Phenotypic and Genotypic Antimicrobial Resistance in Non-O157 Shiga Toxin-Producing Escherichia coli Isolated From Cattle and Swine in Chile

Abstract

resistance against antimicrobials that are critical for human and veterinary medicine, representing a major threat for public health. Additionally, these strains could have a competitive advantage in the presence of antimicrobial selective pressure, leading to an increase in food contamination. This study highlights the need for coordinated local and global actions regarding the use of antimicrobials in animal food production.

Antimicrobial Usage Factors and Resistance Profiles of Shiga Toxin-Producing Escherichia coli in Backyard Production Systems From Central Chile

“…Little information is known regarding AMR of STEC strains and other enteropathogens isolated from animals raised in BPS in Latin America. Regarding phenotypic AMR in the STEC isolated strains analyzed, our results show phenotypical resistance against cephalexin in all the STEC strains isolated from animals raised in BPS, similar results to reports for cattle and swine samples under industrialized production systems in the same region of Chile ( 47 ). Even though cephalexin resistance is reported as a common feature in STEC isolates and is an antimicrobial of non-frequent use in animals or humans, non all STEC strains show this feature ( 74 ), suggesting that this resistance pattern is a threat to global health ( 75 , 76 ).…”

“…Similar resistance patterns, including β-lactamases and particularly to cephalexin, has been described for piglets, humans, free-range birds, water sources, and even STEC strains isolated from flies ( 78 – 80 ). Resistance to chloramphenicol was reported in five STEC strains, being different from that reported for industrialized species in Chile, where AMR was detected for a wider variety of drugs at phenotypical analysis ( 47 ). Resistance to the phenicols is mainly due to the presence of cat genes, encoding for chloramphenicol acetyltransferases, specific to chloramphenicol, or to the presence of cml genes, encoding for efflux pumps, among other mechanism, such as nfs B nitroreductase expression ( 81 ).…”

“…Several genes have been linked to AMR in bacteria isolated from backyard animals, humans and even seafood, against tetracycline ( tet A, tet B, tet C, and tet G) ( 43 ), amoxicillin, amoxicillin+clavulanic acid, ampicillin, and ceftiofur ( bla PSE−1 , bla TEM , and bla CMY ) ( 44 ), among other resistance genes related to antimicrobials widely used ( 45 ). Thus, MDR STEC strains have been described as a major public health threat worldwide and in Chile ( 46 , 47 ). In this context, Adesiji et al ( 43 ) described an increase in the incidence of AMR in developing countries, related to inappropriate or uncontrolled use of these drugs in farming practices.…”

Molecular Detection of Antibiotic Resistance Genes in Shiga Toxin-Producing E. coli Isolated from Different Sources

“…Antibiotic treatment of STEC infections in humans is not recommended since there is evidence that treatment may worsen the disease by inducing toxin-related tissue damage and symptoms in patients [ 9 ]. However, toxin production depends on type and concentration of the antibiotic used [ 10 ]. In addition, it is widely accepted that extensive use of antibiotics in animal production systems is a major driver of multidrug resistance (MDR) in bacteria [ 10 ].…”

“…However, toxin production depends on type and concentration of the antibiotic used [ 10 ]. In addition, it is widely accepted that extensive use of antibiotics in animal production systems is a major driver of multidrug resistance (MDR) in bacteria [ 10 ]. An alarming rise in the prevalence of MDR E. coli strains has been reported worldwide, and this is due to the spread of plasmids and other genetic elements.…”