Low prevalence of rmpA and high tendency of rmpA mutation correspond to low virulence of extended spectrum β-lactamase-producing klebsiella pneumoniae isolates

Wen Liang Yu, Mei Feng Lee, Hung Jen Tang, Ming Chung Chang, Yin Ching Chuang

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17 Citations (Scopus)


Invasive syndrome caused by Klebsiella pneumoniae (KP), including liver abscess, is mainly caused by communityacquired strains with characteristics of positive hypermucoviscosity (HV) phenotype and regulator of mucoid phenotype A (rmpA) and transcriptional activator (rmpA2) genes. Extended-spectrum b-lactamase-producing KP (ESBLKP) is commonly nosocomial and rarely HV-positive. We aimed to explore the reasons of the rarer prevalence of HV phenotype, rmpA and rmpA2 as well as the virulence phenotype among the ESBL-KP isolates from clinical specimens than those non-ESBL isolates. The β-lactamase genes, rmpA, rmpA2 and genes for K capsule serotype of 440 KP isolates were analyzed. The virulence of the isolates was characterized by the mouse lethality experiments. The prevalence rates of HV phenotype (~50% vs. <10%) as well as rmpA and rmpA2 genes (~50-60% vs. <20-30%) were significantly higher in non-ESBL group than in the ESBL group (p <0.0001). Expression of HV phenotype in the rmpA-positive KP isolates was significantly rarer in the ESBL group than in non-ESBL group (33.3% vs. 91.9%, p <0.0001). The frameshift mutations of rmpA and/or rmpA2 corresponded to negative HV phenotype of KP isolates that harbored the rmpA and?or rmpA2, resulting in variable mouse lethality (LD50, ~103->5 × 107CFU). The mutation rates might significantly differ among KP isolates from various sources. Virulence was dependent on rmpA-related HV phenotype. In conclusion, ESBL-KP isolates were less hypermucoviscous and less virulent than non-ESBL KP isolates, mostly due to concurrently lower carriage and higher mutation rates of the rmpA and rmpA2 genes.

Original languageEnglish
Pages (from-to)162-172
Number of pages11
Issue number2
Publication statusPublished - Apr 1 2015



  • ESBL hypermucoviscosity
  • Klebsiella pneumoniae
  • RmpA gene
  • Spontaneous mutation

ASJC Scopus subject areas

  • Infectious Diseases
  • Microbiology
  • Parasitology
  • Immunology
  • Microbiology (medical)

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