A Novel Type of AmpC β-Lactamase, ACC-1, Produced by a Klebsiella pneumoniae Strain Causing Nosocomial Pneumonia

Abstract

A Klebsiella pneumoniae strain resistant to oxyimino cephalosporins was cultured from respiratory secretions of a patient suffering from nosocomial pneumonia in Kiel, Germany, in 1997. The isolate harbors a bla resistance gene located on a transmissible plasmid. An Escherichia coli transconjugant produces a β-lactamase with an isoelectric point of 7.7 and a resistance phenotype characteristic of an AmpC (class 1) β-lactamase except for low MICs of cephamycins. Thebla gene was cloned and sequenced. It encodes a protein of 386 amino acids with the active site serine of the S-X-X-K motif at position 64, as is characteristic for class C β-lactamases. Multiple alignment of the deduced amino acid sequence with 21 other AmpC β-lactamases demonstrates only very distant homology, reaching at maximum 52.3% identity for the chromosomal AmpC β-lactamase ofSerratia marcescens SR50. The β-lactamase ofK. pneumoniae KUS represents a new type of AmpC-class enzyme, for which we propose the designation ACC-1 (Ambler class C-1).

Resistance to cephalosporins and carbapenems in Gram-negative bacterial pathogens

“…Likely Bauernfeind et al (1999) between these promoter boxes increase the promoter activity and entail in high-level ampC expression as described previously (Siu et al, 2003). Examples of the promoter region of ampC found in clinical isolates of E. coli are displayed in Fig.…”

High Prevalence of CTX-M-15-Producing O25b-ST131Escherichia coliClone in Bulgarian Hospitals

“…1,18 Polymerase chain reaction (PCR) was performed to detect the beta-lactamase genes of the SHV-, TEM-, CTX-M, and OXA-groups. 17 Nineteen isolates (6 from 2006 to 2009 and 13 from 2002 to 2003) representative for hospital centers, betalactamase groups, and random amplified polymorphic DNA (RAPD)-types were selected for sequencing of their bla genes as previously described.…”

What’s new in β-lactamases?

“…The MIR-1 and ACT-1 ␤-lactamases appear to have originated from the AmpC enzyme of Enterobacter cloacae [8•,9]; BIL-1, CMY-2, -3, -4, and -5; LAT-1, -2, -3, and -4 appear to be from Citrobacter freundii [5••,10]; CMY-1, FOX-1, -2, -3, and -4, and MOX-1 appear to be from P. aeruginosa [5••,11,12]; DHA-1 appears to be from Morganella morganii [13]. One of the most recent additions to this group is ACC-1, which was found to have strong homology to the chromosomally mediated inducible ␤-lactamase in H. alvei [14,15]. The ACC-1 enzyme was recently implicated in an outbreak of Klebsiella pneumoniae in an intensive care unit in Tunisia [16].…”