Microorganisms involved in deep neck infection (DNIs) in Greece: detection, identification and susceptibility to antimicrobials

BACKGROUND: To determine, from October 2010 to October 2018, the epidemiology of Deep Neck Infections (DNIs), regarding the detection, the identification and the susceptibility to antimicrobials of causative microorganisms, in Thessaly-Central Greece. METHODS: An analysis of data from a prospective database was conducted on 610 consecutive patients with DNIs treated in the Otolaryngology / Head & Neck Surgery Department of University Hospital of Larissa. Demographics, clinical features and microbiological data were analyzed. RESULTS: Among the 610 patients (1,9/1 male to female ratio, mean age: 39,24 ± 17,25) with DNIs, 579 had a single space (94,9%), while the remaining 31 had a multi-space (5,1%) DNI. The most common areas affected were the peritonsillar space (84,6%) followed by the submandibular space (6,5%). Clinical samples were obtained from 462 patients, and were tested by culture and by the application of 16S rRNA PCR. Two hundred fifty-five samples (55,2%) gave positive cultures, in which Streptococcus pyogenes and Staphylococcus aureus were predominant. The application of the 16S rRNA PCR revealed that 183 samples (39,6%) were positive for bacterial DNA; 22 of them, culture negative, were found to be positive for anaerobic (Fusobacterium necrophorum, Actinomyces israellii etc) and for fastidious microorganisms (Brucella mellitensis, Mycobacterium avium). CONCLUSION: DNIs represent a medical and surgical emergency and evidence-guided empirical treatment with intravenous infusion of antibiotics at the time of diagnosis is mandatory, highlighting the importance of epidemiological studies regarding the causative microorganisms. Although, in our study, the predominant pathogens were S. pyogenes and S. aureus, the combination of culture and molecular assay revealed that anaerobic bacteria play also a significant role in the pathogenesis of DNIs. Based on the local epidemiology, we propose as empirical therapy the intravenous use of a beta-lactam /beta-lactamase inhibitor; metronidazole or clindamycin can be added only in specific cases such as in immunocompromised patients.