Search

Land use reflects human activities on land. Urban land use is the highest level human alteration on Earth, and it is rapidly changing due to population increase and urbanization. Urban areas have widespread effects on local hydrology, climate, biodiversity, and food production. However, maps, that contain knowledge on the distribution, pattern and composition of various land use types in urban areas, are limited to city level. The mapping standard on data sources, methods, land use classification schemes varies from city to city, due to differences in financial input and skills of mapping personnel. To address various national and global environmental challenges caused by urbanization, it is important to have urban land uses at the national and global scales that are derived from the same or consistent data sources with the same or compatible classification systems and mapping methods. This is because, only with urban land use maps produced with similar criteria, consistent environmental policies can be made, and action efforts can be compared and assessed for large scale environmental administration. However, despite of the fact that a number of urban-extent maps exist at global scales [3,4], more detailed urban land use maps do not exist at the same scale. Even at big country or regional levels such as for the United States, China and European Union, consistent land use mapping efforts are rare.

Global and local land-cover mapping products provide important data on land surface. However, the accuracy of land-cover products is the key issue for their further scientific application. There has been neglect of the relationship between inclusion probability and spatial heterogeneity in traditional spatially balanced sampling. The aim of this paper was to propose an improved spatially balanced sampling method using landscape pattern-based inclusion probability. Compared with other global land-cover datasets, Globeland30 has the advantages of high resolution and high classification accuracy. A two-stage stratified spatially balanced sampling scheme was designed and applied to the regional validation of GlobeLand30 in China. In this paper, the whole area was divided into three parts: the Tibetan Plateau region, the Northwest China region, and the East China region. The results show that 7242 sample points were selected, and the overall accuracy of GlobeLand30-2010 in China was found to be 80.46%, which is close to the third-party assessment accuracy of GlobeLand30. This method improves the representativeness of samples, reduces the classification error of remote sensing, and provides better guidance for biodiversity and sustainable development of environment.

A novel virulent bacteriophage, φAbp2, infecting multidrug-resistant (MDR) Acinetobacter baumannii was isolated from the wastewater of a sewage management centre at Southwest Hospital, China. Transmission electron microscopy and phylogenetic analysis revealed that φAbp2 belongs to the subfamily Peduovirinae. A one-step growth curve demonstrated that φAbp2 had a latent period of 15 min, a lysis period of 35 min, and a burst size of 222 particles per infected host cell. Moreover, φAbp2 showed a relatively broad host range in local A. baumannii, and it also exhibited tolerance over a wider range of thermal and pH conditions. Genomic sequencing revealed that φAbp2 has a circular double-stranded DNA genome with no sequence similarity to our previously isolated φAbp1. Eighty-eight putative open reading frames (ORFs) encoding 41 proteins of known function and 47 of unknown function were identified, and the G/C content was 37.84%. φAbp2 is a new member of the subfamily Peduovirinae of the family Myoviridae. Its genome sequence is very similar to that of the A. baumannii phage LZ35. Electronic supplementary material The online version of this article (10.1007/s00705-019-04213-0) contains supplementary material, which is available to authorized users.

Antimicrobial resistance (AMR) is one of the most significant threats to global public health. As antibiotic failure is increasing, phages are gradually becoming important agents in the post-antibiotic era. In this study, the therapeutic effects and safety of kpssk3, a previously isolated phage infecting carbapenem-resistant hypermucoviscous Klebsiella pneumoniae (CR-HMKP), were evaluated in a mouse model of systemic CR-HMKP infection. The therapeutic efficacy experiment showed that intraperitoneal injection with a single dose of phage kpssk3 (1 × 107 PFU/mouse) 3 h post infection protected 100% of BALB/c mice against bacteremia induced by intraperitoneal challenge with a 2 × LD100 dose of NY03, a CR-HMKP clinical isolate. In addition, mice were treated with antibiotics from three classes (polymyxin B, tigecycline, and ceftazidime/avibactam plus aztreonam), and the 7 days survival rates of the treated mice were 20, 20, and 90%, respectively. The safety test consisted of 2 parts: determining the cytotoxicity of kpssk3 and evaluating the short- and long-term impacts of phage therapy on the mouse gut microbiota. Phage kpssk3 was shown to not be cytotoxic to mammalian cells in vitro or in vivo. Fecal samples were collected from the phage-treated mice at 3 time points before (0 day) and after (3 and 10 days) phage therapy to study the change in the gut microbiome via high-throughput 16S rDNA sequence analysis, which revealed no notable alterations in the gut microbiota except for decreases in the Chao1 and ACE indexes.

