One new LEN enzyme and two new OKP enzymes in Klebsiella pneumoniae clinical isolates and proposed nomenclature for chromosomal beta-lactamases of this species.

Three families of chromosomally encoded beta-lactamases have been identified so far in Klebsiella pneumoniae clinical isolates: SHV (7), LEN (1), and very recently, OKP (5). These enzymes are closely related to OHIO-1 (10). We determined the sequences of the bla genes of nine isolates of K. pneumoniae producing a penicillinase with an isoelectric point different from 7.6, the pI of the most commonly encountered SHV-1 (6). The strains were susceptible to cephalosporins (except for one isolate that also produced CTX-M-3). The bla gene was amplified with primers Pro3-F (9) and Gra2-R (8).