Kroger Co, the biggest U.S. supermarket operator, reported a 9 percent rise in quarterly profit, helped by the acquisition of grocer Harris Teeter Supermarkets Inc. Shares of Kroger, which owns the Ralphs, Smith's and Food 4 Less grocery chains and supplement seller Vitacost.com, rose 2.4 percent to $53.12 in premarket trading. Net income attributable to Kroger rose to $347 million, or 70 cents per share, in the second quarter ended Aug. 16 from $317 million, or 60 cents per share, a year earlier.