Mothers May Be Key Source of LOD Strep in Neonates

Lara C. Pullen, PhD

January 07, 2013

Mothers appear to be the source of most neonatal group B Streptococcus (GBS) late-onset disease (LOD) infections, according to a the results of a prospective cohort study. In addition, preterm neonates have a high rate (1.4/1000 births) of group B Streptococcus (GBS) late-onset disease (LOD). They also carry the highest rate of mortality. Intrapartum antibiotics are associated with milder LOD (mild vs severe; P = .03) and delayed presentation of symptoms.

Alberto Berardi, MD, from the Azienda Ospedaliero-Universitaria Proclinico in Moddena, Italy, and colleagues published the results of their online January 7 in Pediatrics. They evaluated GBS-LOD infections during an 8-year period between 2003 and 2010. The study included a high percentage of preterm newborns.

LOD primarily presented as sepsis, meningitis, and/or focal infection. The investigators found that the earlier the presentation of LOD, the higher the risk for meningitis and death.

Approximately 50% of the preterm infants who were diagnosed with LOD were diagnosed as inpatients. This population had lower birth weight, younger gestational age, and more severe disease.

The rate of GBS-LOD in full term neonates was 0.24 per 1000 live births.

At the time of neonatal diagnosis, the authors found that most mothers (64%) carried GBS and some (6%) had mastitis.

Previous case reports have suggested that infected breast milk (even in the absence of mastitis) may be a cause of LOD. The authors also identified GBS-infected milk as a source of infection, noting that in some cases the milk was infected even if the mother did not have mastitis. The authors point out, however, that bacterial counts of milk cultures were not routinely available for mothers without mastitis.

One third of mothers who were screened antenatally and at the time of LOD diagnosis were culture-negative. More than half of women who were identified by screening as GBS-positive received antibiotics, and yet many women went on to transmit the organism to their infants.

Lately, there have been few reports of GBS outbreaks. The authors, however, note that population-based reports on GBS vary a great deal. Most studies agree that low birth weight is associated with an increased risk for GBS infection. Few studies, however, have included a significant number of preterm neonates.

The research leading to these results received funding from the European Community’s Seventh Framework Programme. This study was also supported by the Italian Ministry of Health. The authors have disclosed no relevant financial relationships.

Pediatrics. Published online January 7, 2012.