Molecular Characteristics and Antibiotic Resistance of Staphylococcus aureus Isolated from Patient and Food Samples in Shijiazhuang, China.

Staphylococcus aureus (S. aureus) is a common opportunistic and zoonotic pathogen in the world and could easily cause human infections and food contaminations. This study investigated the sequence typing and resistance profiles of S. aureus isolates from patient and food samples in Shijiazhuang, China. A total of 101 S. aureus isolates were distributed into six clonal complexes (CCs) and 16 singletons. A total of 86 patient isolates were distributed into six clonal CCs and 12 singletons, including a new ST. CC59, CC5, CC22, and CC398 were the predominant CCs of patient isolates. A total of 15 foodborne S. aureus isolates were distributed into 3 CCs and 4 STs, and CC1 was the most prevalent CC. Moreover, 101 S. aureus isolates had high resistance to penicillin and low resistance to chloramphenicol and rifampicin. A total of 39 strains of methicillin-resistant Staphylococcus aureus (MRSA) were detected in this study, including thirty-eight strains of patient isolates (44.2%, 38/86) and one strain of food isolates (6.7%, 1/15). MRSA-ST5, MRSA-ST59, and MRSA-ST239 were the predominant MRSA isolates in hospitals. The present study explained the relationship between S. aureus isolated from patient and food samples and indicated the risks of S. aureus in infectious diseases.

Molecular Characteristics of Staphylococcus aureus From Food Samples and Food Poisoning Outbreaks in Shijiazhuang, China.

As an opportunistic pathogen worldwide, Staphylococcus aureus can cause food poisoning and human infections. This study investigated the sequence typing, the penicillin (blaZ) and methicillin (mec) resistance profiles of S. aureus from food samples and food poisoning outbreaks in Shijiazhuang City, and the staphylococcal enterotoxin (SE) types of the S. aureus isolates from food poisoning. A total of 138 foodborne S. aureus isolates were distributed into 8 clonal complexes (CCs) and 12 singletons. CC1, CC5, CC8, CC15, CC97, CC59, CC398, CC88, and CC7 were the predominant CCs of foodborne S. aureus isolates. Moreover, CC59, CC15, and CC5 were the most prevalent CCs in food poisoning outbreaks. SEE was the most commonly detected SE in food poisoning isolates. One hundred thirty-three S. aureus isolates harbored the penicillin-resistant gene blaZ, and nine isolates carried the mec gene. The present study further explained the relationship between S. aureus and foods and food poisoning and indicated the potential risk of S. aureus infection.

Ferulic acid attenuates non-alcoholic steatohepatitis by reducing oxidative stress and inflammation through inhibition of the ROCK/NF-κB signaling pathways.

Ferulic acid (FA) is a natural polyphenol compound existing in many plants. The purpose of this study was to investigate the effect of FA on non-alcoholic steatohepatitis (NASH) induced by high-cholesterol and high-fat diet (HCHF) and its possible mechanism. Rats were fed HCHF for 12 weeks to establish NASH model. FA improved liver coefficients and had no effect on body weight changes. FA could reduce serum alanine transferase (ALT) and aspartate transferase (AST) activities. FA attenuated the increase of total cholesterol (TC), triglyceride (TG) and low-density lipoprotein (LDL) levels caused by NASH, improved the liver pathological damage induced by NASH, and inhibited the progression of liver fibrosis. FA prevented the production of reactive oxygen species (ROS) and the increase of malondialdehyde (MDA) levels, and attenuated the decrease in superoxide dismutase (SOD) activity. Meanwhile, FA significantly restored the levels of interleukin (IL)-1ß, IL-6 and tumor necrosis factor-α (TNF-α). In addition, we also found that FA inhibited the activity of ROCK and the activation of NF-κB signaling pathway in the liver of NASH rats. Overall, FA has a hepatoprotective anti-oxidative stress and anti-inflammatory effects in NASH rats, and its mechanism may be related to the inhibition of ROCK/NF-κB signaling pathway.

Biochemical characterization and mutational analysis of alanine racemase from Clostridium perfringens.

