Healthcare stocks were at the top of the pile on Wednesday on the back of continued M&A activity in the sector, with UK-listed medical device maker Smith & Nephew in focus on reports of bid interest from overseas.The Financial Times reported today that US group Stryker had hired banks and was working on the funding for a possible bid for the wound management, endoscopy and orthopaedics group.Smith & Nephew shares initially surged 17.5% to an intraday high of 1,120p after the news first broke, but had quickly pared gains to just 2.8% after it was reported that Stryker is not looking to make an offer."At the request of the UK Takeover Panel, Stryker confirms that it does not intend to make an offer for Smith & Nephew," it said on Wednesday.Nevertheless, the reports follow a wave of M&A deals and rumours across the global healthcare and pharmaceutical sectors which have given sentiment a lift in recent months. These included Biomet's $13.35bn purchase of Zimmer, a multi-billion pound asset swap between GlaxoSmithKline and Novartis, and, most recently, Pfizer's failed near-£70bn takeover of AstraZeneca.Healthcare equipment and service peers such as Tristel, CareTech and NMC Health were all making gains today.The pharma sector, however, was stuck in the red on Wednesday as GlaxoSmithKline dropped after the Serious Fraud Office opened a criminal investigation into the "commercial practices" of the firm.While details regarding this particular case are not yet known, the news will come as a further blow to shareholders after a wave of allegations against the company relating to international bribery.Top performing sectors so far todayHealth Care Equipment & Services 5,466.47 +2.49%Aerospace and Defence 4,816.04 +1.41%Technology Hardware & Equipment 1,116.91 +1.41%Insurance (non-life) 1,864.32 +1.06%Fixed Line Telecommunications 4,566.01 +1.01%Bottom performing sectors so far todayIndustrial Transportation 3,054.46 -1.58%Beverages 14,254.25 -1.04%Mining 16,828.57 -0.80%Pharmaceuticals & Biotechnology 12,728.03 -0.47%Oil Equipment, Services & Distribution 23,743.08 -0.36%BC