Clinical and Imaging Characteristics of Primary Severe Community-Acquired Pneumonia Caused by Hypervirulent Klebsiella Pneumoniae.

Background: To investigate the CT imaging features and microbial phenotypes of primary severe community-acquired pneumonia caused by hypervirulent Klebsiella pneumoniae (hvKp).

Methods: Patients diagnosed with primary hvKp pneumonia were included, and their clinical data were analyzed, including the baseline characteristics and CT imaging results. After hypermucoviscosity phenotyping, the strains, serological types, and virulence genes of hvKp were identified using multiplex PCR.

Results: Twelve patients with primary hvKp pneumonia were included (11 males, 1 female). All patients were infected via respiratory tract inhalation. Ten patients were long-term drinkers. Four patients (33.3%), who were long-term alcohol abusers, died within 30 days after diagnosis. No extrapulmonary metastatic infection was found in any patient. The imaging of lung lesions at the early disease stage exhibited an extensive consolidation in the lungs. As the disease progressed, the most common imaging features were pleural effusion (9/12), cavitation and necrosis (8/12), and pneumothorax (3/12). The serological typing of the capsular polysaccharides on hvKp strains were K1 (6/12) and K2 (6/12). Furthermore, the virulence genotyping showed rmpA (11/12), magA (11/12), ureA (12/12), mrkD (12/12), fim-1 (12/12), wabG (12/12), ybtS (12/12), and iucB (11/12).

Conclusions: Primary severe community-acquired hvKp-associated pneumonia is more common in men, especially those with a long-term history of alcohol consumption. CT scanning at the early disease stage mostly showed extensive pulmonary consolidation, which was prone to be combined with cavitation, necrosis, and pleural effusion. K1 and K2 serotypes were identified among the hvKp strains, which were not prone to form extrapulmonary metastasis via the bloodstream.