SACRAMENTO -- Some Pelican Bay State Prison inmates have been isolated and employees are taking extra precautions for fear of spreading an antibiotic-resistant strain of staph bacteria, Department of Corrections officials said Thursday.

About four inmates each month for the last year have been treated for Methicillin Resistant Staphylococcus aureus, more commonly called MRSA, said spokeswoman Margot Bach. One inmate is currently undergoing treatment.

Four correctional officers at the prison near Crescent City have filed claims alleging they suffered exposure, but one was determined to have a different infection. The remaining three are being reviewed by the State Compensation Insurance Fund.

An officer died Dec. 20 from complications of a stroke, pneumonia and diabetes, not MRSA as some officers had feared, Bach said.

The problem became an issue this fall in a federal judge's ongoing oversight of problems at Pelican Bay, but the infection alleged by an officer in that case turned out to be a different disease, said Bach and California Correctional Peace Officers Association Vice President Lance Corcoran.

The prison system suffers periodic sporadic outbreaks of MRSA, Bach said. Prisons are particularly vulnerable because so many people are jammed into tight quarters, and inmates suffer from more health problems than the general population, she said.

Inmates suspected of contracting the bacteria are housed separately in a separate unit, denied visitors, and their cells, clothing and linens are sanitized by employees who take extra precautions like wearing gloves and masks, she said. Inmates and employees throughout the prison also are getting extra education on avoiding contamination.

Staph bacteria are common on the skin and in the nose of all people, but sometimes result in infections, according to the federal Centers for Disease Control and Prevention. Most of the infections result in simple pimples or boils that go away without treatment.

But the bacteria also can infect surgical wounds or cause pneumonia, which for the last 50 years has been treated with various antibiotics. Over that time, strains of the bacteria have become progressively more resistant to the antibiotics.

Those strains have caused problems recently in health care facilities, particularly among patients who are elderly, very ill, or have an open wound, according to the CDC. Clusters of MRSA infections are also common in other situations including prisons, the CDC said.