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Meningococcemia is a bloodstream infection cause by the
bacteriumNeisseria meningitidis.
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N. meningitidis is a contagious bacterium and is spread
from person to person via respiratory secretions.
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Initially, patients present with fever and general aches. A rash is often present. Patients with
meningococcemia are seriously ill.
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Complications include shock,
failure of multiple organs, lack of circulation to the extremities, and death.
Patients may also develop or present with meningitis.
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Meningococcemia is treated with intravenous antibiotics.
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Case fatality rates are as high as 19% in industrialized
countries. Early treatment reduces the risk of complications and death.
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A vaccine is available to help prevent four of the
five most common serogroups that cause meningococcemia. The vaccine is
recommended at 11 years of age, with a booster dose at 16 years of age.
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People who have a certain type of immune deficiency in the
complement system and people with missing or damaged spleens are at increased
risk and should be vaccinated.
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People who travel to areas where outbreaks are occurring should
be vaccinated before travel.
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People who have had close contact with an infected patient (for
example, a household member with face-to-face contact, a child's playmate,
etc.) should receive antibiotics to reduce the risk of disease. These
"prophylactic" antibiotics should be started as soon as possible but
certainly within two weeks of exposure.
What is meningococcemia?
Meningococcemia
is a bacterial infection of the blood due to Neisseria meningitidis. This bacterium is most famous
for causing meningococcal meningitis which may also be present in
meningococcemia. Bloodstream infections are sometimes called "blood
poisoning" or septicemia. Many
bacteria can cause bloodstream infections including staphylococci,
Streptococcus B, or Streptococcus A. In addition, other bacteria can cause
meningitis, including Streptococcus pneumoniae or leptospirosis. However, N. meningitidis is concerning because it is more
contagious than these other bacteria and typically infects older children andadolescents.
What causes meningococcemia?
As mentioned, the
bacterium that causes meningococcemia is called N. meningitidis,
also known as "meningococcus." Meningococcemia may also be called
meningococcal bacteremia. Under the microscope, the bacteria may appear in
pairs, looking like two small kidney beans side by side. N. meningitidis is surrounded by a capsule made of complex
carbohydrates called polysaccharides. These polysaccharides stimulate the
immune system, which helps the body fight the infection. There are several
different types (serogroups) of meningococci. Most human disease is caused by
serogroups A, B, C, Y, and W135. Bacteria from other serogroups are called
"nonpathogenic," meaning that they do not cause disease.
Transmission of N. meningitidis is from person to person through respiratory
secretions. Some people can harbor the bacteria in their throats and not get
sick, which is called a "carrier" state. In others, the bacteria
rapidly invade the tissues and bloodstream, causing disease.
What are risk factors for meningococcemia?
Children and adolescents 5 to
19 years of age are at highest risk for meningococcemia. Newborns acquire antibodies from their mothers via
the placenta, although these antibodies fade after a few weeks or months. Toddlers are not immune, and there have been several
exposures in day-care settings. As children age, they gradually gain immunity
to meningococcal strains by coming into contact with milder strains of the
bacteria. However, because this immunity is imperfect, it is still possible for
adults to get meningococcemia.
The immune system is critical
in fighting off the bacteria. Patients who have a history of a specific genetic
deficiency in the complement system are at high risk for severe disease. The
spleen is also needed for an effective immune response, so people are at higher
risk for severe disease if they have had their spleens taken out or have
spleens that function poorly.
People who have been in close
contact with an infected patient are at increased risk to acquire the disease
themselves. People who live together in close quarters such as military
barracks are at especial risk for disease. One study showed that the attack
rate in household contacts was 500 times greater than that of the general
population.
In some parts of the world,
outbreaks of meningococcal disease occur regularly. This is true of a group of
countries in sub-Saharan Africa, which is known as the "meningitis
belt." Because travelers from this area visit Saudi Arabia during the
Hajj, there have been outbreaks associated with the pilgrimage. Saudi Arabia
now requires proof of vaccination before admitting pilgrims.
What
are symptoms and signs of meningococcemia?
After an average incubation
period of three to seven days (range one to 10 days), infected patients
initially experience fatigue, fever, headache, and
body aches, similar to those experienced by people with influenza, including swine
flu or bird flu.
Shaking chills may be present. Rash is common and appears
like small red dots (petechiae) associated with low platelet counts or a bleed
into the skin (purpura) associated with vasculitis. The rash may appear anywhere on
the body, even on the palms or soles or inside the mouth.
In addition to the rash,
physical examination reveals a fast heart rate and often a low
blood pressure and other
signs of shock. Laboratory examination shows increases in white blood cell
counts and may show low platelet counts (thrombocytopenia). The
bacteria may spread to the heart, causing myocarditis. In severe cases, multiple organ
systems may fail, including the kidneys, lungs and airways, liver, or heart.
Uncommonly, the bacteria may cause a low-grade bloodstream infection (chronic
meningococcemia) with fever, joint
pain, and rash that lasts one to three weeks.
