Group B Strep (GBS) colonizes just under one out of every three US women. It is one of the primary organisms responsible for invasive disease in newborns and is generally spread through vertical transmission during the birth process. Generally speaking, GBS disease is either Early Onset or Late Onset. Per Puopolo et al. “GBS early-onset disease (EOD) occurs within the first week after birth, usually before 72 hours. GBS late-onset disease (LOD) accounts for about 20% of cases, usually occurring between 1 to 4 weeks after birth, but rarely seen up to 6 months of age. Late, late-onset infections, which occur from 1 to 6 months of age, and infections in non-pregnant adults often are associated with immunodeficiency.” We always ask about GBS status in our newborn patients, especially those with fever.

GBS can be a devastating pathogen. Overall mortality is 2-3% and the long term complications include cerebral palsy, intellectual disability, seizures, hearing loss, and visual impairment. These babies also have higher rates of hospitalizations subsequently in the first 5 years of life. At least one in five babies with GBS meningitis have neurologic sequelae, and seizures have the highest overall conferred risk of long term issues.

With that said, let’s explore some common questions regarding this important pathogen that will hopefully better prepare you for your next ED shift.

How are pregnant women screened and treated for GBS?

The current guideline recommends universal screening at 36 to 37 weeks gestational age. this screening is done via vaginal swab. The recommended intrapartum antibiotics for a positive GBS screen include penicillin, ampicillin, or cefazolin. They are most effective when given > 4 hours prior to delivery, though there is still some efficacy if given > 2 hours prior to delivery. Clindamycin or Vanocmycin can be used in those rare occasions in which mothers have a history of anaphylaxis to beta lactase or cephalosporins. These latter two agents are not as effective and do not reach as high concentrations in the amniotic fluid – so they aren’t technically effective for prophylaxis. Finally, these antibiotics reduce the risk of Early Onset GBS disease only – not late onset disease.

How does GBS Early Onset Disease Present? How is it treated?

EOD occurs within the first week after birth, usually before 72 hours

Signs and symptoms of EOD are most often seen in the first 12 to 24 hours after delivery. You can see everything from fever, temperature instability, tachycardia, poor feeding, emesis, lethargy, irritability, respiratory problems (tachypnea, apnea, increased work of breathing), shock, encephalopathy and more. The overall prevalence of EOD is 0.5 cases per 1,000 live births. This rate of EOD is about half of what it used to be in the 1990s – however the rate of Late Onset Disease hasn’t changed.

if a mother who is GBS positive received inadequate or no intrapartum antibiotics the most effective way to monitor the infant is still your clinical assessment over the first 36 to 48 hours of life. CBC and CRP – among other labs – don’t adequately predict which infants are ill. So, if you are worried, get blood, urine, and CSF studies and start the good ole septic workup. And because you aren’t sure if it is GBS or something else – go broad and cover for multiple agents. This includes Ampicillin + Cefotaxime (or Ceftazidime if there’s a shortage) OR Ampicillin + Gentamicin. You’ll also want to consider HSV, and in most infants under 21 days of age you’ll add Acyclovir. If you isolate GBS alone mono therapy with Penicillin G or Ampicillin is reasonable.

OK, so what about Late Onset Disease?

LOD usually occurs between 1 to 4 weeks after birth, but up to 6 months of age

When at home infants can acquire GBS from their mother or colonized household contacts. Two-thirds of LOD is bacteremia without focus. Another 25% have meningitis, and the rest are focal infections. These babies are less likely to be in shock than EOD, but those with meningitis will be more likely to seize – since the smallest babies don’t convulse per se. You may see upper respiratory symptoms preced LOD – and in meningitis the bulging fontanel, nuchal rigidity etc,. are not all that common. In fact, meningitis generally presents in a manner that is indistinguishable from bacteremia – that’s why you need the LP!

Some of the notable focal LOD infections of note include pneumonia, septic arthritis, osteomyelitis, cellulitis, and adenitis. Septic arthritis and osteomyelitis (5%) present with decreased movement and pain. Fever is actually uncommon. Septic arthritis is most common in the lower extremities whereas oseto presents in an insidious manner. half of these babies are also bactermeic. Cellulitis and adenitis (~4%) are most often seen in the face and neck – but can be seen elsewhere. Greater than 90% of these have concomitant bacteremia. Lack of fever and reassuring appearance can’t necessarily exclude the possibility of meningitis either.

Treatment is initially broad until you isolate GBS. You could consider monotherapy in the well-appearing febrile infant older than 28 days but less than 60 days (cefotaxime or ceftazidime) or in those greater than 60 days (ceftriaxone). But, since this is a GBS post, and if you have a patient in whom you are worried about GBS cover with Ampicillin + something else.

Late-late onset GBS is seen after 6 months of age, is usually bacteremia without focus and can be a sign of immunodeficiency like HIV.

Can you tell me how long to treat various types of GBS disease?

Sure, here you go:

  • Bacteremia without a focus – 10 days
  • Meningitis – 14 days for uncomplicated meningitis; complicated CNS infections require longer treatment
  • Cellulitis – 10 to 14 days
  • Septic arthritis – 14 to 21 days
  • Osteomyelitis – 21 to 28 days
  • Urinary tract infection – 10 days

What are some of the risk factors for GBS disease?

There are many, and the list includes;

  • Lower gestational age (25-30% of cases of GBS are preterm; mortality is much higher here)
  • Any premature rupture of membranes
  • Prolonged rupture of membranes ≥18 hours prior to delivery
  • Maternal fever ≥38°C (100.4°F)
  • Maternal age < 20 years
  • Black race
  • GBS bacteriuria during this pregnancy
  • Delivery of prior infant with GBS EOD
  • Invasive obstetric practices (fetal monitoring or frequent vaginal examinations) 

What about twins? Should we work them up too?

In short, probably – at least you should be watching them very closely. There is an increased risk in twin siblings of developing GBS disease as well. Those of us who would fit into the bucket of “old-timers” have definitely seen this. If they show any signs or symptoms then work up and treat empirically.

References

Puopolo KM, Lynfield R, Cummings JJ. Management of Infants at Risk for Group B Streptococcal Disease. Pediatrics. 2019 Aug;144(2). doi: 10.1542/peds.2019-1881. Epub 2019 Jul 8. Review. PubMed PMID: 31285392.

American Academy of Pediatrics. Group B streptococcal infections. In: Red Book: 2018 Report of the Committee on Infectious Diseases, 31st ed, Kimberlin DW, Brady MT, Jackson MA, Long SS (Eds), American Academy of Pediatrics, Itasca, IL 2018. p.762.