Identification of pneumococcal serotypes with individual recognition of vaccine types by a highly multiplexed real-time PCR-based MeltArray approach

BACKGROUND

Pneumococcus serotyping is important for monitoring serotype epidemiology, vaccine-induced serotypes replacement and emerging pathogenic serotypes. However, the lack of high-resolution serotyping tools has hindered its widespread implementation.

METHODS

We devised a single-step, multiplex real-time polymerase chain reaction (PCR)-based MeltArray approach termed PneumoSero that can identify 92 serotypes with individual recognition of 54 serotypes, including all 24 currently available vaccine types. The limit of detection (LOD) and the ability to coexisting serotypes were studied, followed by analytical evaluation using 92 reference pneumococcal strains and 125 non-pneumococcal strains, and clinical evaluation using 471 pneumococcus isolates and 46 pneumococcus-positive clinical samples.

RESULTS

The LODs varied with serotypes from 50 to 100 copies per reaction and 10 % of the minor serotypes were detectable in samples containing two mixed serotypes. Analytical evaluation presented 100 % accuracy in both 92 reference pneumococcal strains and 125 non-pneumococcal strains. Clinical evaluation of 471 pneumococcus isolates displayed full concordance with Sanger sequencing results. The 46 clinical specimens yielded 45 typeable results and one untypeable result. Of the 45 typeable samples, 41 were of a single serotype and four were of mixed serotypes, all of which were confirmed by Sanger sequencing or separate PCR assays.

CONCLUSION

We conclude that the PneumoSero assay can be implemented as a routine tool for pneumococcal serotyping in standard microbiology laboratories and even in clinical settings.

Deciphering the pivotal role of people with high-frequency occupational animal exposure in antibiotic resistance transmission between humans and animals

BACKGROUND

The spread of antibiotic-resistant bacteria (ARB) and antibiotic resistance genes (ARGs) among humans and food-producing animals has been widely reported. However, the transmission routes and associated risk factors remain incompletely understood.

METHODS

Here, we used commensal Escherichia coli bacteria strains from faeces of pigs and local citizens [HEG: high exposure group (pig breeders, butchers or restaurant chefs) and LEG: low exposure group (other occupations)] to explore the dynamics of ARB and ARG transmission between animals and humans.

RESULTS

Most ARGs (96%) present in pigs were shared with humans. Carriage rates of the shared ARGs suggest two transmission patterns among pigs, the HEG and LEG: one pattern was highest in pigs, gradually decreasing in the HEG and LEG (e.g. floR and cmlA1); the other pattern was increasing from pigs to the HEG but then decreasing in the LEG (e.g. mcr-1.1). Carriage rates of the HEG were higher than in the LEG in both patterns, implicating the HEG as a crucial medium in transmitting ARB and ARGs between food-producing animals and humans. Moreover, frequent inter/intragroup transmission via strains, plasmids and/or mobile elements was evident. Carriage of mcr-1.1 on human-gut-prevalent plasmids possibly promoted its enrichment in the HEG.

CONCLUSIONS

The HEG is a crucial factor in transmitting ARB and ARGs between food-producing animals and humans. Rational measures to contain the risks of occupational exposure are urgently needed to keep dissemination of antibiotic resistance in check and safeguard public health.

Establishment and Modification of Ninety-seven Pneumococcal Serotyping Assays Based on Quantitative Real-time Polymerase Chain Reaction

Objective

To establish and modify quantitative real-time polymerase chain reaction (qPCR)-based serotyping assays to distinguish 97 pneumococcal serotypes.

Methods

A database of capsular polysaccharide ( cps) loci sequences was generated, covering 97 pneumococcal serotypes. Bioinformatics analyses were performed to identify the cps loci structure and target genes related to different pneumococcal serotypes with specific SNPs. A total of 27 novel qPCR serotyping assay primers and probes were established based on qPCR, while 27 recombinant plasmids containing serotype-specific DNA sequence fragments were constructed as reference target sequences to examine the specificity and sensitivity of the qPCR assay. A panel of pneumococcal reference strains was employed to evaluate the capability of pneumococcal serotyping.

Results

A total of 97 pneumococcal serotyping assays based on qPCR were established and modified, which included 64 serotypes previously reported as well as an additional 33 serotypes. Twenty-seven novel qPCR serotyping target sequences were implemented in the pneumococcal qPCR serotyping system. A total of 97 pneumococcal serotypes, which included 52 individual serotypes and 45 serotypes belonging to 20 serogroups, could not be identified as individual serotypes. The sensitivity of qPCR assays based on 27 target sequences was 1-100 copies/µL. The specificity of the qPCR assays was 100%, which were tested by a panel of 90 serotypes of the pneumococcal reference strains.

Conclusion

A total of 27 novel qPCR assays were established and modified to analyze 97 pneumococcal serotypes.

Emergence of blaIMI-2- and blaIMI-16-Producing Enterobacter asburiae in the Aquaculture Environment of Jiangsu, China

Carbapenem-resistant Enterobacteriaceae strains have emerged as a serious threat to global public health. In recent years, blaIMI, a carbapenemase gene that drew less attention before, has been increasingly detected in both clinical and environmental settings. However, the environmental distribution and transmission of blaIMI, especially in aquaculture, require systematic investigation. In this study, the blaIMI gene was detected in fish (n = 1), sewage (n = 1), river water (n = 1), and aquaculture pond water samples (n = 17) collected from Jiangsu, China, demonstrating a relatively high sample-positive ratio of 12.4% (20/161). Thirteen blaIMI-2- or blaIMI-16-carrying Enterobacter asburiae strains were isolated from blaIMI-positive samples of aquatic products and aquaculture ponds. We also identified a novel transposon (Tn7441) carrying blaIMI-16 and a conserved region containing several truncated insertion sequence (IS) elements harboring blaIMI-2, all of which may play important roles in blaIMI mobilization. The occurrence of blaIMI-carrying Enterobacter asburiae in aquaculture-related water samples and fish samples highlights the risk of transmission of blaIMI-carrying strains through the food chain and the need for effective measures to prevent further dissemination. IMPORTANCE IMI carbapenemases have been detected in clinical isolates of many bacterial species with systemic infection and cause a further burden on clinical treatment in China, but their source and distribution are still unclear. The study systematically investigated the distribution and transmission of the blaIMI gene in aquaculture-related water bodies and aquatic products in Jiangsu Province, China, which is famous for its rich water resources and developed aquaculture industry. The relatively high prevalence of blaIMI in aquaculture samples and the identification of novel mobile elements harboring blaIMI enhance our knowledge of blaIMI gene distribution and highlight the public health risk and urgency of surveillance of aquaculture water systems in China.