Although meningococcemia refers
to an infection of the bloodstream, it is important to note that some patients
with meningococcemia will develop meningococcal meningitis. Meningococcemia
poses a higher risk of shock and death than meningococcal meningitis. Thus,
although they are defined differently and have different prognoses, there is
significant overlap between meningococcemia and meningococcal meningitis.
How is meningococcemia diagnosed?
Patients
are often presumptively diagnosed with meningococcemia from the patient's
history and physical exam, but a definitive diagnosis is usually sought. This
presumptive diagnosis is important because treatment needs to be started as
soon as possible if meningococcemia is suspected. Meningococcemia is diagnosed
by culturingN. meningitidis from
a sample of blood. The bacteria grow in one to two days in most cases, and
biochemical methods are used to identify them as N. meningitidis.
Samples of the growth can also be stained and examined under the microscope to
detect the characteristic double kidney bean appearance of the bacteria, although
the biochemical tests are needed for definitive diagnosis.
In some
instances, skin scrapings from pustular lesions can reveal the organisms; other
investigators have occasionally used a PCR test to detect N. meningitidis.
What is the treatment for meningococcemia?
Intravenous
antibiotics are needed to treat meningococcemia. Most strains remain sensitive
to older treatments such as ampicillin (Omnipen,
Polycillin, Principen) or penicillin
G (Bicillin
L-A), although a few strains are resistant and require therapy with a newer
agent such as ceftriaxone (Rocephin). The laboratory will test the bacteria to
see which antibiotics will work best, but treatment will need to start before
the results of these antimicrobial sensitivity tests come back. Therefore,
doctors usually select antibiotics that are known to work against most strains
of N. meningitidis.
Blood pressure is supported
with intravenous fluids or medications. Meningococcemia often requires treatment
in an intensive-care unit.
Recently, a newer agent called drotrecogin alpha (Xigris) has shown some efficacy in
reducing complications of severe bloodstream infections, although only a small
number of patients with meningococcemia have been tested. This agent has the
potential to cause serious bleeding, so it should not be used in patients who
are already at increased risk for bleeding. Thus, use of drotrecogin alpha
remains controversial.
What is the prognosis of meningococcemia?
Case-fatality rates for
meningococcemia are as high as 19% in industrialized countries but probably
average 8%. Patients who present earlier with milder symptoms and normal immune
systems are still at risk, but mortality rates are lower. In developing
countries, mortality rates reach 70%. Patients with severe infection may
require amputation of limbs due to ischemia or low blood pressure. Other
complications may include nerve, muscle and heart problems, and arthritis and rarely, major adrenal hemorrhage
(termed Waterhouse-Friderichsen syndrome).
Can meningococcemia be
prevented?
Meningococcemia can be
prevented in several ways. People who have come into close contact with an
infected patient should strongly consider taking antibiotics to reduce the risk
of disease. These antibiotics are usually given in pill form, although
sometimes a shot is needed if the organism is resistant to common oral
antibiotics. Close contact usually means household contacts, day-care or
child-care contacts, or those who have been exposed to potentially infected
saliva in the week before the patient got sick. Routine patient care does not
warrant prophylaxis in health-care workers, unless the worker has had very
close contact with respiratory secretions such as when giving mouth-to-mouth
resuscitation or inserting a breathing tube. Prophylaxis should be given as
soon as possible after the exposure but certainly within two weeks of the
event. The antibiotics eliminate carriage of the bacteria and may also be used
in the final step of treatment for infected patients.
For caretakers and health-care
workers, frequent hand washing is recommended to minimize the transfer of
infected secretions to the mouth or nose. In the hospital, patients with
meningococcemia are placed in private rooms and staff will wear surgical masks
when approaching the patient.
There is an effective and safe vaccine to protect against most serogroups of
meningococcus that cause meningococcemia. Unfortunately, no effective vaccine
exists for serogroup B. For the other major disease-causing serogroups (A, C,
Y, W135), there are two vaccines available in the United States: the
meningococcal polysaccharide vaccine (Menomune, MPSV4) and the meningococcal
conjugate vaccine (Menactra, Menveo, MCV4). The choice of vaccine depends on
the age of the patient.
The vaccine is recommended
starting at 11 years of age. A booster dose is given at 16 years of age. Older teens who have never been vaccinated need only a
single dose. The vaccine may be required for admission to college, and students
should have received the vaccine less than five years before starting college.
Others for whom vaccination is recommended include military recruits, college
students living in dormatories, individuals with missing or damaged spleens,
people with certain immune deficiencies in the complement system, those
traveling to areas where the disease is common, and scientists who perform
research on the bacteria.
What research is being done on meningococcemia?
There is research
under way to produce a vaccine that is effective against serogroup B strains of N. meningitidis. This serogroup exists throughout the United
States, so a vaccine would be a major advance in reducing the disease burden.
Source: MedicineNet.com
Reviewed by Charles Patrick Davis, MD, PhD on 10/14/
