Integration of the blaNDM-1 carbapenemase gene into a novel SXT/R391 integrative and conjugative element in Proteus vulgaris.

OBJECTIVES: To characterize the genetic environment of the carbapenem resistance determinant in Proteus vulgaris of swine origin. METHODS: The carbapenem-resistant P. vulgaris strain BC22 was isolated from a faecal swab from a diseased pig with diarrhoea in Sichuan Province of China in 2018. The presence of carbapenemase genes was screened by PCR. WGS and bioinformatics analysis were performed to analyse the genetic environment of the carbapenem resistance determinant. RESULTS: P. vulgaris strain BC22 was found to harbour the carbapenemase gene blaNDM-1. WGS data revealed that blaNDM-1 was located in a truncated ISAba125 composite transposon. The carbapenem resistance gene blaNDM-1 and 20 other resistance genes, including the multiresistance gene cfr and the bifunctional aminoglycoside/quinolone resistance gene aac(6')-lb-cr, were located in a novel SXT/R391 integrative and conjugative element (ICE). This new SXT/R391 ICE of 148.7 kb was chromosomally located, and could be transferred to Escherichia coli. CONCLUSIONS: Here, we report a carbapenemase gene, blaNDM-1, integrated into an SXT/R391 ICE. Our study highlights that this SXT/R391 ICE may facilitate the dissemination of clinically important resistance genes such as blaNDM-1, cfr and aac(6')-lb-cr.

Characterization of a Novel SXT/R391 Integrative and Conjugative Element Carrying cfr, blaCTX-M-65, fosA3, and aac(6')-Ib-cr in Proteus mirabilis.

A novel 139,487-bp SXT/R391 integrative and conjugative element, ICEPmiChnBCP11, was characterized in Proteus mirabilis of swine origin in China. ICEPmiChnBCP11 harbors 20 different antimicrobial resistance genes, including the clinically important rRNA methyltransferase gene cfr, the extended-spectrum ß-lactamase gene blaCTX-M-65, fosfomycin resistance gene fosA3, and fluoroquinolone resistance gene aac(6')-Ib-cr An ISPpu12-mediated composite transposon containing various resistance genes and 10 copies of IS26 is inserted in hot spot 4. ICEPmiChnBCP11 was successfully transferred to Escherichia coli.

Various Sequence Types of Enterobacteriaceae Isolated from Commercial Chicken Farms in China and Carrying the blaNDM-5 Gene.

A total of 108 meropenem-resistant Enterobacteriaceae isolates were obtained from 1,658 rectal swabs collected from 15 unrelated commercial chicken farms in China between 2014 and 2016. These samples yielded 16 Escherichia coli and 2 Klebsiella pneumoniae isolates of diverse sequence types carrying a blaNDM-5-bearing IncX3 plasmid. K. pneumoniae strain sequence type 709 (ST709) has two blaNDM-5-carrying plasmids that were transferred together to E.coli.

An IncX1 plasmid isolated from Salmonella enterica subsp. enterica serovar Pullorum carrying blaTEM-1B, sul2, arsenic resistant operons.

We have identified an IncX1 plasmid named pQJDSal1 from Salmonella enterica subsp. enterica serovar Pullorum (S. Pullorum). The plasmid is 67,685 bp in size and has 72 putative genes. pQJDSal1 harbors a conserved IncX1-type backbone with predicted regions for conjugation, replication and partitioning, as well as a toxin/antitoxin plasmid addiction system. Two regions (A and B) that have not been previously reported in IncX1 plasmids are inserted into the backbone. Region A (10.7 kb), inserted between parA and taxD, consists of a new Tn6168-like transposon containing an arsenic resistant operon arsB2CHR and sulfonamide resistance gene sul2. Region B contains another arsenic resistant operon arsADHR, resistance gene blaTEM-1B and three transposable elements. Conjugation experiments showed that pQJDSal1 could transfer from S. Pullorum to Escherichia coli (E. coli) J53. Statistical analysis of 70 sequenced IncX1 plasmids revealed that IncX1 plasmids harbored various antibiotic resistance genes. The results highlight the importance of IncX1 plasmids in disseminating antibiotic resistance genes.

Vertical transmission of Salmonella Enteritidis with heterogeneous antimicrobial resistance from breeding chickens to commercial chickens in China.

Human salmonellosis caused by the consumption of eggs and chicken meat contaminated with Salmonella Enteritidis has become a continuing public health concern worldwide. In this study we adopted whole genome sequencing (WGS) to determine the genetic relationship and antimicrobial resistance of S. enterica strains isolated from a poultry breeding enterprise that consists of one breeding chicken farm, one egg hatchery and one commercial chicken farm. A total of 148 S. enterica including 147 S. Enteritidis strains were isolated from 2100 fecal swab samples, with 16 (5.3 %, 16/300) from breeding chicken farm, 38 (4.2 %, 38/900) from egg hatchery and 94 (10.4 %, 94/900) from commercial chicken farm. WGS revealed that all 147 S. Enteritidis strains belonged to ST11, and further divided into 4 different ribosomal STs and 64 core genome STs. Single nucleotide polymorphism typing suggested the presence of the vertical transmission of S. Enteritidis from breeding chicken to commercial chicken. Three different antimicrobial-resistant plasmids including one blaCTX-M-14-carrying plasmid and two virulence-resistance plasmids were characterized, resulting in the heterogeneous antimicrobial resistance of clonally related S. Enteritidis strains. Routine surveillance in breeding chicken farms is conducive to the control of S. Enteritidis from farm to fork.