Clostridium perfringens is a gram-positive, anaerobic, pathogenic bacterium that can cause a wide range of diseases in humans, poultry and agriculturally important livestock. A pyridoxal-5-phosphate-dependent alanine racemase with a function in the racemization of d- and l-alanine is an attractive drug target for C. perfringens and other pathogens due to its absence in animals and humans. In this study alanine racemase from C. perfringens (CPAlr) was successfully expressed and purified in Escherichia coli and biochemically characterized. The purified CPAlr protein was a dimeric PLP-dependent enzyme with high substrate specificity. The optimal racemization temperature and pH were 40°C and 8.0, respectively. The kinetic parameters Km and kcat of CPAlr, determined by HPLC at 40°C were 19.1 mM and 17.2 s-1 for l-alanine, and 10.5 mM and 8.7 s-1 for d-alanine, respectively. Gel filtration chromatographic analysis showed that the molecular weight of mutant Y359A was close to monomeric form, suggesting that the inner layer residue Tyr359 might play an essential role in dimer-formation. Furthermore, the mutation at residues Asp171 and Tyr359 resulted in a dramatic increase in Km value and/or decreased in kcat value, indicating that the middle and inner layer residues Asp171 and Tyr359 of CPAlr might have the key role in substrate binding, catalytic activity or oligomerization state through the hydrogen-bonding interaction with the pentagonal ring waters and/or PLP cofactor.

Betaine Improves Polymer-Grade D-Lactic Acid Production by Sporolactobacillus inulinus Using Ammonia as Green Neutralizer.

The traditional CaCO3-based fermentation process generates huge amount of insoluble CaSO4 waste. To solve this problem, we have developed an efficient and green D-lactic acid fermentation process by using ammonia as neutralizer. The 106.7 g/L of D-lactic acid production and 0.89 g per g of consumed sugar were obtained by Sporolactobacillus inulinus CASD with a high optical purity of 99.7% by adding 100 mg/L betaine in the simple batch fermentation process. The addition of betaine was experimentally proven to protect cell at high concentration of ammonium ion, increase the D-lactate dehydrogenase specific activity and thus promote the production of D-lactic acid.

A new 4-Amino-7-Nitro-2,1,3-Benzoxadiazole (ANBD)-Based Fluorescent Probe for the Detection of Hg2.

Based on the photoinduced electron transfer (PET) principle, 4-amino-7-nitro-2,1,3-benzoxadiazole (ANBD) has been used as a fluorophore to develop a new fluorescent probe, 4-(2-N,N-dimethylthioacetamide)amino-7-nitro-2,1,3-benzoxadiazole (2), for the detection of Hg2+. Upon the addition of Hg2+, a 46-fold fluorescence enhancement occurs. Moreover the probe 2 exhibits a high selectivity and sensitivity to Hg2+, even in the presence of other common metal ions. Under optimal reaction conditions, a good linearity can be obtained in the range of 0.5-2.5 µM, and the detection limit is 0.05 µM. In addition, the desulfurization reaction mechanism is proposed based on electrospray ionization mass spectrum. The present study is not only a supplement to the detection method of Hg2+, but also a merit to the development of ANBD-based fluorescent probes.

The genotypic characterization of Cronobacter spp. isolated in China.

Cronobacter spp. (Enterobacter sakazakii) is an important pathogen contaminating powdered infant formula (PIF). To describe the genotypic diversity of Cronobacter isolated in China, we identified the isolates using fusA allele sequencing, and subtyped all of the isolates using pulsed-field gel electrophoresis (PFGE), multi-locus sequence typing (MLST), and multiple-locus variable-number tandem-repeat analysis (MLVA). A total of 105 isolates were identified, which included C. sakazakii (58 isolates), C. malonaticus (30 isolates), C. dublinensis (11 isolates), C. turicensis (5 isolates), and C. muytjensii (1 isolate). These isolates were showed to have 85 PFGE-patterns, 71 sequence types (STs), and 55 MLVA-patterns. Comparisons among the three molecular subtyping methods revealed that the PFGE method was the most distinguishable tool in identifying clusters of Cronobacter spp. through DNA fingerprinting, and MLST method came second. However, ESTR-1, ESTR-2, ESTR-3, and ESTR-4 were not effective loci for subtyping Cronobacter spp. such that the MLVA method requires further improvement.

Molecular characterization of foodborne-associated Staphylococcus aureus strains isolated in Shijiazhuang, China, from 2010 to 2012.

