Novel plasmid-mediated beta-lactamase from Escherichia coli that inactivates oxyimino-cephalosporins

Abstract

A highly cephem-resistant Escherichia coli strain, FP1546, isolated from the fecal flora of laboratory dogs previously administered 1-lactam antibiotics was found to produce a P-lactamase, FEC-1, of 48-kilodalton size and pl 8.2. FEC-1 hydrolyzed cefuroxime, cefotaxime, cefmenoxime, and ceftriaxone, as well as the enzymatically less-stable antibiotics cephaloridine, cefotiam, and cefpiramide. Of the oxyimino-cephalosporins, ceftizoxime was fairly stable to FEC-1. FEC-1 differed notably from chromosomal E. coli cephalosporinase, especially in its broad-spectrum substrate profile and its high inhibition by clavulanic acid, sulbactam, and imipenem. A conjugation study revealed that FEC-1 was encoded by a 74-megadalton plasmid, pFCX1. This may be the first instance of a plasmid-mediated oxyimino-cephalosporinase from E. coli.Over 30 plasmid-mediated f-lactamases (mostly penicillinases) have been found in gram-negative bacteria and classified according to characteristics such as substrate specificity, isoelectric point, and molecular weight. Common are the TEM, OXA, SHV, and PSE types (10,(17)(18)(19)24), with the TEM type of penicillinase being the most frequently isolated plasmid P-lactamase from such gram-negative bacteria as members of the family Enterobacteriaceae, Pseudomonas aeruginosa, Haemophilus influenzae, and Neisseria gonorrhoeae. On the other hand, there have been only two reports of plasmid-mediated cephalosporinases, from Proteus mirabilis (2) and Achromobacter spp. (14).We evaluated the possible resistance mechanisms of oxyimino-cephalosporin-resistant Escherichia coli isolated from the fecal flora of laboratory dogs, and we identified a 3-lactamase which hydrolyzes oxyimino-cephalosporins such as cefuroxime, cefotaxime, cefmenoxime, and ceftriaxone in addition to cephaloridine. The physiological properties of this enzyme were quite distinct from those of chromosomal cephalosporinases from E. coli (20,23). We confirmed that this enzyme was plasmid mediated and had properties similar to those of oxyimino-cephalosporinase type I (7). MATERIALS AND METHODSBacterial strains. E. coli FP1546 was isolated from the fecal flora of a laboratory dog being used for pharmacokinetic studies of P-lactam antibiotics. The nalidixic acidresistant derivative of E. coli CSH2 (metB F-) was kindly provided by T. Yokota of Juntendo University.Antibiotics. Commercially available cephaloridine, cephalothin, cefamandole, cefotiam, cefmetazole, cefsulodin, cefuroxime, cefotaxime, cefmenoxime, ceftriaxone, ceftazidime, cefoperazone, cefpiramide, cefoxitin, moxalactam, and imipenem were used. Cefazolin and ceftizoxime were from Fujisawa Pharmaceutical Co., Ltd., Osaka, Japan. * Corresponding author.Clavulanic acid, sulbactam, and nitrocefin were synthesized in our laboratories.Susceptibility testing. Antibacterial activity of test antibiotics was determined by the agar dilution method. Hundredfold dilutions of overnight cultures in Mueller-Hinton broth (Difco Laboratories, Detroit, Mich.) were inoculated with a multipoint replic...

Nosocomial Outbreak Caused by Salmonella enterica Serotype Livingstone Producing CTX-M-27 Extended-Spectrum β-Lactamase in a Neonatal Unit in Sousse, Tunisia

“…Among 16 neonates, 10 had received cefotaxime and 2 had received ceftazidime. As previously reported (24,30,42), the emergence of highly resistant Salmonella in an environment characterized by a heavy use of antimicrobial agents may provide a setting that is conducive to nosocomial transmission. In our study, the emergence of the CTX-M-27 ESBL in the neonatal ward could be correlated with heavy use of extended-spectrum cephalosporins by the physicians.…”

“…This report describes the first identification of CTX-M-27 in the genus Salmonella and the second CTX-M-type ESBL-producing Salmonella isolate in Tunisia. CTX-M ␤-lactamases, which preferentially hydrolyze cefotaxime, form a growing family that was characterized in the second half of the 1980s with the report of FEC-1 (24). Currently, the CTX-M family comprises at least 40 enzymes belonging to six groups (6).…”

At fekal orijinli Escherichia coli izolatlarında antimikrobiyal direnç ve genişlemiş spektrumlu beta laktamaz üretiminin araştırılması

“…Türkiye'de GSBL sentezleyen izolatlar ilk kez 1992 yılında Tıp Hekimliği alanından bildirilmiştir (16). GSBL'nin hayvan kökenli bir bakteriden ilk tespiti ise Japonya'da bir laboratuvar köpeğinden izole edilen E. coli'de 1988 yılında rapor edilmiştir (21). GSBL'leri en çok üreten suşlar K. pneumoniae, diğer Klebsiella türleri (K. oxytoca gibi) ve E. coli'dir (24).…”

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“…Extended Spectrum β-lactamases (ESBLs) are often plasmid mediated, derived from mutations in the classic TEM and SHV genes by one or more amino acid substitutions around the active site [3]. There are also new families of ESBLs, including the CTX-M, OXA, AmpC, KPC -type enzymes as well as novel, unrelated β-lactamases [4], notably the CTX-M types, are becoming increasingly common, evolved via the escape and mutation of chromosomal β-lactamases from Kluyvera spp., which is a environmental non pathogenic bacteria [1,4]. ESBLs have been reported worldwide in many different genera of Enterobacteriaceae and Pseudomonas spp [5,6].…”