Aggregative Behavior of Bacteria Isolated from Canine Dental Plaque

Abstract

Interbacterial adhesion of bacteria isolated from canine dental plaque was assessed by performing a visual coaggregation assay. Using conditions mimicking those likely to be encountered in vivo, the entire cultivable plaque microbiota from a single dog was assessed, and eight (6.7%) unique coaggregation interactions were detected for 120 crosses. Transmission electron microscopy was used to visualize several of the bacteria in isolation and as coaggregates, which revealed surface structures that may be involved in adhesion and coaggregation. The results of this study indicate that the prevalence of coaggregating pairs of dental plaque bacteria in dogs is similar to the prevalence of coaggregating pairs of dental plaque bacteria reported in humans. In addition, genera found in both hosts generally exhibited similar coaggregation reactions; however, autoaggregation was found to be more common among oral bacteria isolated from dogs.Coaggregation is the term used to describe adhesion of genetically distinct microbial cells to each other in a suspension (12), and autoaggregation is the term used to describe the same phenomenon for genetically identical cells. These processes, in conjunction with adhesion to a substratum, are important factors in the development of bacterial biofilms (14). Coaggregation may have evolved in concert with structural and metabolic codependencies which in turn facilitate the development of complex biofilm communities, such as dental plaque. This possibility is supported by the findings of Bradshaw et al.(1), who showed that certain bacterial aggregates could allow obligate anaerobes to persist in aerated cultures.Gibbons and Nygaard (5) were the first workers to realize the potential importance of cell-to-cell adhesion in the development of dental plaque and to develop a method for measuring interbacterial aggregation, which is now more commonly called coaggregation. They used this method to assess the coaggregation of 23 strains of numerically dominant culturable bacteria and found that 18 of these strains participated in coaggregation reactions; a total of 23 interactions were observed for the 253 pairs tested. This work has been continued by many workers, who often assess coaggregation by using the convenient visual assay described by Cisar et al. (2), which uses a system of scores from 0 to 4. Kolenbrander and Andersen (10) extended this work further by using radioactively labeled cells in coaggregation assays, which allowed them to address more elaborate questions, such as the stability of coaggregation bonds and the trapping of noncoaggregating cells by coaggregation networks.Coaggregation research has focused primarily on bacteria isolated from human dental plaque; however, coaggregation has recently been shown to occur between bacteria from water systems, leading to the suggestion that it may be a universal phenomenon among biofilm-forming bacteria (14). Coaggregation studies using bacteria from the canine oral microbiota should allow comparisons with the large volume of data relat...

Autoaggregation Response of Fusobacterium nucleatum

“…In F. nucleatum ATCC strain 25586, we found a rapid autoaggregation response in the presence of saliva but found no evidence for this ability in the closely related strain ATCC 23726. Recently, two separate reports examining multiple fresh clinical isolates of F. nucleatum both reported autoaggregation in their strains (20,35), and a similar finding was recently reported with canine fusobacterial isolates as well (10). Thus, it may be that some laboratory strains of F. nucleatum have lost this ability upon subculturing, similar to what is routinely seen with A. actinomycetemcomitans (11,18).…”

Coaggregation occurs amongst bacteria within and between biofilms in domestic showerheads

“…No correlation to whole cell-hydrophobicity was discerned suggesting that autoaggregation and coaggregation may be mediated by specific complementary cell-surface molecules that have limited effect on gross hydrophibic properties. Autoaggregation has the potential to mask coaggregation interactions (Elliott et al, 2006; Reid et al, 1988). When coaggregation was suspected between two isolates that autoaggregated, cells from both isolates were stained with different Styo® dyes prior to mixing, so they could be differentiated by fluorescence, and the autoaggregative and coaggregative abilities were assessed using confocal microscopy.…”

“…When mixed together these autoaggregating isolates adhered to one-another to form larger inter-generic flocs and, based upon microscopic and visual observations, gave a visual score of 4. Our protocol for determining the degree of coaggregation between two isolates with the ability to autoaggregate differed from previous work categorizing aggregative abilities in that a subtractive scoring would have resulting in a visual coaggregation score of a zero for the pair M. hispanicum AH007 and M. trichothecenolyticum HM016 (Elliott et al, 2006; Rickard et al, 2003b). This scoring would have been a mischaracterization of the actual interactions between the two species and the ability of these isolates to coaggregate would not have been discovered.…”

Prospective randomised blinded clinical trial assessing effectiveness of three dental plaque control methods in dogs

“…While the impact that PD has on oral health is well recognised, the influence of PD as a causal factor in systemic disease and the benefit of effective oral care has recently received increased interest (Rawlinson et al 2011, Whyte et al 2014. The development of PD is recognised as having multiple risk factors (Van Dyke & Sheilesh 2005), although plaque accumulation with its highly complex polymicrobial communities is recognised as the primary causative factor for the initiation of gingivitis and progression to PD (Lindhe et al 1973, Elliott et al 2006, Davis et al 2014.…”