Campylobacter concisus is a fastidious, hydrogen-requiring, gram negative bacterium, normally found in the human oral cavity and is considered as an emerging pathogen. It is genetically diverse and can be grouped into 2 genomospecies by amplification of the 23S rDNA gene. C. concisus was found to produce biofilms on glass, stainless steel, and polystyrene plastic. Regulation of biofilm formation has been linked to the luxS gene in many oral pathogens. However, no thorough investigation on biofilm formation in this species has been performed yet.
In this study, biofilm formation by C. concisus clinical strains from children with gastroenteritis and biofilm formation by oral strains from healthy individuals was investigated. The genomospecies of these strains was confirmed by PCR amplification of the 23S rDNA. All strains were screened for biofilm production by the crystal violet assay. For C. concisus this assay was optimized in brucella broth with an inoculum size of (106 cfu/ml) with 4 days incubation time. The biofilms were phenotypically characterized by phase contrast and by confocal microscopy. PCR amplification of the luxS gene, which may play a critical role in biofilm formation in this species, was performed using oligonucleotides designed from the genome sequence of C. concisus13826.
Among the tested 15 clinical strains, 3 produced no biofilm, 8 were weak biofilm producers and 4 isolates produced medium to high amounts of biofilm. However, among the 19 oral strains, 7 produced weak biofilms, and 11 isolates produced medium to high amounts of biofilm indicating that the oral strains were better biofilm producers than the clinical strains regardless of their genomospecies (A or B). The luxS gene sequence was detected in the genomic DNA of all clinical and oral strains from both genomospecies. Further molecular studies are underway to assess biofilm formation in selected C. concisus strains.