A rhodamine-based fluorescent probe used to determine nitroxyl (HNO) in lysosomes.

The reactive nitrogen species (RNS) in lysosomes play a major role during the regulation of lysosomal microenvironment. Nitroxyl (HNO) belongs to active nitrogen species (RNS) and is becoming a potential diagnostic and therapeutic biomarker. However, the complex synthesis routes of HNO in biosystem always hinder the exact determination of HNO in living cells. Here, a rhodamine-based fluorescent probe used to determine nitroxyl (HNO) in lysosomes was constructed and synthesized. 2-(Diphenylphosphino)benzoate was utilized as the sensing unit for HNO and morpholine was chose as the targeting group for lysosome. Before the addition of HNO, the probe displayed a spirolactone structure and almost no fluorescence was found. After the addition of HNO, the probe existed as a conjugated xanthene form and an intense green fluorescence was observed. The fluorescent probe possessed fast response (3 min) and high selectivity for HNO. Furthermore, fluorescence intensity of the probe linearly related with the HNO concentration in the range of 6.0 × 10-8 to 6.0 × 10-5 mol L-1. The detection limit was found to be 1.87 × 10-8 mol L-1 for HNO. Moreover, the probe could selectively targeted lysosome with excellent biocompatibility and had been effectually utilized to recognize exogenous HNO in A549 cells.

A new lysosome-targeted fluorescent probe for hydrogen peroxide based on a benzothiazole derivative.

As an important member of reactive oxygen species, hydrogen peroxide (H2O2) plays a key role in oxidative stress and cell signaling. Abnormal levels of H2O2 in lysosomes can induce damage or even loss of lysosomal function, leading to certain diseases. Therefore, real-time monitoring of H2O2 in lysosomes is very important. In this work, we designed and synthesized a novel lysosome-targeted fluorescent probe for H2O2-specific detection based on a benzothiazole derivative. A morpholine group was used as a lysosome-targeted unit and a boric acid ester was chosen as the reaction site. In the absence of H2O2, the probe exhibited very weak fluorescence. In the presence of H2O2, the probe showed an increased fluorescence emission. The fluorescence intensity of the probe for H2O2 displayed a good linear relationship in the concentration range of H2O2 from 8.0 × 10-7 to 2.0 × 10-4 mol·L-1. The detection limit was estimated to be 4.6 × 10-7 mol·L-1 for H2O2. The probe possessed high selectivity, good sensitivity and short response time for the detection of H2O2. Moreover, the probe had almost no cytotoxicity and had been successfully applied to confocal imaging of H2O2 in lysosomes of A549 cells. These results illustrated that the developed fluorescent probe in this study could provide a good tool for the determination of H2O2 in lysosomes.

Evaluation of the Autof MS1000 mass spectrometer in the identification of clinical isolates.

BACKGROUND: To evaluate the accuracy and performance of the Autof MS1000 mass spectrometer in bacteria and yeast identification, 2342 isolates were obtained from microbial cultures of clinical specimens (e.g. blood, cerebrospinal fluid, respiratory tract samples, lumbar puncture fluid, wound samples, stool, and urine) collected in 2019 in Henan Provincial People's Hospital. Repetitive strains from the same patient were excluded. We tested the Autof MS1000 and Bruker Biotyper mass spectrometry systems and the classical biochemical identification system VITEK 2/API 20C AUX. Inconsistencies in strain identification among the three systems were identified by 16S rDNA and gene sequencing. RESULTS: At the species level, the Autof MS1000 and Bruker Biotyper systems had isolate identification accuracies of 98.9 and 98.5%, respectively. At the genus level, the Autof MS1000 and Bruker Biotyper systems were 99.7 and 99.4% accurate, respectively. The instruments did not significantly differ in identification accuracy at either taxonomic level. The frequencies of unreliable identification were 1.1% (26/2342) for the Autof MS1000 and 1.5% (34/2342) for the Bruker Biotyper. In vitro experiments demonstrated that the coincidence rate of the Autof MS1000 mass spectrometer in the identification of five types of bacteria was > 93%, the identification error rate was < 3%, and the no identification rate was 0. This indicates that the Autof MS1000 system is acceptable for identification. CONCLUSIONS: The Autof MS1000 mass spectrometer can be utilised to identify clinical isolates. However, an upgradation of the database is recommended to correctly identify rare strains.

