Gram Negative Bacteria

Why they are called Gram Negative Bacteria?
Gram-Negative Bacteria (Pseudomonas Aeruginosa) are simply called so because of their detection by the Gram’s Stain test in which they do not retain the crystal violet color (dye) in their cell wall. The Gram-Negative bacteria cell-wall holds the pink or reddish dye once a counterstain chemical is used.

Cell-wall Structure of Gram-Negative Bacteria:
The outer layer of Gram Negative bacteria cell-wall is made up of Lypopolysaccharide and Protein (core and O-polysaccharide and Lipid A) and it covers a very few thinner layers of Peptidoglycan as compared to Gram Positive bacteria (Peptidoglycan forms the outer layer of the Gram Positive bacteria cell-wall) and does not contain lipoproteins. The outer layer of the cell wall contains porins (pore like structure for a specific type of molecule). Below the outer layer of Lypopolysaccharide, there exist layers of peri-plasmic space (space between two layers of peptidoglycan and internal cell membrane) and plasma membrane. Some Gram Negative bacteria also have flagella with four surrounding rings.

The cell wall of Gram Negative bacteria also home a component that helps in Endotoxic activity and it also has pyrogenic effects associated with the Gram Negative infections. The Gram-Negative bacteria side wall also has a part which is called side chain that is made up of Lipopolysaccharide (and has hexoses in various chemical compositions as part of its structures). These side chains carry bases of somatic antigen. These side chains are very important in order to classify the Gram Negative bacteria based on their chemical composition.

Gram-Negative Bacteria Examples:
There are many groups of Gram-Negative bacteria such as Cyanobacteria, Spirochaetes, Green-Sulphur and Green Non-Sulphur Bacteria and Proteobacteria etc. Out of which, proteobacteria is one of the major group of known Gram-Negative bacteria (it includes bacteria like E-coli, Salmonella, Pseudomonas, Moraxella, Helicobacter, Stenotrophomonas, Legionella, Acetic Acid Bacteria etc.).

Along with the above mentioned bacteria, there are several other type of Gram-Negative bacteria such as Hemophilus influenzae (also known as Bacillus influenzae), Neisseria Meningitidis, Moraxella Catarrhalis, Neisseria Gonorrhoeae, Acinetobacter Baumanii (which comes under Nosocomical Gram-Negative bacteria group).

What do Gram-Negative bacteria cause?
Gram-Negative bacteria infection leads to endotoxemia in which the endotoxin (a toxic substance associated with bacteria cell wall or core) come in contact with blood streams and gets mixed with blood. Once the endotoxin is mixed in blood, it becomes very hard to stop the toxic substance from harming/destroying healthy tissues and also causing inflammation of the tissues. The substance can reach any part of the body and start harm to the tissues. The Gram-Negative bacteria can be killed using medication but the endotoxin substance is very hard to clean from the blood.

Generally millions of Gram-Negative bacteria are present in animal intestine and a very small level of endotoxin associated with these bacteria is also cleaned/detoxified by liver, but once the level of endotoxin increases it may reach blood streams and spread to various parts of the body. Once the spread of endotoxin starts in body, the body immune system releases inflammatory substance in the body and causes the body temperature to rise (mild fever). If the presence of endotoxin inside the body is below the normal level which our immune system can fight back, then in such case destruction and inflammation of tissues at a very small level is the only harm the infection causes, but if the level of endotoxin is higher than the normal, then in such case the infection can be life-threatening in extreme cases (the effect/intensity of the infection depends on the amount of endotoxin present inside the body of host). The spread of endotoxin inside the host body and inflammatory reaction by the immune system is called endotoxic shock.

What are primary symptoms of endotoxic shock?
The preliminary symptoms of the endotoxic shock are:
1) Due to the inflammatory substance released by the body’s immune system in reaction to the endotoxin, the host experiences mild fever in the beginning of the endotoxic shock.
2) The host may also experience lack of hunger
3) Mild mental and physical depression
4) Due to the spread of toxic substance the host also experiences increase in heart rates and low pulse pressure
5) Problems like cold feet, cold ears and dehydration also are seen in the host suffering from endotoxic shock
6) The body temperature of the host shows sudden increase of decrease at any given time
7) Diarrhea, etc.

Treatments available for Gram-Negative bacteria?
Gram-Negative bacteria are protected against most of the antibiotics, detergents and chemicals by their outer cell-wall. Many commonly used antibiotics do not work against Gram-Negative bacteria; fortunately there are few antibiotics which work against them. In order to let the antibiotics work properly and stop the Gram-Negative bacteria from building resistance against those medicines, it is necessary that the patient should complete the course of antibiotics prescribed by doctor.