A divergently oriented ampR has been located upstream of blaL2 in Stenotrophomonas maltophilia. AmpR is necessary for L1 and L2 beta-lactamase induction in response to beta-lactam challenge, and activation of AmpR is sufficient to induce L1 and L2 production. L1 induction requires more activation of AmpR than does L2 induction.
Department of Cellular and Molecular Medicine, University of Bristol, School of Medical Sciences, University Walk, Bristol BS8 1TD, United Kingdom. matthewb.avison@bris.ac.uk.