Rcs Phosphorelay Responses to Truncated Lipopolysaccharide-Induced Cell Envelope Stress in Yersinia enterocolitica.

Lipopolysaccharide (LPS) is the major component of the outer membrane of Gram-negative bacteria, and its integrity is monitored by various stress response systems. Although the Rcs system is involved in the envelope stress response and regulates genes controlling numerous bacterial cell functions of Yersinia enterocolitica, whether it can sense the truncated LPS in Y. enterocolitica remains unclear. In this study, the deletion of the Y. enterocolitica waaF gene truncated the structure of LPS and produced a deep rough LPS. The truncated LPS increased the cell surface hydrophobicity and outer membrane permeability, generating cell envelope stress. The truncated LPS also directly exposed the smooth outer membrane to the external environment and attenuated the resistance to adverse conditions, such as impaired survival under polymyxin B and sodium dodecyl sulfate (SDS) exposure. Further phenotypic experiment and gene expression analysis indicated that the truncated LPS was correlated with the activation of the Rcs phosphorelay, thereby repressing cell motility and biofilm formation. Our findings highlight the importance of LPS integrity in maintaining membrane function and broaden the understanding of Rcs phosphorelay signaling in response to cell envelope stress, thus opening new avenues to develop effective antimicrobial agents for combating Y. enterocolitica infections.

Clinical and molecular characteristics of Klebsiella pneumoniae ventilator-associated pneumonia in mainland China.

BACKGROUND: Klebsiella pneumoniae is a prominent nosocomial pathogen that accounts for up to 10 % of all hospital-acquired infections. It is a frequent cause of ventilator-associated pneumonia (VAP). The purpose of this study was to investigate the clinical characteristics of K. pneumoniae-associated VAP and the molecular characteristics of K. pneumoniae strains. METHODS: We retrospectively reviewed 70 mechanically ventilated patients with K. pneumoniae isolated. All K. pneumoniae strains were examined to determine hypermucoviscosity (HV) phenotype, capsular serotypes, virulence genes, multilocus sequence typing and antimicrobial susceptibility. RESULTS: Hypermucoviscosity was found in 14 of 70 (20 %) isolates of K. pneumoniae. Among the 70 patients, 43 cases (61.4 %) developed VAP. Furthermore, VAP was more frequently induced by HV-positive K. pneumoniae (14/14, 100 %) than by HV-negative strains (29/56, 51.7 %). HV-positive K. pneumoniae-associated VAP patients were more inclined to develop bacteremia and had a higher mortality rate than HV-negative strains VAP patients. Antibiotic resistance was more frequent in HV- negative strains- than in HV- positive strains-infected patients. The prevalence of rmpA and aerobactin genes were 85.7 % and 85.7 % respectively, and serotypes K1 and K2 accounted for 14.3 % and 28.6 % of the hypermucoviscosity strains, respectively. Strains carrying rmpA and aerobactin genes were significantly associated with HV-phenotype, and rmpA and aerobactin coexisted in HV-positive strains. Multilocus sequence typing analysis identified 24 different sequence types from K. pneumoniae VAP samples. CONCLUSIONS: HV-phenotype is the major virulence determinant for mechanically ventilated patients. There was a specific sequence typing (ST) distribution between HV-positive and HV-negative strains.

A coumarin-naphthalimide-based ratiometric fluorescent probe for nitroxyl (HNO) based on an ICT-FRET mechanism.

