CONCORD, N.H. — A former medical technician at ­Exeter Hospital accused of spreading hepatitis C to dozens of patients nationwide pleaded not guilty Monday in federal court and was given a trial date of early February.

David M. Kwiatkowski, appear­ing stocky in a tan prison uniform and displaying a trim haircut and goatee, was indicted last week in an elaborate scheme to steal powerful painkillers, causing patients to become infected with his strain of the liver-damaging virus. Prosecutors say he grabbed ­syringes loaded with the painkiller fentanyl, and, in an effort to avoid detection, replaced them with syringes that he had previously used. The substitute syringes, refilled with saline ­solution and tainted with hepatitis C, were used on patients by unknowing Exeter Hospital ­clinicians.