of healing and some of the complications of certain infections (herpesviruses). Preventing or reducing some symptoms of cold and paillomaviruses. Slowing the progress of certain cancers, including bone cancer and cervical cancer and certain leukemia ad lymphomas. Treating rare cancer hairy-cell leukemia, hepatitis C, genital warts, and Kaposis's sarcom in AIDS patients.
How do microbes become resistant?
Spontaneous mutation in critical chromosomal genes. Acquisition of entire new genes or sets of genes via transfer from another species.
Where do resistance through intermicrobial transfer originate from?
Chromosomal genes and plasmids called resistance (R) factors being transferred through the process of conjugation, transformation or transduction.
What are drugs inactivation mechanims?
Microbes inactivate drugs by producing enzymes that permanently alter dug structure. Resistance of microbes due to mechanism that prevents the drug form entering the cell and acting on its target. Many bacteria possess multidrug-resistant (MDR) pumps that actively transport drugs and other chemical out of cells.
What are examples of enzymes that permanently alter drug structure?
bacterial exoenzymes - beta lactamases - hydrolyze beta-lactam ring.
Examples of penicillinase ad cephalosporinase.
Staphylococcus aureus - penicillinase
Neisseria gonorrhoease, called PPNG - pneicillinase
How do sulfonamides affect the kidney?
Can crystalize in the kidney and form stones than obstruct the flow of urine.
What kind of mechanims is used for aminoglycosides?
Changes in drug permeability cased by point mutations in proteins of the transprt syste or outer membrane.
What mechanism bacteria used for tetracyclines?
plasmid-encoded proteins that pumt the drug out of the cell
What are the side effects of chloramphenicol?
severely depress blood-forming cells in the bone marrow, resulting in reversible or a permanent (fatal) anemia
What is the side effect of aminoglycosides?
damages nerves (eight cranial nerve) leading to dizziness, deafness or motor or sensory disturbances.
Why are tetracycline contraindicated for children and pregnant women?
Children below 8 years of age because they bind enamel of the teeth, creating a permanet gray to brown discoloration. In pregnant women, it can cross the placenta an can affect developing fetal bones and teeth.
What is superinfection?
When antimicrobial destroys beneficial residents species, resistant microbes that were once small numbers begin to overgrow and cause disease.
What is pseudomembranous colitis?
antibiotic-associated colitis due to overgrowth of Clostridium difficile. Oral therapy with tetracyclines, clindamycin, and broad-spectrum penicillins
How to identify infectious agent?
Direct examination of body fluids, sputum, or stool
What is MIC?
Minimum inhibitory concentration is the smallest concentration (highest dilution) of drug that can visibly inhibits growth
What is MIC used for?
Useful for determining the smallest effective dosage of a drug and in providing a comparative index against antimicrobials
What are the reason why antimicrobial fails?
Inability of the drug to diffuse into body compartment (brain, joints, skin). A few resistant cells in the culture did not appear in the sensitivity test. An infection is caused by more than one pathogen (mixed infection)
What is Therapeutic Index?
TI is the ratio of the drug that is toxic to humans as compared to its minimum effective (therapeutic) dose.