A Novel Dual-Emission Fluorescence Probe Based on CDs and Eu3+ Functionalized UiO-66-(COOH)2 Hybrid for Visual Monitoring of Cu2

In this work, CDs@Eu-UiO-66(COOH)₂ (denoted as CDs-F2), a fluorescent material made up of carbon dots (CDs) and a Eu³⁺ functionalized metal-organic framework, has been designed and prepared via a post-synthetic modification method. The synthesized CDs-F2 presents dual emissions at 410 nm and 615 nm, which can effectively avoid environmental interference. CDs-F2 exhibits outstanding selectivity, great sensitivity, and good anti-interference for ratiometric sensing Cu²⁺ in water. The linear range is 0-200 µM and the limit of detection is 0.409 µM. Interestingly, the CDs-F2's silicon plate achieves rapid and selective detection of Cu²⁺. The change in fluorescence color can be observed by the naked eye. These results reveal that the CDs-F2 hybrid can be employed as a simple, rapid, and sensitive fluorescent probe to detect Cu²⁺. Moreover, the possible sensing mechanism of this dual-emission fluorescent probe is discussed in detail.

[Serotyping methods of Streptococcus pneumonia]

More than 100 serotypes of Streptococcus pneumonia have been identified, which has been one bottleneck problem for pneumococcal disease diagnosis, surveillance, development of pneumococcal vaccine and effectiveness evaluation of pneumococcal vaccines. Three categories of approaches for pneumococcal serotyping will be discussed including phenotyping based on anti-serum, biochemical typing based on pneumococcal capsular characteristics and genotyping based on pneumococcal capsular locus sequences. We reviewed the development and applications of different serotyping of pneumococcus to provide guidance for pneumococcal disease prevention and control.

[Exploration on the construction of analysis indicators system for antibiotic resistance monitoring]

Antibiotic resistance (AR) is a severe and fast-growing public health challenge with rapid globalization, especially in China. Although some monitoring systems were established in different fields, fragmentation of information failed to show the overall trend and spread of AR. It is necessary to establish a national monitoring system to reveal the occurrence, development, and spread of AR. The new AR monitoring system needs an updated analysis indicators system. We intend to recommend a new analysis indicators system for AR was constructed and applied to AR data monitoring and analysis for humans, animals, the environment, and foods. After investigating and analyzing the 5 Chinese major AR monitoring systems and literature, we have formulated 15 AR monitoring analysis indicators and initially established an evaluation system for the country's new AR monitoring system.

A Nosocomial Respiratory Infection Outbreak of Carbapenem-Resistant Escherichia coli ST131 With Multiple Transmissible bla KPC-2 Carrying Plasmids

Escherichia coli sequence type 131 (ST131) is well known for its multidrug resistance profile. Carbapenems have been considered the treatment of choice for E. coli ST131 infections, and resistance to carbapenems is emerging due to the acquisition of carbapenemase-encoding genes. In this study, 45 carbapenem-resistant E. coli strains were collected in a hospital. The resistance mechanisms, plasmid profiles, and genetic relatedness of these strains were determined. Phylogenetic relationships between these strains were assessed by molecular profiling and aligned with patient clinical details. The genetic context of bla KPC-2 was analyzed to trace the potential dissemination of bla KPC-2. The 45 carbapenem-resistant E. coli ST131 strains were closely related. Initially prevalent only in a single ward, ST131 subsequently spread to other ward, resulting in a respiratory infection outbreak of carbapenem-resistant E. coli ST131. Eight of the 30 patients died within 28 days of the first isolation of E. coli ST131. The bla KPC-2-positive plasmid profiles suggest that the carbapenem resistance was due to the acquisition by E. coli ST131 of transmissible plasmids pE0272_KPC and pE0171_KPC carrying bla KPC-2. Additionally, diverse multidrug resistance elements were transferred and rearranged between these plasmids mediated by IS26. Our research indicates that clinical attention should be paid to the importance of E. coli ST131 in respiratory infections and the spread of bla KPC -carrying E. coli ST131.

Changes in colistin resistance and mcr-1 abundance in Escherichia coli of animal and human origins following the ban of colistin-positive additives in China: an epidemiological comparative study

BACKGROUND

Following the discovery and emergence of the plasmid-mediated colistin resistance gene, mcr-1, the Chinese government formally banned colistin as an animal growth promoter on April 30, 2017. Herein, we report patterns in colistin resistance and mcr-1 abundance in Escherichia coli from animals and humans between 2015 and 2019, to evaluate the effects of the colistin withdrawal.

METHODS

We did an epidemiology comparative study to investigate: annual production and sales of colistin in agriculture across mainland China according to data from the China Veterinary Drug Association from 2015 to 2018; the prevalence of colistin-resistant E coli (CREC) in pigs and chickens in 23 Chinese provinces and municipalities as reported in the China Surveillance on Antimicrobial Resistance of Animal Origin database from Jan 1, 2015, to Dec 31, 2016, and Jan 1, 2017, to Dec 31, 2018; the presence of residual colistin and mcr-1 in faeces from 118 animal farms (60 pig, 29 chicken, and 29 cattle) across four provinces over July 1, 2017, to August 31, 2017, and July 1, 2018 to August 31, 2018; the prevalence of mcr-1-positive E coli (MCRPEC) carriage in healthy individuals attending routine hospital examinations across 24 provinces and municipalities from June 1 to July 30, 2019, comparing with equivalent 2016 data (June 1 to September 30) from our previous study in the same hospitals; and the patterns in CREC prevalence among hospital E coli infections across 26 provinces and municipalities from Jan 1, 2015, to Dec 31, 2016, and Jan 1, 2018, to Dec 31, 2019, reported on the China Antimicrobial Surveillance Network.

