Comparison of the indigenous oral microbiota and immunoglobulin responses of athymic (nu/nu) and euthymic (nu/+) mice

Abstract

The role of the immune system in the homeostasis of indigenous oral bacterial populations is poorly understood. In this study, we compared the evolution of the indigenous oral microbiota of specific pathogen-free athymic nude (nu/nu) BALB/c mice with that of their corresponding phenotypically normal (nu/-) littermates. We also evaluated corresponding salivary and serum antibody activities (IgA and IgG) against the predominant indigenous oral bacteria. The bacterial species recovered from the two mouse strains were Lactobacillus murinus, Enterococcus faecalis, Streptococcus oralis and Staphylococcus epidermidis. From 27 days of age, nu/+ and nu/nu mice had significantly different proportions of oral bacterial populations. When the microbiota stabilized (at 40 days of age), the total cultivable microbiota of nu/+ mice was dominated by L. murinus (65-85%), while that of nu/nu mice was dominated by E. faecalis (40-60%). The precise factors that alter the oral resident microbiota in nu/nu mice are unknown. We found that total salivary IgA levels were significantly lower in nu/nu mice, but no association were observed between the level of salivary IgA antibody against indigenous bacteria and the proportion of these indigenous bacteria in the oral microbiota. The change in the microbiota of nude mice may have been caused by other factors such as defects in other immune functions or cold stress.

Oral Microbial Ecology and the Role of Salivary Immunoglobulin A

“…We have extensively studied the composition of the oral microbiota of mice (34,94,150,294,295,296,396,398,500). We have isolated more than 20 species from six different mouse strains (BALB/c, CD-1, C3H/He, C57BL/6, DBA/2, and C57BL/10) originating from different suppliers.…”

The analysis of oral microbial communities of wild-type and toll-like receptor 2-deficient mice using a 454 GS FLX Titanium pyrosequencer

“…The role of the immune system in the selection of indigenous microbiota has been demonstrated in several studies. The total cultivable oral microbiota of athymic nu / nu mice was dominated by Enterococcus faecalis , while that of nu /+ mice was dominated by Lactobacillus murinus [11]. In contrast, B-cell-deficiency had no apparent influence on the indigenous oral microbiota of mice [12].…”

Lactobacillus plantarum for oral peptide delivery

“…The inability to recover other lactobacillus strains transformed with pKTH2121 after feeding suggests that either these strains lack the ability to adhere to murine oral mucosa or that the erythromycin‐resistance marker in pKTH2121 is lost. The inability of L. murinus and endogenous lactobacilli isolated from the host mice to persist in the oropharynx after feeding was particularly surprising, because L. murinus has been demonstrated to comprise up to 75% of total oral bacteria in other inbred mice (12) and endogenous lactobacilli would be naturally adapted for oral persistence. The low transformation efficiency and beta‐lactamase expression of endogenous lactobacilli suggest that the reason they cannot be recovered after oropharyngeal feeding is that they may be rapidly shedding or degrading the pKTH2121 after transformation or unable to survive selection by erythromycin resistance.…”

“…To harvest bacteria, mice were anesthetized with pentobarbital (Nembutal, Abbott Pharmaceuticals, Austin, TX) 50–90 mg/kg by intraperitoneal injection. Type 4 Calgiswabs (Puritan Medical Supplies, Houston, TX) were dipped in citrate collection buffer and swabbed over the buccal, palatal and tongue mucosa gently for 20 s, dissolved in citrate buffer, then cultured as previously described (12). The Calgiswab collections were cultured in serial dilutions on minimum required strength agar plates with or without erythromycin 10 μ g/ml to distinguish transformed bacteria from total lactobacilli.…”