title: Characterization of CTX-M-140, a Variant of CTX-M-14 Extended-Spectrum β-Lactamase with Decreased Cephalosporin Hydrolytic Activity, from Cephalosporin-Resistant Proteus mirabilis.
abstract: CTX-M-140, a novel CTX-M-type extended-spectrum β-lactamase (ESBL), was identified in cephalosporin-resistant clinical isolates of Proteus mirabilis CTX-M-140 contained an alanine-to-threonine substitution at position 109 compared to its putative progenitor, CTX-M-14. When it was expressed in an Escherichia coli isogenic background, CTX-M-140 conferred 4- to 32-fold lower MICs of cephalosporins than those with CTX-M-14, indicating that the phenotype was attributable to this single substitution. For four mutants of CTX-M-14 that were constructed by site-directed mutagenesis (A109E, A109D, A109K, and A109R mutants), MICs of cephalosporins were similar to those for the E. coli host strain, which suggested that the alanine at position 109 was essential for cephalosporin hydrolysis. The kinetic properties of native CTX-M-14 and CTX-M-140 were consistent with the MICs for the E. coli clones. Compared with that of CTX-M-14, a lower hydrolytic activity against cephalosporins was observed for CTX-M-140. blaCTX-M-140 is located on the chromosome as determined by I-CeuI pulsed-field gel electrophoresis (I-CeuI-PFGE) and Southern hybridization. The genetic environment surrounding blaCTX-M-140 is identical to the sequence found in different plasmids with blaCTX-M-9-group genes among the Enterobacteriaceae Genome sequencing and analysis showed that P. mirabilis strains with blaCTX-M-140 have a genome size of ∼4 Mbp, with a GC content of 38.7% and 23 putative antibiotic resistance genes. Our results indicate that alanine at position 109 is critical for the hydrolytic activity of CTX-M-14 against oxyimino-cephalosporins.
authors.affiliation: Program of Immunology, Affiliated Guangzhou Women and Children's Medical Center, Zhongshan School of Medicine, Sun Yat-sen University, Guangzhou, China Department of Immunology, Institute of Human Virology, Zhongshan School of Medicine, Sun Yat-sen University, Guangzhou, China Key Laboratory of Tropical Diseases Control, Sun Yat-sen University, Ministry of Education, Guangzhou, China.
authors.forename: Guo-Bao
authors.initials: GB
authors.lastname: Tian
authors.affiliation: BGI Genomics Co., Ltd., Shenzhen, Guangdong, China.
authors.forename: Yi-Qi
authors.initials: YQ
authors.lastname: Jiang
authors.affiliation: Department of Immunology, Institute of Human Virology, Zhongshan School of Medicine, Sun Yat-sen University, Guangzhou, China Key Laboratory of Tropical Diseases Control, Sun Yat-sen University, Ministry of Education, Guangzhou, China Department of Laboratory, Central Hospital of Panyu District, Shiqiao, Guangzhou, Guangdong, China.
authors.forename: Ying-Min
authors.initials: YM
authors.lastname: Huang
authors.affiliation: Program of Immunology, Affiliated Guangzhou Women and Children's Medical Center, Zhongshan School of Medicine, Sun Yat-sen University, Guangzhou, China Department of Immunology, Institute of Human Virology, Zhongshan School of Medicine, Sun Yat-sen University, Guangzhou, China Key Laboratory of Tropical Diseases Control, Sun Yat-sen University, Ministry of Education, Guangzhou, China.
authors.forename: Yun
authors.initials: Y
authors.lastname: Qin
authors.affiliation: Program of Immunology, Affiliated Guangzhou Women and Children's Medical Center, Zhongshan School of Medicine, Sun Yat-sen University, Guangzhou, China Department of Immunology, Institute of Human Virology, Zhongshan School of Medicine, Sun Yat-sen University, Guangzhou, China Key Laboratory of Tropical Diseases Control, Sun Yat-sen University, Ministry of Education, Guangzhou, China.
authors.forename: Lian-Qiang
authors.initials: LQ
authors.lastname: Feng
authors.affiliation: Program of Immunology, Affiliated Guangzhou Women and Children's Medical Center, Zhongshan School of Medicine, Sun Yat-sen University, Guangzhou, China Department of Immunology, Institute of Human Virology, Zhongshan School of Medicine, Sun Yat-sen University, Guangzhou, China Key Laboratory of Tropical Diseases Control, Sun Yat-sen University, Ministry of Education, Guangzhou, China.
