Higher serum zinc micronutrient levels are associated with reduced susceptibility to Group B Streptococcus rectovaginal colonisation in pregnant women

Background: Maternal recto-vaginal colonisation by Group B Streptococcus (GBS) is a major risk factor for severe invasive GBS disease in newborns. Zinc is a key micronutrient known to promote defence against bacterial infections. We hypothesized that adequate zinc micronutrient levels in pregnant women would negatively affect GBS colonisation and persistence during pregnancy. Objective: To determine the association between serum zinc levels and risk of recto-vaginal GBS colonisation acquisition in pregnant women, as well as the potential for clearance of colonisation later in pregnancy. Methods: Zinc concentrations were analysed in serum samples from women who acquired rectovaginal GBS colonisation and from women who cleared GBS colonisation between 20 weeks and 37–40 weeks of gestational age. Zinc concentration at 20–25 weeks and 37–40 weeks gestational age was measured using inductively coupled plasma mass spectrometry. Results: Higher baseline serum zinc concentration was associated with a lower risk of new GBS acquisition [Odds ratio (OR) 0.15, p = 0.001]. Zinc geometric mean concentration was higher in women who were persistently un-colonised by GBS compared with those with a new acquisition of GBS (20.18 vs 13.68 µmol/L; p = 0.03). The lowest zinc threshold ≥15 µmol/L was associated with significantly reduced odds of new GBS acquisition (27.2% in new acquisition vs 40.5% in persistently un-colonised; OR 0.55; 95%CI 0.31–0.96; p = 0.03). An association was also evident between 15–20 umol/L serum zinc levels and greater odds of GBS colonisation clearance. Conclusions: This study demonstrates a potential role of serum zinc nutrition in the reduced risk of recto-vaginal GBS colonisation during pregnancy.