Jing-yi Zhao

Coexistence of SFO-1 and NDM-1 β-lactamase genes and fosfomycin resistance gene fosA3 in an Escherichia coli clinical isolate

This study aims to characterize antimicrobial resistance and antimicrobial resistance genetic determinants of an Escherichia coli clinical isolate HD0149 from China in 2012. This strain displayed high-level resistance to cephalosporins, carbapenems, fluoroquinolones, aminoglycosides and fosfomycin. A range of antimicrobial resistance genes was detected responsible for its multiple antimicrobial resistances, involving the blaCMY-2, blaCTX-M-65, blaNDM-1, blaSFO-1, blaTEM-1, fosA3, rmtB, sul1 and sul2 genes. Four amino acid substitutions were detected in the quinolone resistance-determining regions (QRDRs) of GyrA (S83L and D87N), ParC (S80I) and ParE (S458A). Conjugation experiments revealed two multiresistance plasmids present in E. coli HD0149. The blaSFO-1 gene associated with blaNDM-1 gene was located in a 190 kb IncA/C plasmid and the blaCTX-M-65, fosA3 and rmtB genes were located in a 110 kb IncF plasmid. This is the first identification of the blaSFO-1 gene in an E. coli isolate and on a conjugative IncA/C plasmid. This may dramatically enhance the international prevalence and dissemination of blaSFO-1 among Enterobacteriaceae.

Identification of an NDM-5-producing Escherichia coli Sequence Type 167 in a Neonatal Patient in China.

Emergence of New Delhi metallo-β-lactamase-producing Enterobacteriaceae has become a challenging threat to public health. Two carbapenem-resistant Escherichia coli, strain QD28 and QD29, were recovered from the aspirating sputum of a neonate and the urine of an adult in a Chinese hospital in 2013. Molecular typing revealed that both isolates belonged to the sequence type 167, but they were clonally diverse. Both isolates exhibited resistance to carbapenems, cephalosporins, ciprofloxacin, gentamicin, piperacillin-tazobactam and trimethoprim-sulfamethoxazole. In addition, strain QD28 was also resistant to aztreonam, and strain QD29 was resistant to amikacin, fosfomycin and minocycline. Antimicrobial resistance gene screening revealed that strain QD28 harbored aac(6′)-Ib, blaCTX-M-14, blaNDM-5, blaTEM-1 and sul1 genes, and strain QD29 harbored aac(6′)-Ib, blaCTX-M-3, blaNDM-5, blaTEM-1, rmtB, sul1 and sul2 genes. The blaNDM-5 gene was found to be located on a 46-kb plasmid in two isolates, and further sequence analysis showed that this plasmid was highly similar to the previously reported IncX3 plasmid pNDM-MGR194 in India. This is the first identification of blaNDM-5-carrying E. coli in the neonatal infection.

Thermophilic production of polyhydroxyalkanoates by a novel Aneurinibacillus strain isolated from Gudao oilfield, China

Polyhydroxyalkanoates (PHAs) are usually biosynthesized using mesophilic strains, but the fermentation processes often suffer from bacterial contamination. This work reports the screening of thermophilic bacteria capable of producing PHAs under elevated temperatures to reduce the contamination risk. Strain XH2 was isolated from an oilfield and identified as Aneurinibacillus sp. by morphology, physiological‐biochemical characterization, and 16S rDNA phylogenetic analysis. This strain can produce PHA granules, which was detected by Nile red staining and transmission electron microscopic imaging. At 55 °C, 111.6 mg l−1 of PHA was produced in a fermentation medium containing glucose, peptone, and yeast extract. If peptone was removed from the medium, the yield of PHA would be enhanced by 2.4 times. The main monomers of the PHA product were identified to be 3‐hydroxybutyrate and 3‐hydroxyvalerate with a molar ratio of 17.2:1 by gas chromatography‐mass spectroscopy (GC‐MS) and nuclear magnetic resonance analyses. Two minor homologues, 3‐hydroxyoctanoate, and 3‐hydroxy‐4‐phenylbutanoate, were tentatively identified by GC‐MS as well. This is the first report of thermophilic PHA bacterial producer from the Firmicutes phylum.

Identification of an integron containing the quinolone resistance gene qnrA1 in Shewanella xiamenensis.

This study investigated multidrug resistance in Shewanella xiamenensis isolated from an estuarine water sample in China during 2014. This strain displayed resistance or decreased susceptibility to ampicillin, aztreonam, cefepime, cefotaxime, chloramphenicol, ciprofloxacin, erythromycin, kanamycin and trimethoprim-sulfamethoxazole. The antimicrobial resistance genes aacA3, blaOXA-199, qnrA1 and sul1 were identified by PCR amplification and by sequencing. Pulsed-field gel electrophoresis and DNA hybridization experiments showed that the quinolone resistance gene qnrA1 was chromosomally located. qnrA1 was located in a complex class 1 integron, downstream from an ISCR1, and bracketed by two copies of qacEΔ1-sul1 genes. This integron is similar to In825 with four gene cassettes aacA3, catB11c, dfrA1z and aadA2az. An IS26-mel-mph2-IS26 structure was also detected in the flanking sequences, conferring resistance to macrolides. This is the first identification of the class 1 integron in S. xiamenensis. This is also the first identification of the qnrA1 gene and IS26-mediated macrolide resistance genes in S. xiamenensis. Presence of a variety of resistance genetic determinants in environmental S. xiamenensis suggests the possibility that this species may serve as a potential vehicle of antimicrobial resistance genes in aquatic environments.

