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- Comparison of virulence between matt and mucoid colonies of Klebsiella pneumoniae coproducing NDM-1 and OXA-232 isolated from a single patient
- Haejeong Lee , Jin Yang Baek , So Yeon Kim , HyunJi Jo , KyeongJin Kang , Jae-Hoon Ko , Sun Young Cho , Doo Ryeon Chung , Kyong Ran Peck , Jae-Hoon Song , Kwan Soo Ko
- J. Microbiol. 2018;56(9):665-672. Published online August 23, 2018
- DOI: https://doi.org/10.1007/s12275-018-8130-3
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Abstract
- Nine Klebsiella pneumoniae isolates coproducing NDM-1 and OXA-232 carbapenemases were successively isolated from a single patient. Although they were isolated simultaneously and were isogenic, they presented different colony phenotypes (matt and mucoid). All nine isolates were resistant to most antibiotics except colistin and fosfomycin. In addition, matt-type isolates were resistant to tigecycline. No differences were detected in the cps cluster sequences, except for the insertion of IS5 in the wzb gene of two matt-type isolates. In vitro virulence assays based on production of capsular polysaccharide, biofilm formation, and resistance to human serum indicated that the mucoid-type isolates were significantly more virulent than the matt-type. In addition, mucoid-type isolates showed higher survival rates than the matt-type ones in infection experiments in the fruit fly, suggesting a higher virulence of K. pneumoniae isolates with a mucoid phenotype. To our knowledge, this is the first report of K. pneumoniae colonies with different phenotypes being isolated from the same sample. In addition, we show that virulence varies with colony phenotype. Dissemination of K. pneumoniae isolates expressing both antibiotic resistance and high virulence would constitute a great threat.
Research Support, Non-U.S. Gov't
- Outbreaks of Imipenem-Resistant Acinetobacter baumannii Producing Carbapenemases in Korea
- Seok Hoon Jeong , Il Kwon Bae , Kwang Ok Park , Young Jun An , Seung Ghyu Sohn , Seon Ju Jang , Kwang Hoon Sung , Ki Suk Yang , Kyungwon Lee , Dongeun Young , Sang Hee Lee
- J. Microbiol. 2006;44(4):423-431.
- DOI: https://doi.org/2410 [pii]
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Abstract
- Among 53 Acinetobacter baumannii isolates collected in 2004, nine imipenem-resistant isolates were obtained from clinical specimens taken from patients hospitalized in Busan, Korea. Nine carbapenemase-producing isolates were further investigated in order to determine the mechanisms underlying resistance. These isolates were then analyzed via antibiotic susceptibility testing, microbiological tests of carbapenemase activity, pI determination, transconjugation test, enterobacterial repetitive consensus (ERIC)-PCR, and DNA sequencing. One outbreak involved seven cases of infection by A. baumannii producing OXA-23 β-lactamase, and was found to have been caused by a single ERIC-PCR clone. During the study period, the other outbreak involved two cases of infection by A. baumannii producing IMP-1 β-lactamase. The two clones, one from each of the outbreaks, were characterized via a modified cloverleaf synergy test and an EDTA-disk synergy test. The isoelectric focusing of the crude bacterial extracts detected nitrocefin-positive bands with pI values of 6.65 (OXA-23) and 9.0 (IMP-1). The PCR amplification and characterization of the amplicons via direct sequencing showed that the clonal isolates harbored blaIMP-1 or blaOXA-23 determinants. The two clones were characterized by a multidrug resistance phenotype that remained unaltered throughout the outbreak. This resistance encompassed penicillins, extended-spectrum cephalosporins, carbapenems, monobactams, and aminoglycosides. These results appear to show that the imipenem resistance observed among nine Korean A. baumannii isolates could be attributed to the spread of an IMP-1- or OXA-23-producing clone. Our microbiological test of carbapenemase activity is a simple method for the screening of clinical isolates producing class D carbapenemase and/or class B metallo-β-lactamase, in order both to determine their clinical impact and to prevent further spread.
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