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Actinobacillus actinomycetemcomitans, Porphyromonas gingivalis, and Tannerella forsythensis are Components of a Polymicrobial Intracellular Flora within Human Buccal Cells

¹ Department of Oral Science, School of Dentistry, and
² Biomedical Imaging and Processing Laboratory, Department of Neuroscience, University of Minnesota, 17-252 Moos Tower, 515 Delaware St. SE, Minneapolis, MN 55455, USA;

^* corresponding author, jrudney{at}tc.umn.edu

	ABSTRACT

TOP ABSTRACT INTRODUCTION MATERIALS & METHODS RESULTS DISCUSSION REFERENCES

 
Previously, we used in situ hybridization and confocal microscopy to detect the periodontal pathogens Actinobacillus actinomycetemcomitans, Porphyromonas gingivalis, and Tannerella forsythensis within buccal epithelial cells taken directly from the mouth. This study tested the hypothesis that the intracellular flora of buccal cells is polymicrobial. Mixtures containing a red fluorescent universal probe paired with green fluorescent versions of either A. actinomycetemcomitans-, P. gingivalis-, or T. forsythensis-specific probes were hybridized with buccal cells collected from each of 38 healthy humans. We verified co-localization of probe pairs within cells by generating three-dimensional reconstructions. Intracellular bacteria were detected in every subject. Each cell that was labeled with a species-specific probe also contained bacteria recognized only by the universal probe. Bacteria labeled with specific probes often occupied smaller regions within larger masses of bacteria. Those findings suggest that future studies of invasion by oral bacteria may need to include microbial consortia.

KEY WORDS: polymicrobial • bacterial invasion • Actinobacillus actinomycetemcomitans • Porphyromonas gingivalis • Tannerella forsythensis

	INTRODUCTION

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The species Actinobacillus actinomycetemcomitans, Porphyromonas gingivalis, and Tannerella forsythensis (formerly Bacteroides forsythus) are all present at multiple oral sites. Numerical dominance of one or more of those species in the gingival crevice is strongly associated with periodontal disease, but they also are present at lower numbers at sites including subgingival biofilm, supragingival biofilm, the tongue, buccal mucosa, and saliva. It has been suggested that those sites may provide reservoirs for re-colonization of the gingival crevice after periodontal treatment (Quirynen et al., 2001; Mager et al., 2003).

All the above species are fastidious anaerobes when grown in culture. Yet they are able to maintain themselves under the aerobic conditions associated with saliva and buccal mucosa. The buccal mucosa presents those species with the additional challenge of remaining in place as epithelial cells are shed. All of them have been shown to be capable of invading oral epithelial cells in tissue culture (Lamont et al., 1995; Madianos et al., 1996; Meyer et al., 1996; Han et al., 2000). In previous studies, we addressed the question of whether buccal cell invasion might provide a protected environment in vivo. Fluorescence in situ hybridization (FISH) and confocal microscopy (LSCM) were used to detect, first, intracellular A. actinomycetemcomitans and P. gingivalis and, later, T. forsythensis, within buccal epithelial cells (BEC) taken directly from the mouths of human subjects (Rudney et al., 2001; unpublished data).

In those studies, a FISH probe directed toward a 16S rRNA sequence present in all bacterial species consistently detected larger masses of intracellular bacteria than could be accounted for by 16S rRNA probes specific to our 3 target species (Rudney et al., 2001). One possible explanation for that observation could be that the intracellular flora of BEC is polymicrobial. In this study, we used double-labeling with universal and species-specific FISH probes to test that hypothesis.

	MATERIALS & METHODS

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Human Subjects
Informed consent was obtained according to a protocol approved by the University of Minnesota Institutional Review Board, after the nature and possible consequences of the studies were explained to a convenience sample of 38 adults (20 males and 18 females). BEC were collected from each person with sterile cytological brushes, according to our published protocol (Rudney et al., 2001).

Bacterial Loads
A portion of each sample was frozen at –80°C, then set aside for determination of bacterial loads for A. actinomycetemcomitans, P. gingivalis, and T. forsythensis. We found it difficult to estimate bacterial numbers by direct counting of confocal FISH images, because a typical image stack for a single BEC contained approximately 80 z-sections. Thus, a count of all bacteria from 100 cells for each subject would have required direct examination of about 280,000 z-sections. We therefore chose to use quantitative polymerase chain-reaction (qPCR) assays instead. The qPCR approach cannot distinguish intracellular bacteria from bacteria on cell surfaces. However, it is much easier to apply to complex biological samples than the antibiotic protection assay used to study single-species invasion of host cells in tissue culture.