Nitroxyl (HNO) is an important reactive nitrogen that is associated with various states in physiology and pathology and plays a unique function in living systems. So, it is important to exploit fluorescent probes with high sensitivity and selectivity for sensing HNO. In this paper, a novel ratiometric fluorescent probe for HNO was developed utilizing intramolecular charge transfer (ICT) and fluorescence resonance energy transfer (FRET) mechanisms. The probe selected coumarin as energy donor, naphthalimide as energy receptor and 2-(diphenylphosphino)benzoate as the sensing site for detecting HNO. When HNO was not present, the 2-(diphenylphosphino)benzoate unit of the probe restricted electron transfer and the ICT process could not occur, leading to the inhibition of FRET process as well. Thus, in the absence of HNO the probe displayed the intrinsic blue fluorescence of coumarin. When HNO was added, the HNO reacted with the 2-(diphenylphosphino)benzoate unit of the probe to yield a hydroxyl group which resulting in the opening of ICT process and the occurring of FRET process. Thus, after providing HNO the probe displayed yellow fluorescence. In addition, the probe showed good linearity in the ratio of fluorescence intensity at 545 nm and 472 nm (I545 nm/I472 nm) with a concentration of HNO (0.1-20 µM). The probe processed a detection limit of 0.014 µM and a response time of 4 min. The probe also specifically identified HNO over a wide pH scope (pH = 4.00-10.00), including physiological conditions. Cellular experiments had shown that this fluorescent probe was virtually non-cytotoxic and could be applied for ratiometric sensing of HNO in A549 cells.

Preliminary Results on the Effects of Soybean Isoflavones on Growth Performance and Ruminal Microbiota in Fattening Goats.

Soybean isoflavones (SIFs), a group of secondary metabolites, have antioxidant, anti-inflammatory, and hormone-like activities. Supplementation with SIFs in the diet was reported to promote lactation performance in ruminants. The present study was performed to further decipher the effect of various concentrations of SIFs on growth and slaughter performance, serum parameters, meat quality, and ruminal microbiota in fattening goats. After a two-week acclimation, a total of 27 5-month-old Guanzhong male goats (18.29 ± 0.44 kg) were randomly assigned to control (NC), 100 mg/d SIF (SIF1), or 200 mg/d SIF (SIF2) groups. The experimental period lasted 56 days. The weight of the large intestine was greater (p < 0.05) in the SIF1 and SIF2 groups compared with the NC group. Meat quality parameters indicated that SIF1 supplementation led to lower (p < 0.05) cooking loss and shear force (0.05 < p < 0.10). The 16S rRNA sequencing analysis demonstrated that SIF1 supplementation led to lower (p < 0.05) proportions of Papillibacter and Prevotellaceae_UCG-004 but greater (p < 0.05) CAG-352 abundance in the rumen; these responses might have contributed to the improvement in production performance. In conclusion, meat quality and ruminal microbiome could be manipulated in a positive way by oral supplementation with 100 mg/d of SIFs in fattening goats. Thus, this study provides new insights and practical evidence for the introduction of SIFs as a novel additive in goat husbandry.

Microbiological Analysis and Mortality Risk Factors in Patients with Polymicrobial Bloodstream Infections.

Purpose: To study the etiological characteristics and risk factors affecting the prognosis of patients with polymicrobial bloodstream infections. Patients and Methods: Overall, 141 patients with polymicrobial bloodstream infections in Henan Provincial People's Hospital during 2021 were included. Laboratory test indexes, department of admission, sex, age, intensive care unit (ICU) admission, surgical history, and central venous catheter placement were collected. Patients were divided into surviving and deceased groups based on outcomes at discharge. Mortality risk factors were identified by univariate and multivariable analyses. Results: Seventy-two of 141 patients survived. Patients were mainly from the ICU and the Departments of Hepatobiliary Surgery and Hematology. Overall, 312 microbial strains were detected: 119 gram-positive, 152 gram-negative, and 13 anaerobic bacteria and 28 fungi. Among the gram-positive bacteria, coagulase-negative staphylococci were most frequent (44/119, 37%), followed by enterococci (35/119, 29.4%). Among coagulase-negative staphylococci, methicillin-resistant coagulase-negative staphylococci incidence was 75% (33/44). Among gram-negative bacteria, Klebsiella pneumoniae was most common (45/152, 29.6%), followed by Escherichia coli (25/152, 16.4%) and Pseudomonas aeruginosa (13/152, 8.6%). Among K. pneumoniae, the incidence of carbapenem-resistant (CR) K. pneumoniae was 45.7% (21/45). On univariate analysis, mortality risk factors included increased white blood cells and C-reactive protein, decreased total protein and albumin, CR strains, ICU admission, central venous catheter, multiple organ failure, sepsis, shock, pulmonary diseases, respiratory failure, central nervous system diseases, cardiovascular diseases, hypoproteinemia, and electrolyte disturbances (P < 0.05). Multivariable analysis showed that ICU admission, shock, electrolyte disorders, and central nervous system diseases were independent mortality risk factors. The survival curve shows that the survival rate of patients with polymicrobial CR bloodstream infections was lower than that of patients with polymicrobial non-CR bloodstream infections (P=0.029). Conclusion: Patients with polymicrobial bloodstream infections are typically critically ill and harbor multidrug-resistant bacteria. Thus, to minimize mortality rate in critically ill patients, changes in infectious flora should be monitored, antibiotics selected reasonably, and invasive procedures reduced.

Validation of a predictive model for coronary artery disease in patients with diabetes.

BACKGROUND: No reliable model can currently be used for predicting coronary artery disease (CAD) occurrence in patients with diabetes. We developed and validated a model predicting the occurrence of CAD in these patients. METHODS: We retrospectively enrolled patients with diabetes at Henan Provincial People's Hospital between 1 January 2020 and 10 June 2020, and collected data including demographics, physical examination results, laboratory test results, and diagnostic information from their medical records. The training set included patients ( n  = 1152) enrolled before 15 May 2020, and the validation set included the remaining patients ( n  = 238). Univariate and multivariate logistic regression analyses were performed in the training set to develop a predictive model, which were visualized using a nomogram. The model's performance was assessed by area under the receiver-operating characteristic curve (AUC) and Brier scores for both data sets. RESULTS: Sex, diabetes duration, low-density lipoprotein, creatinine, high-density lipoprotein, hypertension, and heart rate were CAD predictors in diabetes patients. The model's AUC and Brier score were 0.753 [95% confidence interval (CI) 0.727-0.778] and 0.152, respectively, and 0.738 (95% CI 0.678-0.793) and 0.172, respectively, in the training and validation sets, respectively. CONCLUSIONS: Our model demonstrated favourable performance; thus, it can effectively predict CAD occurrence in diabetes patients.

A naphthalimide-based and Golgi-targetable fluorescence probe for quantifying hypochlorous acid.

The Golgi apparatus (GA) is a vital organelle in biological systems and excess reactive oxygen species (ROS) is produced during stress in the Golgi apparatus. Hypochlorous acid (HOCl) is a significant reactive oxygen species and has strong oxidative and antibacterial activity, but excessive secretion of hypochlorous acid can affect Golgi structure or function abnormally, it will lead to a series of diseases including Alzheimer's disease, neurodegenerative diseases, autoimmune diseases, and Parkinson's disease. In present work, a novel fluorescent probe for Golgi localization utilizing naphthalimide derivatives was constructed to detect hypochlorous acid. The fluorescent probe used a derivatived 1,8-naphthalimide as the emitting fluorescence group, phenylsulfonamide as the localization group and dimethylthiocarbamate as the sensing unit. When HOCl was absent, the intramolecular charge transfer (ICT) process of the developed probe was hindered and the probe exhibited a weak fluorescence. When HOCl was present, the ICT process occurred and the probe showed strong green fluorescence. When the HOCl concentration was altered from 5.0 × 10-7 to 1.0 × 10-5 mol·L-1, the fluorescence intensity of the probe well linearly correlated with the HOCl concentration. The detection limit of 5.7 × 10-8 mol·L-1 was obtained for HOCl. The HOCl fluorescent probe possessed a rapid reaction time, a high selectivity and a broad working pH scope. In addition, the probe possessed good biocompatibility and had been magnificently employed to image Golgi HOCl in Hela cells. These characteristics of the probe demonstrated its ability to be used for sensing endogenous and exogenous hypochlorous acids within the Golgi apparatus of living cells.

Characteristics of humoral and cellular responses to coronavirus disease 2019 (COVID-19) inactivated vaccine in central China: A prospective, multicenter, longitudinal study.

