Seven Miami-Dade hospitals fell below national standards for combating infections acquired by patients in hospitals, and patients at one hospital — North Shore Medical Center in Miami — were more likely to develop infections than patients at any other hospital in South Florida, according to data collected by the federal government as part of a national effort to reduce such infections. The Centers for Disease Control and Prevention tracks how hospitals around the nation perform on preventing six types of frequently occurring infections, including bloodstream and urinary tract infections that result from catheters and surgical site infections that develop after colon and hysterectomy operations.