FRANKFURT (Reuters) -Elliott Investment Management has taken a stake in Fresenius SE, a person familiar with the matter told Reuters on Wednesday, sparking speculation the activist investor might push for a break up of the diversified healthcare company. Fresenius and Elliott were not immediately available for comment. Shares in the company, which is controlled by charitable trust Else Kroener Fresenius-Stiftung, were up 9% at 1202 GMT. Before the news, shares in Fresenius had lost about 40% this year, in part because of ballooning costs at subsidiary Fresenius Medical Care. Bloomberg earlier …