Introduction: In China, the long-term immunogenicity and adverse effects of inactivated vaccines produced by different or the same manufacturer remain unclear. Therefore, the objective of this study was to evaluate the cellular immune responses and neutralizing antibody kinetics of homologous and heterologous administrations of an inactivated coronavirus disease 2019 (COVID-19) vaccine 240 days after the second vaccination. Methods: This prospective, multicenter, observational, longitudinal study involved 595 participants with a negative SARS-CoV-2 polymerase chain reaction result who were serologically tested and followed for 8 months after vaccination. Neutralizing antibodies, interferon-gamma (IFN-γ), interleukin (IL)-6, CD4+ T-lymphocyte, and B-lymphocyte counts were evaluated in serum samples after stimulation with 2 µg/mL SARS-CoV-2 spike protein for 16 h at follow-up intervals of 2 months. Results: Most participants [582/595; 146 male participants, 449 female participants; mean age 35 (26-50 years)] rapidly developed neutralizing antibodies after two doses of the vaccine administered 3-weeks apart. The positive rate of neutralizing antibodies peaked at 97.7% at 60-90 days, decreased, and stabilized at 82.9% at 181-240 days post-vaccination. Lower antibody concentrations were correlated with older age, longer duration after vaccination, non-health care workers, mixed-manufacturer vaccinations, and intervals of less than 40 days between two doses of vaccination, whereas lower IFN-γ levels and B-lymphocyte counts were associated with older age, blood type A, and non-health care workers. A higher IL-6 level was associated with older age, mixed-manufacturer vaccinations, intervals of less than 40 days between two doses of vaccination, and medical staff. Adverse reactions were mild or moderate and self-limited, with no serious events reported. Discussion: Two doses of the Chinese inactivated vaccine induced robust and rapid antibody expression and cellular immune responses. Boosting vaccination is considered important, as antibodies and cellular immune responses were reduced in susceptible populations.

Evaluation of Commercial Products for Colistin and Polymyxin B Susceptibility Testing for mcr-Positive and Negative Escherichia coli and Klebsiella pneumoniae in China.

Purpose: To evaluate the performance of five widespread commercial products for colistin and polymyxin B susceptibility testing in China for mcr-positive and -negative Escherichia coli and Klebsiella pneumoniae. Methods: A total of 132 E. coli and 83 K. pneumoniae strains (including 68 mcr-1-positive E. coli and 28 mcr-8-positive K. pneumoniae) were collected. We analysed the performance of colistin susceptibility (with Vitek 2 and Phoenix M50) and the performance of polymyxin B susceptibility (with DL-96II, MA120, and a Polymyxin B Susceptibility Test strip; POL E-strip). Broth microdilution was used as the gold standard. Categorical agreement (CA), essential agreement (EA), major error (ME), and very major error (VME) were calculated for comparisons. Results: For E. coli, the total CA, EA, ME, and VME to colistin were as follows: Vitek 2, 98.5%/98.5%/0%/2.9%; and Phoenix M50, 98.5%/97.7%/0%/2.9%. The total CA, EA, ME, and VME to polymyxin B were as follows: POL E-strip, 99.2%/63.6%/1.6%/0%; MA120, 70.0%/-/0%/58.8%; and DL-96II, 80.2%/-/1.6%/36.8%. Only Vitek 2 and Phoenix M50 presented satisfactory performances for mcr-1-positive E. coli. For K. pneumoniae, the total CA, EA, ME, and VME to colistin were as follows: Vitek 2, 73.2%/72.0%/0%/61.6%; and Phoenix M50, 74.7%/74.7%/0%/58.3%. The total CA, EA, ME, and VME to polymyxin B were as follows: POL E-strip, 91.6%/74.7%/2.1%/16.7%; MA120, 92.8%/-/2.1%/13.9%; and DL-96II, 92.2%/-/2.1%/8.3%. All systems were unsatisfactory for mcr-8-positive K. pneumoniae. When the susceptibility of mcr-negative strains was tested, all systems presented excellent performance. Conclusion: Vitek 2 and Phoenix M50 with colistin for E. coli showed acceptable performance regardless of mcr-1 expression, while DL-96II, MA120, and the POL E-strip performed worse for mcr-1-positive strains. Furthermore, mcr-8 greatly affected the performance of all systems with both colistin and polymyxin B for K. pneumoniae isolates.

