IDENTIFICATION OF CLINICAL ISOLATES OF INDOLE-POSITIVE KLEBSIELLA SPP, INCLUDING KLEBSIELLA-PLANTICOLA, AND A GENETIC AND MOLECULAR ANALYSIS OF THEIR BETA-LACTAMASES

In a collection of 43 indole-positive Klebsiella clinical isolates, wh ich were initially identified as Klebsiella oxytoca, there were 18 iso lates which exhibited a pattern characteristic of extended-spectrum be ta-lactamase (ESBL) resistance, This study aimed to confirm their iden tity by biochemical tests and by PCR and to determine the genetic basi s for their resistance to the beta-lactams and broad-spectrum cephalos porins. Chromosomal beta-lactamase genes were analyzed by PCR, and pla smid-mediated beta-lactamase genes were analyzed by conjugation and tr ansformation, There were 39 isolates which grew on melezitose but fail ed to grow on 3-hydroxybutyrate, confirming them as K. oxytoca, PCR an alysis of their beta-lactamase genes divided these isolates into two g roups, the bla(OXY-1) group and the bla(OXY-2) group, Each group had b eta-lactamases with different isoelectric points; the bla(OXY-1) group had beta-lactamases with isoelectric points at 7.2, 7.8, 8.2, and 8.8 , and the more common bla(OXY-2) group had beta-lactamases with pIs at 5.2, 5.4 (TEM-1), 5.7, 5.9, 6.4, and 6.8, A pi of 5.2 was the most fr equently detected and accounted for 59% of all the bla(OXY-2) beta-lac tamases. Hyperproduction of clavulanate-inhibited chromosomal beta-lac tamases was detected in 17 K. oxytoca isolates, resulting in an ESBL p henotype, K. oxytoca isolates having a plasmid-mediated genetic basis for their ESBL phenotype were not found, confirming that, in K. oxytoc a, plasmids are rarely involved in conferring resistance to the newer cephalosporins. Four isolates proved to be isolates of K. planticola i n which the beta-lactamase genes failed to react with the primers used in the PCR, One K. planticola isolate contained a transferable plasmi d harboring the SHV-5 beta-lactamase gene and showed an ESBL phenotype , while the other non-ESBL K. planticola isolates contained chromosoma l beta-lactamases with isoelectric points at 7.2, 7.7, and 7.9 plus 7. 2.