Killer in the Bloodstream

Assaulting the body

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Meningococcal bacteria can cause two life-threatening conditions: meningitis and sepsis.

In meningitis, the bacteria attack the lining around the brain called the meninges. They breach the meninges to infect the fluid running into the spinal cord. One clear, early symptom is a stiff, sore neck. The meninges and brain start to swell, putting pressure on essential nerves. Fewer than one in 50 victims of meningococcal meningitis will die, but survivors are often left deaf or with permanent brain damage.

The other type of infection is much more deadly, killing roughly 20 percent of its victims. It's a severe blood poisoning called meningococcal sepsis that affects the entire body. The bacterial toxins rupture blood vessels and can rapidly shut down vital organs.

Entering the throat

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Meningococcal bacteria commonly live in the human throat without causing harm. But sometimes they break through the throat's lining and enter the bloodstream. The reasons why and how are only now being unraveled. Damage to the throat from flu and other infections could be one factor.

Hurtling through the bloodstream

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Every meningococcal bacterium is surrounded by a slimy outer coat that contains a poisonous chemical called an endotoxin. While many bacteria produce endotoxin, the levels produced by meningococcal bacteria are 100 to 1,000 times greater than normal.

As the bacteria multiply and move through the bloodstream, they shed bubbles that contain concentrated amounts of toxin. These bubbles also act as decoys, confusing the body's immune system. The endotoxin targets the heart, affecting its ability to pump and also causes blood vessels throughout the body to leak. As every vessel starts to hemorrhage, major organs like the lungs and kidneys are damaged and eventually destroyed.

Two things can stop this runaway infection before the patient dies: antibiotics like penicillin, and the patient's own immune system.

Attacked by antibiotics

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As soon as doctors suspect meningococcal disease, patients are given a large dose of antibiotic, usually penicillin. Penicillin flowing through the bloodstream rapidly kills the bacteria. But it cannot penetrate the bubbles that contain the endotoxin. In fact, as the bacteria are killed, they release even more toxin. It takes up to two days for the poison to be cleared from the body and the siege to end.

Killing tissue

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As soon as the bacteria entered the bloodstream, unleashing the poisonous endotoxin, the body began responding on its own. White blood cells, the hunter-killers of the immune system, locked onto the bacteria, engulfing them and coming into contact with the endotoxin.

The poison causes the white cells to release chemicals that make the blood vessel walls sticky. The white cells then become trapped on the walls, leaving a trail of damage. Gradually the lining of the blood vessels is stripped away. And as the damage increases, the vessel walls break up and pieces fall off. The blood's repair cells, called platelets, rush to plug up the damaged areas.

Dangerous clots begin to form. The proteins that normally prevent clotting have all been destroyed. Within minutes the small blood vessels of the body are completely blocked. The damaged blood vessels disintegrate, and blood and other fluids hemorrhage into the surrounding tissue. It is this cascade of events that causes the distinctive rash that appears beneath the skin and kills tissue throughout the body.