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YORK (Reuters Health) - The common method of testing for the
bacterium that is a leading cause of meningitis only detects
about one quarter of all carriers of the bacteria, study findings
suggest.
The
bacterium, Neisseria meningitidis, is normally detected
by examining cells swabbed from the back of the throat.
In a study of 32 patients who were having their tonsils
removed, swabbing detected N. meningitidis in about 10%
of the participants. This is roughly similar to the estimated
infection rate in the general population.
But
based on an analysis of tissue samples taken from the same
participants, the meningitis-causing bacterium was present
in 45% of the patients, UK researchers report in the November
11th issue of The Lancet.
In addition,
the bacteria were found deep within tissue, not only on
the surface of the tonsils as previously believed. They
appear to be able to hide out inside cells, evading detection
and avoiding eradication by antibiotics.
``The
results show that N. meningitidis is far more widespread
than previously thought,'' Dr. Christoph M. Tang, of John
Radcliffe Hospital in Oxford, UK, and colleagues conclude.
The
findings may lead to improved understanding of how the bacterium
spreads and why most infected people do not develop meningitis,
according to the researchers. The vast majority of people
do not suffer any ill effects of N. meningitidis. But in
a small group of people, the bacteria will invade other
parts of the body and in the case of meningitis, cause a
dangerous inflammation of the membranes surrounding the
brain and spinal cord.
In another
article in the same issue, investigators report that healthcare
workers have a greater risk of infection with N. meningitidis
than the general population does.
Based
on a review of cases of meningococcal disease in healthcare
workers in England and Wales from 1982 to 1996, Dr. Anna
Gilmore of Gloucestershire Royal Hospital in Gloucester,
UK, and colleagues estimate that about 0.8 out of every
100,000 hospital workers exposed to the bacterium becomes
sick. This risk is about 25 times greater than that of the
general population, but it is considerably lower than that
of people who live with someone who has meningitis.
Guidelines
for how healthcare workers should protect themselves from
the meningitis-causing bacterium vary from country to country,
the report indicates. Antibiotic treatment can reduce the
risk of becoming sick after being exposed to the organism,
but the drawbacks of antibiotics--including the risk that
the bacteria may become resistant to drugs--may outweigh
the benefits of treating all workers, the researchers note.
Assuming
that antibiotics are effective 90% of the time, about 144,000
healthcare workers would have to be treated to prevent one
case of disease, Gilmore's team explains. They suggest that
the current findings should be used to develop guidelines
for preventing meningococcal disease in healthcare workers.
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