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Background: Fosfomycin is an important broad-spectrum bactericidal antibiotic to treat multidrug-resistant bacteria infections. It is generally accepted that heteroresistant bacteria are an intermediate stage in the formation of drug resistance, but there are few studies on the formation mechanism underlying fosfomycin heteroresistance (FHR).Objectives: To reveal the characteristics and formation mechanisms of FHR in Escherichia coli isolates obtained from chickens.Methods: We identified the FHR according to the population analysis profile (PAP) test and in vitro time-kill assay. Growth curves for FHR E. coli and their subpopulations were measured. Also, the subpopulations were repeatedly cultured in fosfomycin-free medium for 5-20 overnight incubation periods. The formation mechanisms of FHR in E. coli isolates were identified through accumulation assay, carbohydrate utilization testing, real-time relative quantitative PCR analysis, DNA sequencing, transcriptomic analysis, intracellular ATP and cAMP-level assessment.Results: Four of six E. coli strains were confirmed to show FHR, with a total of six subpopulations. The subpopulations restored phenotypic susceptibilities to fosfomycin within 5-20 overnight incubation sessions, but four of six subpopulations still maintained FHR characteristics. Differing from their parental isolates, the uptake of fosfomycin in the subpopulations through GlpT was reduced remarkably. Further studies identified that the low expression of glpT was due to the decrease of intracellular cAMP levels in the subpopulations, which was caused by the decreased ATP levels in cells.Conclusions: Our findings revealed the formation mechanism of E. coli isolates showing FHR obtained from chicken in China and characterized the dynamic change traits in vitro of the subpopulations. [ABSTRACT FROM AUTHOR]

To characterize the formation mechanism and characteristics of two cointegrate plasmids in Salmonella enterica serotype Enteritidis strain S13, plasmids from strain S13 and three corresponding transconjugants were subjected to whole genome sequencing and analyzed using bioinformatics tools. The traits of two fusion plasmids in transconjugants were characterized by stability and conjugation experiments. Sequence analysis indicated that strain S13 contained four plasmids, including mcr-1 -bearing pS13-1, bla CTX–M–55-carrying pS13-2, tet (M)-bearing pS13-3, and floR -carrying pS13-4. IncN1-F33:A–:B– plasmid pS13-2, respectively, fused with IncFI:A–:B– plasmid pS13-3 and IncX1 plasmid pS13-4, which generated two cointegrate plasmids, designated pS13D and pS13F, which involved in two intermolecular replicative mechanisms mediated by IS 26 and the novel transposon Tn 6952 (Δ Tn AS3 -IS 26 - Δ IS Ecp1 - ramA - Δ IS 26 - Δ Tn AS1), respectively. This is the first report of the fusion of the IncN1-F33:A–:B– plasmid and IncFI:A–:B– plasmid mediated by IS 26 , and with IncX1 plasmid mediated by Tn 6952. The formation and evolution of cointegrate plasmids could expand the resistance and host spectrum of fusion plasmids. [ABSTRACT FROM AUTHOR]

ICE Hpa1 was identified in the genome of a serovar 8 Haemophilus parasuis ST288 isolate YHP170504 from a case of swine lower respiratory tract infection. The aim of the present study was to characterize the integrative conjugative element ICE Hpa1 and its multiresistance region. Susceptibility testing was determined by broth microdilution and the complete ICE Hpa1 was identified by WGS analysis. The full sequence of ICE Hpa1 was analyzed with bioinformatic tools. The presence of ICE Hpa1 , its circular intermediate and integration site were confirmed by PCR and sequence analysis. Transfer of ICE Hpa1 was confirmed by conjugation. ICE Hpa1 has a size of 68,922 bp with 37.42% GC content and harbors 81 genes responsible for replication and stabilization, transfer, integration, and accessory functions, as well as seven different resistance genes [ bla Rob–3, tet (B), aphA1 , strA , strB , aac(6)′-Ie-aph(2′)-Ia , and sul2 ]. Conjugation experiments showed that ICE Hpa1 could be transferred to H. parasuis V43 with frequencies of 6.1 × 10–6. This is the first time a multidrug-resistance ICE has been reported in H. parasuis. Seven different resistance genes were located on a novel integrative conjugative element ICE Hpa1 , which suggests that the ICE Hpa1 is capable of acquiring foreign genes and serving as a carrier for various resistance genes. [ABSTRACT FROM AUTHOR]

