title: Group B streptococcal colonization in 160 mother-baby pairs: a prospective cohort study.
abstract: OBJECTIVE
  To identify the source of postnatal colonization with group B Streptococcus (GBS) and to evaluate the impact of intrapartum antibiotic prophylaxis (IAP) administration in newborn infant transmission.
  
  
  METHODS
  A prospective, longitudinal study evaluated GBS colonization in 160 mother-baby pairs. Specimens were collected from the time of delivery to 8 weeks post-partum, from rectum, vagina, and milk of mothers, and from throat and rectum of neonates. Women were grouped according to their GBS status at discharge from the hospital: culture-positive carriers (n = 83), culture-negative carriers (n = 26), and noncarriers (n = 51). Newborns were considered colonized if GBS was yielded from at least 1 site.
  
  
  RESULTS
  A total of 35 (21.9%) neonates were colonized; 30 were born to culture-positive carriers, 2 to culture-negative carriers, and 3 to noncarriers. Infants of culture-positive carriers exposed to IAP were less likely to be colonized (15/57 vs 15/26, P = .01), or heavily colonized, (7/57 vs 9/26, P = .04). Of all newborns, those exposed to IAP and discharged GBS-free from hospital, often became colonized subsequently (12/57 vs 1/26, P = .09). Molecular typing analysis (available for 30 of 32 carrier mothers and their infants) confirmed an identical strain of GBS in all mother-baby pairs. Six of 83 culture-positive carrier mothers had a positive milk culture. Their respective neonates all were heavily colonized.
  
  
  CONCLUSIONS
  Newborns exposed to IAP and GBS-free at hospital discharge subsequently acquire GBS from their mothers. Culture-positive milk is associated with heavy neonatal colonization.
authors.affiliation: Neonatal Intensive Care Unit, Polyclinic University Hospital, Modena, Italy. Electronic address: berardi.alberto@policlinico.mo.it.
authors.forename: Alberto
authors.initials: A
authors.lastname: Berardi
authors.forename: Cecilia
authors.initials: C
authors.lastname: Rossi
authors.forename: Roberta
authors.initials: R
authors.lastname: Creti
authors.forename: Mariachiara
authors.initials: M
authors.lastname: China
authors.forename: Giovanni
authors.initials: G
authors.lastname: Gherardi
authors.forename: Claudia
authors.initials: C
authors.lastname: Venturelli
authors.forename: Fabio
authors.initials: F
authors.lastname: Rumpianesi
authors.forename: Fabrizio
authors.initials: F
authors.lastname: Ferrari
mesh_terms: D000293:Adolescent; D000328:Adult; D005260:Female; D006801:Humans; D007231:Infant, Newborn; D018445:Infectious Disease Transmission, Vertical; D008137:Longitudinal Studies; D008297:Male; D008895:Milk, Human / Q000382:microbiology; D009035:Mothers; D011446:Prospective Studies; D013290:Streptococcal Infections / Q000453:epidemiology* / Q000517:prevention & control / Q000635:transmission*; D013292:Streptococcus agalactiae; D013997:Time Factors; D055815:Young Adult
keywords: EOD; Early-onset disease; GBS; Group B Streptococcus; IAP; Intrapartum antibiotic prophylaxis; LOD; Late-onset disease; PFGE; Pulsed field gel electrophoresis; THB; Todd-Hewitt broth