Gram Negative Bacteria

Gram negative bacteria (Pseudomonas aeruginosa) are simply called so because of their detection by the Gram staining test in which they do not retain the crystal violet color (dye) in their cell wall. The Gram negative bacterial 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 bacterial cell wall is made up of lipopolysaccharide 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 bacterial 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 lipopolysaccharide, there exist layers of periplasmic 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 bacterial 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 a 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.

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

Along with the bacteria mentioned above, there are several other types of Gram negative bacteria such as Haemophilus influenzae (also known as Bacillus influenzae), Neisseria meningitidis, Moraxella catarrhalis, Neisseria gonorrhoeae, Acinetobacter baumanii (which comes under Nosocomial Gram negative bacterial group).

What are the Causes of Gram Negative Bacterial Infection
Gram negative bacterial infection leads to endotoxemia in which the endotoxin (a toxic substance associated with bacterial cell wall or core) comes in contact with bloodstreams 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 to harm the tissues. The Gram negative bacteria can be killed using medication but the endotoxin 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 bloodstreams and spread to various parts of the body. Once the spread of endotoxin starts in the body, the body's immune system releases an inflammatory substance in the body and causes the body temperature to rise (mild fever). If the presence of endotoxin inside the body is below normal level, which our immune system can fight back, then in such a 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 normal, then in such cases, 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 the 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 endotoxic shock are:

• Due to the inflammatory substance released by the body's immune system in reaction to the endotoxin, the host experiences mild fever at the beginning of the endotoxic shock.
• The host may also experience lack of hunger.
• Mild mental and physical depression can be experienced.
• Due to the spread of toxic substance, the host also experiences increase in heart rate and low pulse pressure.
• Problems like cold feet, cold ears and dehydration also are seen in the host suffering from endotoxic shock.
• The body temperature of the host shows sudden increase or decrease at any given time.
• Diarrhea is another symptom that is experienced.

Treatments Available for Gram Negative Bacterial Infection
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 a 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 the doctor.