IS26-Mediated Genetic Rearrangements in Salmonella Genomic Island 1 of Proteus mirabilis.

Salmonella genomic island 1 (SGI1) is an integrative mobilizable element integrated into the chromosome of bacteria, which plays an important role in the dissemination of antimicrobial resistance genes. Lots of SGI1 variants are found mainly in Salmonella enterica and Proteus mirabilis. In this study, a total of 157 S. enterica and 132 P. mirabilis strains were collected from food-producing animals in Sichuan Province of China between December 2016 and November 2017. Detection of the SGI1 integrase gene showed that three S. enterica and five P. mirabilis strains were positive for SGI1, which displayed different multidrug resistance profiles. Five different SGI1 variants, including two novel variants (SGI1-PmBC1123 and SGI1-PmSC1111), were characterized by whole genome sequencing and PCR linkage. In two novel SGI1 variants, IS26-mediated rearrangements resulted in large sequence inversions of the MDR regions extending outside the SGI1 backbone. The sul3-type III class 1 integron (5'CS-sat-psp-aadA2-cmlA1-aadA1-qacH-IS440-sul3) and gene cassettes aac(6')-Ib-cr-bla OXA- 1-catB3-arr-3 are found in SGI1-PmSC1111. Mobilization experiments indicated that three known variants were conjugally mobilized in trans to Escherichia coli with the help of a conjugative IncC plasmid. However, the two novel variants seemed to lose the mobilization, which might result from the sequence inversion of partial SGI1 backbone. The identification of the two novel SGI1 variants in this study suggested that IS26-mediated rearrangements promote the diversity of SGI1.

Whole-genome sequencing of Enterococcus hirae CQP3-9, a strain carrying the phenicol-oxazolidinone-tetracycline resistance gene poxtA of swine origin in China.

OBJECTIVES: The aim of this study was to characterise the whole genome sequence of linezolid-intermediate Enterococcus hirae strain CQP3-9 isolated from a large-scale swine farm in Sichuan Province, China, in August 2018. METHODS: An Illumina MiSeq platform (400-bp paired-end reads with 230-fold average coverage) and PacBio RS II sequencing instrument (100-fold average read depth) were used for genome sequencing. The chromosome and two plasmids were assembled using the software SMRT portal v.3.2.0. Acquired antimicrobial resistance genes were identified using ResFinder 3.1. RESULTS: The genome of E. hirae strain CQP3-9 consists of one 2 695 881-bp chromosome, one 125 915-bp plasmid (pCQP3-9_1) and one 33 132-bp plasmid (pCQP3-9_2). The genome of CQP3-9 contains 2458 coding sequences and 89 RNA genes. The poxtA gene is the only linezolid resistance gene in CQP3-9, located on plasmid pCQP3-9_2 that co-harbours erm(B) (macrolide resistance), fexB (chloramphenicol and florfenicol resistance), and tet(M) and tet(L) (tetracycline resistance). CONCLUSION: Here we report for the first time the phenicol-oxazolidinone-tetracycline resistance gene poxtA in E. hirae, located on a plasmid that co-harbours erm(B), fexB, tet(L) and tet(M). The genome sequence of E. hirae CQP3-9 provides valuable information for the dissemination of poxtA among enterococci.

Detection of transferable oxazolidinone resistance determinants in Enterococcus faecalis and Enterococcus faecium of swine origin in Sichuan Province, China.

OBJECTIVES: The aim of this study was to detect transferable oxazolidinone resistance determinants (cfr, optrA and poxtA) in Enterococcus faecalis and Enterococcus faecium isolates of swine origin in Sichuan Province, China. METHODS: A total of 158 enterococcal isolates (93 E. faecalis and 65 E. faecium) isolated from 25 large-scale swine farms (2016-2017) were screened for the presence of cfr, optrA and poxtA by PCR. The genetic environments of cfr, optrA and poxtA were characterised by whole-genome sequencing. Transfer of oxazolidinone resistance determinants was determined by conjugation or electrotransformation experiments. RESULTS: The transferable oxazolidinone resistance determinants cfr, optrA and poxtA were detected in zero, six and one enterococcal isolates, respectively. The poxtA gene in one E. faecalis isolate was located on a 37 990-bp plasmid that co-harboured fexB, cat, tet(L) and tet(M) and could be conjugated to E. faecalis JH2-2. One E. faecalis isolate harboured two different OptrA variants, including one variant with a single substitution (Q219H) that has not been reported previously. Two optrA-carrying plasmids, pC25-1 (45 581bp) and pC54 (64 500bp), shared a 40 494-bp identical region containing the genetic context IS1216E-fexA-optrA-erm(A)-IS1216E that could be electrotransformed into Staphylococcus aureus. Four different chromosomal optrA gene clusters were found in five strains, in which optrA was associated with Tn554 or Tn558 inserted into the radC gene. CONCLUSION: This study highlights the fact that mobile genetic elements, such as plasmids, IS1216E, Tn554 and Tn558, may facilitate the horizontal transmission of optrA and poxtA genes.