Background As a kind of nosocomial infection pathogen which can cause high mortality, its susceptibility and death risk factors are still unclear. Aim To analyze the epidemiological characteristics of and risk factors for Elizabethkingia meningoseptica infection. Methods Relevant literature from 2011 to 2019 with the key words “E. meningoseptica” or “Elizabethkingia meningoseptica” in the title and abstract was retrieved from the PubMed database. The risk factors of infection and death for infected patients treated at Southwest Hospital during the above period were analyzed by logistic regression. Results From 2011 to 2019, 366 patients infected with E. meningoseptica were reported in 132 articles in the PubMed database. The mortality rate was 63.20%. During the same period, 92 infected patients were treated at our hospital. The overall mortality rate was approximately 28.3% (26/92) to 39.1% (36/92). The resistance rate for carbapenems was 100%; for cephalosporins, it was more than 90%; and for minocycline, it was 0. Central venous catheterization (p E. meningoseptica infection. According to logistic regression, bacteria type (p = 0.037), platelet level (p = 0.014), and mechanical ventilation (p = 0.043) were risk factors for death. Conclusion The incidence of E. meningoseptica infection worldwide shows a trend toward increasing yearly. Invasive operations, multiple bacterial or fungal infections and the use of carbapenems may be predisposing factors, and platelet level, bacteria type, and mechanical ventilation were risk factors for death.

Although composting is effective in deactivating antibiotic substances in manure, the influence of compost fertilization on the occurrence and dissemination of antibiotic resistance in arable soils remains to be controversial. Herein, the abundance and diversity of two sulfonamide resistance genes (sul1 and sul2) in soil fertilized by compost spiked with two concentrations of sulfadiazine (1 and 10 mg kg−1) were studied intensively by qPCR and high throughput sequencing based on a two-month microcosm experiment. The concentration of sulfadiazine decreased rapidly after spiking from 25% at Day 1 to less than 2.7% at Day 60. Relative abundance of both sul1 and sul2 were significantly higher in soil amended with compost than the non-amended control at Day 1 and slightly decreased with incubation time except for sul2 in the S10 treatment. Soil bacterial communities were transiently shifted by compost fertilization regardless of the presence of sulfadiazine. Relative abundance of genera in three hubs positively interlinked with sul1 and sul2 were significantly higher in compost treated soil than the control at Day 1, 7 and 21, but not at Day 60. High throughput sequencing analyses revealed that most detected (&gt, 67% in relative abundance) sul1 and sul2 genotypes sharing &gt, 99% similarity with those found in gammaproteobacterial pathogens frequently were commonly present in compost and soil. These results indicated that compost fertilization might increase the abundance rather than diversity of sulfadiazine-resistant populations in soil, which may be facilitated by the presence of sulfadiazine.

Background Acinetobacter baumannii (A. baumannii) is one of the pivotal pathogens responsible for nosocomial infections, especially in patients with low immune response, and infection with carbapenem-resistant A. baumannii has been increasing in recent years. Rapid and accurate detection of carbapenem-resistance genes in A. baumannii could be of immense help to clinical staff. Methods In this study, a 15-μL reaction system for recombinase polymerase amplification (RPA) was developed and tested. We collected 30 clinical isolates of A. baumannii from the Burn Institute of Southwest Hospital of Third Military Medical University (Army Medical University) for 6 months and tested antibiotic susceptibility using the VITEK 2 system. A. baumannii was detected based on the blaOXA-51 gene by PCR, qPCR and 15 μL-RPA, respectively. Sensitivity and specificity were evaluated. In addition, PCR and 15 μL-RPA data for detecting the carbapenem-resistance gene blaOXA-23 were comparatively assessed. Results The detection limit of the blaOXA-51 gene by 15 μL RPA was 2.86 CFU/ml, with sensitivity comparable to PCR and qPCR. No positive amplification signals were detected in non-Acinetobacter isolates, indicating high specificity. However, only 18 minutes were needed for the 15 μL RPA assay. Furthermore, an antibiotic susceptibility test showed that up to 90% of A. baumannii strains were resistant to meropenem and imipenem; 15 μL RPA data for detecting blaOXA-23 showed that only 10% (n = 3) of A. baumannii isolates did not show positive amplification signals, and the other 90% of (n = 27) isolates were positive, corroborating PCR results. Conclusion We demonstrated that the new 15 μL RPA assay for detecting blaOXA-23 in A. baumannii is faster and simpler than qPCR and PCR. It is a promising alternative molecular diagnostic tool for rapid and effective detection of A. baumannii and drug-resistance genes in the field and point-of-care testing.

