US STOCKS-Wall St dips after China stocks tumble
* Chinese shares post biggest drop in eight years
* Oil prices, commodities lower following China market rout
* Dow hits lowest level in five months
* Teva, Allergan jump after $40.5 bln deal
* Indexes down: Dow 0.58 pct, S&P 0.36 pct, Nasdaq 0.55 pct (Adds details, changes comment, updates prices)
By Tanya Agrawal
July 27 (Reuters) - Wall Street began the week in the red on Monday and fell sharply on concerns about China's slowing growth in the wake of the biggest drop in Shanghai shares in eight years.
The Dow Jones industrial average fell to its lowest level in over five months while the Nasdaq composite was at a four-week low and the S&P 500 touched its lowest in more than two weeks.
Chinese shares tumbled more than 8 percent as an unprecedented government rescue plan to prop up valuations abruptly ran out of steam, raising doubts about the viability of Beijing's efforts to stave off a deeper crash. Continuación...