Question

1. Do a search online or look in your textbook for 1-2 antibiotics that affect Gram-positive bacteria and list them. On what part of the cell do the antibiotics usually work? List one or two antibiotics that affect Gram-negative bacteria? On what part of the cell do the antibiotics usually work? (Be sure to cite your sources in your answer.)

(textbook is openstax microbiology)

Answer 1

Two of the antibiotics that affect Gram-positive bacteria are Vancomycin and Teicoplanin.

These antibiotics interfere with the cell wall synthesis of bacteria.

Vancomycin tightly binds to the D alanyl D alanine residues of the phosphodisaccharide-pentapeptide during the second layer cell wall synthesis, thereby inhibiting further synthesis of cell wall.

(Watanakunakorn, C. (1984). Mode of action and in-vitro activity of vancomycin. Journal of Antimicrobial Chemotherapy, 14(suppl D), 7–18. doi:10.1093/jac/14.suppl_d.7 )

Two of the antibiotics affect the Gram negative bacteria are cephalosporins and aztreonam.

In general, the gram negative bacteria are covered with outer membrane. This prevents entry of most of the antibiotics.

Hence they have to be modiied for their entry via the pore channels of outer membrane. Though the mode of action for antibiotics is the same, means destroying the peptidoglycan layer. Or antibiotics like fluoroquinolones (e.g ciprofloxacin), bind to the DNA gyrase enzyme inhibiting the cell division process.

Kapoor, Garima, Saurabh Saigal, and Ashok Elongavan. "Action and resistance mechanisms of antibiotics: A guide for clinicians." Journal of anaesthesiology, clinical pharmacology 33.3 (2017): 300.