Having recovered from acute respiratory disease, a patient has made an appointment with a dentist. The patient complains of pain in the gums, foul breath, inability to take food, general weakness. Objectively: the gums are hyperemic, swollen, covered with necrotic dirty-gray coating; the gums bleed when the coating is removed.Microbiological study of tissues revealed a great number of cocci, bacilli, fusobacteria, and spirochaete. Specify the drug for etiotropic treatment: