BACKGROUND Concomitant with the recent emergence of CTX-M-type extended-spectrum beta-lactamases (ESBLs), Escherichia coli has become the enterobacterial species most affected by ESBLs. Multiple locales are encountering CTX-M-positive E. coli, including specifically CTX-M-15. To gain insights into the mechanism underlying this phenomenon, we assessed clonality and diversity of virulence profile...

The goal of this study was to determine if the interpretations of extended-spectrum and advanced-spectrum cephalosporins (ESCs and ASCs, respectively) for isolates of Enterobacteriaceae would be impacted by the results of aminophenylboronic acid (APBA) testing. Fifty-three isolates of Escherichia coli, 21 Klebsiella species, and 6 Proteus species that were resistant to at least one ESC were tes...

Multidrug-resistant Escherichia coli is an emerging clinical challenge in domestic species. Treatment options in many cases are limited. This study characterized MDR E. coli isolates from urinary tract infections in dogs, collected between 2002 and 2011. Isolates were evaluated in terms of β-lactamase production, phylogenetic group, ST type, replicon type and virulence marker profile. Compariso...

INTRODUCTION While the Clinical and Laboratory Standards Institute (CLSI) recommends against routine screening for extended spectrum β-lactamases (ESBLs), knowledge of these data can provide valuable insights regarding epidemiology and drug therapy decisions. The purpose of this study was to compare the impact of minimum inhibitory concentration (MIC)-based screening versus phenotypic confirmat...

Therapeutic options for infections caused by gram-negative organisms expressing plasmid-mediated AmpC beta-lactamases are limited because these organisms are usually resistant to all the beta-lactam antibiotics, except for cefepime, cefpirome, and the carbapenems. These organisms are a major concern in nosocomial infections and should therefore be monitored in surveillance studies. Six families...

Extended-spectrum β-lactamases (ESBLs) and plasmid-mediated AmpC β-lactamases (pAmpC) are enzymes able to hydrolyze a large variety of β-lactam antibiotics, including third-generation cephalosporins and monobactams. Broilers and broiler meat products can be highly contaminated with ESBL- and pAmpC-producing Escherichia coli strains, also known as extended-spectrum cephalosporin (ESC)-resistant ...

Dear Sir, Enterobacteriaceae, other than Escherichia spp. and Klebsiella spp., can cause serious nosocomial infections and appear to have become increasingly drug resistant. Citrobacter freundii, belonging to the Enterobacteriaceae family, is a prominent opportunistic pathogen responsible for serious infections in immunocompromised individuals. C. freundii is characterized by the presence of ch...

Understanding the interplay between antibiotic resistance and bacterial fitness and virulence is essential to guide individual treatments and improve global antibiotic policies. A paradigmatic example of a resistance mechanism is the intrinsic inducible chromosomal β-lactamase AmpC from multiple Gram-negative bacteria, including Pseudomonas aeruginosa, a major nosocomial pathogen. The regulatio...

Extended-spectrum beta-lactamases (ESBLs) are enzymes found in gram-negative bacilli that mediate resistance to extended-spectrum cephalosporins and aztreonam. In 1999, the National Committee for Clinical Laboratory Standards (NCCLS) published methods for screening and confirming the presence of ESBLs in Klebsiella pneumoniae, Klebsiella oxytoca, and Escherichia coli. To evaluate the confirmati...

OBJECTIVES The aim of this study was to evaluate CHROMagar CTX (CHROMagar France), a novel agar for the selective isolation of Enterobacteriaceae expressing the bla(CTX-M) gene in the presence of enteric bacteria expressing AmpC enzymes. METHODS A panel of 150 Gram-negative bacteria (mainly Escherichia coli, Enterobacter, Klebsiella, Pseudomonas and Salmonella) isolated from humans and animal...