Staphylococcus aureus nasal carriage in relation to iron status in a Norwegian adolescent population

Abstract

Staphylococcus aureus (S. aureus) needs iron to survive and replicate and has evolved systems to harvest iron from its host. In humans, excess iron could potentially increase the risk of S. aureus carriage and infections. Moreover, iron plays a vital role in the development and function of the host immune system. Adolescence is a growth spurt period with increased iron requirements. The aim of this study was to examine whether iron status is associated with persistent S. aureus nasal carriage in a general adolescent population. S. aureus carriage was assessed by repeated nasal swab cultures among 375 females and 401 males, aged 15-19 years, in the population based Tromsø Study Fit Futures 1 in 2010-2011. Iron, haemoglobin, and ferritin in blood were measured. Levels of iron biomarkers according to S. aureus nasal carriage status were examined by descriptive analysis. Separate binary multivariable logistic regression models including age, measured BMI, serum vitamin D, snuff use, atopic eczema and hormonal contraceptive use (female only), were applied to test whether level of each iron biomarker (stratified by quintiles) was associated with S. aureus nasal carriage. We found statistically significant associations between iron biomarkers and S. aureus carriage in males. Males with [12,16) versus [16-19) µmol/L quintile of serum iron; <12.51 versus [13.21,14.11) g/dL quintile of EDTA-blood haemoglobin and <19 versus [30, 44) µg/L quintile of serum ferritin had 2.05 times, 2.27 times and 2.48 times higher odds of carriage, respectively. There were only minor changes in the estimates when suggested outliers were removed in regression analysis. Our data did not demonstrate any relationship between iron biomarkers and S. aureus carriage in females. The current study supports an association between low iron status and persistent S. aureus nasal carriage in males. The relationship between iron-status and S. aureus carriage should be addressed in future prospective studies and among other age-groups.