The Oral Microbiome and Cross-Kingdom Interactions during Pregnancy

Pregnancy initiates a temporary transition in the maternal physiological state, with a shift in the oral microbiome and a potential increase in frequency of oral diseases. The risk of oral disease is higher among populations of Hispanic and Black women and those with lower socioeconomic status (low SES), demonstrating a need for intervention within these high-risk populations. To further our understanding of the oral microbiome of high-risk pregnant women, we characterized the oral microbiome in 28 nonpregnant and 179 pregnant low-SES women during their third trimester living in Rochester, New York. Unstimulated saliva and supragingival plaque samples were collected cross-sectionally, followed by assessment of the bacterial (16S ribosomal RNA) and fungal (18S ITS) microbiota communities. Trained and calibrated dentists performed oral examinations to determine the number of decayed teeth and plaque index. Initially, plaque from 28 nonpregnant women and 48 pregnant women were compared; these data showed significant differences in bacterial abundances based on pregnancy status. To further our understanding of the oral microbiome within the pregnant population, we next examined the oral microbiome within this population based on several variables. Streptococcus mutans, Streptococcus oralis, and Lactobacillus were associated with a greater number of decayed teeth. The composition of fungal communities differed between plaque and saliva, demonstrating 2 distinct "mycotypes" that were represented by a greater abundance of Candida in plaque and Malassezia in saliva. Veillonella rogosae, a common oral bacterium, was negatively associated with both plaque index and salivary Candida albicans colonization by culture data. This was further emphasized by in vitro inhibition of C. albicans by V. rogosae. Identification of interactions between the bacterial or fungal oral communities revealed that V. rogosae was positively associated with the oral commensal Streptococcus australis and negatively with the cariogenic Lactobacillus genus, suggesting V. rogosae as a potential biomarker of a noncariogenic oral microbiome.

Oral Candida Predicts Streptococcus mutans Emergence in Underserved US Infants

Despite the cariogenic role of Candida suggested from recent studies, oral Candida acquisition in children at high risk for early childhood caries (ECC) and its association with cariogenic bacteria Streptococcus mutans remain unclear. Although ECC disproportionately afflicts socioeconomically disadvantaged and racial-minority children, microbiological studies focusing on the underserved group are scarce. Our prospective cohort study examined the oral colonization of Candida and S. mutans among 101 infants exclusively from a low-income and racial-minority background in the first year of life. The Cox hazard proportional model was fitted to assess factors associated with the time to event of the emergence of oral Candida and S. mutans. Oral Candida colonization started as early as 1 wk among 13% of infants, increased to 40% by 2 mo, escalated to 48% by 6 mo, and remained the same level until 12 mo. S. mutans in saliva was detected among 20% infants by 12 mo. The emergence of S. mutans by year 1 was 3.5 times higher (hazard ratio [HR], 3.5; confidence interval [CI], 1.1-11.3) in infants who had early colonization of oral Candida compared to those who were free of oral Candida (P = 0.04) and 3 times higher (HR, 3.0; CI, 1.3-6.9) among infants whose mother had more than 3 decayed teeth (P = 0.01), even after adjusting demographics, feeding, mother's education, and employment status. Infants' salivary S. mutans abundance was positively correlated with infants' Candida albicans (P < 0.01) and Candida krusei levels (P < 0.05). Infants' oral colonization of C. albicans was positively associated with mother's oral C. albicans carriage and education (P < 0.01) but negatively associated with mother's employment status (P = 0.01). Future studies are warranted to examine whether oral Candida modulates the oral bacterial community as a whole to become cariogenic during the onset and progression of ECC, which could lead to developing novel ECC predictive and preventive strategies from a fungal perspective.