ABSTRACT
Two ampD homologues, ampD
I and ampD
II, of Stenotrophomonas maltophilia have been cloned and analyzed. Comparative genomic analysis revealed that the genomic context of the ampD
II genes is quite different, whereas that of the ampD
I genes is more conserved in S. maltophilia strains. The ampD system of S. maltophilia is distinct from that of the Enterobacteriaceae and Pseudomonas aeruginosa in three respects. (i) AmpDI of S. maltophilia is not encoded in an ampDE operon, in contrast to what happens in the Enterobacteriaceae and P. aeruginosa. (ii) The AmpD systems of the Enterobacteriaceae and P. aeruginosa are generally involved in the regulation of ampR-linked ampC gene expression, while AmpDI of S. maltophilia is responsible for the regulation of two intrinsic β-lactamase genes, of which the L2 gene, but not the L1 gene, is linked to ampR. (iii) S. maltophilia exhibits a one-step L1 and L2 gene derepression model involving ampD
I, distinct from the two- or three-step derepression of the Enterobacteriaceae and P. aeruginosa. Moreover, the ampD
I and ampD
II genes are constitutively expressed and not regulated by the inducer and AmpR protein, and the expression of ampD
II is weaker than that of ampD
I. Finally, AmpDII is not associated with the derepression of β-lactamases, and its role in S. maltophilia remains unclear.
Comparative Genomic Analysis of Multidrug-Resistant Pseudomonas aeruginosa Clinical Isolates VRFPA06 and VRFPA08 with VRFPA07
