Molecular Epidemiological Characteristics of Klebsiella pneumoniae Associated with Bacteremia among Patients with Pneumonia

Abstract

e Some important virulence factors have been elucidated in Klebsiella pneumoniae infections. We investigated the relationship between virulence factors and multilocus sequence types (STs) and assessed the risk factors for bacteremia in patients with pneumonia due to K. pneumoniae. From April 2004 through April 2012, a total of 120 K. pneumoniae isolates from patients with pneumonia (23 with bacteremia and 97 without bacteremia) were collected from 10 medical institutions in Japan. Additionally, 10 strains of K. pneumoniae serotype K2 that were isolated >30 years ago were included in this study. These isolates were characterized using multilocus sequence typing (MLST), and the characteristics of their virulence factors, such as hypermucoviscosity phenotype and RmpA and aerobactin production between patients with and without bacteremia, were examined. MLST analysis was performed on the 120 isolates from patients with pneumonia, and some sequence type groups were defined as genetic lineages (GLs). GL65 was more prevalent among patients with bacteremia (21.7%) than in those without bacteremia (7.2%). The majority of the strains with serotype K2 were classified into GL14 or GL65, and rmpA and the gene for aerobactin were present in all GL65-K2 strains but absent in all GL14-K2 strains. In a multivariate analysis, the independent risk factors for bacteremia included GL65 ( K lebsiella pneumoniae is a member of the family Enterobacteriaceae and is one of the most common pathogens causing pneumonia, abscess, bacteremia, and urinary tract infections (1, 2).Over several decades, some virulence factors of K. pneumoniae, including a capsular serotype, the presence of mucoviscosity-associated gene A (magA), and a regulator of mucoid phenotype A (rmpA) gene, have been identified. The strains of serotypes K1 and K2 were found to be virulent in a mouse model (3), and the magA and rmpA genes were found to be associated with hypermucoviscosity (HV), which has an antiphagocytic effect against macrophages and neutrophils (4-6).Clinically, K. pneumoniae was identified as an independent risk factor for mortality in severe community-acquired pneumonia (7). Some studies assessed the relationship between clinical findings and microbiological factors, such as capsular serotype and the presence or absence of rmpA and magA. The site of infections in these studies was mostly intra-abdominal, especially as a liver abscess (5,8). Few studies have focused on respiratory tract infections and investigated the relationship between clinical findings and microbiological factors, including genetic characteristics (9, 10).It is well-known that multilocus sequence typing (MLST), a nucleotide sequence-based genotyping method, is used to characterize genetic relationships among bacterial isolates and to identify and track the global spread of drug-resistant strains (11,12). In order to predict and evaluate bacterial pathogenicity, it is important to first determine the genetic background of the bacteria causing severe infections. Recently, using MLST, s...

Complete Sequence of bla KPC-2 -Harboring Plasmid with a Mosaic of IncN1- and IncN3-Type Plasmids in a Klebsiella pneumoniae Isolate from South Korea

“…The isolate belongs to ST1612, which has been found in Japan (1). Because Japanese ST1612 isolates do not produce KPC-2, the South Korean isolate probably acquired the plasmid bearing bla KPC-2 from other species or a clone.…”

Molecular characterization of Klebsiella pneumoniae isolates from stool specimens of outpatients in sentinel hospitals Beijing, China, 2010–2015

“…This study identified ST23 as the most common genotype, which were reported in many previous hospital-acquired infection studies in Asia [12, 13]. Noticeable this study isolated one ST65 strain, a mucoid phenotype and harbored rmpA gene for aerobactin, which more likely caused community-acquired infection [14, 15] and indicated as one of the independent risk factors for bacteremia in patients with pneumonia [13]. Moreover, the microbiological character of newly detected ST2362, ST2363, ST2364, ST2365, ST2366, ST2367, ST2368, ST2369, and ST2370, these strains presented clinical character are not thoroughly explicit, which needs further studies.…”

A Genomic Approach To Identify Klebsiella pneumoniae and Acinetobacter baumannii Strains with Enhanced Competitive Fitness in the Lungs during Multistrain Pneumonia

“…A recent study found over 150 distinct phylogenetic lineages of this pathogen and suggested that more remain to be identified (25). Many of these lineages can be found within a single hospital (26,27) and even within an individual patient (28), yet genotyping studies indicate that a relatively small number of lineages are responsible for a disproportionately large number of pneumonia cases (25,(29)(30)(31). For example, multilocus sequence typing has indicated that sequence type 11 (ST11), ST14, ST15, ST42, ST43, ST258, ST340, ST416, and ST512 strains are frequent causes of pneumonia over large geographic regions (25).…”