| Summary: | Chao Liu,1 Jiaojiao Shi,2 Jun Guo3,4 1Department of Respiratory Medicine, Peking Union Medical College, Chinese Academy of Medical Sciences, China-Japan Friendship Hospital, Beijing, China; 2Department of Respiratory Medicine, Peking University Third Hospital, Peking University, Beijing, China; 3Department of Respiratory Medicine, Beijing Tsinghua Changgung Hospital, School of Clinical Medicine, Tsinghua University, Beijing, China; 4Department of Geriatric Respiratory Medicine, Chinese PLA General Hospital, Beijing, China Purpose: Aerobactin is a critical factor for hypervirulent Klebsiella pneumoniae (hvKp) in genetic backgrounds, but data based on the genotype for the elderly is limited. Materials and methods: A retrospective study was conducted on elderly patients from June 2008 to July 2017 in 2 teaching hospitals. The clinical and microbiological data, including antimicrobial susceptibility testing, string test, extended-spectrum β-lactamase (ESBL) production, virulence gene, and multilocus sequence typing, of the hvKp group defined as aerobactin positive were compared with those of classic K. pneumoniae isolates. Results: A total of 45.7% of 202 K. pneumoniae isolates were hvKp.ST23, which were predominant in 2 hospitals, but they were not highly associated with hvKp in different hospitals. Hypermucoviscosity, K1, K2, magA, and rmpA/A2 genes were highly related to hvKp (P=0.000). With regard to the host, invasive infections (P=0.000), liver abscess (P=0.000), abdominal infection (P=0.000), pneumonia (P=0.037), and septic shock (P=0.045) were significantly higher in the elderly with hvKp. In the hvKp group, patients with better nutritional status were associated with a more severe sequential organ failure assessment score and a more serious inflammation reaction. Patients with diabetes (odds ratio [OR]=2.566) are more likely to be infected with hvKp. Previous hvKp is associated with hypermucoviscosity (OR=15.249) are often paralleled with hvKp. Importantly, 26% of hvKp isolates produced ESBLs, and most of them showed a carbapenems-resistant (CR) phenotype. Multivariate analysis implied that patients with a history of surgery within the last 1 month (OR=15.999) is an independent risk factor for CR-hvKp infection. Conclusion: The prevalence of hvKP is high in the elderly. ESBL-hvKp, especially CR-hvKp, is emerging, which is a sign that clinical awareness and infection monitoring needs to improve. Keywords: Klebsiella pneumoniae, hypervirulent, aerobactin, risk factor, ESBL-hvKp, CR-hvKp
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