We have recently published detailed endpoint qPCR protocols for enumeration of A. actinomycetemcomitans, P. gingivalis, and T. forsythensis (Rudney et al., 2003). The same methods were used here. Briefly, Masterpure kits (Epicentre, Madison, WI, USA) were used for DNA extraction from bacterial standards and BEC. Total DNA was then determined with Picogreen kits (Molecular Probes, Eugene, OR, USA). Our qPCR approach is based on the Amplifluor^TM system (Chemicon Inc., Temecula, CA, USA). A manufacturer-designed sequence (Z-tail) was added to the 5' end of one of each pair of species-specific primers. The Z-tail also constitutes the 3' end of a universal primer (UniPrimer^TM), incorporating a quenched fluorescein. During the earliest stages of amplification, the specific tailed primer incorporates the Z-sequence into the PCR product. The complement to the Z-tail can then anneal to the UniPrimer^TM. When the complementary strand is extended, the fluorescein is forced away from the quencher molecule. We determined the number of A. actinomycetemcomitans, P. gingivalis, and T. forsythensis cells in each BEC sample by semi-log regression against standard curves prepared as dilutions of DNA extracts from known quantities of each target species (grown in culture).

FISH
The balance of each BEC sample was fixed and processed for FISH. Probes were obtained from Oligos Etc. (Wilsonville, OR, USA) as 5' conjugates of Alexa Fluor^® dyes from Molecular Probes. The FISH protocol we have previously published was used, with modifications as described in the online Appendix (Rudney et al., 2001). Instead of using single probes, we prepared 3 probe mixtures. Each mixture contained a red fluorescent (Alexa Fluor 594^®) universal probe (EUB338), paired with green fluorescent (Alexa Fluor 488^®) versions of either the A. actinomycetemcomitans-, P. gingivalis-, or T. forsythensis-specific probes.

A mixture of red and green versions of the complement to EUB338 was used as the negative control. The probe sequence for T. forsythensis was 5' TTC ACC GCG GAC TTA ACA 3'. It was derived from a published PCR primer previously found to be specific for T. forsythensis 16S rDNA (Meurman et al., 1997). All other probe sequences were as previously described (Rudney et al., 2001). We confirmed the specificities of each universal/specific probe pair by hybridization to cultures of target species mixed with cultures of other oral species (Appendix Fig. 1).

Confocal Microscopy
Weak autofluorescence from BEC was sufficient to allow their outer edges to be seen at the red and green wavelengths. We verified this by triple-labeling some cells with probe pairs plus Alexa Fluor 647^®-conjugated peanut agglutinin (Molecular Probes), which binds to BEC membranes. Cells stained with peanut agglutinin without FISH were also compared with those cells, which confirmed that the FISH protocol did not change the appearance of BEC (Appendix Fig. 2). We used LSCM to determine whether labeled bacteria were intracellular. For each subject, z-section image files of fields that contained bacteria labeled with each species-specific probe were acquired with the use of Laser Sharp 3.1 software (Bio-Rad, Hercules, CA, USA) on a MRC-1024 confocal microscope (Bio-Rad) with a 60x oil immersion objective. In some cases, bacteria were visualized within BEC by the use of Confocal Assistant 4.02 (T. Brelje, Minneapolis, MN, USA) to run "movies" of z-section stacks (Rudney et al., 2001). To determine co-localization of the universal and species-specific probes, we superimposed z-sections imaged at the red and the green wavelengths. We generated three-dimensional reconstructions for printing by processing stacks of z-sections in the red and green channels in Huygens2 Professional software (Scientific Volume Imaging B.V., Hilversum, The Netherlands) for noise reduction, and then merging them in Amira 3.0 (Indeed-Visual Concepts, Berlin, Germany) for three-dimensional reconstruction. Distinct colors were assigned to bacteria visible only in the red stack (universal probe), bacteria co-localized in both stacks (recognized by both the universal and specific probes), and BEC surfaces.

	RESULTS

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Bacterial loads
We estimated the number of BEC per sample by dividing total sample DNA by 6 pg, an estimate of DNA yield per mammalian cell (Qiagen, 2004). The mean value ± SD was 7,959,239 ± 3,194,068. Mean bacterial loads per sample were expressed as logs, because they were strongly skewed to the right. The loads were highest for T. forsythensis (5.87 ± 2.62), lowest for P. gingivalis (2.41 ± 2.37), and intermediate for A. actinomycetemcomitans (3.90 ± 2.30). We divided bacterial loads (determined by qPCR) by the number of BEC to estimate the average numbers of bacteria per BEC. Those values also were highly skewed. As logs, they were –0.97 ± 0.62 for T. forsythensis, –4.40 ± 0.42 for P. gingivalis, and –2.95 ± 0.40 for A. actinomycetemcomitans.