FINDINGS

After the ban on colistin as a growth promoter, marked reductions were observed in the production (27 170 tonnes in 2015 vs 2497 tonnes in 2018) and sale (US$71·5 million in 2015 vs US$8·0 million in 2018) of colistin sulfate premix. Across 118 farms in four provinces, mean colistin residue concentration was 191·1 μg/kg (SD 934·1) in 2017 versus 7·5 μg/kg (50·0) in 2018 (p<0·0001), and the median relative abundance of mcr-1 per 16S RNA was 0·0009 [IQR 0·0001-0·0059] in 2017 versus 0·0002 [0·0000-0·0020] in 2018 (p=0·0001). Across 23 provinces and municipalities, CREC was identified in pig faeces in 1153 (34·0%) of 3396 samples in 2015-16 versus 142 (5·1%) of 2781 in 2017-18 (p<0·0001); and in chickens in 474 (18·1%) of 2614 samples in 2015-16 versus 143 (5·0%) of 2887 in 2017-18 (p<0·0001). In hospitals across 24 provincial capital cities and municipalities, human carriage of MCRPEC was identified in 644 (14·3%) of 4498 samples in 2016 versus 357 (6·3%) of 5657 in 2019 (p<0·0001). Clinical CREC infections in 26 provinces and municipalities comprised 1059 (1·7%) of 62 737 E coli infections in 2015-16 versus 794 (1·3%) of 59 385 in 2018-19 (p<0·0001).

INTERPRETATION

The colistin withdrawal policy and the decreasing use of colistin in agriculture have had a significant effect on reducing colistin resistance in both animals and humans in China. However, continuous colistin monitoring is essential, in particular to act as an early warning system for colistin stewardship in Chinese hospitals.

FUNDING

National Key Research and Development Program of China, National Natural Science Foundation of China, and UK Medical Research Council.

A New High-throughput Real-time PCR Assay for the Screening of Multiple Antimicrobial Resistance Genes in Broiler Fecal Samples from China

OBJECTIVE

Antimicrobial resistance (AMR) has become a global concern and is especially severe in China. To effectively and reliably provide AMR data, we developed a new high-throughput real-time PCR assay based on microfluidic dynamic technology, and screened multiple AMR genes in broiler fecal samples.

METHODS

A high-throughput real-time PCR system with an new designed integrated fluidic circuit assay were performed AMR gene detection. A total of 273 broiler fecal samples collected from two geographically separated farms were screened AMR genes.

RESULTS

The new assay with limits of detection ranging from 40.9 to 8,000 copies/reaction. The sensitivity rate, specificity rate, positive predictive value, negative predictive value and correct indices were 99.30%, 98.08%, 95.31%, 99.79%, and 0.9755, respectively. Utilizing this assay, we demonstrate that AMR genes are widely spread, with positive detection rates ranging from 0 to 97.07% in 273 broiler fecal samples. blaCTX-M, blaTEM, mcr-1, fexA, cfr, optrA, and intI1 showed over 80% prevalence. The dissemination of AMR genes was distinct between the two farms.

CONCLUSION

We successfully established a new high-throughput real-time PCR assay applicable to AMR gene surveillance from fecal samples. The widespread existence of AMR genes detected in broiler farms highlights the current and severe problem of AMR.

Multiple Cross Displacement Amplification Coupled With Gold Nanoparticles-Based Lateral Flow Biosensor for Detection of the Mobilized Colistin Resistance Gene mcr-1

Fast dissemination of the mobilized colistin resistance (mcr) gene mcr-1 in Enterobacteriaceae causes a huge threat to the treatment of severe infection. In the current report, a multiple cross displacement amplification (MCDA) coupled with the detection of amplified products by gold nanoparticles-based lateral flow biosensor (LFB) assay (MCDA-LFB) was established to identify the mcr-1 gene with simpleness, rapidity, specificity, and sensitivity. The MCDA-LFB assay was performed at a isothermal temperature (63°C) for only 30 min during the amplification stage, and the reaction products were directly identified by using LFB which obtained the result within 2 min. The entire process of experiments, from templates extraction to result judging, was accomplished in <60 min. For the analytical specificity of this method, all of the 16 mcr-1-producing strains were positive, and all of the non-mcr-1 isolates produced the negative results. The sensitivity of mcr-1-MCDA-LFB assay was as little as 600 fg of plasmid DNA per reaction in pure culture, and approximately 4.5 × 10³ CFU/mL (~4.5 CFU/reaction) in spiked fecal samples. Therefore, this technique established in the present study is suitable for the surveillance of mcr-1 gene in clinic and livestock industry.

Gut microbiota community characteristics and disease-related microorganism pattern in a population of healthy Chinese people

China’s population accounts for about 1/5^th of the world’s total population. Owing to differences in environment, race, living habits, and other factors, the structure of the intestinal flora of Chinese individuals is expected to have unique features; however, this has not been thoroughly examined. Here, we collected faecal samples from healthy adults living in three cities of China and investigated their gut microbiome using metagenomics and bioinformatics technology. We found that 11 core bacterial genera were present in all of the Chinese faecal samples; moreover, several patient characteristics (age, region, body mass index, physical exercise, smoking habits, and alcoholic drink, and yogurt consumption) were found to have different effects on the gut microbiome of healthy Chinese people. We also examined the distribution patterns of disease-related microorganisms (DRMs), revealing which DRMs can potentially be used as markers for assessment of health risk. We also developed a program called “Guthealthy” for evaluating the health status associated with the microbiome and DRM pattern in the faecal samples. The microbiota data obtained in this study will provide a basis for a healthy gut microbiome composition in the Chinese population.