authors.forename: Xue-Fei
authors.initials: XF
authors.lastname: Zhang
authors.affiliation: Department of Clinical Laboratory, Sun Yat-sen Memorial Hospital, Sun Yat-sen University, Guangzhou, China.
authors.forename: Hong-Yu
authors.initials: HY
authors.lastname: Li
authors.affiliation: Program of Immunology, Affiliated Guangzhou Women and Children's Medical Center, Zhongshan School of Medicine, Sun Yat-sen University, Guangzhou, China Department of Immunology, Institute of Human Virology, Zhongshan School of Medicine, Sun Yat-sen University, Guangzhou, China Key Laboratory of Tropical Diseases Control, Sun Yat-sen University, Ministry of Education, Guangzhou, China.
authors.forename: Lan-Lan
authors.initials: LL
authors.lastname: Zhong
authors.affiliation: Program of Immunology, Affiliated Guangzhou Women and Children's Medical Center, Zhongshan School of Medicine, Sun Yat-sen University, Guangzhou, China Department of Immunology, Institute of Human Virology, Zhongshan School of Medicine, Sun Yat-sen University, Guangzhou, China Key Laboratory of Tropical Diseases Control, Sun Yat-sen University, Ministry of Education, Guangzhou, China.
authors.forename: Kun-Jiao
authors.initials: KJ
authors.lastname: Zeng
authors.affiliation: Program of Immunology, Affiliated Guangzhou Women and Children's Medical Center, Zhongshan School of Medicine, Sun Yat-sen University, Guangzhou, China Department of Immunology, Institute of Human Virology, Zhongshan School of Medicine, Sun Yat-sen University, Guangzhou, China Key Laboratory of Tropical Diseases Control, Sun Yat-sen University, Ministry of Education, Guangzhou, China.
authors.forename: Sandip
authors.initials: S
authors.lastname: Patil
authors.affiliation: Program of Immunology, Affiliated Guangzhou Women and Children's Medical Center, Zhongshan School of Medicine, Sun Yat-sen University, Guangzhou, China Department of Immunology, Institute of Human Virology, Zhongshan School of Medicine, Sun Yat-sen University, Guangzhou, China Key Laboratory of Tropical Diseases Control, Sun Yat-sen University, Ministry of Education, Guangzhou, China.
authors.forename: Yong
authors.initials: Y
authors.lastname: Xing
authors.affiliation: Program of Immunology, Affiliated Guangzhou Women and Children's Medical Center, Zhongshan School of Medicine, Sun Yat-sen University, Guangzhou, China Department of Immunology, Institute of Human Virology, Zhongshan School of Medicine, Sun Yat-sen University, Guangzhou, China Key Laboratory of Tropical Diseases Control, Sun Yat-sen University, Ministry of Education, Guangzhou, China huangxi6@mail.sysu.edu.cn.
authors.forename: Xi
authors.initials: X
authors.lastname: Huang
mesh_terms: D000409:Alanine / Q000378:metabolism; D019943:Amino Acid Substitution; D000900:Anti-Bacterial Agents / Q000378:metabolism* / Q000494:pharmacology; D001482:Base Composition; D002511:Cephalosporins / Q000378:metabolism* / Q000494:pharmacology; D003001:Cloning, Molecular; D024881:Drug Resistance, Bacterial / Q000235:genetics; D004926:Escherichia coli / Q000235:genetics / Q000378:metabolism; D015870:Gene Expression; D059646:Genome Size; D016680:Genome, Bacterial; D006868:Hydrolysis; D007527:Isoenzymes / Q000235:genetics / Q000378:metabolism; D008826:Microbial Sensitivity Tests; D009154:Mutation; D011513:Proteus mirabilis / Q000187:drug effects / Q000201:enzymology* / Q000235:genetics; D011994:Recombinant Proteins / Q000235:genetics / Q000378:metabolism; D013912:Threonine / Q000378:metabolism; D001618:beta-Lactamases / Q000235:genetics* / Q000378:metabolism
chemical_list: D000900:Anti-Bacterial Agents; D002511:Cephalosporins; D007527:Isoenzymes; D011994:Recombinant Proteins; D013912:Threonine; C456080:beta-lactamase CTX-M-14; D001618:beta-Lactamases; D000409:Alanine