Siheyuan: Rebirth in a prosperous era, great doctors are sincere

penicillin.

Streptomycin.

Oxytetracycline.

Sulfa drugs.

Nalidixic acid.

There are already a lot of antibiotics available now. As countries pay more attention to antibiotic research, there will be more and more various antibiotics and their derivatives.

then.

Even in the top laboratories in various countries, the mechanism of action of antibiotics is not well studied. Many people know it but do not know why. Even some researchers only know that certain antibiotics have an effect on certain bacteria. But why this happens is unknown.

The hospital was even more chaotic.

Especially after oxytetracycline was mass-produced, it was quickly used in the treatment of various diseases because of its low price and the ability to treat many diseases.

Oxytetracycline is a tetracycline antibiotic that is used as a broad-spectrum bacteriostatic agent against Chlamydia, Mycoplasma, Spirochaete, Rickettsia, Amoeba, some Plasmodium, Bacillus anthracis, Clostridium, Campylobacter and Listeria monocytogenes are sensitive to oxytetracycline, but oxytetracycline cannot cure all diseases.

In particular, oxytetracycline allergy may cause skin symptoms, gastrointestinal symptoms, and possibly respiratory symptoms.

Although drug resistance has not emerged at present, various antibiotics cannot be used casually. Only targeted use of various antibiotics can cure various diseases.

"Health News" constantly reported that various diseases in hospitals could not be cured. Li Ping'an knew that it was not the emergence of drug resistance, but the wrong choice of antibiotics.

With the electron microscope in the laboratory of the Sixth Academy, Li Ping'an wanted to conduct more in-depth research on various bacteria, and at the same time, he used drug susceptibility tests to find out the effects of various antibiotics on various bacteria.

in fact.

There is no need to bother to do experiments. These are some basic knowledge. They have been clearly studied in later generations and have been deeply imprinted in Li Ping'an's mind.

As long as the mechanism of action of various antibiotics remains unchanged, their effect on a certain type of bacteria is certain, and it is clear at a glance whether they can inhibit it.

To study the effect of antibiotics on certain bacteria, drug susceptibility testing is required.

In vitro antimicrobial susceptibility testing, referred to as drug susceptibility testing, refers to a test that measures the bacteriostatic or bactericidal ability of drugs in vitro.

For non-caustic bacteria (Enterobacteriaceae, Pseudomonas aeruginosa, and other non-enterobacteria, Staphylococcus bacteria, Enterococcus bacteria) and caustic bacteria (Haemophilus bacteria, Neisseria gonorrhoeae, pneumoniae and other streptococci), select the first choice drug for routine drug susceptibility testing (group A antibiotics) or the main antibiotic used clinically (group B antibiotics) for drug susceptibility testing.

The main methods for drug susceptibility testing in the laboratory include disk diffusion method, dilution method (including agar and broth dilution method), antibiotic concentration gradient method and automated instruments.

What can be done now is the first two methods,

The disk diffusion method is to stick a filter paper containing a quantitative amount of antibacterial drugs on the surface of agar that has been inoculated with test bacteria. The drugs in the paper diffuse in the agar. As the diffusion distance increases, the concentration of the antibacterial drugs decreases logarithmically. , thereby forming a concentration gradient around the paper.

At the same time, strains within the inhibitory concentration range around the paper cannot grow, while strains outside the inhibitory range can grow, thus forming a transparent inhibitory zone around the paper. The diameter of the inhibitory zone of different antibacterial drugs varies depending on the It may be affected by the diffusion rate of the drug in agar. The size of the inhibition zone can reflect the sensitivity of the test bacteria to the drug and is negatively correlated with the minimum inhibitory concentration of the drug against the test bacteria.

The dilution method drug susceptibility test can be used to quantitatively test the in vitro activity of antibacterial drugs against a certain bacteria, and is divided into agar dilution method and broth dilution method.

During experiments, the concentration of antibacterial drugs is usually diluted twice (lg2). The lowest drug concentration that can inhibit the visible growth of the bacteria to be tested becomes the minimum inhibitory concentration. The test concentration range of a specific antibacterial drug should include the interpretability that can detect the bacteria. The breakpoint (susceptible, intermediate and resistant) concentrations should also include the minimum inhibitory concentration of the quality control reference strain.

When there was no surgery scheduled, Li Ping'an took Qin Huairu to the laboratory to continuously culture, isolate and purify various bacteria, and then conduct various drug sensitivity tests.

When doing drug susceptibility testing, you can also conduct research on the mechanisms of action of various antibiotics.

The mechanism of action of various antibiotics on allergic bacteria can be observed through electron microscopy, including damaging the structure of cells.

Electron microscopes use a beam of electrons rather than visible light to form images, and their resolution is much higher than that of light microscopes.

The ultrastructure of DNA, including the helical arrangement of base pairs and the overall shape of the helix, can be observed with an electron microscope.

but.

With the microscopy technology of that era, if the mechanism of action of antibiotics was to hinder DNA transcription or reverse transcription, it would not be visible.

Domestic electron microscopes can only observe the overall shape of DNA.

but.

If there are more objects to observe, relevant conclusions can also be drawn.

therefore.

It would be reasonable for Li Ping'an to propose that certain antibiotics such as nalidixic acid kill pathogens by inhibiting DNA synthesis.

The mechanism of action of oxytetracycline is to bind to the 30S subunit of the ribosome of sensitive bacteria and prevent the elongation of the peptide chain, thereby exerting a bactericidal effect. At the same time, the drug can also interfere with the biosynthesis of bacterial cell walls, causing bacteria to swell, rupture, and die.

Under the conditions at the time, it could only be observed that oxytetracycline interferes with the synthesis of bacterial cell walls and thereby inhibits and kills pathogens. If Li Ping'an were to write a test report, that would be all he could say.

Penicillin's mechanism of action is to inhibit bacterial cell wall synthesis.

The mechanism of action of streptomycin is mainly to act on the ribosomes in bacteria, inhibit bacterial protein synthesis, and destroy the integrity of bacterial cell membranes, thereby achieving a bactericidal effect.

Sulfa drugs are bacteriostatic drugs that inhibit the growth and reproduction of bacteria by interfering with their folic acid metabolism.

This effect is also difficult to explain clearly.

Li Ping'an conducted countless sets of drug sensitivity tests and observed the action mechanisms of various antibiotics during the tests.

finally.

He wrote out all the experimental reports.

It's eloquent, with dozens of pages of content, and even the dedicated summary is several pages long.

Qin Huairu was unable to help most of the time when Li Pingan was doing experiments, and Li Pingan could do many experiments by himself.

Qin Huairu comes to clean the laboratory every morning and evening, and works in the pharmacy the rest of the time. Of course, Li Ping'an can also go to her when he needs help.

Li Pingan was familiar with these experiments and completed them in only a few days.

He knew that there were many key things that could not be disclosed casually, and experimental reports could not be published in newspapers or medical journals.

Li Pingan thought for a long time.

The reports he made could only have three destinations.

One is to hand it over to the Institute of Microbiology of the Ministry of Health. Ran Qian and his wife both work in the institute, so it is easy to hand it over to them.

The second is to give it to Xiaolu and ask her to give it to her father Chushan. Chushan is a biochemist and he should be interested in these things.