Methicillin-resistant S. aureus (MRSA) has attracted more and more attention in recent years, especially in burn medical centers. Here we conducted a 5-year period study to evaluate the MRSA infection in our burn center. The staphylococcal chromosomal cassette mec (SCCmec) typing, antimicrobials susceptibility and virulence profiles were also performed among the MRSA isolates. Of the 259 S. aureus isolates, 239 (92.28%) isolates were identified as MRSA. A decreased trend of MRSA isolation rate over time was found (P = 0.0063). Majority of MRSA isolates in our center belonged to SCCmec type III (230/239, 96.23%). Antimicrobials susceptibility tests of the MRSA isolates revealed significantly decreased resistance to clindamycin (P = 0.0183), and increased resistance to chloramphenicol (P = 0.0020) and minocycline (P 0.0001) over time. Trimethoprim/sulfamethoxazole, clindamycin, vancomycin, teicoplanin and linezolid were suggested to be good choice for MRSA infection in our center. Virulence factors profiling showed that most of MRSA isolates in our center carried the virulence factor pattern of cna-clfA-clfB-eno-fib-icaA-icaD-sea-psmα-lukED-hlg-hlgv-hla-hld (214/239, 89.54%). In conclusion, our study suggests that MRSA infection is serious in our burn center, but presented decreased trend over time. Most of MRSA isolates in our center presented the same virulence factor profile. More attention should be attached to nosocomial infection in burn medical center. Antimicrobials susceptibility changing over time was observed. Antimicrobials susceptibility monitoring is necessary and helps to select appropriate drugs against MRSA infections.

The requirements for anti-permeation, anti-infection and antifouling when treating a malicious wound bed raise new challenges for wound dressing. The present study used N,N-dimethylformamide to treat poly(vinylidene fluoride) (PVDF) in order to obtain a dressing impregnated with in situ generated nano-silver particles (NS) via an immersion phase inversion method. Scanning electron microscopy (SEM) images showed that the film was characterized by a two-layer asymmetric structure with different pore sizes (top layer: ∼0.4 μm; bottom layer: ∼1.8 μm). The moisture permeability test indicated that the film had an optimal water vapor transmission rate (WVTR: ∼2500 g m−2 per day). TEM images revealed the successful formation of spherical NS, and Fourier-transform infrared spectroscopy (FTIR) demonstrated the integration of PVDF and NS (i.e., PVDF/NS). Correspondingly, the water contact angle measurements confirmed increased membrane surface hydrophobicity after NS integration. The inductively coupled plasma (ICP) spectrometry showed that the PVDF/NS displayed a continuous and safe release of silver ions. Moreover, in vitro experiments indicated that PVDF/NS films possessed satisfactory anti-permeation, antibacterial and antifouling activities against A. baumannii and E. coli bacteria, while they exhibited no obvious cytotoxicity toward mammalian HaCaT cells. Finally, the in vivo results showed that the nanoporous top layer of film could serve as a physical barrier to prevent bacterial penetration, whereas the microporous bottom layer could efficiently prevent bacterial infection caused by biofouling, leading to fast re-epithelialization via the enhancement of keratinocyte proliferation. Collectively, the results show that the PVDF/NS25 film has a promising application in wound treatment, especially for wounds infected by multi-drug-resistant bacteria such as A. baumannii.

Carbapenem-resistant Klebsiella pneumoniae (CRKP) has spread globally and emerged as an urgent public health threat. Bacteriophages are considered an effective weapon against multidrug-resistant pathogens. In this study, we report a novel lytic phage, kpssk3, which is able to lyse CRKP and degrade exopolysaccharide (EPS). The morphological characteristics of kpssk3 observed by transmission electron microscopy, including a polyhedral head and a short tail, indicate that it belongs to the family Podoviridae. A one-step growth curve revealed that kpssk3 has a latent period of 10 min and a burst size of 200 plaque-forming units (pfu) per cell. kpssk3 was able to lyse 25 out of 27 (92.59%) clinically isolated CRKP strains, and it also exhibited high stability to changes in temperature and pH. kpssk3 has a linear dsDNA genome of 40,539 bp with 52.80% G+C content and 42 putative open reading frames (ORFs). No antibiotic resistance genes, virulence factors, or integrases were identified in the genome. Based on bioinformatic analysis, the tail fiber protein of phage kpssk3 was speculated to possess depolymerase activity towards EPS. By comparative genomics and phylogenetic analysis, it was determined that kpssk3 is a new T7-like virus and belongs to the subfamily Autographivirinae. The characterization and genomic analysis of kpssk3 will promote our understanding of phage biology and diversity and provide a potential strategy for controlling CRKP infection.

