Establishment of a bacteria-HOKs co-culture model

Method: Selected oral bacteria S. mutans, A. israelii, A. actinomycetemcomitans and P. gingivalis were cultured on blood agar. The planktonic bacteria were then added into the medium of cultured HOKs under various conditions, including addition of antibiotics, different multiplicity of infection (MOI), a range of time duration, and aerobic/anaerobic environments. The viability of both bacterial and HOK cells in the co-culture model under different circumstances was assessed using spiral plate and colony forming unit counting, MTT and qPCR, in order to determine the appropriate condition for the co-culture model. 

Result: The co-culture model incubated in aerobic chamber was found to be appropriate for maintaining the viability of HOKs. All bacterial species were unable to survive in the HOKs medium (OKM) with antibiotics. In the OKM without antibiotics, all bacteria could grow and proliferate to more than 10 times for 2h. However, when co-culture duration increased to 24h, Pg failed to show any viability in the aerobic chamber in contrast to Sm. MOI 1 was chosen to be the appropriate, since it contained substantial cells of both bacteria and HOKs in the co-culture model. No significant difference existed in the viability of HOKs in the co-culture models with reference to the control (p>0.05). Both bacteria and host cells were substantial in the co-culture model of MOI 1 for 2h.  

Conclusion: This study shows that the in vitro co-culture model of periodontal commensals or pathogens with HOKs can be established appropriately, through adding live bacteria to the non-antibiotics contained OKM using a MOI 1 for incubation of 2h in aerobic environment.