The thirteen stand accused of beating, tying up and neglecting patients and elderly residents at the care home in Montaquila, dubbed the "clinic of horrors" by investigators.
The suspects include a doctor, nurses, health workers and the owner of the care home who is also the town's mayor, Francesco Rossi, Ansa reported on Wednesday.
The arrests were made at dawn by police from the southern towns of Naples, Bari, Foggia and Salerno.
Twenty others are also being investigated at the care home, which treats around 150 patients.
The alarm was raised by relatives of one of the patients at the care home, who noticed injuries on their body.
Police are expected to show a video showing the abuse at a press conference.
Quoted by Ansa, chief prosecutor of Isernia Paolo Albano said the patients were “confined in that structure like in a concentration camp”.
The prosecutor added that “males and females were made to wash in the same bathroom and dried with dirty sheets”.