Increasing drug resistance necessitates the discovery of novel bactericides. Human defensin (HD) peptides can eliminate resistant bacteria and are promising candidates for next-generation antibiotics. T7E21R-HD5 is a potent bactericide designed by site mutations at enteric HD5. To facilitate the development of T7E21R-HD5 into an intestinal antibiotic, we employed a mesoporous silica nanoparticle (MSN) as the peptide carrier. Despite its ineffectiveness at killing bacteria, the MSN intensified the outer membrane penetration and inner membrane permeabilization abilities of T7E21R-HD5 and thus enhanced its antibacterial action against multidrug resistant (MDR) E. coli, which broadened the role of MSNs in drug delivery. For the reduction in T7E21R-HD5 losses in the stomach, we further modified MSN@T7E21R-HD5 with succinylated casein (SCN), a milk protein that can be specifically degraded by intestinal protease. SCN coating decreased T7E21R-HD5 release from the MSNs, especially in a highly acidic environment. The controlled release of MSN@T7E21R-HD5 from SCN encapsulation was confirmed in the presence of trypsin. MSN@T7E21R-HD5@SCN was nontoxic to host cells, and it was capable of inactivating MDR E. coli in vivo and alleviating intestinal inflammation by suppressing the production of inflammatory factors TNF-α, IL-1β, and MMP-9. This study provides a peptide-based nanobiotic with efficacy to combat intestinal infection, especially against drug-resistant bacteria. The biocompatible and readily prepared MSN/SCN delivery system may benefit further intestinal antibiotic design and promote the drug transformation of additional enterogenic functional molecules.

Previous research has reported the transcriptomic phage-host interactions in Escherichia coli and Pseudomonas aeruginosa, leading to the detailed discovery of transcriptomic regulations and predictions of specific gene functions. However, a direct relationship between A. baumannii and its phage has not been previously reported, although A. baumannii is becoming a rigorous drug-resistant threat. We analyzed transcriptomic changes after φAbp1 infected its host, extensively drug-resistant (XDR) A. baumannii AB1, and found defense-like responses of the host, step-by-step control by the invader, elaborate interactions between host and phage, and elevated drug resistance gene expressions of AB1 after phage infection. These findings suggest the detailed interactions of A. baumannii and its phage, which may provide both encouraging suggestions for drug design and advice for the clinical use of vital phage particles., Acinetobacter baumannii is a growing threat, although lytic bacteriophages have been shown to effectively kill A. baumannii. However, the interaction between the host and the phage has not been fully studied. We demonstrate the global profile of transcriptional changes in extensively drug-resistant A. baumannii AB1 and the interaction with phage φAbp1 through RNA sequencing (RNA-seq) and bioinformatic analysis. Only 15.6% (600/3,838) of the genes of the infected host were determined to be differentially expressed genes (DEGs), indicating that only a small part of the bacterial resources was needed for φAbp1 propagation. Contrary to previous similar studies, more upregulated rather than downregulated DEGs were detected. Specifically, φAbp1 infection caused the most extensive impact on host gene expression at 10 min, which was related to the intracellular accumulation phase of virus multiplication. Based on the gene coexpression network, a middle gene (gp34, encoding phage-associated RNA polymerase) showed a negative interaction with numerous host ribosome protein genes. In addition, the gene expression of bacterial virulence/resistance factors was proven to change significantly. This work provides new insights into the interactions of φAbp1 and its host, which contributes to the further understanding of phage therapy, and provides another reference for antibacterial agents. IMPORTANCE Previous research has reported the transcriptomic phage-host interactions in Escherichia coli and Pseudomonas aeruginosa, leading to the detailed discovery of transcriptomic regulations and predictions of specific gene functions. However, a direct relationship between A. baumannii and its phage has not been previously reported, although A. baumannii is becoming a rigorous drug-resistant threat. We analyzed transcriptomic changes after φAbp1 infected its host, extensively drug-resistant (XDR) A. baumannii AB1, and found defense-like responses of the host, step-by-step control by the invader, elaborate interactions between host and phage, and elevated drug resistance gene expressions of AB1 after phage infection. These findings suggest the detailed interactions of A. baumannii and its phage, which may provide both encouraging suggestions for drug design and advice for the clinical use of vital phage particles.

