Abstract
BACKGROUD: To investigate the molecular epidemiology of intestinal colonization by carbapenem-resistant Enterobacteriaceae (CRE) and identify risk factors for subsequent infection, providing evidence for early risk stratification and targeted prevention. METHODS: From August 2023 to August 2024, we retrospectively enrolled CRE-positive patients identified through active rectal swab screening at the First Affiliated Hospital of Kunming Medical University and monitored them for subsequent infections. Colonizing and infecting isolates were collected and tested for carbapenem-resistance genes, major virulence genes, capsular serotypes, and were subjected to multilocus sequence typing (MLST). Clinical data were integrated and multivariate logistic regression was performed to identify risk factors associated with secondary infections. RESULTS: Among 8,088 patients who underwent active intestinal CRE screening, the positivity rate was 0.53% (43/8,088). Among patients with colonization, the incidence of secondary infection was 37.2% (16/43). All patients with secondary infections were colonized and infected with Klebsiella pneumoniae, with the lower respiratory tract, bloodstream, and urinary tract being the primary infection sites. Multivariable analysis showed that having more than three comorbidities was an independent risk factor for hospital-acquired infection among colonized patients (odds ratio [OR]=0.118; 95% CI:0.017-0.812; P=0.030). The carriage rate of bla (KPC) was 77.8% among colonizing strains and 100% among infecting strains. Among virulence genes, aerobactin, allS, and peg344 were significantly more prevalent in infecting strains (P<0.05). Homology analysis revealed that, except for one patient, the colonizing and infecting isolates in patients with secondary infections were highly homologous ST11-KL64, KPC-producing K. pneumoniae. CONCLUSION: Although the intestinal colonization rate of CRE was relatively low, the risk of secondary infection remained substantial. Bacterial genetic traits and host conditions contribute to secondary infections. Establishing surveillance systems based on clinical and molecular epidemiology coupled with intensified screening in high-risk departments may help identify high-risk patients early and enable proactive interventions to reduce CRE-related secondary infections.