[Dissemination of insertion sequence common regions 1 and int1 gene and drug resistance of 483 Escherichia coli and Klebsiella pneumonia broiler isolates]

Objective: To investigate and analyze distribution characteristics of two multidrug resistance related genes in broiler isolates in Shandong province. Methods: The pre slaughter broilers were chosen from Shandong province in this study in June, 2014. A total of 400 fecal samples from five different zones (east, south, west, north and middle) of the hen house were collected. 373(77.2%) Escherichia coli and 110 (22.8%) Klebsiella pneumonia strains were isolated, and ISCR1 and int1 gene were detected by PCR assay and sequencing. The resistance to 10 drugs belonging to 8 classes antimicrobial drugs were obtained by using minimal broth dilution method and data analysis. The difference between isolates and drug resistance profiles was analyzed. Results: Among 483 isolates, 440 isolates (91.1%), 126 isolates (26.1%) and 126 isolates (26.1%) were detected as int1, ISCR1 and both two gene carriers, respectively. The rate of 37 E. coli isolates not carried ISCR1 or int1 gene resistant to 0 to 2, 3 to 5, 6 to 8 classes antimicrobial agents was 13.5% (n=5), 78.4% (n=29), and 8.1% (n=3), respectively; the rate of 288 only int1 gene E. coli carriers resistant to 0 to 2, 3 to 5, 6 to 8 groups antimicrobial agents was 2.4% (n=7), 74.7% (n=215), and 22.9% (n=6), respectively. The data above showed significant difference (P<0.001). The rate of 26 only int1 gene K. pneumonia carriers resistant to 0 to 2, 3 to 5, 6 to 8 classes antimicrobial agents was 11.5% (n=3), 76.9% (n=20), and 11.5% (n=3), respectively; the rate of 78 both two gene K. pneumonia carriers resistant to0 to 2, 3 to 5, 6 to 8 groups antimicrobial agents was 0, 35.9% (n=28), and 64.1% (n=50), respectively. The data above showed significant difference (P<0.001). Conclusion: Gene int1 and ISCR1 showed high prevalence in E. coli and K. pneumonia isolates. High level multi-drug resistance profile could be mediated by int1 and ISCR1 gene co-existence.

Extreme diversity and multiple SCCmec elements in coagulase-negative Staphylococcus found in the Clinic and Community in Beijing, China

Background

Coagulase-negative staphylococci (CoNS) are recognized as a large reservoir of staphylococcal cassette chromosome mec (SCCmec) harboured by Staphylococcus aureus. However, data of SCCmec in CoNS are relatively absent particularly in China.

Methods

Seventy-eight CoNS clinical and 47 community isolates were collected in Beijing. PCR was performed to classify SCCmec types. Under oxacillin treatment, quantitative real-time reverse transcription PCR (qRT-PCR) was performed to compare mecA mRNA levels and mRNA half-life between isolates with single SCCmec element and those with multiple one. Their growth curves were analysed. Their bacterial cell wall integrity was also compared by performing a Gram stain. All ccr complex segments were sequenced and obtained ccr segments were analysed by phylogenetic analyses.

Results

All 78 clinical isolates had mecA segments compared with 38% in community isolates (total 47). Only 29% clinical isolates and 33% community isolates (among mecA positive isolates) harboured a single previously identified SCCmec type; notably, 17% clinical isolates and 28% community isolates had multiple SCCmec types. Further studies indicated that isolates with multiple SCCmec elements had more stable mecA mRNA expression compared with isolates with single SCCmec elements. CoNS with multiple SCCmec elements demonstrated superior cell wall integrity. Interestingly, phylogenetic analyses of obtained 70 ccr segments indicated that horizontal gene transfer of the ccr complex might exist among various species of clinical CoNS, community CoNS and S. aureus.

Conclusions

CoNS recovered from patients carried extremely diverse but distinctive SCCmec elements compared with isolates from the community. More attention should be given to CoNS with multiple SCCmec not only because they had superior cell wall integrity, but also because CoNS and S. aureus might acquire multiple SCCmec through the ccr complex.

Electronic supplementary material

The online version of this article (doi:10.1186/s12941-017-0231-z) contains supplementary material, which is available to authorized users.

Detection and dissemination of the colistin resistance gene, mcr-1, from isolates and faecal samples in China

PURPOSE

A recently identified colistin resistance gene, mcr-1, has been reported in many countries. In this study, we established a new real-time PCR method to detect it.

METHODOLOGY

We used a real-time PCR method to detect the mcr-1 gene in a variety of isolates and faecal samples from 20 provinces and municipal cities in China.

RESULTS

Of the 2330 isolates (from 10 species) screened, 54 (2.3 %) isolates were positive for mcr-1. All of the mcr-1-positive isolates that were identified belonged to Escherichia coli strains, among which 9, 1, and 44 were identified as enteropathogenic E. coli, enteroadherent E. coli, and non-pathogenic E. coli, respectively. The majority of the mcr-1-positive isolates were obtained from farm animals from eight provinces and municipal cities across China. A total of 337 faecal samples, including 229 human and 108 pet animal faecal samples, were also screened for the mcr-1 gene. Of the 337 samples analyzed, six and eight human and pet animal faecal samples were positive for the mcr-1 gene, respectively.

CONCLUSION

The data demonstrate that the mcr-1 gene is highly prevalent in human and animal populations in China. This occurrence suggests that active surveillance of the mcr-1 gene is imperative in curtailing its spread.

The Activities of Adhesion and Biofilm Formation by Candida tropicalis Clinical Isolates Display Significant Correlation with Its Multilocus Sequence Typing

Adhesion and biofilm formation, which can occur on abiotic and biotic surfaces, are key components in Candida pathogenicity. The aims of this study were to infer about the C. tropicalis clinical isolates ability to adhere and form biofilm on abiotic and biotic surfaces and to correlate that with the multilocus sequence typing and other virulence factors. Adhesion and biofilm formation were measured in 68 C. tropicalis isolates from 3 hospitals in China on abiotic (polystyrene) and biotic (human urinary bladder epithelial cell) surfaces by crystal violet assay and 2,3-bis (2-methoxy-4-nitro-5-sulfo-phenyl)-2H-tetrazolium-5-carboxanilide reduction assay. In our study, almost all C. tropicalis isolates could adhere and produce biofilm on abiotic and biotic surfaces in a strain-dependent manner. The isolates from blood showed relatively lower adhesion and biofilm capacity on polystyrene surface, but had strong secreted aspartyl proteinase activity. Moreover, significant differences were found among MLST groups for adhesion and biofilm capacity. C. tropicalis in multilocus sequence typing group5 and group6 showed high adhesion and biofilm, while isolates in group1 exhibited low adhesion and biofilm formation. Overall, it is important to note that C. tropicalis isolates adhere to and produce biofilm on abiotic and biotic surfaces with strain specificity. These data will play an important role in subsequent research on the pathogenesis of C. tropicalis.

Distinct Expression Levels of ALS, LIP, and SAP Genes in Candida tropicalis with Diverse Virulent Activities

Candia tropicalis is an increasingly important human pathogen, causing nosocomial fungemia among patients with neutropenia or malignancy. However, limited research has been published concerning its pathogenicity. Based on the phenotypes of C. tropicalis in our previous study, we selected nine representative strains with different activities of virulence factors (adhesion, biofilm formation, secreted aspartic proteinases, and hemolysins), and one reference strain, ATCC750. The present study aimed to investigate the filamentation ability, the expression of virulence genes (ALST1-3, LIP1, LIP4, and SAPT1-4) and the cell damage of C. tropicalis strains with diverse virulences. C. tropicalis exhibited strain-dependent filamentation ability, which was positively correlated with biofilm formation. Reverse transcriptase PCR analysis showed that the ALST3 and SAPT3 genes had the highest expression in their corresponding genes for most C. tropicalis. The expressions of virulence genes, except ALST3 on polystyrene, were upregulated compared with growth in the planktonic and on human urinary bladder epithelial cell line (TCC-SUP) surface. Clustering analysis of virulence genes showed that isolates had a high biofilm forming ability on polystyrene formed a group. Lactate dehydrogenase assays showed that the cell damage induced by C. tropicalis markedly increased with longer infection time (24 and 48 h). Strain FXCT01, isolated from blood, caused the most serious cell damage; while ZRCT52, which had no filamentation ability, caused the least cell damage. Correlation analysis demonstrated significant correlation existed between adhesion on epithelial cells or the expression of ALST2-3 and cell damage. Overall, our results supported the view that adhesion and filamentation may play significant roles in the cell damage caused by C. tropicalis.

Anti-platelet and anti-thrombosis characteristics of Z4A5, a novel selective platelet glycoprotein IIb/IIIa inhibitor, compared with eptifibatide under long-term infusion

Platelet Glycoprotein IIb/IIIa inhibitors are approved for the treatment of acute coronary syndromes and percutaneous coronary interventions due to their effects on the final common pathway of platelet aggregation. Z4A5 is a new hexapeptide IIb/IIIa inhibitor with antiplatelet and antithrombotic effects. This study was performed to assess the characteristics of Z4A5 compared with another IIb/IIIa inhibitor eptifibatide. Light-transmission aggregometry was used to measure platelet aggregation to assess the antiplatelet efficacy of Z4A5 in vitro and ex vivo in beagles. The time course of platelet inhibition and bleeding time prolongation during i.v. bolus plus infusion and after infusion of the Z4A5 were evaluated in beagles following two 2 x 2 Latin square designs. We also compared the antithrombotic activity of Z4A5 with eptifibatide in arterial thrombosis and arteriovenous shunt thrombosis model in beagles. Our data showed that Z4A5 completely inhibited adenosine diphosphate (ADP)-, thrombin- and arachidonic acid-induced in vitro platelet aggregation with values of IC50 of 260 nM, 128.6 and 56.4 n respectively. Z4A5 also markedly and stably prevented ADP-induced ex vivo platelet aggregation and prolonged the bleeding time throughout the 8-hour infusion. Both platelet function and bleeding time returned to normal sooner after cessation of Z4A5 infusion than after eptifibatide. Z4A5 inhibited thrombosis and had the same potent antithrombotic activity as eptifibatide. In conclusion, Z4A5 has the same potent antiplatelet effect and antithrombotic activity with the advantage of a faster on and off time compared to eptifibatide.

[Study on virulence factors of Candida tropicalis isolated from clinical samples]

OBJECTIVE

To determine the in vitro production of virulence factors for Candida (C.) tropicalis, including aspartyl proteinases, phospholipases and hemolytic activities, describe the regulation of virulence factors varying with time in C. tropicalis, and analyze the differences in aspartyl proteinases and hemolytic activities of C. tropicalis isolated from anatomically distinct sites.

METHODS

A total of 64 C. tropicalis strains were spot-inoculated onto bovine albumin agar, egg yolk agar and sheep blood agar plates, respectively. Then the plates were incubated for 24, 48 and 72 hour at 37 °C, respectively. The aspartyl proteinases, phospholipase and hemolytic activities were determined at each time point, respectively.

RESULTS

All the C. tropiclais isolates showed positive aspartyl proteinases and hemolytic activities at each time point, but no phospholipases activity was detected in C. tropicalis. On comparison of aspartyl proteinases and hemolytic activities at different time points, aspartyl proteinases activity at 48 and 72 hour was higher than that at 24 hour. During 72 hour, hemolytic activity of C. tropicalis increased. No statistical significant differences in aspartyl proteinases and hemolytic activities of C. tropicalis were observed among different infection sites (P=0.368 and 0.985).

CONCLUSION

The C. tropicalis clinical isolates in China have aspartyl proteinases activity, hemolytic activity, but have no phospholipase activity.

[Study on genotype and virulence of Cryptococcus neoformans and Cryptococcus gattii clinical isolates in Guigang, Guangxi Zhuang Autonomous Region]

OBJECTIVE

To understand the species, genotypes and mating types of Cryptococcus neoformans and Cryptococcus gattii isolated from clinical samples in Guigang, Guangxi Zhuang Autonomous Region.

METHODS

A total of 20 Cryptococcus strains were isolated from clinical samples in Guigang from 2009 to 2012. The biological identification was conducted by polymerase chain reaction (PCR) to amplify internal transcribed spacer (ITS) sequences. The serotypes and mating types of C. neoformans and C. gattii were identified by PCR with serotype-specific and mating type-specific primers. The genotype was characterized by PCR fingerprinting and URA5 gene restriction fragment length polymorphism (URA5-RFLP). Phenotype study included growth test at 37 °C, melanin production test and urease test.

RESULTS

Among the 20 strains, 19 (95%) were identified as C. neoformans varieties (var.) grubii (serotype A, mating type α, genotype VN I), and only 1 was identified as C. gattii (mating type α, genotype VG I). The results of virulence test showed that all the strains grew well at 37 °C and positive in both urease test and melanin production test.

CONCLUSION

C. neoformans var. grubii (serotype A, genotype VN I and mating type α) was the predominant pathogen causing cryptococcosis in Guigang, and C. gattii strain was also detected.

