Biochemical Characterization of PER-2 and Genetic Environment of bla PER-2

Abstract

PER-2 was the first detected and the second most prevalent extended-spectrum β-lactamase in clinical pathogens isolated in Argentina and was also reported only in other South American countries. Citrobacter freundii 33587 was isolated in 1999 in Buenos Aires and was resistant to all tested β-lactams except cephamycins and carbapenems. The strain produced both plasmid-borne TEM-1 and PER-2 (pI 5.4), which could be transferred by conjugation. By PCR screening, thermal asymmetric interlaced PCR, and DNA sequencing, we detected an IS Pa12 /IS 1387a insertion sequence upstream of bla _PER-2 , previously reported as also being associated with bla _PER-1 . The presence of similar structures upstream of bla _PER-1 and bla _PER-2 suggests a common origin and mobilization. Compared to bla _PER-1 genes, an additional putative promoter for bla _PER-2 was found. PER-2 kinetic analysis showed its high hydrolysis efficiencies toward both CTX and CAZ ( k _cat / K _m , 0.76 and 0.43 μM ⁻¹ ·s ⁻¹ , respectively).