HPV infection and bacterial microbiota in breast milk and infant oral mucosa

Abstract

Objective: We investigated the association between bacterial microbiota in breast milk and the infant mouth. The influence of human papilloma virus (HPV) infection on infant oral microbiota was also assessed.

Material and methods: Altogether 35 breast milk and 35 infant oral samples with known HPV status were selected from the Finnish Family HPV Study cohort. In total, there were 31 mother-infant pairs. The microbiota composition was characterized by 16S rRNA gene sequencing (V3-V4 region).

Results: HPV DNA was present in 8.6% (3/35) of the breast milk and 40% (14/35) of the infant oral samples. Eight shared genera between breast milk and infant oral were found; these included Streptococcus, Staphylococcus, Unclassified Gemellaceae, Rothia, Veillonella, Haemophilus, Propionibacterium and Corynebacterium. HPV status was not associated with either microbiota richness or diversity in the infant mouth. However, the infant oral microbiota clustered in different groups according to HPV status. We detected higher abundance of Veillonella dispar (p = 0.048) at species level in HPV negative infant oral samples. We did not detect differences in the breast milk microbiota composition related to HPV infection due to only three HPV positive milk samples.

Conclusions: HPV infection is associated with distinct oral bacterial microbiota composition in infants. The direction of causality underlying the phenomenon remains unclear.

Fig 1. Bacterial microbiota composition in breast milk and the infant oral cavity.

The relative abundance of bacteria are presented on the phylum (Fig 1A) and family levels (Fig 1B) for both groups. A Venn diagram with the list of shared and unique bacterial genera both in breast milk and infant oral samples (Fig 1C).

Fig 2. The effect of age on infant oral microbiota.

PCoA chart depicting two different clusters in relation to the time (at birth = blue, at two months of age = red, Fig 2A). Higher richness (p = 0.026, Chao 1 index; Fig 2B) was observed in infant oral samples collected at 2 months of age (red) versus samples collected at birth (blue) but no difference in diversity were evident (Shannon index; Fig 2C). LEfSe test showing different abundances between the two different time groups (blue = two months, red = birth, Fig 2D).

Fig 3. Differences and similarities between breast milk and infant oral microbiota.

Multivariate redundancy discriminant analysis (RDA) showing differences between breast milk (light red) and infant oral cavity (light blue) microbiota profiles (Fig 3A). Higher diversity (p = 0.0044, Shannon index, Fig 3B) was detected in breast milk (light red) as compared to infant oral (light blue) samples, but no differences in richness were observed (Chao 1 index, Fig 3C).

Fig 4. Breast milk microbiota and HPV.

No differerence in richness (Chao 1 index, Fig 4A) or diversity (Shannon index, Fig 4B) were detected between HPV postitive (blue) and HPV negative (red) breast milk samples. The relative abundances of bacteria are presented on the phylum (Fig 4C) and family levels (Fig 4D).

Fig 5. Infant oral HPV infection and bacterial microbiota.

No differences in bacterial richness (Chao 1 index, Fig 5A) or diversity (Shannon index, Fig 5B) between HPV positive (blue) and HPV negative (red) infant oral samples were detected. RDA analysis (Fig 5C) shows significant differences between HPV positive (blue) and HPV negative infant oral samples (red). The relative abundances of bacteria are presented on the phylum (Fig 5D) and family levels (Fig 5E). By LEfSe analysis (Fig 5F), Lysinibacillus and Ureaplasma were significantly enriched in HPV positive (blue) infant oral samples (LDA score >4.17 and 4.10 respectively, p<0.05), while Veillonella (LDA score>4.31, p<0.05) were enriched in HPV negative (red) compared to HPV positive infant oral samples.