Detection of Oxazolidinone Resistance Genes and Characterization of Genetic Environments in Enterococci of Swine Origin, Italy

Abstract

One hundred forty-five florfenicol-resistant enterococci, isolated from swine fecal samples collected from 76 pig farms, were investigated for the presence of optrA, cfr, and poxtA genes by PCR. Thirty florfenicol-resistant Enterococcus isolates had at least one linezolid resistance gene. optrA was found to be the most widespread linezolid resistance gene (23/30), while cfr and poxtA were detected in 6/30 and 7/30 enterococcal isolates, respectively. WGS analysis also showed the presence of the cfr(D) gene in Enterococcus faecalis (n = 2 isolates) and in Enterococcus avium (n = 1 isolate). The linezolid resistance genes hybridized both on chromosome and plasmids ranging from ~25 to ~240 kb. Twelve isolates were able to transfer linezolid resistance genes to enterococci recipient. WGS analysis displayed a great variability of optrA genetic contexts identical or related to transposons (Tn6628 and Tn6674), plasmids (pE035 and pWo27-9), and chromosomal regions. cfr environments showed identities with Tn6644-like transposon and a region from p12-2300 plasmid; cfr(D) genetic contexts were related to the corresponding region of the plasmid 4 of Enterococcus faecium E8014; poxtA was always found on Tn6657. Circular forms were obtained only for optrA- and poxtA-carrying genetic contexts. Clonality analysis revealed the presence of E. faecalis (ST16, ST27, ST476, and ST585) and E. faecium (ST21) clones previously isolated from humans. These results demonstrate a dissemination of linezolid resistance genes in enterococci of swine origin in Central Italy and confirm the spread of linezolid resistance in animal settings.

New Sequence Types and Antimicrobial Drug–Resistant Strains of Streptococcus suis in Diseased Pigs, Italy, 2017–2019

“…One of the florfenicol-resistant isolates was positive for optrA , an oxazolidinone/phenicol resistance determinant carried by mobile genetic elements. optrA in S. suis isolates from China has been previously described and is frequently detected in Enterococcus isolates from pig farms in Italy ( 46 , 47 ). The high levels of AMR and the detection of emerging drug-resistance determinants are a consequence of selective pressure caused by antibiotic overuse.…”

Special Issue “Antimicrobial Resistance: From the Environment to Human Health”

“…Also, in a different animal production environment, 145 florfenicol-resistant enterococci, isolated from swine fecal samples collected from 76 pig farms, were investigated for the presence of optrA, cfr, and poxtA genes by PCR. In this study it was possible to observe a dissemination of linezolid resistance genes in enterococci of swine origin in Central Italy and confirm the spread of linezolid resistance in animal settings [ 2 ]. In another study, the pathogenomics of carbapenem-resistant Aeromonas veronii ( A. veronii ) isolates recovered from pigs in KwaZulu-Natal, South Africa were explored by whole genome sequencing on the Illumina MiSeq platform.…”

Identification of the Multiresistance Gene poxtA in Oxazolidinone-Susceptible Staphylococcus haemolyticus and Staphylococcus saprophyticus of Pig and Feed Origins

“…It was reported that IS 1216 played a major role in the processes of aiding the dissemination and persistence of poxtA among enterococci [ 20 ]. The presence of these homologous gene regions (IS 1216 - poxtA -IS 1216 or IS 1216 - poxtA ) in Staphylococcus spp., Enterococcus spp.…”