, ▁path ogen ic ▁b acter ium . ▁It ▁forms ▁black ▁colon ies ▁on ▁blood ▁ag ar . ▁ ▁It ▁is ▁found ▁in ▁the ▁or al ▁cav ity , ▁where ▁it ▁is ▁imp licated ▁in ▁period ont al ▁disease , ▁as ▁well ▁as ▁in ▁the ▁upper ▁g astro int est inal ▁tract , ▁the ▁resp ir atory ▁tract ▁and ▁the ▁colon . ▁It ▁has ▁been ▁isolated ▁from ▁women ▁with ▁b acter ial ▁v ag inos is . ▁ ▁Col lagen ▁de grad ation ▁observed ▁in ▁chron ic ▁period ont al ▁disease ▁results ▁in ▁part ▁from ▁the ▁col lagen ase ▁en zym es ▁of ▁this ▁species . ▁It ▁has ▁been ▁shown ▁in ▁an ▁in ▁vit ro ▁study ▁that ▁P . ▁ging ival is ▁can ▁in va de ▁human ▁ging ival ▁fib ro bl asts ▁and ▁can ▁surv ive ▁in ▁the ▁presence ▁of ▁ant ib iot ics . ▁P . ▁ging ival is ▁inv ades ▁ging ival ▁ep ith el ial ▁cells ▁in ▁high ▁numbers , ▁in ▁which ▁case ▁both ▁b acter ia ▁and ▁ep ith el ial ▁cells ▁surv ive ▁for ▁extended ▁periods ▁of ▁time . ▁High ▁levels ▁of ▁specific ▁ant ib od ies ▁can ▁be ▁detected ▁in ▁patients ▁har bor ing ▁P . ▁ging ival is . ▁ ▁P . ▁ging ival is ▁in fection ▁has ▁been ▁linked ▁to ▁Al z heimer ' s ▁disease ▁and ▁r he um ato id ▁ar th rit is . ▁It ▁contains ▁the ▁en zym e ▁pe pt id yl - argin ine ▁de imin ase ,