How do antibiotics work?
May 13, 2009 8:56 PM   Subscribe

Woke up Tuesday morning with a killer sore throat, swollen lymph nodes making it painful to swallow and a low-grade fever. A doc visit this afternoon confirmed I've got some sorta creeping crud and I was given a prescription of antibiotics, (Amoxicillin tablets 875mg). Can someone describe in detail what exactly happens when I take the stuff, maybe in a timeline format? How does it wipe out the baddies exactly (i.e. what mechanisms does it use to kill off the bugs?)

In my mind, it's all kind of a black box: pills go in, eventually the bad stuff gets wiped out. I would just like to have a clearer picture in my head of how the battle is being fought in the trenches, so to speak.
posted by captnkurt to Science & Nature (7 answers total) 2 users marked this as a favorite
Best answer:

Sidebar to the main story: This also happens in your GI tract. Keep up with the yogurt/other Acidophilus stuff.
posted by Inspector.Gadget at 9:04 PM on May 13, 2009

Best answer: Explanation and video
posted by clanger at 9:08 PM on May 13, 2009

As with all antibiotics, you should take the full course of pills that you've been prescribed, even if you feel much better and your symptoms subside.

By the way, you probably have strep throat.
posted by Chocolate Pickle at 9:14 PM on May 13, 2009

Best answer: Amoxicillin is a molecule that prevents bacteria from building a cell wall made of a polymer called peptidoglycan. The antibiotic binds a protein needed to form this layer and prevents the protein from working, causing the bacteria to die. Then your immune system can do its job and clear out the dead bacteria.

Since your lymph nodes are swollen, this means that your innate immune system has already responded to the bacteria present in your body and has alerted your adaptive immune system by sending antigen-presenting cells (APCs) to your lymph nodes. These APCs are holding on to a piece of the bacteria to show T cells. T cells that can bind well to the piece of bacteria are activated and start to replicate; the large numbers of T and B cells being made in your lymph nodes is what's causing the swelling. The antibiotic can slow down the rapid growth of bacteria and buys your immune system some time while certain T and B cells are selectively cloned inside your lymph nodes so that you get activated lymphocytes that are specific to this type of bacteria. These lymphocytes can then clear out the bacteria effectively - B cells produce antibodies targeting the bacteria, while CD8 T cells (killer T cells) are able to stop the spread of intracellular bacteria or viruses by killing any of your infected cells. Most of the bacteria that die due to the antibiotic will probably have already been eaten up by neutrophils. Other bugs that might have survived will be covered by the antibodies produced by your activated B cells, which attracts macrophages to come and gobble them up. The antibiotic just adds another blow to the bacteria in addition to your body's defenses (assuming the bugs don't develop resistance to the antibiotic).
posted by extramundane at 10:12 PM on May 13, 2009 [3 favorites]

If you have a viral infection (rather than a bacterial infection) and the doctor has prescribed Amoxicillin as a precautionary measure, then the antibiotic won't be doing anything to combat the "bugs" causing your infection, and your immune system will be doing the job on its lonesome.

In any case, what the drug will also likely be doing is changing the ratio of Amoxicillin-susceptible to Amoxicillin-resistent Staphylococcus aureus currently residing in your nose, by a process of Darwinian selection.
posted by kisch mokusch at 11:49 PM on May 13, 2009

Extramundane has a great explanation. In general though, antibiotics generally work by disrupting the function of enzmes critical to bacterial metabolism, causing the cell to weaken and die. Other antibiotics target cell membranes, protein systhesis, bacterial ribosomes, or other metabolic processes. Antibiotics generally work as drugs because eubacteria are just different enough from animal cells in their chemistry, that a compound with high toxicity against one sometimes has low toxicity against the other. As a result, antibiotics generally have minimal effectiveness against diseases that are not caused by bacteria, such as Influenza (a virus), Candida (a fungus) or amebic dysentery (a protozoan).
posted by KirkJobSluder at 4:57 AM on May 14, 2009

Main targets of various antibiotics include-
Cell wall
Protein synthesis
Nucleic acid synthesis
Folic acid synthesis
posted by brevator at 5:41 AM on May 14, 2009

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