Streptococcus agalactiae – group B streptococcus (GBS) – a threat to the newborn

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Streptococcus agalactiae forms part of the physiological flora of humans. These bacteria can cause serious intra-aquatic infections of the fetus or newborns

Streptococcus agalactiae infections are becoming more frequent

Until the 60s, group B streptococcal infections in humans were reported very rarely. However, already in the 70s, these bacteria were one of the most important microorganisms responsible for infections in newborns and infants before the age of three months. In the USA, before the routine screening of pregnant women for group B streptococcus was introduced, approximately 7500 cases of neonatal infections were reported each year, over 300 of which were fatal. Therefore, in 1996, the Centers for Disease Control and Prevention (CDC) in Atlanta, the United States, recommended a strategy for prophylactic management in pregnant women to avoid infection of newborns by group B streptococci.

In Poland, similar recommendations were developed in 2008 by the Polish Gynecological Society, but unfortunately only a few gynecology and obstetrics hospitals have implemented them so far. Another problem is the question of fees for this test, which, although relatively inexpensive, burdens the pregnant woman’s budget, and therefore not all women decide to perform it.

Streptococcus agalactiae – group B streptococci (GBS)

Epidemiological data show that the presence of group B streptococci is found in 10–40% of healthy women, while in Poland the carrier status of pregnant women is up to 30%. This means that in at least one in four pregnant women, these bacteria are present in the genital tract or the end of the digestive tract. These women usually do not have any clinical symptoms of infection. In such a situation, we are talking about asymptomatic carriage.

Types of GBS infections in newborns

During delivery, when the baby passes through the maternal birth canal, group B streptococci is transferred to the newborn. This applies to as many as 70% of children of mothers with GBS. In these babies, immediately after delivery, streptococci can be detected in the ear, navel and mouth, among others. Fortunately, in most cases, these streptococci do not infect newborns. This is because during pregnancy, the maternal antibodies that protect them against infection are passed on to the baby. Unfortunately, in some extreme situations, such as in preterm newborns, a dangerous infection caused by these bacteria can occur. Such infections are recorded in 2-4 babies out of 1000 live births. The clinical picture is dominated by sepsis, pneumonia and meningitis. Due to the time of infection, we can distinguish early infection, developing in the first seven days of a newborn’s life, and late infection occurring between 7 and 90 days of life.

Methods of preventing Streptococcus agalactiae infections in newborns

In order to prevent the occurrence of infections in newborns, in accordance with global and Polish recommendations, it is recommended to use one of the two methods of prevention, the first based on the assessment of risk factors, the second using microbiological screening of pregnant women. Doctors using the first method qualify for intrapartum chemoprophylaxis women who have not been tested for GBS carrier, but have one of the following risk factors for early-stage disease:

1. Beginning of labor before 37 weeks gestation (with or without rupture of membranes).
2. Delivery on time, i.e. full-term pregnancy, but time since rupture of membranes is greater than 18 hours.
3. The occurrence of body temperature during labor equal to or greater than 38 for unknown reasons^oC.
4. The occurrence of GBS-induced urinary tract infection or bacteriuria during pregnancy, regardless of the number of streptococci.
5. The birth of a child in the past who was diagnosed with an infection caused by Streptococcus agalactiae.
6. In the case of the second method, it is recommended to perform vaginal and rectal microbiological tests in all pregnant women between 35 and 37 weeks of pregnancy for GBS carrier. A positive test result is an indication for the administration of antibiotics during labor. As GBS colonization is often transient, the prognosis based on the result of culture performed earlier than 5 weeks before delivery is unreliable and is recommended only in special cases.

Streptococcus agalactiae in the vagina and anus – smear collection

It should be emphasized that testing for group B streptococcus (Streptococcus agalactiae) cannot be confused with the classic bacteriological examination of the female genital tract, in which various microorganisms present in the vaginal environment are determined. The vaginal and rectal Streptococcus agalactiae carrier test is a simple targeted test to demonstrate the presence of streptococci in vaginal and rectal swabs. Some microbiology laboratories that propose to perform two different carrier tests are inadequate Streptococcus agalactiae, one from the vaginal swab, the other from the rectal swab, paid for as two different orders. This can be confusing for a patient who will choose only one of these tests due to cost constraints. Recognized recommendations do not allow the determination of carriage only in one of the collected materials, these two materials should always be treated as the required set of materials from one patient, examination of which gives only the correct test result.

