Transferable Resistance Gene optrA in Enterococcus faecalis from Swine in Brazil

Abstract

OptrA is an ATP-binding cassette (ABC)-F protein that confers resistance to oxazolidinones and phenicols and can be either plasmid-encoded or chromosomally encoded. Here, we isolated 13 Enterococcus faecalis strains possessing a linezolid MIC of ≥4 mg/liter from nursery pigs in swine herds located across Brazil. Genome sequence comparison showed that these strains possess optrA in different genetic contexts occurring in 5 different E. faecalis sequence type backgrounds. The optrA gene invariably occurred in association with an araC regulator and a gene encoding a hypothetical protein. In some contexts, this genetic island was able to excise and form a covalently closed circle within the cell; this circle appeared to occur in high abundance and to be transmissible by coresident plasmids.

Drug Resistance Determinants in Clinical Isolates of Enterococcus faecalis in Bangladesh: Identification of Oxazolidinone Resistance Gene optrA in ST59 and ST902 Lineages

“…The five isolates with optrA in Bangladesh belonged to ST59, ST902 and ST917, among which ST902 is triple-locus variant of ST21, and ST917 is single-locus variant of ST59 (CC59). This indicates that the Bangladeshi isolates comprise two lineages, ST21-like (ST902) and CC59 clones, which had been revealed to be phylogenetically distinct [52]. ST21 and/or ST59 were reported as minor lineages in China [22,43,45], Malaysia [30], and Germany [49].…”

“…Globally distributed optrA-positive E. faecalis reported to date belong to various STs, including major types ST16, ST116, ST256, ST476, ST480, ST585, with ST16 being dominant [22,45,47,[49][50][51][52]. The five isolates with optrA in Bangladesh belonged to ST59, ST902 and ST917, among which ST902 is triple-locus variant of ST21, and ST917 is single-locus variant of ST59 (CC59).…”

Coexistence of the Oxazolidinone Resistance–Associated Genes cfr and optrA in Enterococcus faecalis From a Healthy Piglet in Brazil

“…b Conjugation efficiency corresponds to the number of CFU transconjugants per CFU donors; ND (not determined): only small bacterial colonies (countless) were obtained, all optrA/fexA-positive. c optrA could be efficiently transferred by conjugation at a frequency of 4 × 10 −7 per donor cell using 25 µg/ml of CHL as previously reported (36), and also decreasing CHL concentration or using LZD instead of CHL.…”

“…LR E. faecalis L9 comes from a collection of 13 LR E. faecalis (linezolid MIC of 8 mg/L) that were screened from 245 MDR E. faecalis isolated from rectal swabs from healthy piglets (45 days old) in different states of Brazil (36). These 13 optrA-positive E. faecalis, epidemiologically unrelated (ST29, ST330, ST591, ST710, ST711), were recovered from different pigs found to be distributed in 6 out of the 7 states chosen for sample collection.…”

“…Conjugation efficiency (CFU/ml of transconjugants per CFU/ml of donors) was calculated as previously described (38). PCR using primer sets specific for optrA, cfr, poxtA, fexA, and cat genes (36) and Sanger sequencing were carried out to detect these resistances in OG1RF transconjugants. Minimum inhibitory concentrations (MIC's) of chloramphenicol, florfenicol, linezolid, and tedizolid were determined by broth microdilution testing according to the guidelines of the Clinical Laboratory Standards Institute (CLSI).…”