The construction of multimodal targeting and therapeutic platforms is a promising strategy for combating multidrug-resistant (MDR) bacteria-associated infections. We report a dual-targeted antibacterial platform integrating a synergistic chemo-photothermal effect based on the boronic acid functionalized graphene-based quaternary ammonium salt (B-CG-QAS). When located at the sites of Gram-negative bacteria associated infections, B-CG-QAS was able to specifically bind to the bacteria and their biofilms via the dual effect of electrostatic adhesion (QAS) and covalent coupling (BA), resulting in a superior targeting ability over the single-targeted agents (B-CG or CG-QAS), improved bactericidal efficacy, a reduced dose of QAS and minimized chemotherapeutic/photothermal toxicity. In addition to the QAS-mediated antibacterial effects, NIR laser irradiation onto CG could further improve the antimicrobial effect via the synergy of hyperthermia. On the other hand, QAS could disrupt the bacterial cell membrane and improve its permeability and sensitivity to heat. Moreover, B-CG-QAS could be effectively utilized for synergistic chemo-photothermal therapy against the in vivo infections of MDR Gram-negative bacteria and their biofilms and accelerate bacteria-infected wound healing as well as exhibit outstanding biocompatibility both in vitro and in vivo. Therefore, our study demonstrates that B-CG-QAS has great potential to treat MDR Gram-negative bacterial infections and their biofilms.

Objective The aims of this study were to evaluate the epidemiological and clinical characteristics of candidemia in a typical burn ICU, and to determine the risk factors associated with candidemia among major burn patients. Method This retrospective observational study of candidemia from 2012 to 2017 in a burn ICU was conducted in the Department of Burn, Southwest hospital, Chongqing, China. Results The study included 410 major burn patients (≥40% total body surface area), 39 (9.51%) of which were diagnosed with candidemia. The annual incidences of candidemia varied from 6.06% to 17.54%, and increased gradually in the 6 years. Candida parapsilosis was the dominant pathogen (28.21% strains). The overall resistance rate of Candida spp. to fluconazole was 35.89%. Candidemia cases most frequently occurred in the 2nd (30.77%) and 3rd (23.08%) weeks after burn, and intravascular catheters were the most common sources of bloodstream Candida infections (31.58%). The crude mortality of candidemia was 23.08%, and the mortality attributable to candidemia was 14.99%. Risk factors of candidemia included inhalation injury, renal dysfunction with replacement therapy, severe gastrointestinal complications, T-cell lymphopenia and prior Candida colonization. Conclusion Candidemia has a high incidence and mortality in major burn patients. The changes in etiology and drug sensitivity may make new challenges for the management of candidemia in burn ICUs.

The requirements for anti-permeation, anti-infection and antifouling when treating a malicious wound bed raise new challenges for wound dressing. The present study used

Methicillin-resistant Staphylococcus aureus (MRSA) infections are prevalent in burn wards, and are especially serious in S. aureus bacteremia (SAB) patients. Glycopeptides and daptomycin are effective against MRSA infections, but MIC creeps can reduce their efficacy. Our object was to perform a molecular epidemiological investigation of S. aureus isolates in our burn center and to evaluate MICs for antimicrobials against SAB-associated MRSA isolates. A total of 259 S. aureus isolates, obtained from August 2011 to July 2016, were used in this study. Multiple molecular typing was used for molecular epidemiological analysis. E-tests were used to determine MICs of vancomycin, teicoplanin, and daptomycin for SAB-associated MRSA isolates. MIC values were stratified by collection date or source and compared. Spearman's test was used to analyze MICs correlations amongst tested antimicrobials. ST239-MRSA-III-t030-agrI clone was found to be dominant in both SAB and non-SAB patients, and significantly more in SAB patients (P < 0.0001). SAB-MRSA isolates exhibited decreased MICs for vancomycin, teicoplanin, and daptomycin during the 5-year period. Compared to those isolated from catheters or wounds, SAB-MRSA isolates from the bloodstream were less susceptible to vancomycin and daptomycin, but more susceptible to teicoplanin. MICs Correlation was found only between vancomycin and daptomycin in MRSA isolates from the bloodstream (rho = 0.250, P = 0.024). In conclusion, our results suggest that MRSA infections are still serious problems in burn centers. In contrast to most other studies, we observed increased susceptibility to glycopeptides and daptomycin against SAB-associated MRSA in our center from 2011 to 2016, suggesting the use of glycopeptides does not lead to MIC creeps. Isolates from different sites of the body may exhibit different levels of susceptibility and change trend over time for different antimicrobials, antimicrobials selection for MRSA infections should be considered comprehensively.

