The University of Michigan is undertaking a five-year, $7.5 million federal study of bacteria that cause an increasing number of serious infections in hospitals and nursing homes.

The National Institutes of Health grant is funding the research on the growing effect of the bacterium called Clostridium difficile (klohs-TRID'-ee-um dih-FIH'-sih-leh).

Scientists will seek the factors in the microbe and in patients that contribute to the disease's spread. The university says about half-million Americans are infected each year.

Lead researcher Dr. Vincent Young says the work will look at genetic variations in bacteria that lead to serious infections and how antibiotics sometimes leave patients vulnerable to infection.