Tetracyclines

Tetracyclines, like macrolides, inhibit protein synthesis in bacteria. The vital element of this process is the energy-requiring transfer of the drug through the cytoplasmic membrane, which leads to its accumulation in the cell. Inside the cell, it reversibly binds with 30 S ribosomal subunits of the bacteria. This process prevents aminoacyl tRNA from binding with mRNA (30 S ribosome), which leads to an inhibition of protein synthesis. The selective toxicity of tetracyclines lies in its diverse ability to penetrate bacterial cells and mammalian cells that lack a proper system of transport. The antimicrobial spectrum of all tetracyclines is practically the same. The difference is only observed in the degree of activity with respect to these or other microorganisms. Tetracyclines are active with respect to a huge variety of microorganisms, including Gram-positive, Gram-negative, aerobic, and anaerobic. They are active with respect to spirochaeta, mycoplasma, Bacteria Rickettsia, chlamydia, and a few protozoal infections. However, they are not active with respect to streptococci infections, blue-pus bacillus, and a few others. Resistance to tetracyclines is exhibited as a reduced ability of bacteria to accumulate the antibiotic inside the cell. This process is mediated by plas-mids. As a rule, resistance with respect to any of these tetracyclines indicates resistance to all of the others.

Tetracyclines are the drug of choice with respect to a broad number of infections, including chlamydia, Bacteria Rickettsia, and others.

Chlorotetracycline: Chlorotetracyline, 7-chloro-4-dimethylamino-1,4,4a,5,5a,6,11,12a-oxtahydro-3,6,10,12,12a-pentahydroxy-6-methyl-1,11-dioxo-2-naphthacencarboxamide (32.3.1), is obtained biosynthetically as a result of the activity of a microorganism, the actin-omycete S. aureofaciens [196-201].

Chlorotetracycline, an antibiotic with a broad spectrum of action, causes a bacteriostatic effect with respect to Gram-positive (staphylococci, including those that produce penicillinase; streptococci, pneumococci; clostridia, listeria, and anthrax bacillus) and Gram-negative microorganisms (gonococci, whooping cough bacillus, colon bacillus, enterobacteria, klebisella, salmonella, shigella), as well as Rickettsia, chlamydia, mycoplasma, and spirochaeta. Blue-pus bacillus, proteus, serracia, most strains of Bacteroides fragilis, most fungi, and small viruses are resistant to this drug. It is used for pneumonia, bronchitis, empyema of the lungs, angina, cholecystitis, whooping cough, endocarditis, endometritis, intestinal infections, prostatitis, syphilis, gonorrhea, brucellosis, osteomyelitis, purulent infections of soft tissues, and others caused by microorganisms sensitive to this drug. Synonyms of this drug are aureomycin, biomycin, xanthomycin, and others.

Oxytetracycline: Oxytetracycline, 4-dimethylamino-1,4,4a,5,5a,6,11,12a-octahydro-3,6,10,12,12a-hexahydroxy-6-methyl-1,11 -dioxo-2-naphthacencarboxamide (32.3.2), is n i ohii n oh o oh o o

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