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