This question involves the use of combinations of drugs and the synergy effects seen when drugs are used together.
Question A: There a variety of possibilities as to why the initial treatment did not work but the foremost possibility is that the organism has developed a resistance to cephalosporin. You can explain that resistance to antibiotics is a common problem and one that can be overcome by using combinations of drugs.
Question B: This new therapy regimen incorporates two drugs as a way of defeating the problem of resistance. More importantly, the combination of drugs is designed to maximize the therapy. Explain that penicillin attacks the cell wall of the bacteria and streptomycin attacks the bacterial ribosome, which is inside the bacterial cell. This double whammy is effective because the penicillin effectively opens up the cell so that streptomycin can get access to its target of the bacterial ribosome. This drug interaction is referred to a synergistic reaction.
Question C: This new approach should be much better at achieving results then the previous use of only one antibiotic since there is less chance of resistance developing to both drugs. In addition, the more powerful combination of two drugs should be much better at fighting of the infection.
This question involves the difference between infections caused by bacteria and viruses and the therapies available.
Question A: The common cold is caused by the rhinovirus. Antibiotics only work against bacteria and so will be absolutely no use in treating a viral infection. Taking antibiotics in this situation could do more harm than good because it could lead to antibiotic resistance, meaning that when the patient does get a bacterial infection the antibiotics might not work.
Question B: There are few effective therapies for viral infections because they get into host cells and once in are very difficult to kill without killing the host cell, which would cause serious side effects. There are some antiviral drugs that act against parts of the lifecycle of certain viruses that are specific to those viruses. The nucleoside analogs AZT and acyclovir that are effective in the treatment of HIV and herpesvirus infections (such as cold sores) respectively are good examples. Researchers are trying to develop drugs that act on a different stage of the lifecycle of the rhinovirues (called protease inhibitors) but there is nothing on the market yet.
Question C: Your patient should stay at home until their symptoms subside. Not only do they risk spreading the infection to others, they are also at an increased risk of getting a secondary bacterial infection because their immune system is busy fighting the virus. If they get a secondary bacterial infection they will need antibiotic treatment, but antibiotics can also have side effects. Secondary infections can be serious.