Changes in antimicrobial resistance of clinical isolates of Proteus, Morganella, and Providencia species from regional hospitals in Zhejiang Province, 2020 ~ 2024

Proteus , Morganella , and Providencia species are important opportunistic pathogens associated with healthcare- and community-acquired infections, but their recent epidemiological and antimicrobial resistance trends in regional secondary hospitals remain insufficiently characterized. This study investigated the distribution and antimicrobial resistance patterns of these three genera collected from 34 regional medical institutions in Zhejiang Province, China, between 2020 and 2024. Clinical isolates of these three genera were collected from 34 secondary-level hospitals across seven regions of Zhejiang. Bacterial identification and antimicrobial susceptibility testing were performed primarily using VITEK-2. Results were interpreted according to Clinical and Laboratory Standards Institute (CLSI) M100 breakpoints. Duplicate isolates from the same patient were excluded. Isolates resistant to meropenem or ertapenem were defined as carbapenem-resistant Enterobacterales (CRE). A total of 7,329 nonduplicate isolates were collected, including 6,181 Proteus (84.4%), 847 Morganella (11.6%), and 301 Providencia (4.1%). Annual isolate counts increased from 2020 to 2024. The leading specimen sources were urine (approximately 42%), respiratory tract specimens (approximately 28%), and wound and secretion specimens (approximately 12%); approximately 2% were from bloodstream infections. Across all years, carbapenem resistance was lowest in Proteus and Morganella but highest in Providencia. In 2020, resistance rates for multiple antibiotics were higher than in 2021, and they increased again by 2024. Phylogenetic analysis revealed that the human intestinal tract may serve as a reservoir for blaNDM-1-carrying Providencia spp. and carbapenemase genes are broadly disseminated across genetically diverse M. morganii strains. The rising prevalence of these bacteria, particularly carbapenem-resistant Providencia, highlights an urgent need for enhanced antimicrobial stewardship and infection control in secondary hospitals. Ongoing resistance surveillance in community healthcare settings is essential to curb the spread of these resistant pathogens.