FISH/LSCM
The universal probe showed that every BEC sample contained invaded cells. The negative control was negative in every subject. BEC with intracellular A. actinomycetemcomitans, P. gingivalis, or T. forsythensis were seen in 37, 32, and 35 subjects. Every BEC sample also contained uninvaded cells. Because of those uninvaded cells, the qPCR-based estimates of the average numbers of bacteria per BEC (see above) appeared to underestimate bacterial numbers within invaded cells. The technical issues described in MATERIALS & METHODS precluded our making direct counts of bacteria within all invaded cells (see above). As an alternative, semi-quantitative estimates were made for the stored z-section image that, in each person, appeared to contain the largest amount of intracellular bacteria labeled with a particular species-specific probe. The modal value for all 3 species was 10–50 bacteria/z-section, with a range from less than 10 to greater than 100 (Table). Every stored z-section that was labeled with a species-specific probe also contained more than 100 bacteria recognized only by the universal probe.

View larger version (91K): [in this window] [in a new window]   Figure 1. Panels A-C show images of z-section No. 39 from a stack of 74 0.2-µm z-sections (magnification 600X; the scale bar in Panel A also applies to Panels B and C). BEC in this field were double-labeled with the EUB338 universal probe (A) and the A. actinomycetemcomitans-specific probe (B). The cell in the center of Panel A contained a large mass of brightly fluorescent intracellular bacteria (red arrow). Other cells in the field contained smaller bacterial masses (not marked). Panel B shows that a portion of the large mass labeled with the universal probe also hybridized with the A. actinomycetemcomitans-specific probe (green arrow). The images from Panels A and B were superimposed (Panel C), confirming that bacteria labeled with both probes (yellow arrow) were adjacent to other bacteria labeled only with the universal probe (red arrow). Panel D presents a three-dimensional reconstruction of the same field. Bacteria recognized only by the universal probe are shown in solid red, while co-localization of the A. actinomycetemcomitans and universal probes is depicted by a green wireframe over a red interior. Reconstructed BEC surfaces are presented in blue. The red and green colors are muted when bacterial masses are intracellular, and brighter when bacteria appear to project out of the surface. The angle of view was rotated along the z-axis, and the image was zoomed. The large mass which appeared to have a lobular structure in z-section No. 39 was seen to be a cohesive unit containing A. actinomycetemcomitans in direct proximity to other species (red and green arrows).

An example of a cell where the species-specific probe was directed toward P. gingivalis showed extensive bacterial invasion, but only a relatively small proportion of the intracellular masses was labeled by the P. gingivalis probe (Fig. 2A). That pattern seemed typical, in the sense that we rarely observed cells in which A. actinomycetemcomitans, P. gingivalis, or T. forsythensis appeared to be the dominant species (also see Table).

View larger version (67K): [in this window] [in a new window]   Figure 2. In Panel A, the green wireframe denotes bacteria labeled by the P. gingivalis-specific probe. There were many bacterial masses within the cell shown, but only small portions of those masses appeared to contain P. gingivalis. In Panel B, the green wireframe indicates bacteria labeled by the T. forsythensis-specific probe. Note that the upper perimeter of that cell could not be properly rendered. The cell seemed to be almost completely filled with bacteria. Large masses of T. forsythensis were present, but species recognized only by the universal probe appeared to dominate the intracellular flora (the scale bar in Panel B applies to Panel A as well).

One drawback of three-dimensional reconstructions made for printing is that the extensive image processing required leads to loss of resolution of individual bacterial cells. Single bacteria can more easily be seen in Confocal Assistant movies for these Figs., which are available online (Appendix Figs. 3–5).

	DISCUSSION

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Bacterial loads for P. gingivalis and T. forsythensis in BEC samples were lower than those we had previously found for disease-related subgingival biofilm, while A. actinomycetemcomitans loads appeared to be higher (Rudney et al., 2003). Analysis of our earlier qPCR data likewise suggests that buccal epithelia in healthy subjects may carry heavier loads of those species than supragingival biofilm (Rudney et al., 2003). That pattern of site distribution is in general agreement with results from a recent study (Mager et al., 2003) in which the authors reported a mean proportion of T. forsythensis from buccal surfaces (1.2%) which was approximately 4 times higher than that obtained for supragingival biofilm (0.3%), and higher than that seen for any other oral surface except subgingival biofilm (1.7%). Likewise, a culture-based study of the oral distribution of A. actinomycetemcomitans in a large number of periodontally healthy subjects also indicated that loads were higher on buccal mucosa than in subgingival or supragingival biofilm (Muller et al., 1996). Overall, there is strong evidence to suggest that the shedding buccal epithelial surface is capable of supporting surprisingly large bacterial populations. Moreover, those populations may include relatively greater numbers of some pathogenic species than are found on supragingival tooth surfaces. This seems consistent with the hypothesis that buccal cells may provide a reservoir for subgingival recolonization.

