| Question |
Answer |
| How are antibiotics produced? |
Antibiotics are produced by organisms such as molds and bacteria. |
| What is the goal of an antimicrobial drug? |
The goal of an antimicrobial drug is to harm the bacteria and not harm the host. This is called selective toxicity. So, drug designers take advantage of the differences between procaryotes and eucaryotes. |
| Describe selective toxicity with respect to DNA. |
Drugs act at various key steps in the metabolism of the cell. Some inhibit the replication of DNA. Others affect transcription or translation. |
| Describe selective toxicity with respect to enzymes and cell walls. |
Some effect the activity or synthesis of specific enzymes. Some injure the bacterial cell wall and others inhibit cell wall synthesis. |
| What is the major difference between eucaryotic and procaryotic cells that drug designers capitalize on to target selective drugs? |
Procaryotes, unlike eucaryotes have peptidoglycan in their cell walls |
| How does pennicillin work? |
Penicillin inhibits the formation of the peptide cross bridges that hold peptidogycan together Gram+ cells have extra outer membrane. Some forms of penicillin are not effective agains gram- bacteria The drug can't pass through outer membrane |
| What are the two major types of pennicillin? |
Those derived from pennicillin mold and those synthesized in the laboratory. |
| Figure 10.3 What changes to form the different types of pennicllin? |
The side chain of the molecule |
| What are two examples of synthesized pennicillin? |
Ampicillin and amoxicillan |
| What are the advantages of Ampicillin and amoxicillan |
Ampicillin and amoxicillin are more effective against gram negatives. |
| Who discovered pennicillin and how did he do it? |
Alexander Flemming discovered penicillin because a mold inhibited the growth of bacteria on his Petri dish |
| A variety of practices have led to antibiotic resistance: What are they? |
Cveruse and misuse of antibiotics, use of ab's as preventative (esp. in the immunosuppressed), failure of pats. to follow treatment (if take less than prescribed somewhat resistant bacteria survive and spread around), ab's in animal feed. World travel |
| What is penicillinase? |
A mechanism for bacterial resistance to penicillin is observed in many Staphyloccocal species. These bacteria make an enzyme, called penicillinase which attacks penicillin. |
| What is one solution to pennicillin resistant bacteria? |
Some synthetic penicillins have been made which are not penicillinase sensitive). One of these is methicillin but bacteria have become resistant to that too. Oxacillin was made to replace it. |
| Ampicillin is active against gram-'s but resistance against this drug has developed. A new derivative has been developed. What is it? |
Carbenicillin |
| What pennicillin is taken orally? Why? |
Penicillin G is best taken orally. Because it can stand up to stomach acid. |
| What can you mix pennicillin with to insure it stays longer in the booldstream |
Procain or bezathine |
| What is the overall effect pennicillin has on the bacterial cell? |
They inhibit cell wall synthesis. |
| What drugs other than pennicillin inhibit cell wall synthesis? |
Cephalosporins(approx. 70 different types), bacitracin-effective in gram+ and is topical, vancomicin-toxic, Rifampin and the quinialones inhibit nucleic acid replication and used for urinary tract infections |
| How does Tetracycline work? |
It interferes with the binding of tRNA to the mRNA-ribosome complex. Because it inhibits protein synthesis tcycl is a broad spect. antibiotic. |
| What are some side effects of Tetracycline? |
Because it kills normal GI flora upset stomach is common. Vaginal infections, liver damage in pregnant women and darkening of teeth in children also occurs. Super infections (Candida albicans) can also occur. |
| Erythromycin binds to the ribosome and keeps it from moving along mRNA. Unfortunately, erythromycin is not effective against gram negatives. Why? |
Erythromycin is not effective agains gram negatives because it does not penetrate the gram negative cell wall. |
| How does Streptomycin work? |
It binds to ribosome and causes the code on mRNA to be read incorrectly |
| For what type of cells is Streptomycin effective? |
Streptomycin is effective against gram negatives. |
| What are some downsides of Streptomycin? |
Drug resistance has developed and there are some toxic effects. So streptomycin is used less than it used to be. |
| How does Chloramphenicol work? |
Chloramphenicol binds the bacterial ribosome and inhibits the formation of peptide bonds |
| What are disadvantages of Chloramphenical? |
It has severe side effects causing anemia in 1 of 40,00 users. So it is not used if something else is available. |
| How does Polymyxin B work? |
Polymyxin B causes direct injury to the bacterial plasma membrane |
| Polymyxin B. Effective against Gram+ or Gram- |
It will affect gram negatives. |
| Polymyxin B How is it used? |
It's used in topical ointments. |
| How do sulfa drugs work? |
Sulfa drugs inhibit the synthesis of a compound which is essential to the cell. |
| What is tetrahydrofolic acid? |
Tetrahydrofolic acid is a precursor needed for by the cell to make DNA and RNA. |
| What enzymes are necessary to convert PABA to tetrahydrofoloc acid? |
The enzymes necessary for these reactions are inhibited by sulfamethoxazole and trimethoprim. |
| When drugs are combined and their effectiveness is greater than the effectiveness of the two drugs used separately what is this called? |
Synergy |
| There are two basic kinds of infections. What are they? |
Bacterial and viral. |
| What drug is used agains the herpes virus? |
Acyclovir is a drug used against herpes virus. |
| What type of drug is Acycolvir? |
It is a nucleoside analog. |
| What is the mechanism that acyclovir uses to confuse viruses? |
The structure of acyclovir is very similar tothe structure of guanine. The viruswill use the drug instead of guanine to make nucleotides. The triphospahate from acyclovir can't incorporated into DNA. Viral replications stop. |
