Abstract
BackgroundThe definition of hypervirulent Klebsiella pneumoniae (hvKp), traditionally regarded as hypermucoviscosity, is controversial. However, data based on both phenotype (hypermucoviscous) and genetic (aerobactin) criteria are limited.MethodsA retrospective study was conducted in 175 geriatric patients between January 2008 and January 2014. The clinical and molecular data, including antimicrobial susceptibility testing, extended-spectrum-β-lactamase (ESBL) production, virulence gene, and multilocus sequence typing of the hvKp-group (hypermucoviscosity and aerobactin positive) were compared with those of classic K. pneumoniae (cKp) isolates.ResultsOf 175 Kp isolates, 45.7% were hvKp. In pathogenicity, K1, K2, magA, rmpA, and rmpA2 genes were strongly associated with hvKp (P < 0.01). In the hvKp group, invasive infections (P < 0.000), liver abscess (P = 0.008), abdominal infection (P = 0.002) and septic shock (P = 0.035) are significantly higher than cKp group. Patients with better nutritional status were frequently infected with hvKp. However, host inflammatory reaction is most severe in hvKp group. Patients with diabetes (odds ratio [OR] = 2.548) and digestive diseases (OR = 2.196) are more likely to be infected with hvKp. Importantly, the detection of hvKp isolates increased from January 2008 to January 2010, January 2010 to January 2012, and January 2010 to January 2014 (12, 30, and 48 isolates, respectively). Overall, 16.3% of hvKp isolates produced ESBLs and 20.0% were MDR-hvKp. Multivariate analysis implied that infection occurred in the ICU (OR = 5.826) and patients with indwelling stomach tubes (OR = 6.461) are independent risk factors for ESBL-hvKp infection.ConclusionsHvKp, especially ESBL-hvKp and MDR-hvKp, is emerging in the elderly. It is essential to enhance clinical awareness and management of hvKp infections.
Highlights
Klebsiella pneumoniae (Kp) are Gram-negative bacteria that can cause various infections
The results showed that invasive infections, hypermucoviscosity and most of virulence factors (K1, K2, K20, rmpA) genes are highly associated with aerobactin-positive Kp
Aerobactin-positive and hypermucoviscous strains were defined as hypervirulent Klebsiella pneumoniae (hvKp), which was determined by Polymerase Chain Reaction (PCR) and string test
Summary
Klebsiella pneumoniae (Kp) are Gram-negative bacteria that can cause various infections. An emerging subtype, termed hypervirulent K. pneumoniae (hvKp), was first described in 1986 [4]. Some controversies exist about the relationship between the virulent and morphological phenotype (hypermucoviscosity) [12, 13]. Using in vitro and in vivo assays, various studies showed that few hypermucoviscous K. pneumonia (hmvKp) strains are associated with high virulence [12, 13]. In vitro and in vivo experiments showed that a few (1/5) hypermucoviscous K. pneumoniae isolates had a high virulence. The definition of hypervirulent Klebsiella pneumoniae (hvKp), traditionally regarded as hypermucoviscosity, is controversial. Data based on both phenotype (hypermucoviscous) and genetic (aerobactin) criteria are limited
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