In our BEC samples, "super-invaded" cells co-occurred with sparsely invaded cells and uninvaded cells. A similar pattern has been described for an in vivo mouse model in which bladder epithelium was invaded by uropathogenic E. coli (Mulvey et al., 2001). Those authors suggested that invasion provided a means for infection to persist, despite the frequent shedding of bladder epithelial cells. Their model was mono-specific, and the bladder contains only shedding surfaces. In the mouth, shedding mucosal surfaces co-occur with non-shedding tooth surfaces that harbor a complex diverse biofilm (Paster et al., 2001; Mager et al., 2003). Our study is the first to show that bacterial masses inside oral mucosal cells share the polymicrobial nature of tooth-surface biofilm.

We do not yet know whether intracellular bacterial masses will prove to be as diverse as tooth-surface biofilm, although we are actively investigating that question. Several scenarios can be proposed. Invasiveness might be limited to a subset of oral species that use it as a virulence factor. Alternatively, a wide range of oral bacteria which principally live in biofilm might be capable of invasion as a means of persisting when they happen to encounter a shedding surface. Since species interaction appears to be widespread in oral biofilm (Cook et al., 1998; Fong et al., 2001; Palmer et al., 2001, 2003; McNab et al., 2003), another alternative could be that non-invasive species gain entrance to cells by forming consortia with invasive species.

Previous studies of invasion have focused on putative periodontal pathogens such as A. actinomycetemcomitans, P. gingivalis, and T. forsythensis (Lamont et al., 1995; Madianos et al., 1996; Meyer et al., 1996; Han et al., 2000). That has tended to bring the virulence factor explanation to the forefront. However, our findings suggest that those 3 species are not dominant members of the buccal intracellular flora. That pattern is consistent with published observations of mucosal surfaces by DNA "checkerboard" analysis (Mager et al., 2003). We are looking at patients with active periodontitis, and it will be interesting to see whether pathogenic species are more prevalent inside buccal cells from those subjects. However, our present results seem more suggestive of invasion by either a broad range of species, or by consortia in which the non-invasive partners grow faster than those responsible for gaining entry to the cell.

Invasive bacteria generally gain entry by co-opting and re-directing host cell mechanisms such as endocytosis (Lamont et al., 1995; Meyer et al., 1996, 1999; Sandros et al., 1996; Progulske-Fox et al., 1999; Han et al., 2000). Investigators have explored the molecular basis for such interactions by looking at mono-specific infections of host cells in tissue culture. As yet, however, there is no information on how such species-specific interactions will be influenced by the presence of multiple species. Such studies are likely to present challenging technical problems, but our results suggest that it will be important to make the attempt.

	ACKNOWLEDGMENTS

 
This study was supported by USPHS grant DE 14214 from the National Institute of Dental and Craniofacial Research, Bethesda, MD 20892, USA.

	FOOTNOTES

 
A supplemental appendix to this article is published electronically only at http://www.dentalresearch.org.

Received September 12, 2003; Last revision October 1, 2004; Accepted October 13, 2004

	REFERENCES

TOP ABSTRACT INTRODUCTION MATERIALS & METHODS RESULTS DISCUSSION REFERENCES

 
Cook GS, Costerton JW, Lamont RJ (1998). Biofilm formation by Porphyromonas gingivalis and Streptococcus gordonii. J Periodontal Res 33:323–327.[ISI][Medline]

Fong KP, Chung WO, Lamont RJ, Demuth DR (2001). Intra- and interspecies regulation of gene expression by Actinobacillus actinomycetemcomitans LuxS. Infect Immun 69:7625–7634.[Abstract/Free Full Text]

Han YW, Shi W, Huang GT, Kinder Haake S, Park N-H, Kuramitsu H, et al. (2000). Interactions between periodontal bacteria and human oral epithelial cells: Fusobacterium nucleatum adheres to and invades epithelial cells. Infect Immun 68:3140–3146.[Abstract/Free Full Text]

Lamont RJ, Chan A, Belton CM, Izutsu KT, Vasel D, Weinberg A (1995). Porphyromonas gingivalis invasion of gingival epithelial cells. Infect Immun 63:3878–3885.[Abstract]