Streptococcus suis has emerged as a causative agent of human meningitis and streptococcal toxic shock syndrome over the last years. The high pathogenicity of S. suis may be due in part to a laterally acquired pathogenicity island (renamed SsPI-1), which can spontaneously excise and transfer to recipients. Cells harboring excised SsPI-1 can potentially lose this island if cell division occurs prior to its reintegration; however, attempts to cure SsPI-1 from the host cells have been unsuccessful. Here, we report that an SsPI-1-borne Epsilon/Zeta toxin-antitoxin system (designated SezAT) promotes SsPI-1 stability in bacterial populations. The sezAT locus consists of two closely linked sezT and sezA genes encoding a toxin and its cognate antitoxin, respectively. Overproduction of SezT induces a bactericidal effect that can be neutralized by co-expression of SezA, but not by its later action. When devoid of a functional SezAT system, large-scale deletion of SsPI-1 is straightforward. Thus, SezAT serves to ensure inheritance of SsPI-1 during cell division, which may explain the persistence of epidemic S. suis. This report presents the first functional characterization of TA loci in S. suis, and the first biochemical evidence for the adaptive significance of the Epsilon/Zeta system in the evolution of pathogen virulence.

Staphylococcus aureus is the most common cause of the difficult-to-treat osteomyelitis (OM). To better diagnose and manage S. aureus OM, especially for severe and long duration cases, indicators for risk prediction and severity evaluation are needed. Here, 139 clinical S. aureus isolates from orthopedic infections were divided into OM group (60 isolates from 60 OM patients) and non-OM group (79 isolates from 79 non-OM patients). Molecular types, antimicrobial susceptibility, and virulence factor profiles were evaluated and compared between the two groups to identify potential indicators associated with the prevalence of S. aureus OM. Clinical manifestations and laboratory data were analyzed to identify indicators affecting OM duration and severity. We found that some sequence types were specific to OM infection. The pvl, bbp, and ebps genes were associated with S. aureus OM prevalence. The pvl, bbp, and sei genes were associated with relatively longer OM duration. Panton-Valentine leucocidin (PVL)-positive S. aureus OM presented more serious inflammatory responses. Our results emphasize the significance of PVL in affecting the prevalence, duration, and severity of S. aureus OM. Diagnosing and monitoring PVL-related S. aureus OM may help direct better prognosis and treatment of these patients.

The increasing incidence of multidrug-resistant Acinetobacter baumannii (MDR Ab ) infections worldwide has necessitated the development of novel antibiotics. Human defensin 5 (HD5) is an endogenous peptide with a complex architecture and antibacterial activity against MDR Ab . In the present study, we attempted to simplify the structure of HD5 by removing disulfide bonds. We found that the Cys2-4 bond was most indispensable for HD5 to inactivate MDR Ab , although the antibacterial activity of the derivative was significantly attenuated. We then replaced the noncationic and nonhydrophobic residues with electropositive Arg to increase the antibacterial activity of HD5 derivative that contains a Cys2-4 bond, obtaining another derivative termed HD5d5. The in vitro antibacterial assay and irradiation-wound-infection animal experiment both showed that HD5d5 was much more effective than HD5 at eliminating MDR Ab . Further investigations revealed that HD5d5 efficiently bound to outer membrane lipid A and penetrated membranes, leading to bacterial collapse and peptide translocation. Compared to HD5, more HD5d5 molecules were located in the cytoplasm of MDR Ab , and HD5d5 was more efficient at reducing the activities of superoxide dismutase and catalase, causing the accumulation of reactive oxygen species that are detrimental to microbes. In addition, HD5 failed to suppress the pathogenic outer membrane protein A of Acinetobacter baumannii ( Ab OmpA) at concentrations up to 50 μg/ml, whereas HD5d5 strongly bound to Ab OmpA and exhibited a dramatic toxin-neutralizing ability, thus expanding the repertoire of drugs that is available to treat MDR Ab infections.

Pseudomonas aeruginosa is the leading cause of infection in burn patients. The increasing carbapenem resistance of P. aeruginosa has become a serious challenge to clinicians. The present study investigated the molecular typing and carbapenem resistance mechanisms of 196 P. aeruginosa isolates from the bloodstream and wound surface of patients in our burn center over a period of 6 years. By multilocus sequence typing (MLST), a total of 58 sequence types (STs) were identified. An outbreak of ST111, a type that poses a high international risk, occurred in 2014. The isolates from wound samples of patients without bacteremia were more diverse and more susceptible to antibiotics than strains collected from the bloodstream or the wound surface of patients with bacteremia. Importantly, a large proportion of the patients with multisite infection (46.51%) were simultaneously infected by different STs in the bloodstream and wound surface. Antimicrobial susceptibility testing of these isolates revealed high levels of resistance to carbapenems, with 35.71% susceptibility to imipenem and 32.14% to meropenem. To evaluate mechanisms associated with carbapenem resistance, experiments were conducted to determine the prevalence of carbapenemase genes, detect alterations of the oprD porin gene, and measure expression of the ampC β-lactamase gene and the mexB multidrug efflux gene. The main mechanism associated with carbapenem resistance was mutational inactivation of oprD (88.65%), accompanied by overexpression of ampC (68.09%). In some cases, oprD was inactivated by insertion sequence element IS1411, which has not been found previously in P. aeruginosa. These findings may help control nosocomial P. aeruginosa infections and improve clinical practice.

