Disease relevance of ampD

• Constitutive high expression of chromosomal beta-lactamase in Pseudomonas aeruginosa caused by a new insertion sequence (IS1669) located in ampD [1].

High impact information on ampD

• Although ampD inactivation has been previously found to lead to a partially derepressed phenotype characterized by increased AmpC production but retaining further inducibility, the regulation of ampC in P. aeruginosa is far from well understood [2].
• On the other hand, six of them harbored inactivating mutations in ampD: four contained frameshift mutations, one had a C-->T mutation, creating a premature stop codon, and finally, one had a large deletion, including the complete ampDE region [3].
• One highly resistant, constitutive beta-lactamase-producing variant contained no mutations in ampD, but a point mutation was observed in ampR, resulting in an Asp-135-->Asn change [1].
• Complementation of these isolates with ampD from the reference P. aeruginosa strain PAO1 caused a dramatic decrease in the expression of AmpC beta-lactamase and a parallel decrease of the MIC of ceftazidime to a level comparable to that of PAO1 [1].

References