NEW 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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