Abstract
BACKGROUND: This study investigated the distribution characteristics and antimicrobial resistance patterns of pathogens isolated from patients with oral and maxillofacial infections during and after the COVID-19 pandemic. METHODS: This retrospective study analyzed microbial cultures of specimens obtained from patients with odontogenic and non-odontogenic oral and maxillofacial infections during the pandemic period (January 2020-December 2022) and the post-pandemic period (January 2023-December 2024). Pathogen identification was performed using matrix-assisted laser desorption/ionization time-of-flight mass spectrometry. Antimicrobial susceptibility testing was conducted using the VITEK 2 Compact automated analyzer, the Kirby-Bauer disk diffusion method, and the Etest. Data were analyzed using WHONET (version 5.6) and R software (version 4.2.1). This study was approved by the Medical Ethics Committee of West China Hospital of Stomatology, Sichuan University (Approval No.: WCHSIRB-D-2025-280). RESULTS: While the microbial culture submission rate remained stable, the culture positivity rate decreased from 20.19 during the pandemic to 18.71% in the post-pandemic period. In odontogenic infections, anaerobic bacteria predominated, with Viridans streptococci, P. intermedia, and P. acnes being the most frequently isolated species. Notably, clindamycin resistance among Viridans streptococci significantly decreased from 93.81 to 82.35%. In contrast, non-odontogenic infections were predominantly caused by aerobic bacteria, most frequently involving K. pneumoniae, A. baumannii, S. aureus, and P. aeruginosa. Resistance to ceftriaxone in K. pneumoniae decreased significantly from 14.91 to 9%, whereas resistance to levofloxacin in P. aeruginosa markedly increased from 2.88 to 11.49%. In addition, the proportion of carbapenem-resistant A. baumannii (CR-AB) rose from 9.52 to 17.11%. CONCLUSION: Following the COVID-19 pandemic, shifts in both the pathogen spectrum and antimicrobial resistance patterns were observed in odontogenic and non-odontogenic infections. These findings reflect an evolving microbial landscape and highlight the need for tailored, etiology-specific antimicrobial strategies in the management of oral and maxillofacial infections. However, as these changes may be attributable to multiple confounding factors, further studies are warranted to establish causality.