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June 13, 2026Infection and Drug Resistance0 citationsOpen Access

Clinical Characteristics, Antimicrobial Resistance Profiles and Carbapenemases Genotypes of Providencia rettgeri: A 5-Year Retrospective Study in a Tertiary Teaching Hospital in Northern China

YLYing LiCapital Medical University YWYan WangCapital Medical University DCDiandian ChenCapital Medical University

Key Points

The study aimed to investigate the clinical characteristics, antimicrobial resistance profiles, and carbapenemase genotypes of Providencia rettgeri isolates.
Conducted a 5-year retrospective analysis (2021–2025) at Xuanwu Hospital.
Identified isolates using MALDI-TOF MS and 16S rRNA sequencing for accuracy.
Performed antimicrobial susceptibility testing per CLSI guidelines, including various assays and whole genome sequencing.
88.0% of isolates were multidrug resistant (MDR), including 52.0% carbapenem-resistant (CRPR) strains.
Ceftazidime-avibactam showed no efficacy against CRPR isolates; aztreonam-avibactam was effective in 61.5% of cases.
All CRPR isolates harbored the bla NDM-1 gene, with high co-occurrence of bla OXA-10 and bla PER genes.

Abstract

Background: Providencia rettgeri is an emerging opportunistic pathogen linked with healthcare-associated infections and increasing antimicrobial resistance. This study aimed to characterize the clinical features, antimicrobial resistance profiles and carbapenemase genotypes of P. rettgeri isolates in a tertiary teaching hospital in northern China. Methods: A 5-year retrospective study (2021– 2025) was conducted at Xuanwu Hospital. Isolates were identified using MALDI-TOF MS, with 16S rRNA sequencing as the gold standard for ambiguous results. Antimicrobial susceptibility testing followed CLSI guidelines, including disk diffusion, broth disk elution assays and Vitek 2 automated systems. Carbapenemases and the genotypes were detected by gold immunochromatography, multiplex fluorescent PCR (mPCR) and whole genome sequencing (WGS). Results: Twenty-five non-duplicate P. rettgeri isolates were collected, primarily from urine (44.0%, 11/25), followed by drainage and secretions (24.0%, 6/25). Multidrug resistance (MDR) was observed in 88.0% (22/25) of isolates, including 52.0% (13/25) carbapenem-resistant P. rettgeri (CRPR) strains. Ceftazidime-avibactam (CZA) showed no in vitro activity against CRPR isolates, while aztreonam-avibactam (AZA) exhibited activity against 61.5% (8/13) of CRPR isolates. The immunochromatography assay identified NDM-type carbapenemase production and mPCR detected the presence of bla NDM gene in all CRPR isolates. WGS combined with Sanger sequencing validated that all CRPR isolates harbored the bla NDM-1 gene. In addition, 92.3% (12/13) CRPR isolates co-harboring bla OXA-10 and 61.5% (8/13) isolates resistant to aztreonam also harbored bla PER genes. Conclusion: P. rettgeri isolates in our study exhibited high rates of MDR and carbapenem resistance with the presence of the bla NDM-1 gene. The co-occurrence of bla NDM-1 , bla OXA-10 and bla PER in these CRPR isolates might complicate the antimicrobial resistant mechanisms. AZA exhibited the better in vitro activity against CRPR isolates compared to other antimicrobials, though its clinical efficacy remains to be validated. Continuous surveillance and further mechanistic studies are critical to combat this emerging threat. Keywords: Providencia rettgeri , antimicrobial resistance, carbapenemase, aztreonam-avibactam, whole-genome sequencing

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