Detection and linkage to mobile genetic elements of tetracycline resistance gene tet(M) in Escherichia coliisolates from pigs

Abstract

BackgroundIn Escherichia coli the genes involved in the acquisition of tetracycline resistance are mainly tet(A) and tet(B). In addition, tet(M) is the most common tetracycline resistance determinant in enterococci and it is associated with conjugative transposons and plasmids. Although tet(M) has been identified in E. coli, to our knowledge, there are no previous reports studying the linkage of the tet(M) gene in E. coli to different mobile genetic elements. The aim of this study was to determine the occurrence of tet(A), tet(B), and tet(M) genes in doxycycline-resistant E. coli isolates from pigs, as well as the detection of mobile genetic elements linked to tet(M) in E. coli and its possible transfer from enterococci.Resultstet(A) was the most frequently detected gene (87.9%) in doxycycline-resistant isolates. tet(M) was found in 13.1% E. coli isolates. The tet(M) gene was detected in relation with conjugative transposons in 10 out of 36 enterococci isolates analyzed but not in any of E. coli isolates positive for tet(M). Southern blot showed that in E. coli and in most of the enterococci isolates the tet(M) gene was carried on a plasmid. According to the phylogenetic analysis, E. coli contained a new tet(M) allele grouping separately. Mating experiments revealed that tet(M) was carried on a mobile element successfully transferred between enterococci and between enterococci and E. coli.ConclusionsThe detection of tet(M) in E. coli isolates from pigs was higher than expected. In our study, tet(M) detected in E. coli seems not to have been transferred from enterococci, although it can not be ruled out that the horizontal transfer of this gene occurred from other intestinal tract bacteria.

Antimicrobial Resistance inEscherichia coli

“…In the same study, the genes tet(A), tet(B), tet(C), and tet(A) + tet(B) were detected in 60, five, one, and two E. coli isolates, respectively, from diarrhea and enterotoxemia in pigs (177). In 99 tetracycline-resistant E. coli isolates from pigs in Spain, the genes tet(A) (n = 46), tet(B) (n = 12), and tet(A) + tet(B) (n = 28) but also tet(A) + tet(M) (n = 11) and tet(A) + tet(B) + tet(M) (n = 2) were detected (178). The tet(M) gene was shown by Southern blot hybridization to be located on plasmids.…”

The unravelled Enterococcus faecalis zoonotic superbugs: Emerging multiple resistant and virulent lineages isolated from poultry environment

“…Thus, the transmission, proliferation and dissemination of multidrug resistant pathogens are core clinical and “One Health” challenges. Earlier studies have indicated that the gut microbial flora of warm blooded animals generously contributes to antibiotic‐resistome exchange to opportunistic intestinal pathogens, exemplified by the emergence of acquired vancomycin resistance in E. faecium from anaerobic gut commensals, and successful transfer of tetracycline genotype tet (M) in between enterococci and E. coli (Jurado‐Rabadán et al, ; van Schaik, ). The transmission of antimicrobial resistance in human or veterinary pathogens is a genetic attribute of Enterococcus species.…”

Prevalence and Antimicrobial Resistance of Enterococci Isolated from Retail Meats in the United States, 2002 to 2014

“…Food also may be a source of Enterococcus causing urinary tract infections (12). In addition, foodborne enterococci can transfer resistance genes to pathogens such as Campylobacter, Listeria, and Escherichia coli (13)(14)(15). Furthermore, due to the ubiquity of enterococci in the animal gut, along with their resilience to environmental stress and their ability to acquire antibiotic resistance, the World Health Organization recommends that integrated antimicrobial resistance-monitoring systems use enterococci as sentinel organisms for resistance to agents with Gram-positive activity (16).…”