Abstract
Antimicrobial resistance is a major worldwide hazard. Therefore, the World Health Organization has proposed a classification of antimicrobials with respect to their importance for human medicine and advised some restriction of their use in veterinary medicine. In Belgium, this regulation has been implemented by a Royal Decree (RD) in 2016, which prohibits carbapenem use and enforces strict restrictions on the use of third- and fourth-generation cephalosporins (3 GC and 4 GC) for food-producing animals. Acquired resistance to β-lactam antibiotics is most frequently mediated by the production of β-lactamases in Gram-negative bacteria. This study follows the resistance to β-lactam antibiotics in Escherichia coli isolated from young diarrheic or septicaemic calves in Belgium over seven calving seasons in order to measure the impact of the RD. Phenotypic resistance to eight β-lactams was assessed by disk diffusion assay and isolates were assigned to four resistance profiles: narrow-spectrum β-lactamases (NSBL); extended-spectrum β-lactamases (ESBL); cephalosporinases (AmpC); and cephalosporinase-like, NSBL with cefoxitin resistance (AmpC-like). No carbapenemase-mediated resistance was detected. Different resistance rates were observed for each profile over the calving seasons. Following the RD, the number of susceptibility tests has increased, the resistance rate to 3 GC/4 GC has markedly decreased, while the observed resistance profiles have changed, with an increase in NSBL profiles in particular.
Highlights
In Gram-negative bacteria, acquired resistance to β-lactam antibiotics is most frequently mediated by the production of plasmid-encoded β-lactamase (BLA) enzymes hydrolysing the β-lactam ring [1]
Amongst the Gram-negative bacteria, the first BLA enzyme was described in Escherichia coli [4], naturally present in the intestinal microbiota of humans and different animal species [5]
The purpose of this study was to compare the evolution of the resistance phenotypes to β-lactams of septicaemic and diarrheagenic E. coli isolated from young calves at ARSIA
Summary
In Gram-negative bacteria, acquired resistance to β-lactam antibiotics is most frequently mediated by the production of plasmid-encoded β-lactamase (BLA) enzymes hydrolysing the β-lactam ring [1]. Amongst the Gram-negative bacteria, the first BLA enzyme was described in Escherichia coli [4], naturally present 4.0/). In the intestinal microbiota of humans and different animal species [5]. Since the 1960s, E. coli has acquired several genes encoding many families of NSBL, ESBL, AmpC, and CP [2,3]. These different BLA families can comprise several dozens of variants [9]. The most common ESBL enzymes, in humans as well as in animals, belong to the CTX-M family [10], which comprises more than 240 variants (available at: http://bldb.eu/BLDB.php?prot=A#CTX-M, last accessed 29 September 2021)
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