Unculturable and culturable periodontal-related bacteria are associated with periodontal inflammation during pregnancy and with preterm low birth weight delivery

Abstract

Recent studies revealed culturable periodontal keystone pathogens are associated with preterm low birth weight (PLBW). However, the oral microbiome is also comprised of hundreds of 'culture-difficult' or 'not-yet-culturable' bacterial species. To explore the potential role of unculturable and culturable periodontitis-related bacteria in preterm low birth weight (PLBW) delivery, we recruited 90 pregnant women in this prospective study. Periodontal parameters, including pocket probing depth, bleeding on probing, and clinical attachment level were recorded during the second trimester and following interviews on oral hygiene and lifestyle habits. Saliva and serum samples were also collected. After delivery, birth results were recorded. Real-time PCR analyses were performed to quantify the levels of periodontitis-related unculturable bacteria (Eubacterium saphenum, Fretibacterium sp. human oral taxon(HOT) 360, TM7 sp. HOT 356, and Rothia dentocariosa), and cultivable bacteria (Aggregatibacter actinomycetemcomitans, Porphyromonas gingivalis, Tannerella forsythia, Treponema denticola, Fusobacterium nucleatum and Prevotella intermedia) in saliva samples. In addition, ELISA analyses were used to determine the IgG titres against periodontal pathogens in serum samples. Subjects were categorized into a Healthy group (H, n = 20) and periodontitis/gingivitis group (PG, n = 70) according to their periodontal status. The brushing duration was significantly lower in the PG group compared to the H group. Twenty-two of 90 subjects delivered PLBW infants. There was no significant difference in periodontal parameters and serum IgG levels for periodontal pathogens between PLBW and healthy delivery (HD) groups. However, ordinal logistic regression analysis revealed that a higher abundance of Treponema denticola, Prevotella intermedia, Fretibacterium sp. HOT360 and lower levels of Rothia dentocariosa were significantly associated with the presence of periodontal disease during pregnancy. Moreover, the amount of Eubacterium saphenum in saliva and serum IgG against Aggregatibacter actinomycetemcomitans were negatively correlated with PLBW. Taken together, unculturable periodontitis-associated bacteria may play an important role both in the presence of periodontal inflammation during pregnancy and subsequent PLBW.

Figure 1

The comparison of IgG titers against periodontal pathogens in groups. The box plots represent the levels of IgG titers against periodontal pathogens evaluated in this study. (A) the comparison of IgG titers between healthy and Periodontitis/Gingivitis groups; (B) the comparison of IgG titers between HD and PLBW groups. The Mann–Whitney U-tests were applied to test the differences between groups; *P < 0.05.

Figure 2

The comparison of bacteria load in groups. The box plots represent the levels of periodontitis-associated bacterial species evaluated in this study. (A) The comparison of bacteria load between healthy and Periodontitis/Gingivitis groups. (B) The comparison of bacteria load between HD and PLBW groups. The Mann–Whitney U-tests were applied to test the differences between groups; *P < 0.05.

Figure 3

Correlation of bacteria load with periodontal parameters and birth results. (A) The heat map of Pearson's correlation coefficient between periodontitis-associated bacteria and periodontal parameters. negative: blue; positive: red; (B) the heat map of Pearson's correlation coefficient between periodontitis-associated bacteria and birth results. negative: red; positive: green. Correlation between bacterial load and periodontal parameters, birth results were analyzed by a Pearson's correlation coefficient test; *P < 0.05.