Characteristics of ventilator-associated pneumonia due to hypervirulent Klebsiella pneumoniae genotype in genetic background for the elderly in two tertiary hospitals in China

BACKGROUND: Aerobactin is a critical factor for the hypervirulent Klebsiella pneumoniae (hvKp), but data for the aerobactin-positive genotype of hvKp in elderly persons with ventilator-associated pneumonia (VAP) is limited. The purpose of this study is to understand the risk factors and characteristics of the hvKp genotype for elderly patients with VAP. METHODS: A retrospective study of 73 elderly patients with Kp was conducted from November 2008 to December 2017 in two tertiary hospitals. The clinical and microbiological data, including inflammatory reaction, nutritional status, antimicrobial susceptibility testing, string test, extended-spectrum-β-lactamase (ESBL) production, virulence-associated gene (capsular serotype-specific gene and rmpA/A2,magA,aerobaction) and multilocus sequence typing, of the hvKp group defined as aerobactin positive were compared with those of classic Kp strains. RESULTS: Of 73 Kp isolates, 46.6% were hvKp. ST23 is highly prevalent in two hospitals but is not highly associated with hvKp in different hospitals. Additionally, ST23, ST37 and ST2906 are more likely to induce lethal VAP. Most hvKp strains are sensitive to common antibiotics, but the number of multidrug-resistant (MDR) hvKp is increasing. Importantly, 38.2% of hvKp isolates produced ESBLs. Hypermucoviscosity and virulence-associated genes (K1,magA and rmpA/A2) were highly clustered in the hvKp group (P < 0.001). Cancer (P = 0.004), digestive disease (P = 0.038) and surgery (P = 0.023) within 1 month are strongly associated with the VAP-hvKp group. The incidence of septic shock (P = 0.016) and Sequential Organ Failure Assessment (SOFA) scores (P < 0.001) are significantly higher in the hvKp group. Multivariate analysis indicated that cancer (odds ratio [OR] = 5.365) is an independent risk factor for VAP-hvKp infection. CONCLUSIONS: The morbidity for elderly patients with VAP due to hvKp is high. MDR-HvKp is emerging, which is a great challenge for clinical practice.