Group B Streptococcal
Infections
Group B streptococcus
(GBS) is a type of bacteria that causes illness in newborn
babies and pregnant women. GBS is the most common cause of
life-threatening infections in newborns.
How common is GBS disease?
GBS is the most common
cause of sepsis (blood infection) and meningitis in
newborns. GBS is a frequent
cause of newborn pneumonia.
Before prevention methods were widely used, approximately
8,000 babies in the United States would get GBS disease each
year. One of every 20 babies with GBS disease dies from
infection. Babies that survive, particularly those who have
meningitis, may have long-term problems, such as hearing or
vision loss or learning disabilities. In pregnant women, GBS
can cause bladder infections, womb infections, and
stillbirth.
Does everyone who has GBS get
sick?
Many people carry GBS
in their bodies but do not become ill. These people are
considered to be "carriers." Adults can carry GBS in the
bowel, vagina, bladder, or throat. One of every four or five pregnant women
carries GBS in the rectum or vagina. A fetus may come in contact with GBS
before or during birth if the mother carries GBS in the
rectum or vagina. People who carry GBS typically do so
temporarily -- that is, they do not become lifelong carriers
of the bacteria.
How does GBS disease affect
newborns?
Approximately one of
every 100 to 200 babies whose mothers carry GBS develop
signs and symptoms of GBS disease. Three-fourths of the
cases of GBS disease among newborns occur in the first week
of life ("early-onset disease"), and most of these cases are
apparent a few hours after birth. Sepsis, pneumonia, and
meningitis are the most common problems. Premature babies
are more susceptible to GBS infection than full-term babies,
but most (75%) babies who get GBS disease are full term. GBS
disease may also develop in infants 1 week to several months
after birth ("late-onset disease"). Meningitis is more
common with late-onset GBS disease. Only about half of
late-onset GBS disease among newborns comes from a mother
who is a GBS carrier; the source of infection for others
with late-onset GBS disease is unknown. Late-onset disease
is very rare.
How is GBS disease diagnosed and
treated?
GBS disease is
diagnosed when the bacteria is grown from cultures of blood
or spinal fluid. Cultures take a few days to complete. GBS
infections in both newborns and adults are usually treated
with antibiotics (e.g., penicillin or ampicillin) given
through a vein.
Can pregnant women be checked
for GBS?
GBS carriage can be
detected during pregnancy by taking a swab of both the
vagina and rectum for special culture. Physicians who
culture for GBS carriage during prenatal visits should do so
late in pregnancy (35-37 weeks' gestation); cultures
collected earlier do not accurately predict whether a mother
will have GBS at delivery. A
positive culture result means that the mother carries GBS --
not that she or her baby will definitely become
ill. Women who carry GBS
should not be given oral antibiotics before labor because
antibiotic treatment at this time does not prevent GBS
disease in newborns. An exception to this is when GBS is
identified in urine during pregnancy. GBS in the urine
should be treated at the time it is diagnosed.
Carriage of GBS, in either
the vagina or rectum, becomes important at the time of labor
and delivery -- when antibiotics are effective in preventing
the spread of GBS from mother to baby.
Can GBS disease among newborns
be prevented?
Most GBS disease in
newborns can be prevented by giving certain pregnant women
antibiotics through the vein during labor. Any pregnant
woman who previously had a baby with GBS disease or who has
a urinary tract infection caused by GBS should receive
antibiotics during labor. Pregnant women who carry GBS should be
offered antibiotics at the time of labor or membrane
rupture.
GBS carriers at highest risk are
those with any of the following conditions:
·fever during
labor
·rupture of membranes (water
breaking) 18 hours or more before delivery
·labor or rupture of membranes
before 37 weeks
Women who carry GBS but do not
develop any of these three complications have a relatively
low risk of delivering an infant with GBS disease.
A GBS carrier with none of the
conditions above has the following risks:
·1 in 200 chance
of delivering a baby with GBS disease if antibiotics are not
given
·1 in 4000 chance of
delivering a baby with GBS disease if antibiotics are given
·1 in 10 chance, or lower, of
experiencing a mild allergic reaction to penicillin (such as
rash)
·1 in 10, 000 chance of
developing a severe allergic reaction--anaphylaxis--to
penicillin. Anaphylaxis requires emergency treatment and can
be life-threatening. If a prenatal culture for GBS was not
done or the results are not available, physicians may give
antibiotics to women with one or more of the risk conditions
listed above.
What research is being done on
prevention of GBS disease?
In spite of testing and
antibiotic treatment, some babies still get GBS disease.
Vaccines to prevent GBS disease are being developed. In the
future, women who are vaccinated may make antibodies that
cross the placenta and protect the baby during birth and
early infancy.
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