Out of gram positive or gram negative or both which one is having a higher resistance to drug or antibiotics? How the organism gains that gene for drug or antibiotics resistance.? Kindly explain it in detail.

  • $\begingroup$ This is basically a homework question (simple question without any effort to solve it yourself), you are lucky that this slipped through. It is also kind of broad. Please do some research yourself in the future and state what your problems are. $\endgroup$ – Chris Aug 1 '16 at 13:54
  • $\begingroup$ @Chris it can still be downvoted and closed as homework, even if it was answered. These kinds of "do all my work for me" questions are unacceptable on this site. $\endgroup$ – MattDMo Aug 2 '16 at 21:18
  • $\begingroup$ @MattDMo Correct point. It will not disappear, though. $\endgroup$ – Chris Aug 2 '16 at 21:28
  • $\begingroup$ Sorry people.. !! 😞 I'll not do it again..!!😞 $\endgroup$ – Ashwin.N Aug 3 '16 at 15:46

The major effect of drugs or antibiotics on bacterium is on its cell wall. Gram positive bacteria have a thick outer layer of a polymer called peptidoglycan (formed by repeated units of a disaccharide: NAG-NAM) which has many cross-linkages. Beta-lactam antibiotics such as penicillin, cephalosporin etc. competitively inhibit an enzyme called transpeptidase (also penicillin binding protein); which forms the cross-linkages in peptidoglycan; and thus weakening the cell wall. As a result of which osmotic pressure now becomes enough to cause lysis of cell wall and hence the bacterium dies. Also drugs such as Vancomycin inhibit the formation of peptidoglycan polymer.

On the other hand, gram negative bacteria have an outer layer of lipopolysaccharide (endotoxin) beneath which lies a thin cell wall of peptidoglycan. Hence beta-lactam antibiotics do not have much of an effect on the gram negative bacteria.

enter image description here

To conclude, gram positive bacteria are much more sensitive to beta-lactam antibiotics and lysozyme than gram negative bacteria. Also it is worth mentioning that gram negative bacteria are more sensitive to the lytic action of anti-bodies because lipopolysaccharide in their outer membrane produces a high immune response (read about Sepsis for more details on endotoxin).

Hope this is helpful.

  • $\begingroup$ Yea thank you.. simple and good explanation...!! 😃 $\endgroup$ – Ashwin.N Aug 1 '16 at 12:05
  • $\begingroup$ Is there any drug or antibiotics which can be effective for gram negative organisms? $\endgroup$ – Ashwin.N Aug 1 '16 at 13:35
  • $\begingroup$ Yes. Gram negative bacteria are sensitive towards detergent like antibiotics which dissolve the outer membrane. Example- Polymyxin disrupts the integrity of the outer membrane (but it has some toxic effect too). $\endgroup$ – Ramil Aug 1 '16 at 14:48
  • $\begingroup$ Hey, remember there are many other ways to inhibit the bacterial infection which do not involve degradation of bacterial cell coat. $\endgroup$ – Ramil Aug 1 '16 at 14:50

Not the answer you're looking for? Browse other questions tagged or ask your own question.