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Part of describing the function of an antibiotic is stating whether it is effective against Gram-positive bacteria, Gram-negative bacteria or both. (There are other aspects such as whether there is effect on aerobic versus anaerobic bacteria (those that can versus cannot survive in the presence of oxygen), but I'll address that some other time).

Some antibiotics have broad spectrum activity, being able to kill Gram-positive and Gram-negative bacteria. At first that might seem like a good thing, and indeed it is when you are treating an infection with an unknown bacterium. However, broad spectrum activity is not desirable when you know exactly what bacterium you are trying to eliminate. If possible, it's much better to target treatment more specifically against the offending bacterium for various reasons, such as to reduce the risk of resistance emerging in other bacterial groups.

Some antibiotics are narrow spectrum. Some are most effective against Gram-positive or Gram-negative bacteria, with little activity against the other. In general, we want to use an antibiotic of the most narrow spectrum possible.

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15y ago

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Why gram positive bacteria typically more resistant that gram negative bacteria to antibiotics that disrupt plasma membranes such as polymyxin B?

Polymixin antibiotics interact with the lipopolysaccharide molecule of Gram negative bacteria. This component forms the outer leaflet of the outer membrane. Gram-positive bacteria do not have an outer membrane or lipopolysaccharide and thus polymixin antibiotics are unable to bind to the cell.


List of antibiotics active against gram positive bacteria?

ciprofloxacin penicillin


What are the positive and negative aspects about bacteria?

The positive aspect about bacteria is that weak bacteria can be used to prevent or defend against other bacteria that harms the body which is the negative aspect of bacteria.


What is a narrow spectrum antibiotic effective against?

Narrow spectrum antibiotics are effective against just gram positive bacteria, just gram negative bacteria, or only a few specified species. Examples include: penicillin G, gentamicin, clindamycin, and gentamicin.


Does Tetracycline kill gram positive or gram negative bacteria?

Tetracycline kills both gram positive and gram negative bacteria. The mode of action to which Tetracycline works to kill bacteria is that it inhibits protein synthesis which works against both gram positive and gram negative bacteria.


What group of antibiotics vancomycin belongs to?

Vancomycin belongs to the class of antibiotics known as glycopeptides. These antibiotics work by inhibiting cell wall synthesis in certain bacteria, making them effective against a variety of gram-positive bacteria.


Differentiate between broad-spectrum and narrow-spectrum antibiotics?

A broad-spectrum antibiotic acts against many different kinds of disease-causing bacteria, including both gram-positive and gram-negative bacteria. A narrow-spectrum antibiotic acts only against specific families of bacteria.


Is penicillin more effective against Gram negative or Gram positive?

Penicillin is more effective against Gram positive bacteria. This is because the peptidoglycan layer of Gram negative bacteria acts as a barrier that makes them less susceptible to penicillin.


Why might a gram-negative infection be harder to treat than gram-positive infection?

In short, it's because they have a membrane around their cell wall that both increases their toxicity, and makes them more resistant to antibiotics. It makes them more resistant because many antibiotics, such as penicillin, work by destroying the cell walls of bacteria. Because they have an extra membrane around their cell walls, gram negative bacteria have extra protection against the antibiotics.


Why don't you treat a virus with antibiotics?

antibiotics are only affective against bacteria, and a virus is different then bacteria


Antimicrobics effective against only gram positive bacteria would be termed?

narrow-spectrum drugs


Do antibiotics work against bacteria?

antibiotics are useful against bacteria because they help to kill off the nasty bacteria or they can also stop the bacteria from reproducing - so the illness doesn't get worse. this then gives your body time to make antibodies which will eventually distroy the bacteria. after this, you won't get the disease again because you are immune to it.