The gastrointestinal microbiome is crucial in human health. With greater than 10 times the cell count of an individual, the gastrointestinal microbiome provides many benefits to the host. It plays an important role in chronic illnesses and immune diseases and also following burns and trauma. This study aimed to determine whether severe burns affect the gastrointestinal microbiome during the early stages of after burn injury and the extent to which the microbiome is disturbed by such burns. We used a rat burn model to investigate any changes occurring in the microbiome after the burn trauma using 16S rRNA sequencing and downstream α-diversity, β-diversity, and taxonomy analysis. With 128631 and 143694 clean sequence reads, an average of 2287 and 2416 operational taxonomic units (OTUs) were recognized before and after the burn injury, respectively. Bacterial diversity within the pre- and post-burn groups was similar according to OTU richness, Chao 1 index, Shannon index and ACE index. However, the constituents of the gastrointestinal microbiota changed after the burn injury. Compared with the pre-burn samples, the post-burn samples showed a tendency to cluster together. The ratio of Firmicutes to Bacteroidetes decreased after the burn injury. Also, the abundance of some probiotic organisms (i.e., butyrate-producing bacteria and Lactobacillus) decreased after the burn injury. In contrast, opportunistic pathogenic bacteria, such as those of the genera Escherichia and Shigella and the phylum of Proteobacteria are more abundant post-burn. In conclusion, dysbiosis in the gastrointestinal microbiome was observed after the burn injury. Although the total number of species in the gastrointestinal microbiome did not differ significantly between the pre- and post-burn injury groups, the abundance of some bacterial components was affected to various extents.

Acinetobacter baumannii is a leading pathogen responsible for nosocomial infections. The emergence of carbapenem-resistant A. baumannii (CRAB) has left few effective antibiotics for clinicians to use. To investigate the temporal evolutionary relationships among CRAB strains, we collected 248 CRAB isolates from a Chinese burns institute over 3 years. The prevalence of the OXA-23 gene was detected by polymerase chain reaction. Multilocus sequence typing was used to type the CRAB strains and eBURST was used to analyze their evolutionary relationships. Wood surfaces (41%), sputa (24%), catheters (15%) and bloods (14%) were the four dominant isolation sources. Except for minocycline (33.5%) and sulbactam/cefoperazone (74.6%), these CRAB strains showed high resistance rates (> 90%) to 16 tested antibiotics. The 248 isolates fall into 26 sequence types (ST), including 9 known STs and 17 unknown STs. The majority (230/248) of these isolates belong to clonal complex 92 (CC92), including eight isolates belonging to seven unreported STs. A new clonal complex containing 11 isolates grouped into four new STs was identified. The OXA-23 gene was detected at high prevalence among the CRAB isolates and the prevalence rate among the various STs differed. The majority of the isolates displayed a close evolutionary relationship, suggesting that serious nosocomial spreading and nosocomial infections of CRAB have occurred in the burn unit. In conclusion, the main clonal complex for CRAB in this Chinese burn unit remain unchanged during the 3-year study period, and a new clonal complex was identified. CC92 is the dominant complex, and more attention should be directed towards monitoring the new clonal complex we have identified herein.

