Purification and properties of a chromosomal .BETA.-lactamase from Klebsiella oxytoca.

Abstract

A /Mactamasewas purified from Klebsiella oxytoca strain GN10650. The enzymewas chromosomally-mediated and gave a single protein band on polyacrylamide gel electrophoresis. Its pi was 5.34 and its MWwas approximately 27,000. The optimal pH and temperature were about 7.0 and 50°C, respectively. The specific activity of the enzyme was 1,207 units per mgof protein for hydrolysis of penicillins and cephalosporins, including cefuroxime, cefotaxime, and aztreonam. The enzyme activity was inhibited by /?-chloromercuribenzoate, iodine, ferrous ion, and by clavulanic acid. Rabbit antibodies raised against the purified K. oxytoca enzymeshowedno cross-reactivity in neutralization tests with /Mactamases produced by other species of Gram-negative bacteria.

A functional classification scheme for beta-lactamases and its correlation with molecular structure

“…ab Other ␤-lactamases described from Klebsiella oxytoca with similar substrate profiles are from strain E23004, enzyme with a pI of 7.4, Class A sequence (11); strain GN10650, enzyme with a pI of 5.3 (125); strain KH111, enzyme with a pI of 5.2 (325); and strain 5445 (TEM-E2 on plasmid pUK721), enzyme with a pI of 5.3 (223).…”

Klebsiella oxytoca: Resistance to aztreonam by overproduction of the chromosomally encoded β-lactamase

“…Klebsiella strains are frequently resistant' to newer/3-1actam antibiotics such as third-generation cephalosporins and monobactams [2]. However, many resistant K. oxytoca isolates have a pattern of resistance that is dissimilar to those of K. pneumoniae producing plasmid-encoded extended-spectrum fl-lactamases: numerous K. oxytoca isolates are resistant to aztreonam [8] and ceftriaxone [3,9], slightly resistant to cefotaxime [3,[8][9][10]21] and susceptible to ceflazidime [3,10]. There is a synergistic effect between clavulanic acid and penicillins, e.g.…”