What is the fine-grained topic of the following text: CSA Energy Infrastructure Switzerland (an investment group of the Credit Suisse Investment Foundation) together with other institutional investors, the Swiss gas industry comprising Swissgas and various Swiss utilities (Holdigaz, Gaznat, EGO, Groupe E and Gas & Com) and Fluxys, a Belgian operator of gas infrastructure in Europe, agreed to acquire a 44.9% stake in FluxSwiss LLC from Global Infrastructure Partners (GIP). Only return the topic.
Acquisition of a stake in FluxSwiss LLC by CSA Energy Infrastructure Switzerland and other investors.