Madianos PN, Papapanou PN, Nannmark U, Dahlén G, Sandros J (1996). Porphyromonas gingivalis FDC381 multiplies and persists within human oral epithelial cells in vitro. Infect Immun 64:660–664.[Abstract]

Mager DL, Ximenez-Fyvie LA, Haffajee AD, Socransky SS (2003). Distribution of selected bacterial species on intraoral surfaces. J Clin Periodontol 30:644–654.[ISI][Medline]

McNab R, Ford SK, El-Sabaeny A, Barbieri B, Cook GS, Lamont RJ (2003). LuxS-based signaling in Streptococcus gordonii: autoinducer 2 controls carbohydrate metabolism and biofilm formation with Porphyromonas gingivalis. J Bacteriol 185:274–284.[Abstract/Free Full Text]

Meurman JH, Wahlfors J, Korhonen A, Alakuijala P, Vaisanen P, Torkko H, et al. (1997). Identification of Bacteroides forsythus in subgingival dental plaque with the aid of a rapid PCR method. J Dent Res 76:1376–1380.[Abstract/Free Full Text]

Meyer DH, Lippmann JE, Fives-Taylor PM (1996). Invasion of epithelial cells by Actinobacillus actinomycetemcomitans—a dynamic, multistep process. Infect Immun 64:2988–2997.[Abstract]

Meyer DH, Rose JE, Lippmann JE, Fives-Taylor PM (1999). Microtubules are associated with intracellular movement and spread of the periodontopathogen Actinobacillus actinomycetemcomitans. Infect Immun 67:6518–6525.[Abstract/Free Full Text]

Muller HP, Zoller L, Eger T, Hoffmann S, Lobinsky D (1996). Natural distribution of oral Actinobacillus actinomycetemcomitans in young men with minimal periodontal disease. J Periodontal Res 31:373–380.[ISI][Medline]

Mulvey MA, Schilling JD, Hultgren SJ (2001). Establishment of a persistent Escherichia coli reservoir during the acute phase of a bladder infection. Infect Immun 69:4572–4579.[Abstract/Free Full Text]

Palmer RJ Jr, Kazmerzak K, Hansen MC, Kolenbrander PE (2001). Mutualism versus independence: strategies of mixed-species oral biofilms in vitro using saliva as the sole nutrient source. Infect Immun 69:5794–5804.[Abstract/Free Full Text]

Palmer RJ Jr, Gordon SM, Cisar JO, Kolenbrander PE (2003). Coaggregation-mediated interactions of streptococci and actinomyces detected in initial human dental plaque. J Bacteriol 185:3400–3409.[Abstract/Free Full Text]

Paster BJ, Boches SK, Galvin JL, Ericson RE, Lau CN, Levanos VA, et al. (2001). Bacterial diversity in human subgingival plaque. J Bacteriol 183:3770–3783.[Abstract/Free Full Text]

Progulske-Fox A, Kozarov E, Dorn B, Dunn W Jr, Burks J, Wu Y (1999). Porphyromonas gingivalis virulence factors and invasion of cells of the cardiovascular system. J Periodontal Res 34:393–399.[ISI][Medline]

Qiagen Inc. (2004). DNeasy^® tissue handbook. Valencia, CA: Qiagen Inc.

Quirynen M, Soete MD, Dierickx K, van Steenberghe D (2001). The intra-oral translocation of periodontopathogens jeopardises the outcome of periodontal therapy. A review of the literature. J Clin Periodontol 28:499–507.[ISI][Medline]

Rudney JD, Chen R, Sedgewick GJ (2001). Intracellular Actinobacillus actinomycetemcomitans and Porphyromonas gingivalis in buccal epithelial cells collected from human subjects. Infect Immun 69:2700–2707.[Abstract/Free Full Text]

Rudney JD, Chen R, Pan Y (2003). Endpoint quantitative PCR assays for Bacteroides forsythus, Porphyromonas gingivalis, and Actinobacillus actinomycetemcomitans. J Periodontal Res 38:465–470.[ISI][Medline]

Sandros J, Madianos PN, Papapanou PN (1996). Cellular events concurrent with Porphyromonas gingivalis invasion of oral epithelium in vitro. Eur J Oral Sci 104:363–371.[ISI][Medline]

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This Article Abstract Figures Only Full Text (PDF) HTML Page - index.htslp Services Similar articles in this journal Similar articles in ISI Web of Science Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via ISI Web of Science (23) Citing Articles via Google Scholar Google Scholar Articles by Rudney, J.D. Articles by Sedgewick, G.J. Search for Related Content PubMed PubMed Citation Articles by Rudney, J.D. Articles by Sedgewick, G.J.