The Secret Life of Bacteria

Bacteria seem to have a limitless capacity to surprise us. They are found living off boiling sulphur on the ocean bed and feeding off rocks deep within the Earth's crust. Once we thought we could control them with antibiotics; then they fought back by developing resistance. Now it seems that they have been making us ill all the time in ways we were not even aware of. New findings suggest that conditions as different as kidney stones, obsessive compulsive disorder, Tourette's syndrome, heart disease and arthritis may all be the result of hitherto unrecognised bacterial infections.

Years ago, a Finnish researcher - Olavi Kajander of Kupio university - caused a stir when he suggested that kidney stones could be caused by a type of tiny bacteria, found in the blood of humans and cows, which build a hard mineral shell round themselves for protection. The coats of these nanobacteria, so-called because they are only 0.1 micrometers long, are made out of a similar sort of material to that found in kidney stones. This set Kajander wondering whether the two were connected. He examined 30 kidney stones and found that they all contained the bacteria. "Not proof," he admits, "but it's strong evidence." Dr Dennis Carson of the University of California, San Diego, has suggested that nanobacteria may also be implicated in other disorders, such as heart disease, some tumours, and dementia caused by excess calcium deposits in the brain.

In fact, bacteria have been turning up as the unsuspected cause of chronic infections ever since 1982, when two young Australian physicians, Barry Marshall and Robin Warren, isolated bacteria from patients with ulcers or gastritis (stomach inflammation). They made the radical proposal that a spiral-shaped bacterium, later named Helicobacter pylori, causes gastritis and possibly ulcers. At the time no one took them seriously; everyone "knew" that ulcers were caused by stress.

It was a neat coincidence that the pylori-ulcer link was made exactly 100 years after Heinrich Koch discovered the link between bacteria and tuberculosis, dismissed at the time because everyone believed an excess of emotions caused tuberculosis. In fact, it was not until February 1994 that the pylori-ulcer connection was officially recognised by the medical profession.

Acceptance was so slow partly because ulcers fail to conform with our notion of an infectious disease. Infections, with some exceptions such as leprosy and tuberculosis, are acute. You have a swelling, inflammation, maybe pain, maybe a fever, you are ill for days or a few weeks at the most, and then you either die or recover. But it now seems that such chronic conditions as arthritis, hardening of the arteries and even cancer may be linked with bacteria.

Pylori, for instance, seems associated with stomach cancer - having pylori increases the risk about sixfold - but there must be other factors, since only 1 per cent of people with pylori get stomach cancer. About 50 per cent of patients with lymphoma, an uncommon form of stomach cancer, do seem to be cured when pylori is wiped out with antibiotics.

Findings like these prompted the International Conference on Emerging Infectious Diseases, held in Atlanta by America's Centers for Disease Control, to devote a session to chronic diseases and bacteria earlier this year. One of the new villains of the occasion was Chlamydia pneumoniae, well known for causing pneumonia, which is now accused of being involved in some cases of arthritis and asthma, and, more seriously, heart disease.

In the last few years this bug, once thought to live only in the nose and throat, has been found taking up residence in the fatty "plaques" that accumulate on the insides of blood vessel walls when the arteries fur up. Research by Dr Sandeep Gupta, of St George's hospital in London, found that patients with evidence of pneumoniae infection were as much as four times more likely to suffer further heart problems over an 18- month period - a difference that vanished after the patients were given a three-day course of antibiotics.

The experts are still cautious about declaring that pneumoniae is helping to build the plaques, rather than just living in them, but the case for the prosecution is getting stronger. A recent experiment by Dr Robert Molestina, at the University of Louisville in Kentucky, has shown that pneumoniae causes cells from the artery wall to produce molecules called chemokines. These are chemical cries for help, and attract the defence team of the immune system, which produce inflammation - the way the body normally deals with infection. Researchers are now trying to clarify why the inflammation does not clear up, as it does with most infections.

In fact, inflammation is at the bottom of this new connection between bacteria and chronic diseases. The origins of a number of conditions that involve long-term inflammation, such as arthritis, Crohn's disease (in the gut) and ulcers have always been mysterious, but now bacteria that cause food poisoning, such as salmonella and campylobacter, are turning out to be likely culprits, at least in some cases.When it is the brain that gets inflamed, behaviour can be affected, which accounts for the even more surprising link between bacteria and psychiatric disorders such as autism and anorexia. The villain of this connection is streptococcus, another bacteria that normally gives you a sore throat. But in rare cases children produce antibodies against the infection, which then destroy cells in an area of the brain known as the caudate nucleus of the basal ganglia. From PET scans we know that this is a region of the brain that is hyperactive in people with obsessive compulsive disorder (OCD). The basal ganglia are involved in the control of movement and emotion.

Dr Susan Swedo, a neuroscientist at the American National Institute of Mental Health, has discovered that a significant proportion of OCD patients suffered from a severe "strep" infection in childhood. She has christened this link Pandas - paediatric autoimmune neuropsychiatric disorders associated with streptococcus - and the panda has now become the mascot of the American OCD support groups.

Now this oddly specific link between streptococcus and the caudate nucleus has been suggested as a possible cause for Tourette's syndrome, a condition that gives sufferers an overwhelming compulsion to repeat certain actions or phrases, often obscene ones. Earlier this month Dr Harvey Singer, of the Johns Hopkins University School of Medicine in Baltimore, Maryland, wrote an article in the British Journal of Medicine pointing out that Tourette's can first appear following strep infection, and it can get much worse if you already have it. She reported a study that found streptococcus antibodies in this area of the brain in a groups of children with Tourette's, compared to none in the brains of a normal group.

Dr Singer is following in the steps of other American researchers who have also found evidence of these antibodies in the blood of patients with autism and with anorexia, both conditions involving strong elements of compulsion and obsession. No one is suggesting this is the only cause. but Dr Mae Sokal, of the Menninger Clinic in Topeka, Kansas, has reported success in treating "elevated antibody anorexics" as they are known, with a course of antibiotics has lead to dramatic improvement.

It seems that bacteria still have plenty of surprises in store for us.

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Provided by ProQuest Information and Learning Company
by Jerome Burne