Staphylococcus aureus is an opportunistic pathogen commonly identified from food poisoning-associated foodstuffs. From 1996 to the present, S. aureus isolates have been found to exhibit increasing resistance to antimicrobial drugs. The aim of this study was to assess the molecular epidemiology properties of various S. aureus isolates through molecular typing and to investigate their characterization based on their production of enterotoxins and hemolysins and their resistance to antibiotics. A total of 78 coagulase-positive staphylococcal strains isolated from food or clinical samples were analyzed. Eight VNTR loci were used to genotype the 78 isolates, and this analysis resulted in 39 different multilocus variable number tandem repeat analysis (MLVA) profiles. The isolates recovered from a single outbreak exhibited the same MLVA profile. According to CLSI, 97.4% of the isolates were resistant to penicillin, whereas only 3.8% were methicillin-resistant Staphylococcus aureus strains. Through multiplex PCR, 87.2% of the isolates were shown to be enterotoxigenic (SEs), and the most common genes present were sea, sem, seg, seu, and sek. In conclusion, this study demonstrates the prevalence of staphylococcal enterotoxins, the contents of virulent factors, and the characteristics of ß-lactam antibiotic resistance in 78 S. aureus isolates. These findings emphasize the need to prevent the presence of S. aureus strains and SE production in foods. Our results also demonstrate that MLVA is a useful and powerful method for epidemiological studies of S. aureus. In contrast to multilocus sequence typing, the MLVA method is a simpler and more rapid method for epidemiological typing with a higher discriminatory power.

Microalterations of esophagus in patients with non-erosive reflux disease: in-vivo diagnosis by confocal laser endomicroscopy and its relationship with gastroesophageal reflux.

OBJECTIVES: Objectively diagnosing non-erosive reflux disease (NERD) is still a challenge. We aimed to evaluate the use of in-vivo confocal laser endomicroscopy (CLE) to examine the microalterations of the esophagus in patients with NERD and its relationship with reflux episodes monitored by multiple intraluminal impedance-pH (MII-pH). METHODS: Patients with gastroesophageal reflux symptoms completed reflux disease questionnaires. NERD was determined by negative gastroscopy. Patients without reflux symptoms were recruited as controls. Pilot clinical study was followed by prospective controlled blinded study. All subjects were examined by white-light mode of the endoscopy followed by the standard CLE mode and then MII-pH monitoring. The microalterations seen on CLE images and the correlation between CLE features and reflux episodes were evaluated, the correlation between CLE and transmission electron microscope (TEM) data was also analyzed. RESULTS: On CLE images, NERD patients had more intrapapillary capillary loops (IPCLs) per image than did controls (8.29 ± 3.52 vs. 5.69 ± 2.31, P=0.010), as well as the diameter of IPCLs (19.48 ± 3.13 vs. 15.87 ± 2.21 µm, P=0.041) and intercellular spaces of squamous cells (3.40 ± 0.82 vs. 1.90 ± 0.53 µm, P=0.042). The receiver operating characteristic analysis indicated that IPCLs number (optimal cutoff >6 per image, area under the curve (AUC) 0.722, 95% confidence interval (CI) 0.592-0.853, sensitivity 67.7%, specificity 71.6%), IPCLs diameter (optimal cutoff >17.2 µm, AUC 0.847, 95% CI 0.747-0.947, sensitivity 81%, specificity 76%), and the intercellular spaces of squamous cells (optimal cutoff >2.40 µm, AUC 0.935, 95% CI 0.875-0.995, sensitivity 85.7%, specificity 90.5%) diagnosed NERD with reasonable accuracy. Combined features of dilatation of intercellular space plus increased IPCLs provided 100% specificity in the diagnosis of NERD patients. The intercellular spaces of squamous cells observed on CLE were highly related to that on TEM findings (r=0.75, P<0.001). Multivariate progressive regression analysis showed that acidic reflux, especially in the supine position, was related to the increased number and dilation of IPCLs in the squamous epithelium (ß=0.063, t=2.895, P=0.038 and ß=0.156, t=1.023, P=0.04). CONCLUSIONS: CLE represents a useful and potentially significant improvement over standard endoscopy to examine the microalterations of the esophagus in vivo. Acidic reflux is responsible for the microalterations in the esophagus of patients with NERD.

Impacts of different promoters on the mammalian one-hybrid assay for detecting nuclear receptor agonists.

