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Over the last two decades, antimicrobial resistance has become a global health problem. In Gram-negative bacteria, metallo-β-lactamases (MBLs), which inactivate virtually all β-lactams, increasingly contribute to this phenomenon. The aim of this study is to characterize VIM-52, a His224Arg variant of VIM-1, identified in a Klebsiella pneumoniae clinical isolate. VIM-52 conferred lower MICs to cefepime and ceftazidime compared to VIM-1. These results were confirmed by steady-state kinetic measurements, where VIM-52 yielded a lower activity toward ceftazidime and cefepime but not against carbapenems. Residue 224 is part of the L10 loop (residues 221 to 241), which borders the active site. As Arg 224 and Ser 228 both play an important and interrelated role in enzymatic activity, stability, and substrate specificity for the MBLs, targeted mutagenesis at both positions was performed and further confirmed their crucial role for substrate specificity.
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http://dx.doi.org/10.1128/AAC.02660-20 | DOI Listing |
Int J Antimicrob Agents
August 2025
Collaborative Innovation Center for Diagnosis and Treatment of Infectious Diseases, State Key Laboratory for Diagnosis and Treatment of Infectious Diseases, the First Affiliated Hospital, Zhejiang University School of Medicine, Hangzhou, China; Jinan Microecological Biomedicine, Shandong Laboratory,
Pseudomonas fulva is an uncommon pseudomonal opportunistic pathogen causing rare clinical infections in humans. The emergence of the novel drug resistance mechanism tmexCD-toprJ and the variants poses new challenges to anti-infective treatment. Here, we describe the complete sequences of two clinical P.
View Article and Find Full Text PDFSci Rep
July 2025
Departamento de Microbiología, Facultad de Medicina, Universidad de Sevilla, Avda Sanchez Pizjuán s/n, 41009, Seville, Spain.
Gene expression heterogeneity has an impact on human bacterial pathogens responses, including antimicrobial resistance genes expression. Promoter region variability in resistance genes may include different regulatory boxes involved in metabolic processes essential for bacterial survival. In this study, a molecular tool was developed to characterize promoter region variability and resistance gene expression.
View Article and Find Full Text PDFInt J Antimicrob Agents
August 2025
Department of Laboratory Medicine, National Taiwan University Hospital, National Taiwan University College of Medicine, Taipei, Taiwan; Departments of Laboratory Medicine and Internal Medicine, China Medical University Hospital, China Medical University, Taichung, Taiwan; Ph.D. Program for Aging, Co
Objectives: The emergence of metallo-beta-lactamases (MBLs) within the Klebsiella oxytoca complex (CRKO) poses a significant challenge in Taiwan, with so far incomplete characterization of species distribution and carbapenemase variants. This study aimed to elucidate the diversity, variants, and clinical presentations of CRKO isolates collected from 2013 to 2022.
Methods: We analyzed production of carbapenemases by the modified carbapenem inhibitory method (mCIM) and the NG test CARBA-5.
Microorganisms
February 2025
Department of Anesthesiology and Intensive Care, University of Zagreb School of Medicine, University Hospital Centre Zagreb, 10000 Zagreb, Croatia.
The management of infectious diseases has proven to be a daunting task for clinicians worldwide, and the rapid development of antibiotic resistance among Gram-negative bacteria is making it even more challenging. The first-line therapy is empirical, and it most often comprises β-lactam antibiotics. Among Gram-negative bacteria, , an important community and hospital pathogen associated primarily with urinary tract and wound infection, holds a special place.
View Article and Find Full Text PDFAntimicrob Resist Infect Control
October 2024
Division of Infectious Diseases, Department of Internal Medicine, College of Medicine, The Catholic University of Korea, Seoul, Republic of Korea.