1. Check it out: GBS pregnancy test – test for group B streptococci

Material for microbiological testing can be collected on an outpatient basis. This can also be done by the pregnant woman herself, after reading the appropriate instructions, or by the doctor. The samples are taken using two separate, sterile swabs (swabs), one from the lower part of the vagina and the other from the rectum, overcoming the resistance of the anal sphincter. As it is recommended to collect material from the lower vagina and not from the cervix, a vaginal speculum should not be used. The use of special media for streptococcus cultivation is also very important here, as it allows to reduce false-negative results. In the bacteriological examination, it is also important to perform the so-called a drug-resistance test, i.e. examining the antibiotics to which antibiotics grown bacteria are susceptible. This allows the doctor to select the appropriate antibiotic for perinatal prophylaxis.

Treatment of Streptococcus agalactiae in the mother

Only in exceptional cases in pregnant women Streptococcus agalactiae can cause premature rupture of membranes, intra-labor fever, urinary tract infection, preterm labor, amniotic infection, postpartum endometritis and postpartum wound infection, and even sepsis. Obviously, in the event of clinical signs of infection, it is advisable to provide the patient with appropriate treatment. On the other hand, treatment of streptococcus agalactiae in a pregnant woman who has been shown to be carrier of these group B streptococci raises a number of doubts and is not recommended. This is because often after discontinuation of the antibiotic, a recurrence of genital tract colonization by GBS is observed, the source of which is the gastrointestinal tract, where these microorganisms are mainly present and where it is extremely difficult to remove them.

Perinatal prophylaxis of infections in newborns is based on the intravenous administration of an antibiotic to the mother during labor. This method is most effective when the antibiotic is administered at least 4 hours before delivery. Since the recommended drug is penicillin G, patients allergic to it should inform their doctor who will choose another appropriate drug.

Treatment of Streptococcus agalactiae infection in children

Children of mothers who have received perinatal antibiotic prophylaxis for GBS should always be followed up for 24 – 48 hours in the ward, without performing additional tests to exclude GBS infection.

Conversely, in children of carrier women Streptococcus agalactiaewho for some reason have not been subjected to perinatal antibiotic prophylaxis, it is possible to additionally test the CRP protein in the blood serum (2-3 times every 12 hours) and perform a routine blood count. If the test results are normal and there are no clinical symptoms, the child may be discharged home after at least 48 hours of observation in the ward.

Newborns who show signs of infection should undergo full diagnosis for group B streptococcal infection and receive empirical treatment, e.g. with ampicillin.

Ten commandments for pregnant women, or how to protect your child against group B streptococci (Streptococcus agalactiae):

1. If you are near 35-37 weeks of gestation (9 months), ask your doctor about testing for group B streptococcus.
2. If you are a carrier of group B streptococcus, make sure that this result is entered in your pregnancy record with drug resistance of these bacteria.
3. If you are allergic to penicillin or other antibiotics, report it to your doctor, this information should also be included in your pregnancy booklet.
4. Agree with your healthcare provider on the appropriate birth prophylaxis plan.
5. Continue to see your doctor regularly and report any symptoms that worry you.
6. After labor begins, go to the hospital as soon as possible. Giving an antibiotic will best protect your baby if it is given at least four hours before birth.
7. On admission to labor, inform the midwife and / or doctor that you are a carrier of group B streptococcus and report if you are allergic to penicillin or other antibiotics.
8. Be prepared for the intravenous administration of an anti-GBS antibiotic.
9. Remember that you can breastfeed your baby naturally after giving birth.
10. After discharge from hospital, monitor your baby for three months and see your baby’s pediatrician immediately if there is any sign of infection.

Text: dr n. Biol. Monika Brzychczy-Włochy

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