GC–FID determination of tetramethylpyrazine and acetoin in vinegars and quantifying the dependence of tetramethylpyrazine on acetoin and ammonium

2,3,5,6-Tetramethylpyrazine (TMP) is an important health functional composition in vinegars, but there are controversial viewpoints about its formation mechanism and scarce relevant records on TMP content enhancement in vinegar products. In this study, a simple and accurate solvent extraction coupled with GC-FID method was developed for the simultaneous determination of TMP and acetoin in vinegars and 137 worldwide samples were analyzed. Meanwhile, the ammonium contents of all the vinegar samples were determined using the salicylate method. By nonlinear surface fitting, the concentrations of TMP in vinegars were found to follow second-order polynomial models of acetoin and ammonium concentrations. By isotopic tracing using 13C labelled acetoin and 15N ammonium, acetoin and ammonium were deduced to be the precursors of TMP in vinegars.

Complete genome sequence of the novel thermophilic polyhydroxyalkanoates producer Aneurinibacillus sp. XH2 isolated from Gudao oilfield in China

Aneurinibacillus sp. XH2 (CGMCC 1.15535) was isolated from Gudao oilfield in China. It is able to use simple carbon resources to accumulate Polyhydroxyalkanoates (PHAs) in a thermophilic fashion. Here, we describe the genomic features of this strain. The total genome size of Aneurinibacillus sp. XH2 is 3,664,835bp and contains 3441 coding sequences and 114 tRNAs. The annotated genome sequence of this strain provides the genetic basis for revealing its role as a themophilic PHAs producing bacterium.

Hydroxy-pentanones production by Bacillus sp. H15-1 and its complete genome sequence

Acyloins are useful organic compounds with reactive adjacent hydroxyl group and carbonyl group. Current research is usually constrained to acetoin (i.e. 3-hydroxy-2-butanone) and the biological production of other acyloins was scarcely reported. In this study, two hydroxy-pentanone metabolites (3-hydroxy-2-pentanone and 2-hydroxy-3-pentanone) of Bacillus sp. H15-1 were identified by gas chromatography-mass spectrometry and authentic standards. Then the complete genome of this strain was sequenced and de novo assembled to a single circular chromosome of 4,162,101bp with a guanine-cytosine content of 46.3%, but no special genes were found for the biosynthesis of the hydroxy-pentanones. Since hydroxy-pentanones are the homologues of acetoin, the two genes alsD and alsS (encoding α-acetolactate decarboxylase and α-acetolactate synthase, respectively) responsible for acetoin formation in this strain were respectively expressed in Escherichia coli. The purified enzymes were found to be capable of transforming pyruvate and 2-oxobutanoate to the two hydroxy-pentanones. This study extends the knowledge on the biosynthesis of acyloins and provides helpful information for further utilizing Bacillus sp. H15-1 as a source of valuable acyloins.

Genetic characterization of plasmid-mediated quinolone resistance gene qnrS2 in Pseudoalteromonas and Shewanella isolates from seawater

Abstract Three qnrS2‐containing isolates of Pseudoalteromonas and Shewanella were collected from the seawater samples of Qingdao in China during 2014. They displayed resistance to ampicillin, ciprofloxacin, kanamycin, nalidixic acid and sulfamethoxazole. The qnrS2 genes were identified in the chromosomes of Pseudoalteromonas strains E8 and S16, and in a 140‐kb plasmid in Shewanella strain S14, respectively. In addition, two copies of qnrS2 were identified in the strain E8. Sequence analyses revealed that there was an identical DNA segment located in the downstream of qnrS2 in strain S14 and E8, coding for a TetR transcriptional regulator, two putative integrases and a hypothetical protein. However, different genetic structures were identified in the upstream sequences: the terB gene associated with tellurite resistance in the strain S14, and a putative integron with dfrA6 and aadA13 gene cassettes or the Tn7‐related gene complex tnsABC in the strain E8. In Pseudoalteromonas strain S16, qnrS2 was bracketed by the endonuclease I and III genes, and the electron transport complex rsxCDGE was located in the upstream sequences. This is the first report of two copies of the qnrS2 gene existing in one bacterial chromosome, and also the first identification of qnrS2 in Shewanella.

5-Hydroxy-γ-decalactone production by Bacillus sp. 1s-1 and its complete genome sequence

Lactones are useful flavor compounds and some 5-hydroxy-γ-butyrolactones also have important biological activities. In this study, a newly isolated Bacillus strain 1s-1 was identified to be capable of producing 5-hydroxy-γ-decalactone (HDL) from peanut oil by gas chromatography-mass spectrometry and authentic standards. The complete genome of this strain was sequenced and de novo assembled to a single circular chromosome of 4,166,290 bp with a guanine-cytosine content of 46.3%. The biosynthesis pathway of HDL in strain 1s-1 was postulated and this study provides helpful information for further utilizing Bacillus sp. 1s-1 as a source of valuable hydroxy lactones.

Solid-state fermentative production of aroma esters by Myroides sp. ZB35 and its complete genome sequence

Consumers prefer biotechnological food products with high nutritional values and good flavors. Solid-state fermentation is a commonly used technique with a long history. In the present study, Myroides sp. ZB35 was used in solid-state fermentative production of aroma volatiles on a rice medium. Using the headspace solid phase microextraction coupled with gas chromatography-mass spectrometry technique and authentic standards, 22 esters with molecular weight ranging from 102 to 172 were identified. At 192h, the esters reached a total concentration of 1774μg/kg. Subsequently, the complete genome of ZB35 was sequenced using the PacBio RS II platform. ZB35 has a single circular chromosome of 4,065,010bp with a GC content of 34.1% and six putative novel esterase genes were found. ZB35 is the first bacterium here discovered being capable of producing so many kinds of aroma esters. The data revealed here would provide helpful information for further developing this strain as a promising source of aroma esters relevant in food and fragrance industries and the source of novel enzymes with potential usages.