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

Abstract

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.