Hospital in the murder case

This is also recommended

Patients hospitalized with large hospital in Kanagawa-ku, Yokohama-shi that has been one after another poisoning death was found.
Because the foreign matter in the drip has been mixed, it seems was also happening disturbing trouble in the fourth floor of the hospital from the previous. In the interior of the crime? While perspective is intensified with, such as had been put in place to touch instillation anyone, it is also questioned sloppy management system of the hospital.

Revealed the dozens of patients in recent months in the hospital were killed, for more than usual, director and "had been suspected nosocomial infection" seems to have been described.

Who what is the culprit?