Multilocus microsatellite markers for molecular typing of Candida tropicalis isolates

Background

Candida tropicalis is considered to be the leading pathogen causing nosocomial fungemia and hepatosplenic fungal infections in patients with cancer, particularly those with leukemia. Microsatellite-based typing methods using sets of genetic markers have been developed and reported for population structure analysis of C. albicans, C. glabrata, and C. parapsilosis, but no studies have been published for genetic analysis of C. tropicalis. The objective of this study was to develop new microsatellite loci that have the ability to distinguish among C. tropicalis isolates.

Results

DNA sequences containing over 10 bi- or tri-nucleotide repeats were selected from the C. tropicalis genome database. Thirty PCR primers sets specific for the microsatellite loci were designed and tested using eight clinically independent isolates. According to the amplification efficiency, specificity, and observed polymorphisms, eight markers were selected for further population structure analysis and molecular typing. Sixty-five independent C. tropicalis isolates were genotyped using these 8 markers. Based on these analyses, six microsatellite loci were confirmed, although two loci were found to be with unstable flanking areas. The six polymorphic loci displayed 4–22 alleles and 7–27 genotypes. The discriminatory power of the six loci ranged from 0.70 to 0.95. Genotyping results obtained by microsatellite analysis were compared to PCR-fingerprinting and multi-locus sequence typing (MLST). The comparisons showed that microsatellite analysis and MLST had the similar discriminatory power for C. tropicalis, which were more powerful than PCR-fingerprinting.

Conclusions

This is the first attempt to develop new microsatellite loci for C. tropicalis. These newly developed markers will be a valuable resource for the differentiation of C. tropicalis isolates. More C. tropicalis isolates will need to be sequenced and analyzed in order to fully show the potential of these newly developed microsatellite markers.

The identification, typing, and antimicrobial susceptibility of Pseudomonas aeruginosa isolated from mink with hemorrhagic pneumonia

The biological characteristics and molecular epidemiology of Pseudomonas aeruginosa associated with mink hemorrhagic pneumonia from Shandong province of eastern China were determined in this study. From 2010 to 2011, 30 mink P. aeruginosa isolates were identified from lung, fecal and feed samples of clinical cases and subjected to serotyping, antimicrobial susceptibility testing and pulsed-field gel electrophoresis (PFGE) using SpeI. The P. aeruginosa isolates belonged to four serotypes-21 of type G, four of type I, three of type M, one of type B, and one non-typable strain. The strains were divided into four large groups as determined by PFGE. Isolates from the group 2 were highly homologous and were obtained from the same region as an epidemic. All of the isolates were sensitive to piperacillin, piperacillin/tazobactam, ceftazidime, cefepime, imipenem, amikacin, gentamicin and tobramycin and resistant to ampicillin, cefuroxime and cefuroxime axetil. A high frequency of resistance was found to ampicillin/sulbactam, cefazolin, cefotetan, ceftriaxone, nitrofurantoin, and trimethoprim/sulfamethoxazole (96.7%). Resistance to ticarcillin/clavulanic acid, ciprofloxacin and levofloxacin was less common (13.3%). There was no relationship between antibiotic resistance and serotype distribution of the isolates. The epidemic serotype of P. aeruginosa from the mink hemorrhagic pneumonia in Shandong province was type G, which was a clone of commonly found in this province. These findings reveal the genetic similarities and antimicrobial susceptibility profiles of P. aeruginosa from clinical cases of mink hemorrhagic pneumonia and will facilitate the prevention and control of the disease in Shandong province of China.

Pichia fabianii blood infection in a premature infant in China: case report

Background

Invasive fungal infections caused by uncommon fungi have increased in recent years. Hospitalized low-birth-weight infants are at high risk for neonatal fungal infections. Pichia fabianii is a rare pathogen causing blood infection, which has reportedly caused only 4 cases of fungemia and 1 case of endocarditis worldwide. Here, we describe the first case of a P. fabianii blood infection in a premature infant in China.

Case presentation

On July 28^th, a low-birth-weight (LBW, 1760 g) female infant born at 33⁺⁴ weeks of gestation was admitted to the pediatric intensive care unit with mild neonatal asphyxia. Until August 2^nd, a mechanical respirator was used to assist respiration under the Continuous Positive Airway Pressure (CPAP) model. The baby had an increased body temperature and a fever. To prevent infection, Ceftriaxone Sodium (CS) was administered intravenously for three days, after which Cefepime was administered until August 13^th. Chest X-rays showed suspected plaque-like shadows in the right lung. Blood cultures twice tested positive for fungal infection caused by Candida pelliculosa (recognized as Pichia fabianii later), which is first mis-identified by commercial kit. Hence, intravenous fluconazole was administered. However, cultures of other body fluids (e.g., urine, feces and sputum) tested negative for fungal infection. Routine tests and biochemistry of cerebrospinal fluid (CSF) were normal. Latex agglutination of Cryptococcus neoformans and fungi cultures in the CSF were also negative. After 14 days of intravenous fluconazole, blood was re-cultured, the result of which was negative. On August 30^th, intravenous fluconazole was suspended. On Sep 3^rd, the infant left the hospital in good health.

Conclusions

This is the first case of a blood infection caused by P. fabianii in a LBW premature female infant in China. Risk factors for fungal infection include premature birth, as well as mechanical invasive operation and antibacterial drug usage. Whether such risk factors necessitate prophylactic use of antifungal drugs is an important question that has yet to be fully addressed. Additionally, the pathogen P. fabianii collected in this study was resistant to amphotericin B (AMB) and itraconazole (ITR). With the exception of the azole-resistant endocarditis case, all other cases have not demonstrated such a resistance. Finally, commercial biochemical methods used in routine practice are limited in their ability to identify P. fabianii. Molecular genetic based methods are imperative for identification of uncommon fungal species from disseminated infections.

Regulation network analysis in the esophageal squamous cell carcinoma

BACKGROUND

The incidence of esophageal squamous cell carcinoma (ESCC) has high regional selectivity. The molecular mechanisms of ESCC are complex and involve multiple oncogenes, tumor suppressor genes, receptor tyrosine kinases, cytoplasmic enzymes, and tumor interstitial elements.

AIM

Here we used bioinformatics to obtain some important genes and pathways involved in ESCC.

