DNA sequence differences of ampD mutants of Citrobacter freundii.

Antimicrobial Agents and Chemotherapy
P StapletonI Phillips

Abstract

Three groups of mutants with increased levels of beta-lactamase synthesis were selected from Citrobacter freundii 382010 by beta-lactam antibiotics at concentrations just above the MIC. Uninduced cultures of the hyperinducible group had 3- to 5-fold more beta-lactamase activity than the parent strain, with one mutant (termed type b) expressing 19 times the activity of the parent strain; the partially derepressed group had a relative 55-fold increase, while fully derepressed strains exhibited a 460-fold increase. Upon induction by growth in the presence of cefoxitin (32 micrograms/ml) for 2 h, the hyperinducible and derepressed groups had similar relative beta-lactamase activities of 650 and 725, respectively. Induction of beta-lactamase activity from partially derepressed mutants resulted in a relative activity of only 240. The ampD gene including its promoter region was amplified from the parent strain and the mutant strains by PCR. The sequence of ampD from the parent strain showed only three nucleotide changes from a previously published sequence, none of which resulted in a change to the deduced amino acid sequence. Hyperinducible mutant strains of type a had an amino acid change of either a tryptophan in codon 95 to an arg...Continue Reading

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Citations

Jun 7, 2005·Journal of Huazhong University of Science and Technology. Medical Sciences = Hua Zhong Ke Ji Da Xue Xue Bao. Yi Xue Ying De Wen Ban = Huazhong Keji Daxue Xuebao. Yixue Yingdewen Ban·Ming NiJunying Qi
Sep 10, 2008·Antimicrobial Agents and Chemotherapy·Amber J Schmidtke, Nancy D Hanson
May 26, 2006·Antimicrobial Agents and Chemotherapy·Amber J Schmidtke, Nancy D Hanson
May 6, 2009·Antimicrobial Agents and Chemotherapy·Tsuey-Ching YangYu-Tzu Lin
Feb 19, 2000·Antimicrobial Agents and Chemotherapy·A KugaM Inoue
Apr 18, 2002·Antimicrobial Agents and Chemotherapy·Joseph F PetrosinoSusan M Rosenberg
Feb 18, 2016·Antimicrobial Agents and Chemotherapy·Andrew P NorganRobin Patel
Apr 14, 2016·Antimicrobial Agents and Chemotherapy·Veronica N KosHumphrey A Gardner
Sep 30, 2015·Antimicrobial Agents and Chemotherapy·Junghyun Hwang, Heenam Stanley Kim
Dec 3, 1998·Antimicrobial Agents and Chemotherapy·T Y LangaeeA Huletsky
Feb 27, 1999·Antimicrobial Agents and Chemotherapy·S TrépanierA Huletsky
Aug 1, 1996·Antimicrobial Agents and Chemotherapy·A F EhrhardtJ S Leser

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