A novel lysosome-located fluorescent probe for highly selective determination of hydrogen polysulfides based on a naphthalimide derivative.

Hydrogen polysulfides (H2Sn, n > 1) belongs to sulfane sulfur in the reactive sulfur species (RSS) family and plays a significant regulatory role in organisms. Highly selective and lysosome-located probes for detecting hydrogen polysulfides are rare. Thus, it is important to develop a technique to detect the changes of H2Sn level in lysosomes. In this work, a lysosome-targeting fluorescent probe for H2Sn was designed and developed based on a naphthalimide derivative. 4-Hydroxynaphthalimide was selected as the fluorescent group and 2-chloro-5-nitrobenzoate group was used as a specific recognition unit for H2Sn. A morpholine unit was chosen as a lysosome-located group. In the absence of H2Sn, the fluorescent probe exhibited almost no fluorescence. In the presence of H2Sn, the fluorescent probe showed strong fluorescence owing to H2Sn-mediated aromatic substitution-cyclization reactions. The fluorescence emission intensity at 548 nm of the probe showed a good linear relationship toward H2Sn in the range of 2.0 × 10-7 - 9.0 × 10-5 mol·L-1, and the detection limit was found to be 1.5 × 10-7 mol·L-1. The probe possessed a wide work range of pH, including the pH of physiological environment, and high selectivity for H2Sn. There are almost no cytotoxicity and the ability of detecting endogenous and exogenous H2Sn in lysosomes. These results indicate that the fluorescent probe can provide a good tool for intracellular and extracellular detection of H2Sn.

Rhodamine-Based Fluorescent Probe for Highly Selective Determination of Hg2.

The determination of mercuric ions (Hg2+) in environmental and biological samples has attracted the attention of researchers lately. In the present work, a novel turn-on Hg2+ fluorescent probe utilizing a rhodamine derivative had been constructed and prepared. The probe could highly sensitively and selectively sense Hg2+. In the presence of excessive Hg2+, the probe displayed about 52-fold fluorescence enhancement in 50% H2O/CH3CH2OH (pH, 7.24). In the meantime, the colorless solution of the probe turned pink upon adding Hg2+. Upon adding mercuric ions, the probe interacted with Hg2+ and formed a 1:1 coordination complex, which had been the basis for recognizing Hg2+. The probe displayed reversible dual colorimetric and fluorescence sensing of Hg2+ because rhodamine's spirolactam ring opened upon adding Hg2+. The analytical performances of the probe for sensing Hg2+ were also studied. When the Hg2+ concentration was altered in the range of 8.0 × 10-8 to 1.0 × 10-5 mol L-1, the fluorescence intensity showed an excellent linear correlation with Hg2+ concentration. A detection limit of 3.0 × 10-8 mol L-1 had been achieved. Moreover, Hg2+ in the water environment and A549 cells could be successfully sensed by the proposed probe.

A Highly Selective Fluorescent Probe for Hypochlorous Acid in Living Cells Based on a Naphthalene Derivative.

Hypochlorous acid (HOCl) was crucial for maintaining the homeostasis in cells and plays vital roles in many physiological and pathological processes. In this work, a highly selective fluorescent probe for hypochlorous acid in living cells was constructed and prepared based on a naphthalene derivative. A naphthalene derivative was utilized as the fluorescent group, and N,N-dimethylthiocarbamate was applied as the selective recognition site for HOCl. Before adding HOCl, the fluorescent probe exhibited weak fluorescence. Upon adding HOCl, the fluorescent probe displayed remarkable fluorescence enhancement. The fluorescence intensity at 502 nm showed a linear response to the concentration of HOCl from 3.0 × 10-7 to 1.0 × 10-5 mol·L-1. The detection limit was estimated to be 1.5 × 10-7 mol·L-1 for HOCl. The fluorescent probe showed fast response and outstanding selectivity toward HOCl. It owned good biocompatibility and had also been successfully applied in the confocal imaging of exogenous and endogenous HOCl in living cells.

