This module present several of the most important antibiotics used in medicine and their modes of action. The primary target of the antibiotic such as cell wall synthesis, DNA replication and metabolic protein inhibition is discussed.
With advances in organic chemistry many antibiotics are now also obtained by chemical synthesis, such as the sulfa drugs. Drugs used in the chemotherapy of infectious diseases are classified into two groups. Drugs that have been synthesized by chemical procedures in the laboratory are called synthetic drugs while those produced by bacteria and fungi are called antibiotics 2.
The effects of the antibiotic drug ceftazidine on Staphylococcus aureus bacteria. The antibiotic kills the bacteria (red) by causing the cell wall to disintegrate (yellow remnants).
Schallmey 21, isolated soil bacteria which shows antibiotic activity under normal growth condition and was found inhibiting some gram positive and some gram negative organism both Bacillus lentus and Bacillus alvei also shows antibacterial activity against Staphylococcus aureus. Bacillus pumillus only show slight zone of inhibition on Proteus spp while it is inactive against others.
“Our structural studies revealed that the streptomycin induces surprisingly large distortions in the bacterial ribosome, which help us understand how this antibiotic interferes with protein synthesis in bacteria,” said lead researcher Gerwald Jogl, an associate professor of biology in Brown's Molecular Biology, Cell Biology & Biochemistry Department. “Continuing from our current findings, we are now studying how mutations in bacterial ribosomes can counteract these structural rearrangements and enable bacteria to survive the otherwise lethal action of streptomycin.”
mechanism, not producing an antisense RNA that is complementary to a mRNA leads to mRNA continues to be translated into enzyme, producing beta-lactamases action, beta-lactam antibiotics no longer bind to transpeptidase examples of beta- lactam antibiotics, altering the membranes and transport systems to prevent the entry of the antibiotic into the bacterium and/or ausing an efflux pump to transport the antibiotic out of the bacterium examples altering porins in the outer membrane of gram-negative cell walls, mutation alters genes Gene products enable the bacterium to become resistant to an antibiotic or chemical agent., result insufficient antibiotic to tie up all the enzyme, when drug is gone, result insufficient antibiotic within the bacterium, Gene products enable the bacterium to become resistant to an antibiotic or chemical agent.
Aminoglycosides are rapidly bactericidal antibiotics which inhibit protein synthesis. These agents mainly interfere with proofreading process. Aminoglycosides are the only bactericidal class among protein synthesis inhibitors.
mechanism altering the membranes and transport systems to prevent the entry of the antibiotic into the bacterium and/or ausing an efflux pump to transport the antibiotic out of the bacterium, action blocks active transport, enhancing the function of RNA polymerase leads to, enzymatically adding new chemical groups to aminoglycosides action, mRNA continues to be translated into enzyme leads to increased synthesis of the limited enzyme, Gene products enable the bacterium to become resistant to an antibiotic or chemical agent.
mechanism, examples not producing an antisense RNA that is complementary to a mRNA, altering porins in the outer membrane of gram-negative cell walls result, producing an altered 30S or 50S ribosomal subunit to which antibiotic no longer binds example
Cephalosporins are mainly bactericidal and act by inhibiting the synthesis of the peptidoglycan layer of bacterial cell walls. Besides cephalosporins (which are derived from cephalosporin C) this class includes oxacephems and carbacephems.
Sulfonamides act by inhibiting the pathway that bacteria use to synthesize folic acid. Sulfonamides with trimethoprim produce synergistic antibacterial activity.
Antibiotics of the penicillin class are bactericidal and work by inhibiting the synthesis of bacterial cell walls. Penicillins are among the safest antibiotics.
Streptomycin was the first antibiotic developed to treat tuberculosis yet until recently, scientists did not completely understand how it works at the molecular level. They knew that streptomycin blocks a critical process, the synthesis of proteins by ribosomes leading to bacterial cell death, but certain details of the interaction remained undiscovered. At Brookhaven National Laboratory’s National Synchrotron Light Source, researchers have used x-ray crystallography to complete the picture.
Streptomycin is a member of a family of antibiotics that work by interrupting the function of bacteria cells' ribosomes, the complex molecular machines that create proteins by linking amino acids together. Ribosomes, a major target for antibiotics that work by inhibiting the synthesis of proteins, have two main parts or “subunits.”