Kyungwon Lee1, Dongeun Yong1, Seok Hoon Jeong1, Khosbayar Tulgaa2, Jean-Denis Docquier3, Gian Maria Rossolini3, Yunsop Chong4. 1. Department of Laboratory Medicine and Research Institute of Bacterial Resistance, Yonsei University College of Medicine, 50-1 Yonsei-ro, Seodaemun-gu, Seoul 03722, South Korea. 2. Department of Molecular Biology and Genetics, Research Center of Antimicrobial Resistance, Health Sciences University of Mongolia, Zorig Str. 4, Ulaanbaatar, Mongolia. 3. Department of Medical Biotechnologies, University of Siena, Viale Bracci 1, I-53100 Siena, Italy. 4. Department of Laboratory Medicine and Research Institute of Bacterial Resistance, Yonsei University College of Medicine, 50-1 Yonsei-ro, Seodaemun-gu, Seoul 03722, South Korea. Electronic address: yunsopchong@gmail.com.
Abstract
OBJECTIVES: The aims of this study were to determine the resistance level of a blaCTX-M-37-carrying Enterobacter cloacae isolate from Mongolia, to analyse kinetic parameters of the purified enzyme and to compare the genetic environment of the gene. METHODS: Minimum inhibitory concentrations (MICs) were determined using the Clinical and Laboratory Standards Institute (CLSI) agar dilution method. Purified CTX-M-37 enzyme was used to determined kinetic parameters. The genetic environment of the blaCTX-M-37 gene in E. cloacae was compared with a Kluyvera cryocrescens isolate. RESULTS: The E. cloacae isolate showed relatively low-level resistance to cefotaxime (MIC=16mg/L) compared with a CTX-M-3-producing strain (MIC=256mg/L), and CTX-M-37 had a lower kcat/Km value for cefotaxime (2.0μM-1s-1) compared with CTX-M-3 (3.5μM-1s-1), possibly due to Asn114Asp substitution. The blaCTX-M-37 gene in the E. cloacae isolate was carried on a conjugative plasmid and was associated with an ISEcp1 element containing the -35 and -10 putative promoter sequences TTGAAA and TACAAT, respectively, unlike in the K. cryocrescens isolate. CONCLUSIONS: The CTX-M-37-producing E. cloacae isolate showed relatively low-level resistance to cefotaxime and the purified enzyme had lower kinetic parameters as the result of Asn114Asp substitution. Presence of an ISEcp1 element and putative promoters upstream of the blaCTX-M-37 gene in E. cloacae, but not in the K. cryocrescens isolate, indicated their roles in mobilisation and expression of the gene.
OBJECTIVES: The aims of this study were to determine the resistance level of a blaCTX-M-37-carrying Enterobacter cloacae isolate from Mongolia, to analyse kinetic parameters of the purified enzyme and to compare the genetic environment of the gene. METHODS: Minimum inhibitory concentrations (MICs) were determined using the Clinical and Laboratory Standards Institute (CLSI) agar dilution method. Purified CTX-M-37 enzyme was used to determined kinetic parameters. The genetic environment of the blaCTX-M-37 gene in E. cloacae was compared with a Kluyvera cryocrescens isolate. RESULTS: The E. cloacae isolate showed relatively low-level resistance to cefotaxime (MIC=16mg/L) compared with a CTX-M-3-producing strain (MIC=256mg/L), and CTX-M-37 had a lower kcat/Km value for cefotaxime (2.0μM-1s-1) compared with CTX-M-3 (3.5μM-1s-1), possibly due to Asn114Asp substitution. The blaCTX-M-37 gene in the E. cloacae isolate was carried on a conjugative plasmid and was associated with an ISEcp1 element containing the -35 and -10 putative promoter sequences TTGAAA and TACAAT, respectively, unlike in the K. cryocrescens isolate. CONCLUSIONS: The CTX-M-37-producing E. cloacae isolate showed relatively low-level resistance to cefotaxime and the purified enzyme had lower kinetic parameters as the result of Asn114Asp substitution. Presence of an ISEcp1 element and putative promoters upstream of the blaCTX-M-37 gene in E. cloacae, but not in the K. cryocrescens isolate, indicated their roles in mobilisation and expression of the gene.
Authors: Ghassan Tayh; Nahed Al Laham; Houssem Ben Yahia; Rym Ben Sallem; Abed Elkader Elottol; Karim Ben Slama Journal: Biomed Res Int Date: 2019-10-13 Impact factor: 3.411
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