Even though gram-positive bacteria has a thick cell wall than the gram-negative bacteria, then why only gram-negative bacteria are more resistant to antibiotics....
resistance to antibiotics refer to genes of resistance, not cell wall.
some class of antibiotics affect forming cell wall even in this case we have gram negative and positive bacteria that are resistance.
some of them change structure of component of cell walls the other secret proteins that inactive antibiotics.
on the other hand maybe more resistance of GN bacteria because they have pre plasmic that cause reaching of antibiotics to bacteria be harder and identification of them be easier by bacteria and they can fight back better.
Antibiotics act on specific site receptors of cell wall and any modifications in that sites causes resistance. Such modifications are genetically encoded and resistance are therefore due to thickning in cell wall or modification else, Resistance are known now in both G -ve and G +ve bacteria. It started since long years in G+ve such as MRSA and VRSA and enterococci (G+ve) and Strepto. pyogenes. Also in G-ve like Pseudomonas. Thickness is not a matter. G-ve bacteria have,in addition to the usuall cytoplasmic membrane, have a second thin phospholipid bilayer external to the peptidoglycan called the outer membrane that make another barrier against certain antibiotics.
Resistance against antibiotics has no relationship with the cell wall thickness but some exeption is there in the case of antibiotics that act on cell wall.
Such antibiotics requires the need of cell wall to alter its production thus affecting it's multiplication.
That is the reason why penicillins don't affect mycoplasma (don't have cell wall)
All other antibiotic resistance origins due to alterations in the genetic make up of the organism due to mutations and other such gene altering processes.
The outer membrane of GNB excludes certain antibiotics from penetrating the cell.
The Gram-Negative Bacteria such as Acinetobacter baumanii, Pseudomonas aeruginosa, Salmonella spp. and other G- bacteria are resistant to antibiotics, because the outer membrane of these bacteria has promoted antimicrobial resistance and interpreted bacterial signals from membrane-damaging agents, including antibiotics. Then it has protected the bacteria against damage come from antibiotics.
The distinctive feature of gram-negative bacteria is the presence of a double membrane surrounding each bacterial cell. Although all bacteria have an inner cell membrane, gram-negative bacteria have a unique outer membrane. This outer membrane excludes certain drugs and antibiotics from penetrating the cell, partially accounting for why gram-negative bacteria are generally more resistant to antibiotics than are gram-positive bacteria.
Gram positive cell walls are highly porous in nature. Gram negative cell walls contain high lipid content and the transport of antibiotics depends mainly on the outer membrane proteins. Multiple drug resistant mechanisms like efflux pump, enzyme alteration , alteration of target sites etc confers resistance to most of the antibiotics.
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