Juhee Ahn

Juhee Ahn

Kangwon National University, Republic of Korea

Title: Comparative assessment of -lactamases produced by multidrug resistant bacteria


Juhee Ahn is interested in the microbial pathogenesis, including the mechanistic studies of antibiotic resistance, bacterial infection, and bacteriophage control. He received his Ph.D. degree majoring in Food Microbiology at the University of Missouri, Columbia, USA and continued his work as a post-doctoral research assistant in Food Microbiology Lab at the University of Missouri (2003-2004) and Food Safety Engineering Lab at the Ohio State University (2004-2006). He was a visiting scholar at the University of Maryland (2012-2013) as well as Zhejiang University (2016-2017). Currently, he is a professor at the department of Medical Biomaterials Engineering, Kangwon National University. South Korea.


The multidrug resistance in K. pneumoniae is primarily mediated by the production of different classes of b-lactamases. The relationship between b-lactamase production and resistance phenotype is essential to understand the resistance mechanisms in K. pneumoniae. However, there is still a lack of information on the phenotypic and genotypic antibiotic resistance profiles in association with the classes of b-lactamases in K. pneumoniae. Therefore, the aim of this study was to evaluate the antibiotic susceptibility and b-lactamase production in ciprofloxacin-induced and clinically-isolated antibiotic-resistant K. pneumoniae strains, based on the interaction between b-lactamases and b-lactamase inhibitors. The antibiotic susceptibility and β-lactamase activity of K. pneumoniae strains, including antibiotic-sensitive K. pneumoniae (KPWT), ciprofloxacin-induced resistant K. pneumoniae (KPCIP), and clinically isolated K. pneumoniae strains (KPCI237, KPCI263, and KPCI272), were determined in the absence and presence of β-lactamase inhibitors (BLI 489, sulbactam, clavulanate, and tazobactam). All strains were highly resistant to ampicillin in the absence of b-lactamase inhibitors (MIC≥512 mg mL-1). In the presence of clavulanate, the MICs of ampicillin and piperacillin against KPWT were decreased by >64-fold and 4-fold, respectively. The resistance of KPCI263 to cefotaxime, ceftazidime, ceftriaxone, and piperacillin were increased in the presence of BLI-489. The antibiotic susceptibilities KPCI237 to b-lactams were not noticeably changed in the presence of β-lactamase inhibitors (clavulanate, sulbactam, and tazobactam). KPWT, KPCIP and KPCI272 were positive for blaSHV, blaAmpC, and blaFOX/MOX, KPCI237 for blaSHV and blaAmpC, and KPCI263 for blaSHV and blaOXA-48. The antibiotic susceptibility corresponded well with the results obtained from dual disc diffusion assay, which was in good agreement with the b-lactamase production. The results provide useful information for understanding the resistance phenotypes in association with b-lactamase production.

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