Bacterial cross-contamination from surfaces to food can contribute to foodborne disease. The cross-contamination rate of Enterobacter aerogenes was evaluated on household surfaces using scenarios that differed by surface type, food type, contact time (<1, 5, 30 and 300 s), and inoculum matrix (tryptic soy broth or peptone buffer). The surfaces used were stainless steel, tile, wood and carpet. The food types were watermelon, bread, bread with butter and gummy candy. Surfaces (25 cm(2)) were spot inoculated with 1 ml of inoculum and allowed to dry for 5 h, yielding an approximate concentration of 10(7) CFU/surface. Foods (with 16 cm(2) contact area) were dropped on the surfaces from a height of 12.5 cm and left to rest as appropriate. Post transfer surfaces and foods were placed in sterile filter bags and homogenized or massaged, diluted and plated on tryptic soy agar. The transfer rate was quantified as the log % transfer from the surface to the food. Contact time, food and surface type all had a highly significant effect (P<0.000001) on log % transfer of bacteria. The inoculum matrix (TSB or peptone buffer) also had a significant effect on transfer (P = 0.013), and most interaction terms were significant. More bacteria transferred to watermelon (∼0.2-97%) relative to other foods, while fewer bacteria transferred to gummy candy (∼0.1-62%). Transfer of bacteria to bread (∼0.02-94%) and bread with butter (∼0.02-82%) were similar, and transfer rates under a given set of condition were more variable compared with watermelon and gummy candy.
Ethanol organosolv pretreated rice straw was used to produce biohydrogen using Enterobacter aerogenes. The effect of temperature (120-180°C), residence time (30-90min), and ethanol concentration (45-75%v/v) on the hydrogen yield, residual biomass, and lignin recovery was investigated using RSM. In contrast to the residual solid and lignin recovery, no considerable trend could be observed for the changes in the hydrogen yield at different treatment severities. The maximum hydrogen yield of 19.73mlg(-1) straw was obtained at the ethanol concentration of 45%v/v and 180°C for 30min. Furthermore, the potential amount of biohydrogen was estimated in the top ten rice producing nations using the experimental results. Approximately 355.8kt of hydrogen and 11.3Mt of lignin could globally be produced. Based on a Monte Carlo analysis, the production of biohydrogen from rice straw has the lowest risk in China and the highest in Japan.
The prevalence of carbapenem-resistant Enterobacteriaceae (CRE) infections is increasing in the United States. However, few studies have addressed their epidemiology in children. To phenotypically identify CRE isolates cultured from patients 1-17 years of age, we used antimicrobial susceptibilities of Enterobacteriaceae reported to 300 laboratories participating in The Surveillance Network-USA database during January 1999-July 2012. Of 316,253 isolates analyzed, 266 (0.08%) were identified as CRE. CRE infection rate increases were highest for Enterobacter species, blood culture isolates, and isolates from intensive care units, increasing from 0.0% in 1999-2000 to 5.2%, 4.5%, and 3.2%, respectively, in 2011-2012. CRE occurrence in children is increasing but remains low and is less common than that for extended-spectrum β-lactamase-producing Enterobacteriaceae. The molecular characterization of CRE isolates from children and clinical epidemiology of infection are essential for development of effective prevention strategies.
Knowledge regarding the genomic structure of Enterobacter spp., the second most prevalent carbapenemase-producing Enterobacteriaceae, remains limited. Here we sequenced 97 clinical Enterobacter species isolates that were both carbapenem susceptible and resistant from various geographic regions to decipher the molecular origins of carbapenem resistance and to understand the changing phylogeny of these emerging and drug-resistant pathogens. Of the carbapenem-resistant isolates, 30 possessed blaKPC-2, 40 had blaKPC-3, 2 had blaKPC-4, and 2 had blaNDM-1 Twenty-three isolates were carbapenem susceptible. Six genomes were sequenced to completion, and their sizes ranged from 4.6 to 5.1 Mbp. Phylogenomic analysis placed 96 of these genomes, 351 additional Enterobacter genomes downloaded from NCBI GenBank, and six newly sequenced type strains into 19 phylogenomic groups-18 groups (A to R) in the Enterobacter cloacae complex and Enterobacter aerogenes Diverse mechanisms underlying the molecular evolutionary trajectory of these drug-resistant Enterobacter spp. were revealed, including the acquisition of an antibiotic resistance plasmid, followed by clonal spread, horizontal transfer of blaKPC-harboring plasmids between different phylogenomic groups, and repeated transposition of the blaKPC gene among different plasmid backbones. Group A, which comprises multilocus sequence type 171 (ST171), was the most commonly identified (23% of isolates). Genomic analysis showed that ST171 isolates evolved from a common ancestor and formed two different major clusters; each acquiring unique blaKPC-harboring plasmids, followed by clonal expansion. The data presented here represent the first comprehensive study of phylogenomic interrogation and the relationship between antibiotic resistance and plasmid discrimination among carbapenem-resistant Enterobacter spp., demonstrating the genetic diversity and complexity of the molecular mechanisms driving antibiotic resistance in this genus.
