She also indicated that AS Biss would build a 'stronger Brussels operation', and said she would remain in control of her 25-strong agency.
According to PRWeek's Top 150 PR Consultancies 2005, AS Biss had a fee income of around £2m in 2004 on turnover of £2.2m.
The acquisitions come as WCRS restructures following its £13m buyout from Havas last week.
Slice MD Jason Gallucci, who joined this summer from Mason Williams, said his future role, and that of Slice founder Damian Mould, were being finalised.
He added that Slice hoped the deal would give it access to Engine's blue-chip clients, which include BMW, Mini and Heinz.
The rebrand to Engine, which owns direct marketing firm Personal and media planning agency Element, sees the WCRS brand maintained for Engine's marketing and advertising arm.
Also joining the restructured Engine board is Ogilvy PR Worldwide finance director Ian Day. He will report to WCRS co-founder and Engine executive chairman Peter Scott, and Engine CEO Stephen Woodford.
Day, who is also Ogilvy & Mather EMEA's finance director, will take the same role at Engine when he joins in December.