Nuclear receptors are a superfamily of ligand-activated transcription factors that play key roles in many biological processes, and have become one class of the most important targets in drug discovery. Mammalian one-hybrid system has been used to develop a cell-based functional transactivation high-throughput screening (HTS) assay for detecting nuclear receptors ligands. In the present study, we proved that different promoters used in the reporter vector had significant different impacts on the performance of HTS assays. The assay using the SV40 promoter in the reporter vector showed the characteristics of much higher signal/noise ratios, acceptable Z' factors (>0.6), low coefficient variation (<12.5%) and higher hits rate, which could be more robust, reproducible, and sensitive. In contrast, utilizing a TATA box promoter in the assay resulted in higher variance and low sensitivity. In addition, it was found that the assay using SV40 had longer signal decay time and was easier to be miniaturized in 384-well format. It has been confirmed that the choice of a promoter is a critical factor in developing a reporter gene HTS assay. However, the SV40 promoter used in the present study has been shown to be more adaptable than the minimal promoter TATA box in the Mammalian one-hybrid HTS assays for detecting nuclear receptor agonists.

Tegaserod for dyspepsia and reflux symptoms in patients with chronic constipation: an exploratory open-label study.

OBJECTIVE: To evaluate the potential role of tegaserod in the management of functional dyspepsia (FD) and gastroesophageal reflux disease (GERD) in patients with chronic constipation and to determine the possible efficacy of tegaserod on solid-phase gastric emptying and gastric hypersensitivity. METHOD: This was an exploratory open-label trial of tegaserod therapy for dyspepsia and reflux symptoms in patients with chronic constipation. The study cohort consisted of 90 patients randomized to three treatment groups for a study period of 4 weeks (tegaserod 6 mg, twice daily; esomeprazole 40 mg, once daily; tegaserod 6 mg, twice daily plus esomeprazole 40 mg, once daily). Twenty healthy volunteers provided control values. Clinical symptoms were evaluated by one of the investigators using a Gastrointestinal Symptom Rating Scale (GSRS). Solid-phase gastric emptying and colonic transit were measured by the radiopaque barium marker method, and the water load test (WLT) was used to evaluate gastric sensation and the function of proximal stomach. The proportions of patients with complete relief of epigastric pain /discomfort, epigastric fullness, early satiety and heartburn in the tegaserod group and the tegaserod plus esomeprazole group were compared with the esomeprazole group, respectively. RESULTS: The mean global gastrointestinal (GI) scores of all three treatment groups reported using the GSRS showed the same trend, with decreasing scores over the 4-week study period indicating a reported decreasing severity of symptoms that was significantly different from baseline values. Patients in the tegaserod plus esomeprazole group reported the lowest global GI scores after 4 weeks, as expected. Solid-phase gastric emptying (GER) and colonic transit (CTT) increased significantly in the tegaserod 6 mg twice daily group compared with baseline. These parameters did not change in the esomeprazole group at week 4 compared with baseline. In terms of gastric sensation, in the tegaserod group, the proportions of patients with hypersensitivity of the first perception threshold did not change at week 2 or week 4 compared with baseline; however, in this group and in the tegaserod plus esomeprazole group, the proportions of patients with hypersensitivity of discomfort threshold decreased significantly at week 4 compared with baseline. In the esomeprazole group, there were no changes in the proportions of patients with hypersensitivity of the first perception threshold and discomfort threshold at week 2 or 4 compared with baseline. No severe adverse events were recorded, and the medications were in general well-tolerated. CONCLUSION: Tegaserod is effective and safe at improving dyspepsia and reflux symptoms in patients with chronic constipation, and tegaserod plus esomeprazole is superior to esomeprazole alone in the resolution of epigastric pain/discomfort and heartburn.

A cell-based high-throughput screening assay for Farnesoid X receptor agonists.

OBJECTIVE: To develop a high-throughput screening assay for Farnesoid X receptor (FXR) agonists based on mammalian one-hybrid system (a chimera receptor gene system) for the purpose of identifying new lead compounds for dyslipidaemia drug from the chemical library. METHODS: cDNA encoding the human FXR ligand binding domain (LBD) was amplified by RT-PCR from a human liver total mRNA and fused to the DNA binding domain (DBD) of yeast GAL4 of pBIND to construct a GAL4-FXR (LBD) chimera expression plasmid. Five copies of the GAL4 DNA binding site were synthesized and inserted into upstream of the SV40 promoter of pGL3-promoter vector to construct a reporter plasmid pG5-SV40 Luc. The assay was developed by transient co-transfection with pG5-SV40 Luc reporter plasmid and pBIND-FXR-LBD (189-472) chimera expression plasmid. RESULTS: After optimization, CDCA, a FXR natural agonist, could induce expression of the luciferase gene in a dose-dependent manner, and had a signal/noise ratio of 10 and Z' factor value of 0.65. CONCLUSION: A stable and sensitive cell-based high-throughput screening model can be used in high-throughput screening for FXR agonists from the synthetic and natural compound library.