Having recovered from acute respiratory disease, a patient has made an appointment with a dentist. The patient complains of pain in the gums, bad breath, inability to take food, general weakness. Objectively: the gums are hyperemic, swollen, covered in necrotic dirty-grey 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.