ANKARA (Turkey), February 11 (SeeNews) – Standard&Poor's Ratings Services said on Tuesday it has downgraded to negative from neutral its outlook on Turkey's Isbank [BIST:ISATR], Garanti Bank [BIST:GARAN], Garanti Leasing [BIST:GRFIN], Yapi Kredi Bank [BIST:YKBNK], HSBC Bank A.S. and Vakifbank [BIST:VAKBN].