The resistance and integrase genes of pACM1, a conjugative multiple-resistance plasmid, from Klebsiella oxytoca

pACM1 is an 85-kb conjugative plasmid from a clinical isolate of Klebsiella oxytoca that encodes resistance to beta-lactams (mediated by SHV-5 extended spectrum beta-lactamase), trimethoprim, sulfonamides, tetracycline, aminoglycosides, and mercuric chloride. The expression of the aminoglycoside resistance is difficult to detect, which could have clinical implications. A region of pACM1 containing five resistance genes and two putative integrons was characterized by restriction mapping and partial DNA sequencing. One integron appears to be class I (sulI type); the second lacks a recognizable 3' conserved segment. Neither integron has the BamHI site predicted for the 5' conserved segment. Plasmids encoding SHV-5 from other bacterial strains appear to be closely related to pACM1 by restriction enzyme analysis, but have resistance/integron regions that vary in size and content from that of pACM1. Integrase-mediated recombination might be responsible for genetic divergence in a widely distributed family of pACM1-like plasmids. (C) 1997 Academic Press.