MATERIALS AND METHODS

In this article, we did Affymetrix microarray data collection from three big databases, and then selected all the differentially expressed genes (DEGs) according to some principles. On this basis, we carried out regulation network analysis and pathway enrichment analysis, obtaining ESCC related regulation network analysis, after which we selected significant pathways on regulation network and established TF-pathway regulation network.

RESULTS

In the transcription factors (TFs) regulation network we found SP1, E2F1, USF2 and SP3 form a local network which suggested that these TFs might play a more important role in ESCC. Some key pathways were also identified, such as P53 signaling pathway, melanoma and prostate cancer pathways.

CONCLUSIONS

The identification of crucial molecular pathways involved in ESCC would ultimately improve therapeutic effects and facilitate the development of new treatment strategies.

A mouse model of inducible liver injury caused by tet-on regulated urokinase for studies of hepatocyte transplantation

Mouse models of liver injury provide useful tools for studying hepatocyte engraftment and proliferation. A representative model of liver injury is the albumin-urokinase (Alb-uPA) transgenic model, but neonatal lethality hampers its widespread application. To overcome this problem, we generated a transgenic mouse in which transcription of the reverse tetracycline transactivator was (rtTA) driven by the mouse albumin promoter, and backcrossed the rtTA mice onto severe combined immunodeficient (SCID)/bg mice to generate immunodeficient rtTA/SCID mice. We then produced recombinant adenoviruses Ad.TRE-uPA, in which the urokinase was located downstream of the tetracycline response element (TRE). The rtTA/SCID mouse hepatocytes were then infected with Ad.TRE-uPA to establish an inducible liver injury mouse model. In the presence of doxycycline, uPA was exclusively expressed in endogenous hepatocytes and caused extensive liver injury. Enhanced green fluorescent protein-labeled mouse hepatocytes selectively repopulated the rtTA/SCID mouse liver and replaced over 80% of the recipient liver mass after repeated administration of Ad.TRE-uPA. Compared with the original uPA mice, rtTA/SCID mice did not exhibit problems regarding breeding efficiency, and the time window for transplantation was flexible. In addition, we could control the extent of liver injury to facilitate transplantation surgery by regulating the dose of Ad.TRE-uPA. Our inducible mouse model will be convenient for studies of hepatocyte transplantation and hepatic regeneration, and this system will facilitate screening for potential genetic factors critical for engraftment and proliferation of hepatocytes in vivo.

Efficient generation of hepatocyte-like cells from human induced pluripotent stem cells

Human induced pluripotent stem (iPS) cells are similar to embryonic stem (ES) cells, and can proliferate intensively and differentiate into a variety of cell types. However, the hepatic differentiation of human iPS cells has not yet been reported. In this report, human iPS cells were induced to differentiate into hepatic cells by a stepwise protocol. The expression of liver cell markers and liver-related functions of the human iPS cell-derived cells were monitored and compared with that of differentiated human ES cells and primary human hepatocytes. Approximately 60% of the differentiated human iPS cells at day 7 expressed hepatic markers alpha fetoprotein and Alb. The differentiated cells at day 21 exhibited liver cell functions including albumin Asecretion, glycogen synthesis, urea production and inducible cytochrome P450 activity. The expression of hepatic markers and liver-related functions of the iPS cell-derived hepatic cells were comparable to that of the human ES cell-derived hepatic cells. These results show that human iPS cells, which are similar to human ES cells, can be efficiently induced to differentiate into hepatocyte-like cells.

Pluripotin combined with leukemia inhibitory factor greatly promotes the derivation of embryonic stem cell lines from refractory strains

Most mouse embryonic stem (ES) cells are derived from a 129 or C57BL/6 background, whereas the derivation efficiency of ES cells is extremely low on certain refractory types of background for which ES cells are highly desired. Here we report an optimized, highly efficient protocol by combining pluripotin, a small molecule, and leukemia inhibitory factor (LIF) for the derivation of mouse ES cells. With this method, we successfully isolated ES cell lines from five strains of mice, with an efficiency of 57% for NOD-scid, 63% for SCID beige, 80% for CD-1, and 100% for two F1 strains from C57BL/6xCD-1. By tracking the Oct4-positive cells in the Oct4-green fluorescent protein embryos in the process of ES cell isolation, we found that pluripotin combined with LIF improved the efficiency of ES cell isolation by selectively maintaining the Oct4-positive cells in the outgrowth. To our knowledge, this is the first report of ES cells being efficiently derived from immunodeficient mice on refractory backgrounds (NOD-scid on a NOD background and SCID beige on a BALB/c background).

Derivation and characterization of hepatic progenitor cells from human embryonic stem cells

The derivation of hepatic progenitor cells from human embryonic stem (hES) cells is of value both in the study of early human liver organogenesis and in the creation of an unlimited source of donor cells for hepatocyte transplantation therapy. Here, we report for the first time the generation of hepatic progenitor cells derived from hES cells. Hepatic endoderm cells were generated by activating FGF and BMP pathways and were then purified by fluorescence activated cell sorting using a newly identified surface marker, N-cadherin. After co-culture with STO feeder cells, these purified hepatic endoderm cells yielded hepatic progenitor colonies, which possessed the proliferation potential to be cultured for an extended period of more than 100 days. With extensive expansion, they co-expressed the hepatic marker AFP and the biliary lineage marker KRT7 and maintained bipotential differentiation capacity. They were able to differentiate into hepatocyte-like cells, which expressed ALB and AAT, and into cholangiocyte-like cells, which formed duct-like cyst structures, expressed KRT19 and KRT7, and acquired epithelial polarity. In conclusion, this is the first report of the generation of proliferative and bipotential hepatic progenitor cells from hES cells. These hES cell–derived hepatic progenitor cells could be effectively used as an in vitro model for studying the mechanisms of hepatic stem/progenitor cell origin, self-renewal and differentiation.

