Study of Antibiotic Resistance of Escherichia coli strains isolated from livestock in the province of Guelma
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Date
2025
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University of 20 August 1955 Skikda
Abstract
Antibiotic resistance is a global health concern, threatening both human and veterinary
medicine, with livestock acting as a major reservoir for the dissemination and persistence of
resistant bacteria particularly third-generation cephalosporin-resistant (3GC-R) and colistinresistant (CL-R) Enterobacterales. This thesis investigated the dissemination of 3GC-R and
CL-R Escherichia coli among poultry, bovine and ovine farms in Guelma province,
northeastern Algeria. A longitudinal surveillance was further performed in order to assess the
persistence of CL-R isolates in poultry farms over production cycles. A total of 919 animal and
environmental samples were collected from 38 farms in Guelma. Samples were screened for
3GC-R and CL-R E. coli in selective media. The screened isolates were identified then
subjected to susceptibility tests, including the disc diffusion test, the determination of colistin
minimum inhibitory concentration, and the phenotypic detection of extended spectrum β-
lactamase and carbapenemase enzymes. Afterwards, standard PCR was performed to the 3GCR isolates to investigate the presence of antibiotic resistance genes and integrons, whereas the
CL-R were submitted to whole genome sequencing. Overall, 112 isolates were collected from
21 farms, including 58 3GC-R and 54 CL-R E. coli strains. The 3GC-R isolates were detected
in poultry, bovine and ovine farms, while CL-R strains were only found in poultry farms.
Phenotypic tests revealed that the majority of the isolates were multidrug resistant and
displayed high resistance rates against β-lactams, tetracyclines, fluoroquinolones and
sulfonamides. The molecular analysis identified critical resistance genes including mcr-1,
blaCTX-M, blaNDM, blaOXA-181, blaCMY and blaDHA. The MLST analysis identified 28 different
Sequence Types (STs), mainly ST162 and ST93, and provided evidence on the clonal
dissemination and the potential persistence of several STs within the farms. These findings
underscore the major role of livestock as a reservoir for resistant bacteria and their genes and
emphasize the urgent need for targeted strategies within a “One Health” framework to mitigate
the spread of these isolates and preserve the effectiveness of critical antibiotic agents
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Keywords
Antibiotic Resistance, Escherichia coli strains