Enterobacterales abundance in oral cancer patients and elevated clindamycin resistance rates in head and neck infections at a Hungarian Tertiary Hospital.

Background: Oral bacteria have been associated with several systemic diseases, and studies have highlighted their potential role in carcinogenesis. A biofilm is considered an antimicrobial resistance gene reservoir, and the oral cavity provides an excellent environment for biofilm formation. The aim of this study was to evaluate the pathogen spectrum and antimicrobial resistance rates of clinical isolates from head and neck infections in the Hungarian population.

Methods: A total of 5185 bacterial isolates were analyzed from 1978 patients between 2018 and 2023. Antimicrobial resistance rates were reported according to the EUCAST guidelines. The primary diagnoses of the patients were categorized into three major groups: abscesses, necrotizing lesions and surgical site infections of patients treated for malignant tumors. Pearson's chi-square test was used to compare the percentages of bacteria in the different patient groups.

Results: The most frequently isolated bacteria were Streptococcus (18.8%) and Prevotella spp. (13.5%), followed by Staphylococcus (13.2%) and Fusobacterium spp. (9.1%). Differences in the pathogen spectrum of three patient groups ('abscess', 'necrosis' and 'tumor') were also evaluated. Compared with the other two patient groups, cancer patients had significantly greater percentages of Enterobacter spp., Enterococcus spp., Pseudomonas spp. and beta-hemolytic streptococci. Substantial resistance rates to clindamycin were observed for Prevotella, Streptococcus and Staphylococcus spp. at 40.9% (95% CI [37.3-44.7%]), 34.8% (95% CI [31.8-37.9%]) and 32.3% (95% CI [28.8-35.9%]), respectively. The percentage of methicillin-resistant Staphylococcus aureus isolates was 13.8% (95% CI [9.2-19.5%]). The percentage of vancomycin-resistant Enterococcus spp. isolates was 2.8% (95% CI [0.6-8.0%]), and the percentages of extended-spectrum beta-lactamase-producing E. coli and Klebsiella spp. isolates were 1% (95% CI [0.02-5.6%]) and 2.6% (95% CI [0.8-5.9%]), respectively.

Conclusion: Our evaluation revealed high percentages of Enterobacterales in patients with diseases such as osteonecrosis or oral cancer. Further investigation of the role of the oral microbiota and its potential impact on the morbidity of patients with advanced disease is needed. Substantial antimicrobial resistance rates, particularly to clindamycin, pose a major concern for treating bacterial infections in the head and neck region.