Double-antigen sandwich ELISA for detection of antibodies to SARS-associated coronavirus in human serum

The study presented here was conducted to evaluate the performance of a double-antigen sandwich ELISA to detect antibodies in human serum against the coronavirus associated with severe acute respiratory syndrome (SARS). A recombinant partial nucleocapsid protein of SARS-associated coronavirus was used as a serodiagnostic antigen in the ELISA. A total of 2892 clinical serum samples were tested with the ELISA kit, which positively identified 25 of 35 (71.4%) samples of patients with confirmed SARS infection, 286 of 407 (70%) samples of patients suspected of having SARS, 229 of 302 (75.8%) samples of convalescent SARS patients, and 0 of 544 samples obtained from healthcare workers; only 1 of 1604 clinical samples obtained from patients with other diseases demonstrated a weakly positive result. These results indicate that the double-antigen sandwich ELISA is an effective screening method for the serodiagnosis of SARS-associated coronavirus.

Characterisation of a potyvirus and a potexvirus from Chinese scallion

Molecular analyses of viruses infecting Chinese scallion (Allium chinense G. Don) showed that the plants did not contain any of the poty-, carla- or allexiviruses that are common in garlic plants in China. The complete sequences of a potyvirus and a potexvirus were determined and these were shown to represent different viruses from any in the databases. They could be transmitted mechanically to scallion but not to other Allium species (including garlic) or to Narcissus. The potyvirus, tentatively named Scallion mosaic virus, has a distant relationship (c. 62% nucleotide identity over the entire genome) to Turnip mosaic virus and Japanese yam mosaic virus, with which it grouped in phylogenetic analyses. Its genome is 9324 nts long, encoding a 341.3 kDa polyprotein of 3001 amino acids. The potexvirus, tentatively named Scallion virus X, has a genome 6987 nts long and its organisation was similar to that of the other potexviruses but with only 46.3-63.2% nucleotides identical to them. It is most closely related to Narcissus mosaic virus but phylogenetic analyses indicate that it should be considered a distinct species. Neither of the viruses have been detected in garlic, although the two host plants are closely related.

Parathyroid hormone receptor internalization is independent of protein kinase A and phospholipase C activation

Parathyroid hormone (PTH) and PTH-related peptide (PTHrP) binding to their common receptor stimulates second messenger accumulation, receptor phosphorylation, and internalization. LLC-PK(1) cells expressing a green fluorescent protein-tagged PTH/PTHrP receptor show time- and dose-dependent receptor internalization. The internalized receptors colocalize with clathrin-coated pits. Internalization is stimulated by PTH analogs that bind to and activate the PTH/PTHrP receptor. Cell lines expressing a mutant protein kinase A regulatory subunit that is resistant to cAMP and/or a mutant receptor (DSEL mutant) that does not activate phospholipase C internalize their receptors normally. In addition, internalization of the wild-type receptor and the DSEL mutant is stimulated by the PTH analog [Gly(1),Arg(19)]hPTH-(1-28), which does not stimulate phospholipase C. Forskolin, IBMX, and the active phorbol ester, phorbol-12-myristate-13-acetate, did not promote receptor internalization or increase PTH-induced internalization. These data indicate that ligand-induced internalization of the PTH/PTHrP receptor requires both ligand binding and receptor activation but does not involve stimulation of adenylate cyclase/protein kinase A or phospholipase C/protein kinase C.

Food insecurity in Canadian households

OBJECTIVES

This article examines the prevalence of food insecurity in Canada, the characteristics of people most likely to live in households lacking sufficient funds for food, and several related health problems.

DATA SOURCE

The data are from the cross-sectional household component of the 1998/99 National Population Health Survey and the Food Insecurity Supplement to that survey.

ANALYTICAL TECHNIQUES

Cross-tabulations were used to estimate the percentage of Canadians experiencing food insecurity and the prevalence of five selected health outcomes among people who were and were not food insecure. Multivariate logistic regression was used to assess the association of several socio-demographic and economic factors with food insecurity and to determine the association of food insecurity with the selected health outcomes.

MAIN RESULTS

In 1998/99, 10% of Canadians, or about 3 million people, were living in food-insecure households. Low-income households, households depending on social assistance, lone-parent families headed by women, tenants, children, and Aboriginal people had significantly high odds of experiencing food insecurity. Food insecurity was significantly associated with poor/fair health, multiple chronic conditions, obesity, distress and depression.

Heats of adsorption of some organic compounds on beta-cyclodextrin determined by gas-solid chromatography

Isosteric adsorptive enthalpies have been derived from the temperature dependence of retention volumes determined by eluted pulse gas-solid chromatography. The heat data were obtained for systems using more than 20 organic liquids as adsorbates, and beta-cyclodextrin as adsorbent. The experimental results have been discussed in the light of intermolecular force between molecules of adsorbate and adsorbent.

HMG-1 as a late mediator of endotoxin lethality in mice

Endotoxin, a constituent of Gram-negative bacteria, stimulates macrophages to release large quantities of tumor necrosis factor (TNF) and interleukin-1 (IL-1), which can precipitate tissue injury and lethal shock (endotoxemia). Antagonists of TNF and IL-1 have shown limited efficacy in clinical trials, possibly because these cytokines are early mediators in pathogenesis. Here a potential late mediator of lethality is identified and characterized in a mouse model. High mobility group-1 (HMG-1) protein was found to be released by cultured macrophages more than 8 hours after stimulation with endotoxin, TNF, or IL-1. Mice showed increased serum levels of HMG-1 from 8 to 32 hours after endotoxin exposure. Delayed administration of antibodies to HMG-1 attenuated endotoxin lethality in mice, and administration of HMG-1 itself was lethal. Septic patients who succumbed to infection had increased serum HMG-1 levels, suggesting that this protein warrants investigation as a therapeutic target.

Bright Spots, Structure, and Magmatism in Southern Tibet from INDEPTH Seismic Reflection Profiling

INDEPTH seismic reflection profiling shows that the decollement beneath which Indian lithosphere underthrusts the Himalaya extends at least 225 kilometers north of the Himalayan deformation front to a depth of approximately 50 kilometers. Prominent reflections appear at depths of 15 to 18 kilometers near where the decollement reflector apparently terminates. These reflections extend north of the Zangbo suture to the Damxung graben of the Tibet Plateau. Some of these reflections have locally anomalous amplitudes (bright spots) and coincident negative polarities implying that they are produced by fluids in the crust. The presence of geothermal activity and high heat flow in the regions of these reflections and the tectonic setting suggest that the bright spots mark granitic magmas derived by partial melting of the tectonically thickened crust.