title: Intrapersonal mutation of rmpA and rmpA2: A reason for negative hypermucoviscosity phenotype and low virulence of rmpA-positive Klebsiella pneumoniae isolates.
abstract: Two Klebsiella pneumoniae isolates were simultaneously recovered from blood and urine cultures of the same patient. Both isolates were identical in genomic pulsotype by pulsed-field gel electrophoresis (PFGE). However, the hypermucoviscosity phenotype was confirmed in the blood strain but not the urine strain. A previously unrelated liver abscess K. pneumoniae hypermucoviscous isolate was used as a control. PCR, DNA cloning and sequencing for the plasmid-borne rmpA and rmpA2 genes and the chromosome-borne rmpA gene (c-rmpA) revealed negative c-rmpA with natural frame-shift mutation of rmpA and rmpA2 genes in the urine strain. The blood strain was negative for c-rmpA with rmpA2 mutation but no mutation in rmpA. The control strain was positive for c-rmpA with rmpA2 mutation but no mutation in rmpA and showed the highest virulence in mouse lethality experiments [median lethal dose (LD50)=50CFU], which was followed by the blood strain (LD50=2.47×103CFU) and the urine strain (LD50>107CFU). The control and blood strains were highly serum resistant, whereas the urine strain was sensitive to serum killing. In conclusion, intrapersonal concurrent mutation of rmpA and rmpA2 genes in the absence of c-rmpA could be a reason for the negative hypermucoviscosity phenotype and low virulence in rmpA-positive K. pneumoniae.
authors.affiliation: Department of Intensive Care Medicine, Chi Mei Medical Center, Tainan City, Taiwan; Department of Medicine, Taipei Medical University, Taipei City, Taiwan.
authors.forename: Wen-Liang
authors.initials: WL
authors.lastname: Yu
authors.affiliation: Department of Medical Research, Chi Mei Medical Center, Tainan City, Taiwan.
authors.forename: Mei-Feng
authors.initials: MF
authors.lastname: Lee
authors.affiliation: Department of Biochemistry and Molecular Biology, College of Medicine, National Cheng Kung University, Tainan City, Taiwan.
authors.forename: Ming-Chung
authors.initials: MC
authors.lastname: Chang
authors.affiliation: Department of Medical Research, Chi Mei Medical Center, Tainan City, Taiwan; Department of Internal Medicine, Chi Mei Hospital, Liouying, Tainan City, Taiwan. Electronic address: chuangkenneth@hotmail.com.
authors.forename: Yin-Ching
authors.initials: YC
authors.lastname: Chuang
keywords: Hypermucoviscosity; Spontaneous mutation; Virulence; rmpA gene