Methods for Identifying Different Mycins

Representative drugs: vancomycin, norvancomycin, polymyxins, etc.

Antibacterial spectrum:
Polypeptide antibiotics generally have a relatively narrow antibacterial spectrum. Polymyxins are mainly effective against certain Gram-negative bacilli, including Escherichia coli, Klebsiella, Salmonella, Shigella, and Pseudomonas aeruginosa. Vancomycin and norvancomycin exhibit strong bactericidal activity against Gram-positive bacteria, particularly against organisms such as Bacteroides fragilis and Clostridium.

Uses:
Polymyxins are mainly used for topical treatment of infections caused by susceptible bacteria, including Pseudomonas aeruginosa infections of the ears, eyes, skin, mucous membranes, and burns. They may also be administered orally for intestinal preparation prior to surgery. Vancomycin and norvancomycin are commonly used to treat serious infections caused by methicillin-resistant staphylococci, including pneumonia, septicemia, endocarditis, osteomyelitis, and colitis.

Tetracycline Antibiotics

Representative drugs: tetracycline, oxytetracycline, aureomycin, demeclocycline, doxycycline, etc.

Antibacterial spectrum:
Tetracyclines possess a broad antibacterial spectrum, covering many Gram-positive and Gram-negative aerobic bacteria, anaerobic bacteria, as well as organisms such as rickettsia, spirochetes, and mycoplasma.

Uses:
This class of antibiotics is particularly effective in the treatment of rickettsial infections such as typhus and scrub typhus. It is also widely used for conditions including inflammatory diseases, salpingitis, and trachoma. In addition, tetracyclines demonstrate therapeutic effects against diseases such as plague, cholera, brucellosis, and granuloma inguinale.

Clinical application:
Tetracyclines are commonly used in clinical practice for treating rickettsial infections, chlamydial infections, mycoplasma infections, and spirochetal diseases. Among them, doxycycline is generally considered the first-line option.

Chloramphenicol Antibiotics

Representative drugs: chloramphenicol, thiamphenicol

Antibacterial spectrum:
The antibacterial spectrum of chloramphenicol is similar to that of tetracyclines and is considered broad-spectrum.

Uses:
Chloramphenicol can be used to treat severe infections caused by susceptible bacteria, such as typhoid fever, paratyphoid fever, and meningitis caused by Haemophilus influenzae. It is also used topically for the treatment of trachoma, conjunctivitis, and superficial ear infections. Thiamphenicol is primarily used clinically to treat typhoid fever, paratyphoid fever, and other Salmonella infections.

Antibacterial range:
Chloramphenicol exhibits broad antibacterial activity. Among aerobic Gram-positive bacteria, it is active against organisms such as Streptococcus viridans, Corynebacterium diphtheriae, Bacillus anthracis, Staphylococcus aureus, Streptococcus hemolyticus, and Streptococcus pneumoniae, although its activity against Group D streptococci is relatively weak.

Among aerobic Gram-negative bacteria, it shows strong activity against Haemophilus influenzae, Shigella, Bordetella pertussis, Neisseria gonorrhoeae, and Neisseria meningitidis. It is also effective against Salmonella, Escherichia coli, Proteus mirabilis, and Vibrio cholerae, while showing limited activity against Serratia marcescens, Enterobacter, and Klebsiella pneumoniae.

Many anaerobic bacteria, including Enterococcus, Streptococcus, Clostridium perfringens, Clostridium, and Bacteroides fragilis, can also be inhibited by chloramphenicol. In addition, it is effective against most rickettsia, chlamydia, and mycoplasma. However, it has no inhibitory effect on Pseudomonas aeruginosa, indole-positive Proteus, Mycobacterium tuberculosis, fungi, viruses, or protozoa.

With long-term clinical use, many bacteria have developed varying degrees of resistance to chloramphenicol, although resistance levels differ by region and time. The primary resistance mechanism involves plasmid-mediated production of chloramphenicol acetyltransferase, which acetylates the 3-hydroxyl group of chloramphenicol, preventing the drug from binding to the 50S ribosomal subunit and thereby inactivating it. These resistance genes can also be transferred to other bacteria through genetic exchange mechanisms such as conjugation or transposition. In some cases, resistant strains may gradually disappear and regain sensitivity after the drug has been discontinued for a period of time.