Ratiometric Determination of Nitroxyl Utilizing a Novel Fluorescence Resonance Energy Transfer-Based Fluorescent Probe Based on a Coumarin-Rhodol Derivative.

Nitroxyl (HNO) is a member of the reactive nitrogen species, and how to detect it quickly and accurately is a challenging task. In this work, we designed and prepared a fluorescent ratiometric probe based on the fluorescence resonance energy transfer (FRET) mechanism, which can detect HNO with high selectivity. The coumarin derivative was used as an energy donor, the rhodol derivative was applied as an energy receptor, and 2-(diphenylphosphine)benzoate was utilized as the recognition group to detect nitroxyl. In the absence of HNO, the rhodol derivative exists in a non-fluorescent spironolactone state, and the FRET process is inhibited. Upon adding HNO, the closed spironolactone form is transformed into a conjugated xanthene structure and the FRET process occurs. This probe could specifically recognize nitroxyl, showing high sensitivity and selectivity. When the HNO concentration was changed from 3.0 × 10-7 to 2.0 × 10-5 mol·L-1, I 543nm/I 470nm exhibited a satisfactory linear correlation with the concentration of HNO. A detection limit of 7.0 × 10-8 mol·L-1 was obtained. In addition, almost no cell toxicity had been verified for the probe. The probe had been successfully applied to the ratiometric fluorescence imaging of HNO in HepG2 cells.

Novel Mitochondria-Targeting and Naphthalimide-based Fluorescent Probe for Detecting HClO in Living Cells.

As a key reactive oxygen species (ROS), hypochlorous acid (HClO) plays an important role in many physiological and pathological processes. The mitochondria-targeting probes for the highly sensitive detection of HClO are desirable. In present work, we designed and synthesized an original mitochondria-localizing and turn-on fluorescent probe for detecting HClO. 4-Aminonaphthalimide was employed as the fluorescent section, the (2-aminoethyl)-thiourea unit was utilized as a typical sensing unit, and the quaternized pyridinium moiety was used as a mitochondria-targeted localization group. When HClO was absent, the probe showed weak fluorescence. In the existence of HClO, the probe revealed a blue fluorescence. Moreover, the turn-on fluorescent probe was able to function in a broad pH scope. There was an excellent linearity between the fluorescence emission intensity at 488 nm and the concentrations of HClO in the range of 5.0 × 10-7 to 2.5 × 10-6 mol·L-1. Additionally, the probe had almost no cell toxicity and possessed an excellent mitochondria-localizing capability. Furthermore, the probe was able to image HClO in mitochondria of living PC-12 cells. The above remarkable properties illustrated that the probe was able to determine HClO in mitochondria of living cells.

Severe Acute Respiratory Syndrome Coronavirus 2 Viral RNA Load Status and Antibody Distribution Among Patients and Asymptomatic Carriers in Central China.

This study aimed to monitor severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) viral loads and specific serum-antibodies (immunoglobulin [Ig] G and M) among confirmed patients and asymptomatic carriers from returning healthy travelers. The throat swabs, sputum, and stool samples from 57 hospitalized coronavirus disease (COVID-19) patients and 8 asymptomatic carriers, among 170 returning healthy travelers were tested using reverse-transcription real-time polymerase chain reaction. SARS-CoV-2 IgM/IgG antibodies were detected via serum chemiluminescence assay. Sequential results showed higher viral RNA loads in the throat, sputum, and stool samples at 3-12 and 6-21 days after symptom onset among severely ill COVID-19 patients. Shorter viral habitation time (1-8 days) was observed in the oropharyngeal site and intestinal tract of asymptomatic carriers. The IgG and IgM response rates were 19/37 (51.4%) and 23/37 (62.6%) among the 29 confirmed patients and 8 asymptomatic carriers, respectively, within 66 days from symptom or detection onset. The median duration between symptom onset and positive IgG and IgM results was 30 (n=23; interquartile range [IQR]=20-66) and 23 (n=19; IQR=12-28) days, respectively. Of 170 returning healthy-travelers to China, 4.7% were asymptomatic carriers (8/170) within 2 weeks, and the IgG and IgM positivity rate was 12.8% (12/94). IgM/IgG-positivity confirmed 3 suspected SARS-CoV-2 cases, despite negative results for SARS-CoV-2 RNA. Compared with other respiratory viral infectious diseases, COVID-19 has fewer asymptomatic carriers, lower antibody response rates, and a longer antibody production duration in recovered patients and the contacted healthy population. This is an indication of the complexity of COVID-19 transmission.