We report a recycling bioresource involving harvesting of Microcystis aeruginosa using the bioflocculant (MBF-32) produced by Enterobacter aerogenes followed by the recovery of the harvested M. aeruginosa as the main substrate for the sustainable production of MBF-32 and biohydrogen. The experimental results indicate that the efficiency of bioflocculation exceeded 90% under optimal conditions. The harvested M. aeruginosa was further recycled as the main substrate for the supply of necessary elements. The highest yield (3.6±0.1g/L) of MBF-32 could be obtained from 20g/L of wet biomass of M. aeruginosa with an additional 20g/L of glucose as the extra carbon source. The highest yield of biohydrogen was 35mL of H2/g (dw) algal biomass, obtained from 20g/L of wet biomass of M. aeruginosa with an additional 10g/L of glycerol. Transcriptome analyses indicated that MBF-32 was mainly composed of polysaccharide and tyrosine/tryptophan proteins. Furthermore, NADH synthase and polysaccharide export-related genes were found to be up-regulated.
Carbapenem-resistant Enterobacteriaceae have become of particular concern, since they were quickly disseminated in various areas in the world. The aim of the study was to investigate the prevalence of carbapenemase production among clinical isolates of Enterobacteriaceae recovered from the Military Hospital of Tunisia. Bacterial isolates (n = 125) were recovered from patients in diverse services from March 2014 to February 2016 and identified by Vitek II Compact®. The multiplex PCR for blaVIM, blaIMP, blaNDM, blaKPC, and blaOXA-48with subsequent amplicon detection by reverse hybridization was performed with the Hyplex SuperBug ID test system (AmplexDiagnostics GmbH, Gars-Bahnhof, Germany). The 125 strains showed resistance to carbapenems of which 102 strains (81.6%) were carbapenemase-producing Enterobacteriaceae and were identified as Klebsiella pneumoniae (85.2%), Enterobacter cloacae (9.8%), Escherichia coli (2.9%), Providencia stuartii (0.9%) and Enterobacter aerogenes (0.9%). These strains were isolated mainly from blood, anal, and urine samples. Patients were mainly hospitalized in the intensive care units, surgery, and medical services. All strains were resistant to ertapenem (100%) and 55.8% showed resistance to imipenem. Carbapenemases genes detected in our study were as follows: blaOXA-48(84 isolates), blaNDM-1(8 isolates), blaOXA-48+ blaVIM(5 isolates), and blaOXA-48+ blaNDM-1(5 isolates). Our research provides epidemiological data showing the quick spread of carbapenem-resistant bacteria in our region, which calls for new surveillance strategies and strict hygiene rules.
Although the use of the pesticide 2,2-bis(p-chlorophenyl)-1,1,1-trichloroethane (DDT) was banned from the mid-1970s, its most abundant and recalcitrant degradation product, 2,2-bis(p-chlorophenyl)-1,1-dichloro-ethylene (DDE), is still present in terrestrial and aquatic ecosystems worldwide. Zucchini (Cucurbita pepo ssp. pepo) has been shown to accumulate high concentrations of DDE and was proposed for phytoremediation of contaminated soils. We performed a field trial covering a full plant life cycle. C. pepo plants inoculated with the plant growth-promoting endophytic strains Sphingomonas taxi UH1, Methylobacterium radiotolerans UH1, Enterobacter aerogenes UH1, or a consortium combining these 3 strains were grown on a DDE-contaminated field for 100 days. The effects of these inoculations were examined at both the plant level, by evaluating plant weight and plant DDE-content, and at the level of the cultivable and total endophytic communities. Inoculating plants with S. taxi UH1, M. radiotolerans UH1, and the consortium increased plant weight. No significant effects of the inoculations were observed on DDE-concentrations in plant tissues. However, the amount of DDE accumulated by C. pepo plants per growing season was significantly higher for plants that were inoculated with the consortium of the 3 strains. Therefore, inoculation of C. pepo with DDE-degrading endophytes might be promising for phytoremediation applications.
A process of isobutanol production from sugarcane bagasse hydrolysates in Enterobacter aerogenes was developed here with a pervaporation-integrated procedure. Isobutanol pathway was overexpressed in a mutant strain with eliminated byproduct-forming enzymes (LdhA, BudA, and PflB). A glucose-and-xylose-coconsuming ptsG mutant was constructed for effective utilization of lignocellulosic biomass. Toxic effects of isobutanol were alleviated by in situ recovery via a pervaporation procedure. Compared to single-batch fermentation, cell growth and isobutanol titer were improved by 60% and 100%, respectively, in the pervaporation-integrated fermentation process. A lab-made cross-linked polydimethylsiloxane membrane was cast on polyvinylidene fluoride and used in the pervaporation process. The membrane-penetrating condensate contained 55-226 g m-2 h-1isobutanol with 6-25 g L-1ethanol after separation. This study offers improved fermentative production of isobutanol from lignocellulosic biomass with a pervaporation procedure.
We report here the draft genome sequences of fourblaKPC-containing bacteria identified asKlebsiella aerogenes,Citrobacter freundii, andCitrobacter koseriAdditionally, we report the draft genome sequence of aK. aerogenesstrain that did not contain ablaKPCgene but was isolated from the patient who had theblaKPC-2-containingK. aerogenesstrain.
A carbapenemase-producing Enterobacter cloacae hhy03 with a blaNDM-1 and blaSHV-12-coharboring plasmid was isolated from a sputum specimen of a patient. This is the third nucleotide sequence report of blaNDM-1-harboring plasmid from Enterobacter cloacae that have caused lethal infections in China, indicating the spread of NDM-1 by IncX3 plasmid between Enterobacteriaceae.