To investigate the prevalence of central venous catheter-related infection (CRI) in burn patients and its risk factors, so as to guide the clinical practice.Clinical data of 5 026 days of 480 cases of central venous catheterization altogether in 228 burn patients admitted to our ward from June 2011 to December 2014, conforming to the study criteria, were retrospectively analyzed. (1) The incidence of CRI and that of catheter-related bloodstream infection (CRBSI) in patients (the infection rates per thousand days were calculated) and mortality due to them, and detection of concerning bacteria were recorded after each case of catheterization. (2) The incidence of CRI after each case of catheterization in patients was recorded according to the classification of their gender, age, total burn area, full-thickness burn area, cause of injury, severity of inhalation injury, location of catheterization, whether catheterization through wound or not, duration of catheterization, and the data were processed with chi-square test. Indexes with statistically significant differences were selected, and they were processed with multivariate logistic stepwise regression analysis to screen the independent risk factors of CRI. (3) To all cases of catheterization and cases with catheterization through wound, incidence of CRI after each case of catheterization in patients at each time period was recorded according to the sorting of duration of catheterization. Data were processed with chi-square test and Fisher's exact test, and the values of P were adjusted by Bonferroni.(1) Infection rate of CRI per thousand days was 50.14‰ (252/5 026), resulting in the mortality rate of 3.51% (8/228). Infection rate of CRBSI per thousand days was 18.70‰ (94/5 026), resulting in the mortality rate of 2.19% (5/228). Respectively 319 and 105 strains of pathogens were detected in CRI and CRBSI, in which the top four bacteria detected were Acinetobacter baumannii, Pseudomonas aeruginosa, Staphylococcus aureus, and Klebsiella pneumoniae, and the most common fungus found was smooth Candida. (2) There were no statistically significant differences in the incidence of CRI after each case of catheterization among patients with different gender, age, cause of injury, severity of inhalation injury, and location of catheterization (with χ(2) values from 0.427 to 6.991, P values above 0.05). There were statistically significant differences in the incidence of CRI after each case of catheterization among patients with different total burn area, full-thickness burn area, whether catheterization through wound or not, duration of catheterization (with χ(2) values from 7.202 to 14.246, P0.05 or P0.01). (3) Total burn area, whether catheterization through wound or not, and duration of catheterization were the independent risk factors of CRI (with odd ratios respectively 1.495, 1.670, 1.924, 95% confidence intervals respectively 1.096-2.040, 1.077-2.590, 1.303-2.841, P0.05 or P0.01). (4) In all cases enduring catheterization, the incidence of CRI in patients after each episode of catheterization was close between cases enduring catheterization shorter than or equal to 3 days and those longer than 3 days and shorter than or equal to 5 days (χ(2)0.001, P0.05); the incidence of CRI in patients after each episode of catheterization was significantly higher in cases enduring catheterization longer than 5 days and shorter than or equal to 7 days, longer than 7 days and shorter than or equal to 14 days, and longer than 14 days than the former two periods (with χ(2) values from 3.625 to 13.495, P values below 0.05). In the cases with catheterization through wound, the incidence of CRI of patients after each episode of catheterization was close between cases enduring catheterization shorter than 5 days and those longer than or equal to 5 days and shorter than 7 days (P0.05); the incidence of CRI of patients after each episode of catheterization was significantly higher in cases enduring catheterization longer than or equal to 7 days and shorter than 14 days and longer than or equal to 14 days than those with longer than or equal to 5 days and shorter than 7 days (with χ(2) values respectively 6.828 and 4.940, P values below 0.05).The infection rate of CRI per thousand days in burn patients is relatively low, while that of CRBSI is relatively high, both resulting in relatively low mortality, and Acinetobacter baumannii is the main pathogen. Total burn area, whether catheterization through wound or not, and duration of catheterization are independent risk factors of CRI in burn patients, and with which its occurrence could be predicted. It is suggested that central venous catheterization should be removed within 5 days, and catheterization through wounds should be avoided as much as possible. If catheterization through wound is unavoidable, removal of the catheter within 7 days is recommended.

Acinetobacter baumannii infection is a serious threat to burn patients. Bacteremia due to A. baumannii is becoming the most common cause of mortality following burn. However, the epidemiology of A. baumannii causing burn-related bloodstream infections has rarely been reported. We retrospectively collected 81 A. baumannii isolates from the bloodstream of burn patients over a three-year period. Antibiotic susceptibility tests, the prevalence of antibiotic-resistant genes and sequence typing (ST) were conducted to characterize these strains. Most of the isolates showed an extensive drug-resistant phenotype. The resistance frequencies to imipenem and meropenem were 94% and 91%, respectively. The blaOXA-23-like gene, AmpC, IS-AmpC, PER and SIM are the five most prevalent resistant genes, and their prevalence rates are 93% (75/81), 86% (70/81), 73% (59/81), 73% (59/81) and 52% (42/81), respectively. The 81 isolates were grouped into 10 known and 18 unknown ST types, with ST368 (38%) being the most prevalent. Except for ST457 and four new types (STn2, STn6, STn11 and STn14), the remaining 23 ST types belonged to one clonal complex 92, which is most common among clinical isolate in China. The above results indicated that ST368 isolates possessing both the blaOXA-23-like gene and ampC gene were the main culprits of the increasing nosocomial A. baumannii infection in this study. More attention should be paid to monitoring the molecular epidemiology of A. baumannii isolates from burn patients to prevent further distribution. Such information may help clinicians with therapeutic decisions and infection control in the Burns Institute.