Prevalence and Genetic Diversity of Clostridium perfringens Isolates in Hospitalized Diarrheal Patients from Central China.

OBJECTIVE: This study aimed to investigate the prevalence, genetic diversity and clinical characteristics of Clostridium perfringens isolates from hospitalized clinical diarrheal patients. METHODS: A prospective study was conducted on 1108 patients with diarrhea during hospitalization. Stool samples were cultured for C. perfringens, and the toxin genes were detected by PCR. The available clinical data of 112 patients were analyzed to study the clinical features of various isolates. Multi-locus sequence typing (MLST) was performed to assess phylogenetic relationship between different isolates. RESULTS: A total of 153 (13.8%) isolates were obtained from patients' stools. C. perfringens type F (49.0%) was the major toxin type in the isolates, followed by type A (n = 59, 38.6%) and type C (n = 14, 9.2%). Patients older than 50 years and those with underlying diseases of cancer, hepatobiliary system, and ulcerative colitis (UC) were more predisposed to C. perfringens type F and type A infection than to type C. The patients infected with type C experienced more severe clinical symptoms compared to those with type A infection. There was a significant association between type FC and foodborne gastrointestinal (GI) diseases (p = 0.018), between type FP and antibiotic-associated diarrhea (AAD) (p < 0.001), and between type A and sporadic diarrhea (SD) (p < 0.001). Phylogenetic analysis indicated that type F isolates carrying a chromosomal cpe gene mainly belonged to ST77 (6/15 isolates). Type F isolates with cpe gene on a plasmid exhibited high genetic diversity. CONCLUSION: High prevalence and considerable genetic diversity of C. perfringens type F were found in clinical diarrheal patients. Elderly people and patients with cancer, hepatobiliary diseases or UC, or suspected of having food poisoning (FP) may be targeted for routine testing of C. perfringens toxin genes and may benefit from early detection of C. perfringens type C isolates that cause more severe clinical symptoms.

A highly selective fluorescent probe for hydrogen polysulfides in living cells based on a naphthalene derivative.

Hydrogen polysulfides (H2Sn, n > 1) are members of reactive sulfur species (RSS) and signaling molecules derived from hydrogen sulfide (H2S). Recently, the functions of H2Sn in physiological and pathological processes have been increasingly recognized. However, their biological effects and detailed mechanisms of action are still little known. Therefore, there is an urgent need to develop highly selective and sensitive techniques for monitoring hydrogen polysulfides (H2Sn) in living cells. In this study, we designed and synthesized a fluorescent probe based on a naphthalene derivative for the detection of hydrogen polysulfides. A naphthalene derivative was applied as the fluorescent main structure and the 2-fluoro-5-nitrobenzoate group was chosen as the recognition unit. In the absence of hydrogen polysulfides, the fluorescent probe displayed almost no fluorescence. In the presence of hydrogen polysulfides, the fluorescent probe exhibited strong fluorescence. The sensing mechanism was based on H2Sn-mediated aromatic substitution-cyclization reactions. The linear range of the response concentration of the probe to hydrogen polysulfide was acquired in a concentration range of H2Sn from 7.5 × 10-7 to 2.5 × 10-5 mol L-1. The detection limit was evaluated to be 5.0 × 10-7 mol L-1 for H2Sn. The fluorescent probe can applied in a wide pH range including physiological condition pH. The fluorescent probe showed high specificity for H2Sn over other reactive sulfur species (RSS). Moreover, the fluorescent probe has been successfully applied to confocal imaging of hydrogen polysulfides in HepG2 cells without cell cytotoxicity. All of such good qualities indicated that it could be used to detect H2Sn in living cells.