The objective of this study was to explore the genetic and biological features of the tet (M)-harboring plasmid pTS14 in Salmonella enterica strain S14 isolated from a chicken fecal sample. Plasmid pTS14 was identified by conjugation, S1-pulsed-field gel electrophoresis (PFGE), Southern hybridization, and plasmid sequencing. The biological characteristics of pTS14 were assessed via stability, growth kinetics, and starvation survival experiments. Strain S14, belonging to ST3007, harbored a 119-kb tet (M)-bearing IncF2:A1:B1 conjugative plasmid pTS14. The plasmid pTS14 contained a novel transposon Tn 6709 with the genetic structure IS 26 - tnpA1 - tnpA2 -Δ orf13 - LP - tet (M)- tnpX -Δ tnpR -IS 26 , and the resistance genes tet (B), tet (D), strAB , sul2 , and bla TEM–1b. In addition, pTS14 was found to be highly stable in the recipient strain E. coli J53. The transconjugant TS14 exhibited a higher survival ratio than E. coli J53 under permanent starvation-induced stress. The tet (M)-bearing IncF2 epidemic plasmid lineage may accelerate the dissemination of tet (M) and other genes by coselection, which could constitute a potentially serious threat to clinical treatment regimens. [ABSTRACT FROM AUTHOR]

Tet(M)-type proteins confer resistance to tetracycline and related antibiotics by interacting with the ribosome. Genes encoding Tet(M) have been found in a range of bacteria, including Escherichia coli. In the current study, conjugation experiments were performed between seven different tetracycline-resistant, azide-susceptible E. coli strains isolated from ducks and tetracycline-sensitive, azide-resistant E.coli J53. Transconjugants were obtained from two of the strains at a frequency of 1.2 × 10−8. PCR, southern blotting and sequencing demonstrated that tet (M) in the transconjugants was located on a ~50 kb IncHI2-type plasmid and was part of a composite transposon, designated Tn6539. This transposon is flanked by two IS26 elements in opposite orientation and contains the Tn3Δ tnpA +Δ orf13 - lp - tet (M)+gamma delta+ tnpX +Δ tnpR sequences. The Δ orf13 - lp - tet (M) sequence was a highly conserved genetic fragment in E. coli harboring tet (M) and mainly located in the composite transposons flanked by IS6-family elements. In summary, Tn6539 is a new composite transposon capable of horizontal transfer of tet (M) among E. coli isolates. [ABSTRACT FROM AUTHOR]

A multi-drug resistant Escherichia coli C21 was isolated from a chicken in China. It was shown to be positive for the presence of the blaTEM-1, blaCTX-M-55 and rmtB genes by PCR. This strain was examined by phylogenetic grouping, conjugation experiments, plasmid analysis, PCR-based replicon typing and multi-locus sequence typed (MLST). The genetic environment of blaCTX-M-55 was investigated by PCR mapping. The strain belonged to phylogroup A, ST156. The blaCTX-M-55 and rmtB genes were found to be present in separate plasmids that belonged to the IncI1 and IncN families, respectively. These antibiotic-resistant plasmids could be transferred to the recipient strain alone or together. A new arrangement of IS Ecp1Δ-IS 1294-ΔIS Ecp1-blaCTX-M-55-ORF 477, in which the IS Ecp1 element was disrupted by another IS 1294 element, was identified initially. Conjugative transfer and IS elements found in this study could lead to the rapid dissemination of blaCTX-M-55 and rmtB among strains of Enterobacteriaceae, which could pose a threat to animal husbandry and public health. [ABSTRACT FROM AUTHOR]

The article presents a study on the molecular epidemiology of the gene cassettes and integrons of Escherichia coli from chicken, which shows that class I integrons were harbored by 44 stains and class II integrons were present in two strains.

The article presents a study regarding the genotypic identification of beta-lactamases produced by Klebsiella pneumoniae isolated from Qicai bird which include the TEM-type and SHV-type. It states that the encoding genes of the beta lactamases were determined by gene cloning, sequence analysis and polymerase chain reaction (PCR). It mentions that bacteria produces extended spectrum beta lactamases (ESBLs) which is multidrug resistant.

The article presents a study which aims to clarify the evolution mechanism of resistant genes from the genotypes of extended spectrum β-lactamases (ESBLs) and AmpC β-lactamases. ESBLs and AmpC β-lactamases are produced by Enterococcus gallinarum, isolated from chloebia gouldiae. The cloned fragments of its polymerase chain reaction products were sequenced for the genotype and subtype identification.

The article offers information on the cloning of SHV-12 and TEM-IV type extended-spectrum β-lactamase (ESBLs) genes produced by chicken shigella in China. It states that ultraviolet spectrophotometer is used to observe the characteristics of antibiotic hydrolyses and inhibition of β-lactamase inhibitors on SHV-12 and TEM-1V extended spectrum beta lactamase (ESBLs). It notes that constructed recombinant plasmids expressed recombinant proteins.