As the development of modern medical techniques, more and more invasive operation such as vein and venous cannula, urinary catheter, trachea cannula, suction device, probes of monitoring instrument bring more conveniences in diagnosis and treatment for patients. Bacteria were dragged in vivo from outside at the moment of invasive operation, and the defensive barrier was destroyed at the same time. All of the operation could increase the rate of hospital infections, and threatened the health of patients and medical staffs. It’s very important for the clinical test of bacteria to identify the pathogenic microorganisms on patients with hospital infections.